A Level Biology Quizzes

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AQA quizzes

Introduction to Water

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Introduction to Water

Q1. Water is a polar molecule. Explain what this means. [1 mark]

Answer:
It has a positive end and a negative end OR The oxygen is (delta/slightly) negatively charged due to unpaired electrons and the hydrogens are (delta/slightly) positively charged as their electrons are closer to the oxygen.

Q2. Water is known as the universal solvent as it has the ability to dissolve many ionic and covalent compounds due to its polar nature. Which of the 3-carbon compounds will not form hydrogen bonds with water and will therefore not dissolve in water? [1 mark]

Glycerol, propanoic acid, propanol and propane chemical structure diagram
Answer:
D

Q3. Hydrogen bonds hold an amylose molecule in its helical shape. Describe how a hydrogen bond is formed. [2 marks]

Answer:
– between oxygen and hydrogen (atoms)
– (between) (electro)negative / δ- and (electro)positive / δ+

Q4. Other than water, list three other examples of where hydrogen bonds are found in biological molecules. [3 marks]

Answer:
– protein secondary structure / α-helix / Beta-pleated sheet / (protein) tertiary structure / between polypeptide chains in (named) quaternary structure
– (between chains of) cellulose/ (coiling of) amylase
– (between, strands of / bases in) DNA

Q5. Describe the formation of a hydrogen bond between two molecules of water and explain why water can form these bonds. [3 marks]

Answer:
– between O and H (of adjacent molecules)
– between (electro)positive / δ+ / delta+ (H) and (electro)negative / δ- / delta- (O)
– (water molecule is) polar / has charge separation

Q6. Water is described as a polar molecule because it has a… [1 mark]

A. positively charged hydrogen end and a negatively charged oxygen end

B. positively charged hydrogen end and a positively charged oxygen end

C. negatively charged hydrogen end and a negatively charged oxygen end

D. negatively charged hydrogen end and a positively charged oxygen end

Answer:
A

Q7. The diagram shows four molecules, P, Q, R and S, found in living organisms. Two molecules of P can be joined together by… [1 mark]

Chemical Structure Diagrams of biological molecules
A. a hydrogen bond
B. a hydrophobic interaction
C. an ionic bond
D. a peptide bond

Answer:
A

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Protein Structure

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Structure and Function of Proteins

Q1. Amino acids form part of the structure of proteins. State the name given to the sequence of amino acids in a protein molecule. [1 mark]

Answer:
primary structure

Q2. Haemoglobin is a protein. Its molecules have a quaternary structure. Explain what is meant by a quaternary structure. [1 mark]

Answer:
More than one polypeptide chain

Q3. Explain how a change in the DNA base sequence for a protein may result in a change in the structure of the protein. [3 marks]

Answer:
– Change in amino acid/s /primary structure
– Change in hydrogen/ionic/ disulfide bonds
– Alters tertiary structure

Q4. Which bonds are involved in forming the secondary structure of proteins? [1 mark]

A. Peptide bonds and Hydrogen bonds

B. Hydrogen Bonds and Ionic Bonds

C. Disulphide bridges and Peptide bonds

D. Ionic Bonds and Disulphide bridges

Answer:
A

Q5. What is the term used to describe the final 3D resting shape of a polypeptide chain? [1 mark]

Answer:
Tertiary structure

Q6. Each amino acid has a different R group. Describe how these R groups can interact to determine the tertiary structure of a protein. [3 marks]

Answer:
– disulfide bridges /bond (between cysteine / SH / S atoms)
– hydrogen/H bonds OR some R groups attract/repel OR hydrophilic R groups on outside of molecule /hydrophobic R groups on inside of molecule
– ionic bonds (between oppositely charged R groups)

Q7. Fig. 4.3 shows some of the chemical bonds that hold the tertiary structure of a protein together. Name the bonds labelled A, B and C. [3 marks]

3D drawing of a protein, labelling bonds
Answer:
A = ionic
B = hydrogen
C = disulfide (bond / bridge)

Q8. When proteins are heated to a high temperature, their tertiary structure is disrupted. Explain how this occurs. [3 marks]

Answer:
– increased kinetic energy / vibrates
– hydrophilic/hydrophobic / hydrogen / ionic bonds break
– change in 3D shape / conformation (of protein)/ denatures

