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A Level Biology > Paper 1 Exam Questions > Flashcards

Paper 1 Exam Questions Flashcards

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1
Q

the movement of Na+ ions out of a cell alllows the absorption of glucose into the cell lining the ileum. explain how

2 marks

A
  1. maintains a concentration gradient for Na+
  2. Na+ moving in via facilitated diffusion
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2
Q

Describe and explain two features you would expect to find in a cell specialised for absorption.

2 marks

A
  1. microvilli so large surface area soa greater amount of substance can be absorbed at one time
  2. large no. of mitochondria so make more ATP
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3
Q

Describe how amino acids join to form a polypeptide so there is always NH2 at one and and COOH at the other end.

2 marks

A
  1. one NH2 group joins to COOH group to form peptide bond
  2. so there is a free amine group at one end and a free COOH group at the other
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4
Q

Describe the role of micelles in the absorption of fats into the cells lining the ileum.

3 marks

A
  1. micelles make fatty acids more soluble in water
  2. bring fatty acids to cell
  3. maintain high concentration of fatty acids to cell
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5
Q

Describe the role of DNA polymerase in the semi-conservative replication of DNA.

2 marks

A
  1. Joins (adjacent DNA) nucleotides
  2. (Catalyses) condensation (reactions)
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6
Q

Describe how an enzyme can be phosphorylated

2 marks

A

1.phosphate is attached to the enzyme
2. released from hydrolysis of ATP

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7
Q

Name three differences between DNA in the nucleus of a plant cell and DNA in a prokaryotic cell.

3 marks

A

plant:
histones
linear
no plasmids
prokaryotic:
no histones
cicrular
plasmids

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8
Q

Define non-coding base sequences and describe where the non-coding multiple repeats are positioned in the genome.

2 marks

A
  1. DNA that does not code for protein
  2. (Positioned) between genes;
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9
Q

Describe how mRNA is formed by transcription is eukaryotes.

5 marks

A
  1. Hydrogen bonds (between DNA bases) break
  2. One DNA strand acts as a template
  3. (Free) RNA nucleotides align by complementary base pairing
  4. RNA polymerase joins (adjacent RNA) nucleotides;
  5. (By) phosphodiester bonds between adjacent nucleotides
  6. Pre-mRNA is spliced (to form mRNA)
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10
Q

Describe how a polypeptide is formed by translation of mRNA

6 marks

A
  1. mRNA attaches to ribosomes
  2. tRNA anticodons bind to complementary mRNA codons
  3. tRNA brings a specific amino acid
  4. amino acids join by peptide bonds
  5. with the use of ATP
  6. tRNA released
  7. the ribosome moves along the mRNA to form a polypeptide
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11
Q

Define gene mutation and explain how a gene mutation can have:
- no effect on an individual
- a positive effect on an individual

4 marks

A
  1. Change in the nucleotide (sequence of chromosomes/DNA)
  2. Results in the formation of new allele

no effect: 3. Genetic code is degenerate

positive effect: 4. Results in change in polypeptide that positively changes the properties (of the protein)

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12
Q

Describe the induced fit model of enzymes action and how an enzyme acts as a catalyst

3 marks

A
  1. substrate binds to enzymes active site
  2. active site changes shape so it is complementary to substrate
  3. enzymes reduce activation energy
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13
Q

Explain the advantage for larger animals of having a specilaised system that facilitates oxygen uptake

2 marks

A
  1. bigger organisms have smaller SA:vol
  2. so faster diffusion
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14
Q

Explain how the counter-current principle allows efficient oxygen uptake in the fish gas exchange system

2 marks

A
  1. water and blood flow in opposite directions
  2. concentration gradient maintained along length of the lamellea
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15
Q

Describe how one amino acid is added to a polypeptide that is being formed at a ribosome during translation

3 marks

A
  1. tRNA brings specific amino acid to ribosome
  2. tRNA anticodon binds to mRNA codon
  3. amino acid joins by condensation reaction
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16
Q

Describe two precautions a student should take when clearing away after a organ dissection

2 marks

A
  1. Wash sharp instruments by holdng the handle
  2. Disinfect instruments/surfaces;
  3. Disinfect hands
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17
Q

Describe how a sample of chloroplasts could be isolated from leaves

4 marks

A
  1. Break open cells and filter
  2. In cold, isotnoic, pH controlled solution;
  3. Centrifuge and remove nuclei
  4. Centrifuge at higher speed, chloroplasts
    settle out
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18
Q

Give the order of the stages of mitosis

1 mark

A

prophase
metaphase
anaphase
telophase

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19
Q

Describe the role of the spindle fibres and behaviour of the chromosomes during prophase

2 marks

A
  1. chromosomes condense;
  2. centromeres attach to spindle fibres;
20
Q

Describe the role of the spindle fibres and behaviour of the chromosomes during metaphase

1 mark

A

chromosomes line up in the centre of cell

21
Q

Describe the role of the spindle fibres and behaviour of the chromosomes during anaphase

2 marks

A
  1. centromeres divide;
  2. chromatids (from each pair) pulled to (opposite) poles of cell
22
Q

Describe how a troglyceride molecule is formed

3 marks

A
  1. One glycerol and three fatty acids
  2. Condensation reactions and removal of
    three molecules of water
  3. Ester bonds form
23
Q

Describe the structure of DNA

5 marks

A
  1. Polymer of nucleotides
  2. Each nucleotide formed from deoxyribose sugar, a phosphate and an nitrogenous base
  3. Phosphodiester bonds (between nucleotides);
  4. Double helix held by hydrogen bonds;
  5. H bonds between adenine, thymine and cytosine, guanine;
24
Q

Name and describe 5 ways substances can move across the cell-surface membrane into the cell

5 marks

A
  1. Simple diffusion of small/non-polar molecules down a concentration gradient
  2. Facilitated diffusion down a concentration gradient via protein carrier/channel;
  3. Osmosis of water down a water potential gradient;
  4. Active transport against a concentration gradient via
    protein carrier using ATP
  5. Co-transport of 2 different substances using a carrier
    protein
25
Q

What data does a student need to collect to calculate index of diversity?

