OCR A-Level Biology B (Advancing Biology) sample questions and answers (H422)
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105 sample questions and answers
Taken from every topic of OCR A-Level Biology B (Advancing Biology), specification H422. The full guide has 2,895.
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The Developing Cell: Cell Division and Cell Differentiation
47 questions in the guide, across 3 subtopics. More from this topic
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The cell cycle and mitosis
What happens to the chromosomes and to the nuclear envelope during prophase?
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The chromosomes condense and become visible as two chromatids joined at a centromere, while the nuclear envelope and the nucleolus break down. -
The cell cycle and mitosis
Explain how the cell plate forms in a dividing plant cell.
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Vesicles from the Golgi apparatus line up along the equator and fuse together, releasing material that forms the middle lamella and the new cell walls and plasma membranes. -
Apoptosis in growth and repair
Define karyorrhexis.
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Karyorrhexis is the fragmentation of the condensed nucleus into pieces, which are then packaged into the apoptotic bodies.
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The Developing Individual: Meiosis, Growth and Development
80 questions in the guide, across 5 subtopics. More from this topic
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Meiosis, haploid gametes and genetic variation
How does the outcome of meiosis in a human female differ from that in a human male?
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In the female the cytoplasm divides unequally, so one large functional egg cell is produced together with small polar bodies that degenerate, whereas in the male all four products mature into functional sperm. -
Meiosis, haploid gametes and genetic variation
Define independent assortment.
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Independent assortment is the random orientation of each bivalent at the equator in metaphase 1, so which member of one homologous pair passes to a given pole is independent of every other pair. -
The stages of meiosis
What is separated during anaphase 1?
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Whole homologous chromosomes are pulled to opposite poles, each still made of two chromatids, because the centromeres do not divide at this stage.
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The Development of Species: Evolution and Classification
87 questions in the guide, across 6 subtopics. More from this topic
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Classification and the species concept
Give the binomial name of modern humans and explain what each part identifies.
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Modern humans are Homo sapiens, where Homo names the genus to which the species belongs and sapiens identifies the particular species within that genus. -
Classification and the species concept
Give one advantage of the phylogenetic species concept over the biological one.
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It can be applied to asexual organisms and to extinct organisms, because it does not depend on observing whether individuals interbreed. -
Evidence for classification and DNA barcoding
How is DNA used to judge how closely two species are related?
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The base sequences of the same gene are compared in the two species, and the fewer the differences between them, the more recently they shared a common ancestor.
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Cells and Microscopy
170 questions in the guide, across 11 subtopics. More from this topic
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Microscopy and the cell theory
What sets the limit of resolution of a light microscope at roughly 200 nm?
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The wavelength of visible light, since two points closer together than about half a wavelength of the light used cannot be resolved. -
Blood smears, staining and microscope drawings
What is meant by differential staining?
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It is the use of a stain, or a mixture of stains, that colours different cell types or different cell components differently so that they can be told apart. -
Blood cells and their structure
What are platelets and where do they come from?
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Platelets are small membrane-bound cell fragments with no nucleus, formed by the breaking up of large cells called megakaryocytes in the bone marrow.
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Water and Its Importance in Plants and Animals
86 questions in the guide, across 5 subtopics. More from this topic
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The properties of water
Why does water have a high latent heat of vaporisation?
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A great deal of energy is needed to break all the hydrogen bonds holding a molecule to its neighbours before it can escape as vapour. -
The properties of water
Explain why ice floats on water and state the biological importance of this.
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In ice the hydrogen bonds hold the molecules in a rigid open lattice that is less dense than liquid water, so ice forms an insulating layer on the surface of a pond and the water beneath stays liquid and habitable. -
Water as a transport medium and the composition of body fluids
How does water maintain turgor in a plant cell?
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Water enters the vacuole by osmosis and pushes the cytoplasm against the cellulose cell wall; because water is incompressible the wall resists and a pressure builds up that makes the cell rigid and supports the tissue.
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Proteins and Enzymes
99 questions in the guide, across 6 subtopics. More from this topic
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Amino acids, peptide bonds and chromatography
Describe how a chromatogram of an amino acid mixture is prepared and run.
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A pencil origin line is drawn near one end of the paper, a small concentrated spot of the mixture is applied and dried, and the paper is suspended in a covered tank with the solvent just below the origin line so that the solvent rises by capillary action until it nears the top, when the solvent front is marked. -
Amino acids, peptide bonds and chromatography
Give the equation used to calculate an Rf value.