Q9. Alpha (α) and beta (β) are prefixes that are frequently used to describe a range of biological molecules, such as α-glucose and β-glucose. The prefixes α and β can also be used when describing protein structure.
Complete the following statements about proteins using the most appropriate terms.
• The secondary structure of a protein may contain many regions folded in zig-zag patterns known as ……………………………………. .
• The secondary structure of a protein is determined by the arrangement of ……………………………………. bonds, which stabilise the structure.
• The …………………………………… structure of collagen is described as a left-handed helix because of the direction in which the polypeptide twists.
• Multiple polypeptide chains form part of the ……………………………………. structure of haemoglobin. [4 marks]

Answer:
beta- / β- pleat(ed sheets)
hydrogen / H
Secondary
Quaternary

Q10. Proteins are made up of amino acids. Describe how amino acids join together to form the three-dimensional structure of a protein. [5 marks]

Answer:
– peptide bonds (joining amino acids)
– between amino group (of one amino acid) and carboxyl group (of another)
– the sequence of amino acids is the primary structure of the protein
– reference to folding (of primary structure) held together by bonds
– disulfide bridges / hydrogen / H bonds / ionic bonds / Van der Waals forces

Q11. Lysozyme is an enzyme found in tears. Lysozyme can destroy some bacteria by breaking down the polysaccharide chains that form part of their cell walls.

The primary structure of lysozyme is a specific sequence of 129 amino acids. Two of the amino acids that make up the active site are in positions 35 and 52 in the primary structure.

Suggest how these two amino acids could be brought closer together to form part of the active site of this enzyme. [2 marks]

Answer:
– idea of formation of secondary or tertiary structure
– idea of bonding (between R groups) OR named bond e.g. disulfide bridges / hydrogen / H bonds / ionic bonds / Van der Waals forces

Q12. The diagrams show four different bonds, A, B, C, and D, found in biological molecules.
1. Which bond occurs in a triglyceride molecule? [1 mark]
2. Which bond may occur in the tertiary, but not the primary, structure of a protein? [1 mark]
3. Which is the peptide bond? [1 mark]
4. Which is the ester bond? [1 mark]

amino acid chemical structure diagrams
Answers:
12.1. D
12.2. A
12.3. B
12.4. D

Q13. The three-dimensional structure of a protein is held together by… [1 mark]

Answer:
disulphide bridges, hydrogen and ionic bonds

Q14. Enzymes, messenger RNA (mRNA) and transfer RNA (tRNA) are involved in the synthesis of proteins.
The diagram below represents the structure of an enzyme. Each circle represents an amino acid.
Using the diagram and your own knowledge of enzymes, explain the importance of the primary structure of an enzyme to its function. [4 marks]

a long chain of amino acids demonstrating primary structure
Answer:
– idea that primary structure determines (three-dimensional) folding
– reference to types of amino acids determine types of bonds OR position of amino acids determines position of bonds OR two cys (amino acids) form bonds
– idea that shape / position of active site is determined by position of amino acids
– reference to shape of active site being correct to bind to substrate

Q15. Haemoglobin is a protein found in red blood cells that helps transport oxygen in the blood.
In sickle cell anaemia, the presence of the allele (a) in place of the normal allele (A) results in a change of one amino acid in the haemoglobin molecule. This mutation changes the properties of haemoglobin and can result in red blood cells becoming less flexible and blocking small blood vessels.

Explain how a change of one amino acid can lead to a change in the structure and properties of the haemoglobin protein. [3 marks]

Answer:
– change in primary structure
– Change in bonds e.g. disulfide bridges / hydrogen / H bonds / ionic bonds / Van der Waals forces
– different folding / secondary / tertiary / 3D structure

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ATP

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ATP

Q1. Write a simple equation to show how ATP is synthesised from ADP. [1 mark]

Answer:
ADP + Pi → ATP [Allow other recognised symbols or words for phosphate ion. Reject P unless in a circle. Accept = as equivalent to arrow]

Q2. Give three ways in which the properties of ATP make it a suitable source of energy in biological processes. [3 marks]

Answer:
– Energy released in small/suitable amounts
– Soluble
– Involves a single/simple reaction

Q3. The table shows four biological molecules and their component elements. Which of the rows, A to D, correctly identifies the elements in each molecule? [1 mark]

Table with sucrose, cholesterol, insulin and ATP elements
Answer:
C

Q4. ATP is useful in many biological processes. Explain why. [4 marks]

Answer:
– Releases energy in small / manageable amounts [Accept less than glucose]
– (Broken down) in a one-step / single bond broken [Accept easily broken down]
– Immediate energy compound / makes energy available rapidly
– Reformed/made again/regeneration