1 mark

A

no. of different species and the no. of individuals in each

26
Q

Give two ways a student ensures their index of diversity was representitive of a habitat

2 marks

A
  1. random sampling of a habitat
  2. large no. of samples
27
Q

Scientists calculated a P value of 0.03 when testing their null hypothesis. What can you conclude from this result?

2 marks

A
  1. null hypothesis is rejected
  2. probability that the difference is due to chance is less than 0.05
28
Q

Describe the structure of human immunodefiency virus

4 marks

A
  1. it has RNA
  2. Reverse transcriptase
  3. (Protein) capsomeres/capsid
  4. (Phospho)lipid (viral) envelope
  5. Attachment proteins
29
Q

Suggest and explain one way the leaf growth of xerophytic plants would be different from the leaf growth of sunflowers

2 marks

A
  1. slow growth
  2. due to smaller no. of stomata
30
Q

Use your knowledge of gas exchange in leaves to explain why plants grown in soil with very little water grow only slowly

2 marks

A
  1. stomata close
  2. less CO2 uptake for less photosynthesis
31
Q

Mammals such a horse and mouse are able to maintain a constant temperature. Use your knowledge of surface area : volume to explain the higher metabolic rate of a mouse compared to a horse.

3 marks

A
  1. (Smaller so) larger surface area to volume
    ratio
  2. More/faster heat loss (per gram/in relation
    to body size)
  3. (Faster rate of) respiration/metabolism
    releases heat
32
Q

Explain 5 properties that make water important for organisms

5 marks

A
  1. A metabolite in condensation reactions
  2. A solvent so (metabolic) reactions can occur
  3. High heat capacity so buffers changes in
    temperature
  4. Large latent heat of vaporisation so provides a
    cooling effect through evaporation
  5. Cohesion (between water molecules) so
    supports columns of water in plants
33
Q

Describe the structure and function of the nucleus

4 marks

A

structure
1. nuclear envelope and pores
2. has chromosomes
function
1. stores genetic info
2. DNA replication

34
Q

Name the main polymer that forms a plant cell wall

1 mark

A

cellulose

35
Q

Name the polymer that forms a fungal cell wall

1 mark

A

chitin

36
Q

Explain how the use of antibiotics has lead to anti-biotic resistant strains of bacteria becoming a common cause of infection acquired when in hospital

3 marks

A
  1. some bacteria have alleles for resistance
  2. resistant bacteria survive and reproduce
  3. in hospitals patients have weakened immune systems
37
Q

Describe how scientists could use aseptic techniques to transfer a liquid culture in a bottle to an agar plate

3 marks

A

1.Wash hands with soap
2.Use sterile pipette/syringe(to transfer bacteria)
3.(Remove bottle lid and) flame neckof bottle
4.Lift lid of (agar) plate at an angle
5.Work close to upward air movement
6.Use sterile spreader
7.Place pipette/spreader into disinfectant (immediately after use)

38
Q

Give two features of all prokaryotic cells that are not features of eukaryotic cells

1 mark

A
  1. DNA free in cytoplasm
  2. DNA not associated with proteins
39
Q

Describe viral replication

3 marks

A
  1. Attachment proteins attach to receptors
  2. (Viral) nucleic acid enters cell
  3. Nucleic acid replicated in cell
  4. Cell produces viral enzymes
  5. Virus assembeled and released from cell
40
Q

How many cells does binary fission produce?

1 mark

A

2 daughter cells

41
Q

Define the quaternary structure of a protein

1 mark

A

more than 1 polypeptide

42
Q

Explain how two enzymes with different amino acid sequences can catalyse the same reaction

2 marks

A
  1. both active sites have similair tertiary structures
  2. so can form enzyme substrate complexes
43
Q

Give 2 differneces between the circulation of blood in fish and the circulation of blood in mammals

2 marks

A
  1. fish have single circulation but mammals have double circulation
  2. fish have one vein but mammals have two
44
Q

Describe the transport of carbohydrate in plants

5 marks

A
  1. Sucrose is actively transported into phloem via facilitated diffusion
  2. by companion cells
  3. lowers water potential and water enters
  4. produces pressure gradient
  5. mass flow to respiring cells
45
Q

Compare and contrast the structure of starch and cellulose

6 marks

A
  1. both made of glucose monomers
  2. both contain C,H and O
  3. both contain glycosidic bonds
  4. starch is branched but cellulose isn’t
  5. starch is helical but cellulose is straight
  6. starch made from a-glucose but cellulose made from b-glucose
46
Q

Describe the digestion of starch by a mammal

4 marks

A
  1. hydrolysis
  2. of glycosidic bonds
  3. starch to maltose by amylase
  4. maltose to glucose by maltase

A Level Biology (19 decks)

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