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Rf equals the distance moved by the solute divided by the distance moved by the solvent. -
Globular protein structure: enzymes and haemoglobin
What is meant by quaternary structure?
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It is the arrangement of two or more separate polypeptide chains, together with any prosthetic group, into a single functional protein molecule.
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Nucleic Acids
71 questions in the guide, across 4 subtopics. More from this topic
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Nucleotides, ADP and ATP
Which base occurs in DNA but not RNA, and which occurs in RNA but not DNA?
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Thymine occurs only in DNA and uracil only in RNA. -
Nucleotides, ADP and ATP
Write a word equation for the hydrolysis of ATP.
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ATP plus water gives ADP plus inorganic phosphate, with the release of energy. -
The structure of DNA and its extraction
State Chargaff's rules.
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In the DNA of any species the amount of adenine equals the amount of thymine and the amount of cytosine equals the amount of guanine, while the ratio of adenine and thymine to cytosine and guanine differs between species.
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Patterns of Inheritance
78 questions in the guide, across 5 subtopics. More from this topic
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Monogenic inheritance and genetic terminology
What does it mean to say an organism is homozygous for a gene?
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It carries two identical alleles of that gene, one at the same locus on each of its two homologous chromosomes. -
Monogenic inheritance and genetic terminology
A plant heterozygous for one gene is self-pollinated. State the expected genotypic and phenotypic ratios of the offspring.
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The expected genotypic ratio is 1 homozygous dominant : 2 heterozygous : 1 homozygous recessive, which gives a 3 : 1 phenotypic ratio. -
Gene mutations and inherited disease
The commonest cystic fibrosis mutation deletes three bases. Explain why this does not cause a frameshift.
Show the answer
Three bases make one complete triplet, so a single amino acid, phenylalanine, is lost and every triplet after it is still read in the correct frame.
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Population Genetics and Epigenetics
59 questions in the guide, across 4 subtopics. More from this topic
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Natural selection, sickle cell and malaria
Describe the phenotype of a person with the genotype Hbˢ Hbˢ.
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They have sickle cell anaemia, with severe haemolytic anaemia and painful crises caused by sickled cells blocking vessels, and without medical treatment their survival is greatly reduced. -
Natural selection, sickle cell and malaria
Sickle cell anaemia results from a change to one amino acid. Explain why such a small change alters the protein so much.
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Glutamic acid is polar and negatively charged while valine is non-polar, so replacing one with the other creates a hydrophobic patch on the surface of the β-globin chain and changes the way the molecules interact. -
The Hardy-Weinberg principle
State the conditions that must hold for the Hardy-Weinberg equations to apply.
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The population must be large, mating must be random, and there must be no mutation, no migration into or out of the population and no natural selection acting on the gene.
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Gene Technologies
81 questions in the guide, across 5 subtopics. More from this topic
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Post-Transcriptional Editing of mRNA
What is added to the 3′ end of a mature mRNA molecule, and why?
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A poly(A) tail of many adenine nucleotides is added, which protects the molecule from being broken down by enzymes in the cytoplasm and so extends the time over which it can be translated. -
Post-Transcriptional Editing of mRNA
How does alternative splicing allow the human genome to code for far more proteins than it has genes?
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Each different combination of exons is translated into a different polypeptide, so one gene can give rise to many related proteins, often with different roles in different tissues. -
Genetic modification of bacteria and insulin production
What are sticky ends, and how are they produced?
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Sticky ends are short single-stranded overhangs of unpaired bases, produced when a restriction enzyme makes a staggered cut across the two strands of the double helix.
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The Principles and Importance of Homeostasis
54 questions in the guide, across 4 subtopics. More from this topic
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Homeostatic principles, normal ranges and feedback
State the normal core body temperature of a healthy adult.
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Core body temperature is normally about 37 °C. -
Homeostatic principles, normal ranges and feedback
Contrast positive feedback with negative feedback.
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Positive feedback amplifies the original change and drives the factor further from its starting value, whereas negative feedback opposes the change and restores the factor to its set point. -
The nervous and hormonal control of heart rate
What effect does increased sympathetic activity have on the heart, and which neurotransmitter brings it about?
Show the answer
Noradrenaline is released, which increases the frequency at which the sinoatrial node fires and the force of ventricular contraction, so heart rate and cardiac output rise.
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The Hormonal Control of Blood Glucose and the Management of Diabetes
64 questions in the guide, across 4 subtopics. More from this topic
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The pancreas as an endocrine gland
Why does the acinar tissue of the pancreas take up stain more heavily than an islet does?