Q5. What is the name of the type of reaction in which ADP + Pi are joined and what is the name of the enzyme that catalyses this reaction? [2 marks]

Answer:
– Condensation reaction
– ATP synthase

Q6. What is the name of the type of reaction in which ATP is split and what is the name of the enzyme that catalyses the reaction? [2 marks]

Answer:
– Hydrolysis
– ATP Hydrolase

Q7. Which is the correct equation to show a reaction in which energy is released from ATP? [1 mark]

A. ADP + Pi → ATP

B. ATP → P + ADP

C. ATP → APP

D. ATP → ADP + Pi

Answer:
D

Q8. Fig. 1.1 represents a molecule of ATP.
1. Name the parts of the ATP molecule labelled X, Y and Z. [3 marks]
2. With reference to Fig. 1.1, describe and explain the role of ATP in the cell. [2 marks]

diagram of a molecule of ATP
Answer:
1.
X = adenine
Y = ribose
Z = (tri / 3) phosphate(s)

2.
– Transfers energy / releases energy / universal energy molecule / energy intermediate / (immediate) source of energy
– (Energy released for) metabolism

Q9. ATP is described as the ‘universal energy currency’. Describe how the structure of ATP is similar to and differs from the structure of a DNA nucleotide. [6 marks]

Answer:
Similarities:
– (Both) have pentose / 5C sugar
– (Both) have phosphate
– (Both) have adenine / (nitrogenous) base

Differences:
– DNA (nucleotide) has deoxyribose and ATP has ribose
– DNA (nucleotide) has 1 phosphate and ATP has 3 phosphates
– DNA (nucleotide) has (4 possible) different bases / can have thymine / can have cytosine / can have guanine, and ATP has only 1 (possible) base / adenine

Q10. The diagram summarises the interconversion of ATP and ADP. Identify:
1. Substance W
2. Reaction S
3. Reaction T [3 marks]

diagram showing the reaction forming ATP
Answer:
1. Inorganic phosphate
2. Hydrolysis
3. Phosphorylation / Condensation

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Introduction to Respiration

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Introduction to Respiration

Q1. Describe how ATP is made in mitochondria. [8 marks]

Answer:
1. Substrate level phosphorylation / ATP produced in Krebs cycle
2. Krebs cycle/link reaction produces reduced coenzyme/reduced NAD/reduced FAD [Accept description of either Krebs cycle or link reaction]
3. Electrons released from reduced coenzymes / NAD / FAD
4. (Electrons) pass along carriers / through electron transport chain / through series of redox reactions
5. Energy released [Allow this mark in context of electron transport or chemiosmosis]
6. ADP / ADP + Pi [Accept H+ or hydrogen ions and cristae]
7. Protons move into intermembrane space [Allow description of movement through membrane]
8. ATP synthase [Accept ATPase]

Q2. Which of the following is a similarity in the way ATP is made in respiration and photosynthesis? [1 mark]

1. both involve NAD

2. both involve substrate level phosphorylation

3. both involve photons

4. both involve proton gradients

Answer:
4

Q3. Aerobic respiration may be summarised by the following equation: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

Although carbon dioxide and water are products of aerobic respiration, the equation is an oversimplification of the process. State and explain one way in which this equation is an oversimplification. [4 marks]

Answer:
1. Glucose is not the only substrate / there are other substrates OR glucose does not combine/react (directly) with oxygen
2. ATP is produced / energy is released (by) substrate level / oxidative phosphorylation OR ATP / energy required (for phosphorylation / glycolysis)
3. Is not a single-step reaction / other steps involved / other products / other intermediates (e.g. oxidative phosphorylation / link reaction / Krebs cycle / glycolysis)
4. Enzymes are involved / coenzymes / NAD involved

Q4. Suggest one benefit of anaerobic respiration to an organism. [1 mark]

Answer:
– ATP produced / energy released / recycles NAD / NAD can be used again / allows glycolysis to take place

Q5. Name the process that produces pyruvic acid. [1 mark]

Answer:
– Glycolysis

Q6. Describe a circumstance that could cause a fall in pH in living muscle. [1 mark]

Answer:
– Anaerobic conditions / respiration OR lack of oxygen OR process that reduces pH

Q7. State the stage or stages of aerobic respiration during which:
1. Carbon dioxide is produced [1 mark]
2. Oxygen is used [1 mark]

Answer:
1. Link reaction and Krebs cycle
2. Oxidative phosphorylation

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OCR quizzes

Properties of Water

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Properties of Water

Q1. Water is an excellent solvent. Define the term ‘solvent’. [1 mark]