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Acinar cells are packed with rough endoplasmic reticulum and with granules of digestive enzyme, and these structures bind a great deal of stain. -
The pancreas as an endocrine gland
How is an eyepiece graticule calibrated so that the diameter of an islet can be measured?
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A stage micrometer with a scale of known length is placed on the stage and viewed through the graticule, and the number of micrometres represented by one graticule division is worked out for that objective lens. -
The regulation of blood glucose by negative feedback
How does insulin increase the rate at which a muscle cell takes up glucose?
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Insulin binding to its receptor causes vesicles carrying GLUT4 glucose transporter proteins to fuse with the cell surface membrane, so there are more channels through which glucose can enter by facilitated diffusion.
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Kidney Functions and Malfunctions
87 questions in the guide, across 6 subtopics. More from this topic
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Excretion and the gross structure of the kidney
Why is ammonia converted into urea rather than being excreted as it is?
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Ammonia is extremely soluble and highly toxic even at low concentrations, so the liver converts it into urea, which is far less toxic and can be carried safely in the blood until the kidney removes it. -
Excretion and the gross structure of the kidney
Trace the path taken by urine from the renal pelvis until it leaves the body.
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It passes down the ureter to the bladder, where it is stored, and then leaves the body through the urethra. -
The nephron: ultrafiltration and selective reabsorption
How are podocytes adapted to their role?
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They have finger-like extensions that wrap around the capillary and leave narrow filtration slits between them, so filtrate passes freely into the capsule without the cells forming a complete barrier.
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The Cellular Basis of Cancer and Treatment
85 questions in the guide, across 6 subtopics. More from this topic
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Risk factors for non-communicable disease
Define the term carcinogen.
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A carcinogen is any agent that increases the risk of cancer developing, usually by causing mutations in DNA. -
Risk factors for non-communicable disease
Why can an epidemiological study never prove on its own that a risk factor causes a disease?
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It can only show a correlation between exposure and disease, and a confounding variable linked to both could be the real cause. -
Cell cycle control and tumour formation
What is checked at the spindle assembly checkpoint during metaphase?
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That every chromosome is correctly attached to spindle fibres from both poles, so the chromatids will be separated evenly.
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Respiratory Diseases and Treatment
62 questions in the guide, across 4 subtopics. More from this topic
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Pollutants and the respiratory system
Name the component of tobacco smoke that contains carcinogens, and state where its long-term damage is seen.
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Tar, which deposits on the lining of the airways and causes mutations in the DNA of the bronchial epithelial cells, leading to lung cancer. -
Pollutants and the respiratory system
How does the risk of lung cancer in someone exposed to asbestos change if they also smoke?
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The two risk factors multiply rather than simply add, so a smoker exposed to asbestos has a far greater risk than the sum of the two risks separately. -
COPD, asthma and lung cancer
Explain why a person with emphysema becomes severely breathless.
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The merging of alveoli greatly reduces the surface area for gas exchange, and the loss of elastin means the lungs cannot recoil to force air out, so stale air is trapped and less fresh air is drawn in.
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Cellular Respiration
75 questions in the guide, across 5 subtopics. More from this topic
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Glycolysis and the link reaction
What happens to hexose bisphosphate in the lysis stage of glycolysis?
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It is split into two molecules of triose phosphate, each with three carbon atoms. -
Glycolysis and the link reaction
Where does the link reaction take place?
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In the matrix of the mitochondrion, where its enzymes are found. -
The Krebs cycle
Account for the number of carbon atoms in citrate and in oxaloacetate.
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Oxaloacetate has four carbon atoms and gains two from the acetyl group to give the six of citrate, and the two carbons lost as carbon dioxide return it to four.
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Metabolism and Exercise
131 questions in the guide, across 9 subtopics. More from this topic
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The consequences of exercise on the body
How does contraction of skeletal muscle help to increase venous return during exercise?
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Contracting muscles squeeze the deep veins running between them, and the valves in those veins ensure the blood is pushed only towards the heart. -
Aerobic fitness and VO₂ max
Describe how VO₂ max is measured directly in a laboratory.
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The subject exercises on a treadmill or cycle ergometer at steadily increasing intensity to exhaustion while their expired air is collected and analysed, and VO₂ max is the oxygen uptake at which it plateaus despite a further increase in workload. -
Training, F.I.T.T. factors and investigating fitness
What does time refer to in an exercise programme?
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Time is the duration of each individual session, typically twenty to sixty minutes for aerobic training.