Answer:
(A liquid/substance that) other substances can dissolve in / in which solutes are dissolved

Q2. How do the properties of water result in sweating being an effective way to cool down in some mammals? [3 marks]

Answer:
1. Large latent heat of vaporisation
2. (As it takes a lot of) energy
3. To break hydrogen bonds (between polar H₂O molecules)

Q3. How are the properties of water essential to transport of fluids in the xylem of plants? [1 mark]

Answer:
– Cohesion: Water molecules stick to each other due to their hydrogen bonds (so can be pulled against gravity). [Accept Cohesion, accept Adhesion]

Q4. Which property of water is important for maintaining a stable internal body temperature? [1 mark]

1. It has a high specific heat capacity

2. The polar molecules are cohesive

3. Water molecules can adhere to other surfaces

4. It is an excellent solvent

Answer:
1

Q5. Ponds provide a very stable environment for aquatic organisms. Three properties of water that contribute to this stability are as follows:
• The density of water decreases as the temperature falls below 4 °C so ice floats on the top of the pond.
• It acts as a solvent for ions such as nitrates (NO₃⁻).
• A large quantity of energy is required to raise the temperature of water by 1 °C.
Explain how these three properties help organisms survive in the pond. [7 marks]

Answer:
1. Ice forms insulating layer
2. Water (below ice) does not freeze / still liquid / remains water / kept at higher temperature
3. Organisms do not freeze OR animals / organisms can still swim / move OR allows currents / nutrients to circulate
4. Solubility – ions attracted to / bind to / interact with water / allows uptake of minerals / nutrients by organisms / plants / animals
5. Temperature stability – many / stable (hydrogen) bonds between molecules / a lot of energy to force apart molecules / break bonds / high (specific) heat capacity
6. Temperature does not change much / small variation in temperature
7. Enzymes / metabolic rate (can remain stable) / gases remain soluble

Q6. Hydrogen bonds allow water to act as a solvent. Why is the ability of water to act as a solvent important for the survival of organisms? [2 marks]

Answer:
1. Medium for (metabolic) reactions OR allows ionic compound(s) to separate OR (organisms can) absorb / take in minerals / ions / (named) gas / food OR able to dilute toxic substances
2. Transport

Q7. Water striders are a type of insect belonging to the Gerridae family. They adapted to live on top of water in lakes and ponds. What property of water allows water striders to move on the surface of the water? [2 marks]

Answer:
1. Surface tension
2. Due to cohesion (between water molecules)

Q8. Which property of water is the most important for transport of substances in organisms? [1 mark]

1. Large latent heat of vaporisation

2. An important metabolite

3. An excellent solvent

4. High specific heat capacity

Answer:
3

Q9. Give an example of a metabolic reaction that requires water. [1 mark]

Answer:
– Condensation OR hydrolysis OR any valid example of a condensation or hydrolysis reaction

Q10. Many of the physical properties of water arise as a result of hydrogen bonds. Describe ways in which the physical properties of water allow organisms to survive over a range of temperatures. [8 marks]

Answer:
1. High latent heat of vaporisation
2. Large amount of energy required to change from liquid to gas OR evaporation is (efficient) cooling mechanism
3. High specific heat capacity
4. Large amount of energy needed to raise / change temperature
5. (Thermally) stable environment for aquatic organisms / (aquatic) organisms use less energy on temperature control OR (internal) temperature of organisms changes only slowly OR (biological) reactions / enzymes / metabolism function(s) correctly
6. Ice is less dense than water / floats
7. (Surface of) ice provides habitat for organisms / water (beneath ice) insulated / remains liquid / does not freeze / (aquatic) organisms do not freeze
8. (Effective) solvent OR medium for reactions / (internal) transport OR able to dilute toxic substances OR cohesion / adhesion / surface tension

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Introduction to Proteins

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Introduction to Proteins

Q1. Describe the structure of an amino acid. [3 marks]

Answer:
1. Presence of amine group
2. Presence of carboxyl group
3. Reference to R group OR reference to central carbon atom

Q2.
1. Name the covalent bond between two adjacent amino acids in a chain of amino acids. [1 mark]
2. Name the type of reaction involved in breaking this bond and describe what happens in this reaction. [2 marks]

Answer:
1. Peptide (bond / link)
2.1 Hydrolysis
2.2 Water/H₂O is added/used

Q3. Which of the following could not be an amino acid? [1 mark]