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Pathogenic Microorganisms
86 questions in the guide, across 6 subtopics. More from this topic
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How pathogens cause communicable disease
Distinguish between a bacterial exotoxin and an endotoxin.
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An exotoxin is a soluble protein actively secreted by a living bacterium, whereas an endotoxin is the lipopolysaccharide of the outer membrane of a Gram-negative cell and is released mainly when the cell dies and breaks apart. -
How pathogens cause communicable disease
How do fungi obtain nutrients from the tissue of their host?
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They secrete hydrolytic enzymes out of their hyphae to digest the host's tissue, then absorb the soluble products. -
Tuberculosis
What is a tubercle?
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A tubercle is a small mass of scar tissue and immune cells formed in the lung, which walls off and contains the bacteria.
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The Immune System
68 questions in the guide, across 4 subtopics. More from this topic
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Primary defences and non-specific responses
Why is a smoker more likely to develop a chest infection?
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Tar in tobacco smoke paralyses and destroys the cilia, so mucus and the pathogens trapped in it collect in the airways instead of being swept out. -
Primary defences and non-specific responses
Name the two main types of phagocyte.
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Neutrophils and macrophages. -
B and T lymphocytes and the specific response
What is the function of a plasma cell?
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A plasma cell secretes very large quantities of one specific antibody into the blood and lymph.
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Controlling Communicable Diseases
51 questions in the guide, across 4 subtopics. More from this topic
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Vaccination and vaccination programmes
Why does a live vaccine usually give stronger and longer-lasting protection than a killed one?
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The attenuated pathogen reproduces inside the body, so its antigens are presented in increasing amounts over a much longer period and a far larger clone of memory cells is produced. -
Vaccination and vaccination programmes
What is herd immunity?
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Herd immunity is the protection of a whole population, including unvaccinated individuals, that arises when so many people are immune that the pathogen cannot find enough susceptible hosts to spread between. -
Problems and ethics of vaccine development and use
Give two reasons, other than its mutation rate, why no effective HIV vaccine has been produced.
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The virus integrates into the host cell's own DNA where it can remain hidden, and it destroys the T helper cells that would otherwise coordinate a response against it.
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Photosynthesis, Food Production and Management of the Environment
181 questions in the guide, across 12 subtopics. More from this topic
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Chloroplast ultrastructure and photosynthetic pigments
Explain the advantage of the thylakoid membranes being arranged in stacks.
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Stacking packs a very large membrane surface area into a small volume, so many more light harvesting complexes and photosystems can be held for absorbing light. -
The light-dependent stage of photosynthesis
What is the final electron acceptor of the light-dependent stage, and what is formed?
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NADP is the final electron acceptor, and it combines with electrons and a proton to form reduced NADP. -
Investigating the factors affecting photosynthesis
Describe how the effect of wavelength on photosynthesis is investigated.
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Coloured filters that transmit known wavelengths are placed between a lamp of fixed intensity and the plant, and the rate of oxygen release is measured for each filter.
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The Impact of Population Increase
61 questions in the guide, across 4 subtopics. More from this topic
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Birth rate, death rate and demographic change
Give three advances in medical technology that have reduced human death rates.
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Vaccination programmes, antibiotics to treat bacterial infection, and improved antenatal and surgical care. -
Birth rate, death rate and demographic change
Describe the pattern of birth and death rates in stage 2 of the demographic transition.
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The death rate falls sharply while the birth rate remains high, so the population grows very rapidly. -
Human impact on ecosystems and biodiversity
Explain how irrigation can eventually make farmland unusable.
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Irrigation water carries dissolved salts that are left behind as the water evaporates, and the accumulating salt lowers the soil water potential so crops can no longer take up water.
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Planning and Implementing Practical Work
46 questions in the guide, across 3 subtopics. More from this topic
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Designing an investigation and controlling variables
Why is a buffer solution added to an enzyme reaction mixture?
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It resists changes in pH, so pH cannot act as a second variable affecting the activity of the enzyme. -
Designing an investigation and controlling variables
What is meant by a null hypothesis?
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It is the statement that there is no significant difference, or no association, between the variables being investigated. -
Choosing apparatus and judging whether a method will work
State the apparatus you would use to hold a reaction mixture at 35 °C.
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A thermostatically controlled water bath, with a thermometer in the mixture to confirm the temperature.
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Analysing and Evaluating Practical Results
95 questions in the guide, across 6 subtopics. More from this topic
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Processing and interpreting experimental results
A student records the time taken for a colour to disappear. Explain how this is converted into a rate.
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The rate is calculated as one divided by the time, so a shorter time gives a larger rate. -
Processing and interpreting experimental results
A student tests one enzyme and concludes that enzymes work best at 40 °C. Explain why the conclusion is faulty.
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Only one enzyme was investigated, so the result can be stated for that enzyme alone and not for enzymes in general. -
Mathematical skills for analysing biological data
How are the degrees of freedom found for a chi-squared test?
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They are one fewer than the number of categories of data.
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Practical Skills, Apparatus and Techniques
171 questions in the guide, across 11 subtopics. More from this topic
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Investigative approaches and working safely
State the steps of a risk assessment for a practical activity.
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The hazards are identified, the people who could be harmed and the seriousness of the harm are considered, and a control measure is given for each hazard. -
Following instructions, recording and presenting data
Why is an incorrect entry in a laboratory record crossed out with a single line rather than erased?
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The original reading stays visible, so the record remains an honest account and the correction can be checked. -
Research, referencing and processing data with software
Why should the date of a source be considered when researching a medical treatment?
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Clinical guidance changes as new evidence appears, so an out-of-date source may describe a treatment that is no longer recommended.
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Fertility and Assisted Reproduction
83 questions in the guide, across 6 subtopics. More from this topic
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The urinogenital systems and gonad histology
Name in order the parts of the female tract that a secondary oocyte passes along after ovulation.
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It is swept from the ovary surface into the oviduct, travels along the oviduct and enters the uterus, whose lower opening is the cervix leading to the vagina. -
The urinogenital systems and gonad histology
How would you distinguish a Graafian follicle from a primary follicle in a section of ovary?
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A Graafian follicle is far larger and contains a big fluid-filled antrum with the oocyte held on a stalk of granulosa cells, whereas a primary follicle is small and solid with only a single layer of cells around the oocyte. -
Gametogenesis and the structure of the gametes
At which stage of meiosis is a primary oocyte arrested, and for how long?
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It is arrested in prophase I, from before birth until the cycle in which that follicle is recruited, which may be several decades later.
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The Effects of Ageing on the Reproductive System
46 questions in the guide, across 3 subtopics. More from this topic
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Ageing and the female reproductive system
Why is a raised FSH concentration useful as an indicator of approaching menopause?
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It reflects the size of the remaining follicle pool directly, so it rises before periods stop and gives a measurable sign of declining ovarian function. -
Ageing and the female reproductive system
Describe the pattern of oestrogen, progesterone, FSH and LH after the menopause.
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Oestrogen and progesterone are permanently low because no follicles develop or luteinise, while FSH and LH are permanently high because there is no negative feedback to restrain them. -
Managing the menopause
Why may a skin patch be preferred to a tablet for a woman at risk of thrombosis?
Show the answer
Oestrogen absorbed through the skin passes into the general circulation without first going through the liver, so it does not increase the liver's output of clotting factors in the way an oral dose does and the risk of thrombosis is much lower.
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Plant Reproduction
57 questions in the guide, across 4 subtopics. More from this topic
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The control of flowering
What is photoperiodism?
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It is the response of a plant, such as the timing of its flowering, to the relative lengths of day and night. -
The control of flowering
Predict and explain the effect on a short-day plant of a brief flash of red light in the middle of a long night.
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The flash converts Pr back into Pfr, restoring the inhibitor, so the plant behaves as though the night were short and does not flower, even though the total darkness was long enough. -
Adaptations of flowers for pollination
Give three features of pollen carried by wind.
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It is produced in enormous quantities, and the individual grains are very small, light and smooth so that they are carried a long way on air currents.
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The Nervous System and the Identification and Consequences of Damage
122 questions in the guide, across 8 subtopics. More from this topic
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Organisation of the nervous system and nervous tissue
How does the number of neurones between the central nervous system and the effector differ in somatic and autonomic pathways?
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A somatic pathway uses a single motor neurone running all the way from the central nervous system to the muscle, whereas an autonomic pathway uses two neurones with a synapse in a ganglion between them. -
The structure and function of the human brain
State the main function of the cerebellum.
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The cerebellum co-ordinates fine muscular movement, balance and posture, making movements smooth and accurate. -
The structure of motor, sensory and relay neurones
Where are relay neurones found, and how does their length compare with the other two types?
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Relay neurones lie entirely within the central nervous system and are short, with many short dendrites and a short axon.
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Monitoring Visual Function
53 questions in the guide, across 3 subtopics. More from this topic
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The structure of the eye
Describe the structure of the iris.