1. A

2. B

3. C

4. D

A series of chemical structure diagrams
Answer:
C

Q4. Amino acids are the basic building blocks for proteins. Fig. 4.1 shows the amino acid cysteine. Select the letter, J, K, L or M, that represents the following groups in cysteine:
1. Carboxyl
2. R group
3. Amine group [3 marks]

A detailed chemical structure diagram of cysteine
Answer:
1. L
2. M
3. J

Q5. The diagram in Fig. 1.1 represents an amino acid. One of the atoms that make up an amino acid has been replaced with the letter X. State the chemical symbol of the atom represented by the letter X in Fig. 1.1. [1 mark]

a simplified chemical structure diagram of an amino acid
Answer:
N

Q6. The primary structure of a protein consists of a chain of amino acids. Describe how a second amino acid would bond to an amino acid such as cysteine in forming the primary structure of a protein. [4 marks]

Answer:
1. Peptide bond
2. Between amine group (of one amino acid) and carboxyl group (of another)
3. H (from amine group) combines with OH (from carboxyl group)
4. Condensation reaction OR water lost / produced

Q7. Proteins, such as enzymes, are important molecules found in all living organisms. Read through the following passage on the primary structure of proteins, then fill in the blanks with the most appropriate word or words to complete the passage. [5 marks]

Proteins are made of monomers called ………………………………….. . These monomers are joined together by …………………………………. bonds, formed during ………………………………… reactions. Each monomer of a protein consists of a central carbon atom attached to a hydrogen atom, an R group, an ………………………………………… group and a ……………………………………. group. The sequence of monomers determines the primary structure of the protein.

Answer:
1. Amino acids
2. Peptide
3. Condensation / Polymerisation
4. Amino / Amine / NH₃⁺ / NH₂
5. Carboxyl / Carboxylic (acid) / COO⁻ / COOH

Q8. The diagram shows four molecules, P, Q, R and S, found in living organisms. A condensation reaction between two molecules of Q forms… [1 mark]

chemical structure diagrams of four biological molecules
A. An ester bond

B. A glycosidic bond

C. A hydrogen bond

D. A peptide bond

Answer:
D

Q9. Caffeine is a drug frequently consumed in a number of drinks such as coffee, cola, hot chocolate and tea. Caffeine is broken down in the liver by a group of enzymes called cytochrome P450 oxidase. The diagram shows the structure of caffeine and its three breakdown products, X, Y and Z.
1. Using the information in the diagram, give two reasons why caffeine is not an amino acid. [3 marks]
2. Using the information in the diagram and your own knowledge of enzyme action, suggest why cytochrome P450 oxidase consists of more than one type of enzyme. [3 marks]

Chemical structure diagrams of caffeine and its breakdown products
Answer:
1.1 No amino / amine group
1.2 No carboxyl / carboxylic acid group
1.3 No central/alpha carbon (atom) OR no R group(s) OR ring structures present

2.1 Idea of specificity of active site/enzyme
2.2 Idea that the products are different shapes / structures
2.3 Idea that P450 consists of (at least) three enzymes / active sites

Q10. Which of the following molecules, A to D, could be a product of breaking a peptide bond during a hydrolysis reaction? [1 mark]

1. A

2. B

3. C

4. D

Four chemical structure diagrams of different molecules
Answer:
A

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Enzymes

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Enzymes

Q1. Fig. 1.1 represents a mechanism of enzyme action. Name the structures represented by the letters A and B. [2 marks]

Enzyme action diagram
Answer:
1. A = Substrate
2. B = Active site

Q2. Describe the induced fit model of enzyme action. [3 marks]

Answer:
1. Active site / enzyme not complementary
2. Active site changes (shape) / is flexible [Award first mark as well for: Active site becomes complementary]
3. (Change in enzyme allows) substrate to fit / E-S complex to form

Q3. Induced fit and lock and key are two models used to explain the action of enzymes. Describe one way that the lock and key model is different from the induced fit model. [1 mark]

Answer:
– Active site does not change (shape) / is fixed (shape) / is rigid / does not wrap around substrate / (already) fits the substrate / is complementary (before binding)

Q4. What is a metabolic pathway? [2 marks]

Answer:
1. A series of enzyme-catalysed reactions
2. Where the product of one reaction is the reactant in the next reaction (Accept alternative wording)

Q5. Which theory of enzyme action is more recent? [1 mark]

1. Lock and Key Model

2. Induced Fit Model

Answer:
2

Q6. Define an enzyme. [2 marks]

Answer:
1. A biological catalyst
2. (That increases the rate of reaction by) lowering the activation energy

Q7. The mechanism of enzyme action was originally explained in terms of the ‘lock-and-key model’. It is now more often explained in terms of the ‘induced-fit’ model.
1. Suggest why the lock-and-key and induced-fit explanations are termed models. [1 mark]
2. Suggest why most scientists now accept the induced-fit model rather than the lock-and-key model. [1 mark]

Answer:
1. Idea of simple representation of the process / structure OR idea of showing people how it works. Examples of acceptable responses: ‘to make the process easy to understand’ / ‘it is a visual representation’
2. Supported by more evidence / new research / more work OR idea of fitting evidence more closely (than lock & key)

Q8. Chronic obstructive pulmonary disease (COPD) is a combination of diseases that can result in coughing, breathing difficulties and fatigue. One form of COPD develops because enzymes are released by phagocytes entering the alveoli. This enzyme action can break down elastin in the lining of the bronchioles and alveoli. Use the example of elastin breakdown to explain the induced-fit hypothesis of enzyme action. [7 marks]

Answer:
1. Elastin is substrate
2. (Elastin / substrate) binds to / fits into active site
3. Active site / enzyme / elastase shape changes [Accept: mould around, Accept substrate/elastin shape changes]
4. Idea of closer fit (between active site and substrate) [Accept: mould around]
5. Forms enzyme-substrate complex / ESC
6. Idea that (change in shape of active site) destabilises / weakens bonds (in substrate) / substrate
7. Activation energy reduced

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Meiosis

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Meiosis

Q1. An animal in an investigation has 4.2 units of DNA in their sample of epithelial tissue. How many units of DNA would you expect to be present in a gamete formed in this animal as a result of meiosis? [1 mark]

Answer:
2.1

Q2. In meiosis I, the following disappear during prophase I in an animal cell: [1 mark]

A. Nucleus and centrioles

B. Nucleus and nucleolus

C. Nucleolus and mitochondria

D. Nucleus and ribosomes

Answer:
B

Q3. How many haploid daughter cells are formed from a single diploid parent cell in meiosis? [1 mark]

Answer:
4

Q4. How many times does telophase take place in a complete cycle of meiosis? [1 mark]

Answer:
Twice / 2

Q5. At what stage of meiosis are sister chromatids pulled apart to opposite poles? [1 mark]

1. Anaphase I

2. Metaphase I

3. Anaphase II

4. Metaphase II

Answer:
3

Q6. The following list shows the names of different stages that occur during meiosis: anaphase I, metaphase II, anaphase II, telophase II, prophase I, metaphase I.
State the stage(s) in which the following events occur: [5 marks]

1. Independent assortment
2. Formation of the spindle apparatus
3. Separation of sister chromatids
4. Formation of nuclear membranes
5. Chromosomes pulled to opposite poles

Answer:
1. Metaphase I and Metaphase II
2. Prophase I
3. Anaphase II
4. Telophase II
5. Anaphase I

Q7. State two ways in which the products of meiosis are different from the products of nuclear division in stem cells. [2 marks]

Answer:
1. In meiosis (cells produced are) not genetically identical OR one set of chromosomes / haploid OR (they are) gametes OR four cells produced
2. (Second mark awarded for another correct answer from the list above)

Q8. What is the correct sequence of stages in meiosis I? [1 mark]

1. A. Metaphase I, Anaphase I, Prophase I, Telophase I

2. B. Prophase I, Anaphase I, Metaphase I, Telophase I

3. C. Prophase I, Metaphase I, Anaphase I, Telophase I

4. D. Telophase I, Metaphase I, Anaphase I, Prophase I

Answer:
C

Q9. Describe the difference between prophase I of meiosis and prophase II of meiosis. [1 mark]

Answer:
– Prophase I: Homologous chromosomes pair up / bivalents form OR chiasmata / crossing-over / recombination

Q10. Name the following stage of meiosis I: Chromosomes on the equator of the spindle. [1 mark]

Answer:
– Metaphase I

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Edexcel quizzes

Eukaryotic Cell Structure

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Eukaryotic Cell Structure

Q1. Palisade cells are found in leaves. The diagram shows a palisade cell. Name structure A. [1 mark]

biological drawing of a palisade plant cell
Answer:
(Cellulose) Cell wall

Q2. Which of the following statements about eukaryotic cells is incorrect? [1 mark]