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The iris is a pigmented disc of muscle in front of the lens, containing a ring of circular muscle and a set of radial muscles arranged like the spokes of a wheel. -
The structure of the eye
Where is the aqueous humour found, and what does it do?
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The aqueous humour is the watery fluid filling the space between the cornea and the lens, and it supplies nutrients and oxygen to the avascular cornea and lens, removes their waste and keeps the front of the eye firm. -
The retina and its role as a transducer
What is the function of the bipolar cells of the retina?
Show the answer
Bipolar cells connect the rods and cones to the ganglion cells and pass on the graded change in potential produced by the photoreceptor.
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The Effect of Ageing on the Nervous System
52 questions in the guide, across 3 subtopics. More from this topic
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Alzheimer's disease: symptoms and causes
Where do beta-amyloid plaques form, and from what?
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They form outside the neurones in the spaces between them, from insoluble fragments produced by the abnormal breakdown of a membrane protein called amyloid precursor protein. -
Alzheimer's disease: symptoms and causes
Give two genetic factors that raise the risk of developing Alzheimer's disease.
Show the answer
Mutations in the gene for amyloid precursor protein or the presenilin genes cause a rare inherited early-onset form, and inheriting the APOE ε4 allele raises the risk of the common late-onset form. -
The effects of ageing on the senses and memory
How does the audiogram of a person with presbycusis differ from that of a young adult?
Show the answer
The threshold is close to normal at low frequencies but rises steeply at high frequencies, so the trace slopes away at the right-hand end in both ears.
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The Heart and Monitoring Heart Function
92 questions in the guide, across 6 subtopics. More from this topic
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The need for a mass transport system
Explain why a small surface area to volume ratio makes diffusion alone inadequate in a mammal.
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There is too little exchange surface for the mass of respiring tissue, and the distances from the surface to the innermost cells are far too great for diffusion to supply oxygen quickly enough. -
The need for a mass transport system
Name three substances that the mammalian mass transport system delivers to respiring tissues.
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Oxygen, glucose and amino acids. -
Structure and dissection of the mammalian heart
Which valve lies between the left atrium and the left ventricle?
Show the answer
The bicuspid valve, which is also called the mitral valve.
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Transport Systems in Mammals
60 questions in the guide, across 4 subtopics. More from this topic
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The closed double circulatory system
Give a typical value for systemic arterial blood pressure and for pulmonary arterial blood pressure in a healthy adult.
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Systemic arterial pressure is about 120/80 mmHg and pulmonary arterial pressure is about 25/10 mmHg. -
The closed double circulatory system
Give one advantage of a closed circulation over an open one.
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Pressure can be kept high so that blood flows quickly, and flow can be directed to particular organs by altering the diameter of the vessels. -
Blood vessels and their microscopic structure
What is the wall of a capillary made of?
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It is a single layer of flattened endothelial cells, one cell thick, with narrow gaps between neighbouring cells.
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Gas Exchange in Mammals and Plants
76 questions in the guide, across 5 subtopics. More from this topic
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Tissues of the mammalian gas exchange system
What is the role of the goblet cells in the airway lining?
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They secrete mucus, which traps dust particles, pollen and pathogens in the incoming air. -
Tissues of the mammalian gas exchange system
Explain why the smallest bronchioles contain no cartilage.
Show the answer
They are held open by the surrounding lung tissue and must be able to change diameter, which rigid cartilage would prevent. -
Gas exchange in the alveoli
Explain how ventilation helps to maintain the concentration gradients at the alveoli.
Show the answer
Breathing brings in fresh air with a high oxygen and low carbon dioxide concentration and removes air that has equilibrated with the blood, so the gradients are kept steep.
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Transport Systems in Plants
79 questions in the guide, across 5 subtopics. More from this topic
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The need for transport systems in plants
Explain why roots need substances to be transported to them.
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Roots are underground and contain no chloroplasts, so they cannot photosynthesise and must receive sugars made in the leaves. -
The need for transport systems in plants
Why can a moss survive without vascular tissue?
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It is only a few cells thick and grows very close to the ground, so water and solutes only have to travel short distances and diffusion is fast enough. -
Vascular tissue in roots, stems and leaves
State two adaptations of a companion cell to its function.
Show the answer
It has dense cytoplasm with many mitochondria to supply ATP for active loading, and numerous plasmodesmata linking it to the sieve tube element.
OCR A-Level Biology B (Advancing Biology) Active Recall Guide
The other 2,790 questions, with the answers printed after each section.