1. Living eukaryotic cells all have a phospholipid membrane

2. Mitochondria are a site of energy production in both plant and animal cells

3. The cellulose cell wall provides structure for animal cells

4. The rough endoplasmic reticulum can be found adjacent to the nucleus in both animal and plant cells.

Answer:
3

Q3. Fig. 1.1 is a diagram of an animal cell as seen using a transmission electron microscope. Name the structures of the cell labelled A, B, C and D. [4 marks]

Answer:
1. A = Smooth endoplasmic reticulum (SER)
2. B = Nuclear membrane / envelope
3. C = Mitochondrion
4. D = Nucleolus

Q4. Which of the following are found in both plant and animal cells? [1 mark]

1. Smooth endoplasmic reticulum

2. Ribosomes

3. Lysosomes

4. Chloroplasts

Answer:
1, 2 and 3

Q5. Fig. 4.1 shows diagrams of two different types of cells, X and Y. The cells are not drawn to scale. State, using only the information in Fig. 4.1, three differences between plant cells and animal cells. [3 marks]

diagrams of two biological cells
Answer:
1. Plant cell (Y) has a cell wall
2. Chloroplasts (Accept thylakoid discs/membranes)
3. (Large/permanent) vacuole [Credit reverse arguments]

Q6. State three features of the cell shown in Fig. 5.1 that indicate it is eukaryotic. [3 marks]

Coloured illustration of a eukaryotic cell
Answer:
1. Nucleus / nuclear envelope / nuclear membrane / nucleolus
2. Membrane-bound organelles / named organelle (Accept SER / RER / vesicle / cilia)
3. Ribosomes larger / (large) cell size / 20μm wide

Q7. In fungi cells, what substance are the cell walls made of? [1 mark]

Answer:
Chitin

Q8. Fig. 1.1 is a diagram of a plant cell.
1. Name the cell components labelled A and B. [2 marks]
2. State the functions of the components labelled C and D. [2 marks]

Answer:
1. A = Nucleus
B = Chloroplast

2. C = Mitochondrion – (Aerobic) respiration / producing ATP / release energy
D = SER / smooth endoplasmic reticulum – Transport / production processing of fats / lipids / steroids / carbohydrates

Q9. Name one structure present in animal cells that is not present in plant cells. [1 mark]

Answer:
Centriole / Glycogen granule

Q10. The diagram below shows a typical animal cell as seen using an electron microscope.
1. Name the organelles labelled A, B and C shown on the diagram. [3 marks]
2. Give the letter of the organelle that doubles just before mitosis and then separates to opposite poles of the cell during mitosis. [1 mark]
3. Give the letter of the organelle that would not be present when this cell is undergoing mitosis. [1 mark]

labelled diagram of an animal cell
Answer:
1. A = Rough endoplasmic reticulum (RER / rER)
B = Mitochondrion / Mitochondria
C = Nucleolus

2. G

3. C

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Structure of the Human Heart

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Structure of the Human Heart

Q1. This diagram shows a human heart seen from the front. Which one or more of vessels A to D contains oxygenated blood? [1 mark]
During a cardiac cycle, the pressure of blood in vessel C is higher than the pressure of blood in vessel B. Explain what causes this difference in pressure. [1 mark]

a simplified diagram of a human heart
Answer:
1. C and D.
2. Left ventricle has a thicker wall / more muscle / (muscle in) left ventricle contracts more forcefully.

Q2. The diagram shows a human heart as seen from the front. The main blood vessels are labelled D to G. The arrows show the pathways taken by the electrical activity involved in coordinating the heartbeat in the cardiac cycle.
Which of the blood vessels, D to G:
1. Carries oxygenated blood to the heart [1 mark]
2. Carries deoxygenated blood to the lungs [1 mark]

A human heart, as seen from the front
Answer:
1. G
2. E

Q3. Explain, in terms of pressure, why the semilunar valves open in the human heart. [1 mark]

Answer:
– Pressure is greater below valve / in ventricle than (artery) [Accept: converse argument]

Q4. Give one way in which blood in the pulmonary artery is different from blood in the aorta. [1 mark]

Answer:
– Deoxygenated OR less pressure

Q5. The blood pressure is high at the start of a capillary. Explain how the left ventricle causes the blood to be at high pressure. [1 mark]

Answer:
– Contracts [Do not accept pumping of heart/heart beating]

Q6. What is the function of the coronary arteries? [2 marks]

Answer:
1. (Carry) oxygen / glucose [Accept: oxygenated blood]
2. (To) heart muscle / tissue / cells / myocytes [Must be supply to heart or cardiac]

Q7. Read through the following passage about the heart and its major blood vessels, then state the most appropriate word or words to complete the passage. [5 marks]

The mammalian heart consists of four chambers, two upper chambers called …………………….. and two lower chambers called ventricles.
The ………………………. carries oxygenated blood away from the ……………………….. ventricle to the cells of the body, and the pulmonary …………………………. carries deoxygenated blood to the lungs.
The ………………………. returns deoxygenated blood back to the heart from the body.

Answer:
1. Atria / Atrium
2. Aorta
3. Left
4. Artery
5. Vena cava

Q8. Explain why a mammalian heart is divided into a right side and a left side. [2 marks]

Answer:
1. Idea that it keeps oxygenated and deoxygenated blood separate.
2. Idea that this results in as much oxygen as possible being carried to the tissues / cells OR reference to different pressures in each side / need for different pressures explained.

Q9. Many animals, such as mammals, have a heart and circulation. This helps them to meet their requirements by overcoming the limitations of diffusion. Describe the structure of the mammalian heart. [10 marks]

Answer:
1. Idea that there are four chambers OR idea of left and right sides separate / septum.
2. Atria above ventricles.
3. Reference to muscular nature of walls OR reference to cardiac muscle.
4. Left ventricle muscle thicker.
5. Atrioventricular valves between atria and ventricles.
6. Semilunar valves between ventricles and arteries.
7. Aorta from left ventricle.
8. Pulmonary artery from right ventricle.
9. Vena cava into right atrium.
10. Pulmonary vein into left atrium.

Q10. The diagram shows a section of a human heart and blood vessels P, Q, R and S.
1. Which letter shows the pulmonary artery? [1 mark]

A labelled diagram of a human heart and blood vessels
Answer:
– Blood vessel Q

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Introduction to Photosynthesis

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Introduction to Photosynthesis

Q1. The concentrations of carbon dioxide in the air at different heights above ground in a forest change over a period of 24 hours. Use your knowledge of photosynthesis to describe these changes and explain why they occur. [5 marks]

Answer:
1. High concentration of carbon dioxide linked with night/darkness [Accept: converse of low in day]
2. No photosynthesis in dark/night / light required for photosynthesis / light-dependent reaction
3. (In dark) plants (and other organisms) respire
4. In light, net uptake of carbon dioxide by plants OR plants use more carbon dioxide than they produce OR rate of photosynthesis greater than rate of respiration [Accept day = light]
5. Decrease in carbon dioxide concentration with height [Accept: converse of increase closer to ground] OR At ground level fewer leaves/less photosynthesising tissue/more animals/less light

Q2. Which of the images, A to D, correctly summarises photosynthesis? [1 mark]

A series of diagrams of photosynthesis, one is correct and the rest are incorrect.
Answer:
C

Q3. One way to determine the rate of photosynthesis is to measure the uptake of carbon dioxide. Discuss why measuring carbon dioxide uptake may or may not give a better indication of photosynthetic activity than measuring oxygen production. [2 marks]

Answer:
1. Oxygen is only produced in one stage of photosynthesis OR oxygen produced might be used for respiration
2. Carbon dioxide (CO₂) is only used in one (named) stage of photosynthesis OR CO₂ produced during respiration might be used for photosynthesis / light-independent reaction / Calvin cycle

Q4. The leaf of a plant that is adapted to living in shade will differ from the leaf of a plant that is adapted to living in sunlight. Suggest one way in which the structure of these leaves will differ. [1 mark]

Answer:
– Shade leaf will have large(r) / more chloroplast(s) OR larger (palisade) mesophyll OR more grana/thylakoids (in chloroplast) OR large(r) surface area (of leaves)

Q5. In which stage of carbon fixation does RuBP combine with carbon dioxide? [1 mark]

A. The light-dependent reactions of the Calvin cycle

B. The light-independent reactions of the Calvin cycle

C. The light-dependent reactions of the Krebs cycle

D. The light-independent reactions of the Krebs cycle

Answer:
B

Q6. Photosynthesis can be divided into two main stages, the light-dependent stage and the light-independent stage. Explain why the light-independent stage cannot take place without the light-dependent stage. [3 marks]

Answer:
1. Products of the light-dependent stage are needed for / used in the light-independent stage / Calvin cycle
2. Reduced NADP and ATP
3. Use of reduced NADP for reduction of carbon dioxide / GP / use of ATP as a source of energy

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