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paper 1 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Give 6 pieces of evidence that supports the theory that mitochondria evolved from prokaryotic cells. (6)

A
  • Circular DNA
  • smaller
  • 70S ribosomes
  • no introns
  • no histones
  • proteins associated with DNA;
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2
Q

Explain how the highest blood pressure is produced in the left ventricle.
[1 mark]

A

Strongest contractions;

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3
Q

Some babies are born with a hole between the right and the left ventricles.
These babies are unable to get enough oxygen to their tissues. Suggest why.
[2 marks]

A
  • Blood flows from left ventricle to right ventricle/ mixing of oxygenated and deoxygenated blood;
  • Lower volume of (oxygenated) blood leaves left ventricle
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4
Q

Suggest 2 advantages of using a pH meter rather than a pH indicator in this experiment. [1 mark]

A
  • Numerical readings not colour changes

- for greater accuracy;

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5
Q

Suggest why the pH remained constant 2 minutes after adding lipase to milk. [2 marks]

A
  • No more (fatty) acids produced;

- All lipids used up

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6
Q

Name the part of a pancreatic cell that produces the inactive form of trypsin (a protein).
[1 mark]

A
  • ribosomes
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7
Q

Suggest the advantage of producing trypsin in an inactive form inside cells in the pancreas. [2 marks]

A
  • Does not digest protein inside cells;

- So (pancreatic) cell/tissue/function not destroyed/damaged;

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8
Q

People who do not have the specific receptor protein in their cell-surface membranes may be infected with the Ebola virus but do not develop the disease (lines 1–5).
Explain why they do not develop the disease.
[2 marks]

A
  • Virus can’t bind (to receptor)/ can’t enter cells;
  • So can’t be replicated/ multiply;
  • So, doesn’t damage cell(s)/tissues (and cause symptoms);
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9
Q

Explain the increase in specific plasma cells and antibody in people infected with the Ebola virus. [2 marks]

A
  1. Antigen/glycoprotein on Ebola binds to/stimulates (a specific) B cell;
  2. (Binding causes) replication/cloning of B cell;
  3. Plasma cells/B cells release/produce antibodies;
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10
Q

Explain how a blood transfusion from a patient recently recovered from Ebola may be an effective treatment (lines 8–10). [3 marks]

A
  1. Lots of antibodies (against Ebola) in recovered patient;
  2. Transfusion/plasma contains antibodies;
  3. Antibodies (specific so) will bind with (Ebola) antigen; 4. (In recipient) virus destroyed/cannot enter cell;
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11
Q

A high mutation rate makes it difficult to develop a vaccine (line 11). Explain why.
[3 marks]

A
  1. (High mutation rate leads to) antigens change/antigenic variability;
  2. Vaccine contains specific antigen;
  3. Antibodies not complementary to (changed) antigen / won’t bind to (changed) antigens;
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12
Q

The rise and fall in blood pressure in the aorta is greater than in the small arteries. Suggest why. [3 marks]

A
  1. (Aorta) (is) close/directly linked to the heart/ventricle / pressure is higher/is very high;
  2. (Aorta has) elastic tissue;
  3. (Aorta has) stretch/recoil;
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13
Q

suggest and explain one other way in which sieve cells are adapted for mass transport. [2 marks]

A
  1. No/few organelles / very little cytoplasm / cytoplasm at edge / more room/hollow/large vacuole/large space/thick walls;
  2. (So) easier/more flow/ (thick/strong walls) resist pressure;
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14
Q

suggest and explain 2 ways in which companion cells are adapted for the transport of sugars between cells. [2 marks]

A
  1. Mitochondria release energy/ ATP/ site of respiration; 2. For active transport/uptake against concentration gradient;
  2. Ribosomes/rough endoplasmic reticulum produce(s) proteins;
  3. (Proteins) linked to transport eg carrier proteins/enzymes;
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15
Q

Humans and grasshoppers have very similar percentages of each base in their DNA but they are very different organisms.
Use your knowledge of DNA structure and function to explain how this is possible. [2 marks]

A
  1. Have different genes;
  2. (So bases/triplets) are in a different sequence/order;
  3. (So) different amino acid(sequence/coded for) / different protein/different polypeptide/different enzyme;
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16
Q

Give 5 ways in which courtship behaviour increases the probability of successful mating. [5 marks]

A
  1. Recognise/identify/attract same species;
  2. Stimulates/synchronises mating/production/release of gametes;
  3. Recognition/attraction of mate/opposite sex;
  4. Indication of (sexual) maturity/fertility/receptivity/readiness to mate;
  5. Formation of a pair bond/bond between two organisms (to have/raise young);
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17
Q

The events that take place during interphase and mitosis lead to the production of two genetically identical cells. Explain how. [4 marks]

A
  1. DNA replicated;
  2. (Involving) specific/accurate/complementary base-pairing;
  3. (Ref to) two identical/sister chromatids;
  4. Each chromatid/ moves/is separated to(opposite) poles/ends of cell;
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18
Q

The student cut thin sections of tissue to view with an optical microscope. Explain why it was important that the sections were thin.
[2 marks]

A
  1. To allow (more) light through;

2. A single/few layer(s) of cells to be viewed;

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19
Q

why is a recessive allele likely to have a higher frequency in a small isolated population [4 marks]

A
  1. Genetic bottleneck;
  2. Less genetic diversity / small(er) gene pool / less variety of alleles;
  3. Individuals breed within group / do not breed with outsiders;
  4. High(er) chance of inheriting allele/high(er) frequency of allele in offspring;
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20
Q

Explain the role of independent segregation in meiosis.

[4 marks]

A
  1. (To provide) genetic variation;
  2. (Allows) different combinations of maternal and paternal chromosomes/ alleles;
  3. (To produce) haploid cells/half the chromosome number;
  4. (Allows) homologous chromosomes/ homologous pairs to arrange randomly (at equator/middle of cell)/separate;
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21
Q

The oxygen dissociation curve for haemoglobin shifts to the right during vigorous exercise. Explain the advantage of this shift. [3 marks]

A
  1. Lower affinity for oxygen / releases more oxygen / oxygen is released quicker / oxygen dissociates/unloads more readily;
  2. (To) muscles/tissues/cells;
  3. (For) high/rapid respiration
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22
Q

The volume of water passing over the gills increases if the temperature of the water increases. Suggest why. [2 marks]

A
  1. Increased metabolism/respiration/enzyme activity;

2. Less oxygen (dissolved in water);

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23
Q

All primates produce a species-specific type of haemoglobin. An antibody against human haemoglobin could be used to compare the evolutionary relationships between different primates. Describe and explain how. [3 marks]

A
  1. Antibody and haemoglobin/blood (of different primates) mixed/added/bind;
  2. Precipitate/complex/band formed;
  3. Amount of precipitate/complex/ thickness of band shows relationship/similarity (in protein/DNA);;
24
Q

What two measurements are needed to calculate an index of diversity?
[2 marks]

A
  1. Number of (individuals of) each species;

2. Total number of individuals / number of species;

25
Q

Suggest how this vaccine could help people to stop smoking.

[3 marks]

A
  1. Antibodies to nicotine produced / antibodies bind to nicotine;
  2. (So) nicotine does not bind to protein/does not reach the brain;
  3. (So) cigarettes/smoking does not satisfy addiction/reward smokers/ release (reward) chemicals;
26
Q

Describe the role of centromere in mitosis. [2 marks]

A
  1. Holds chromatids together;
  2. Attaches (chromatids) to spindle;
  3. (Allows) chromatids to be separated/move to (opposite) poles / (centromere) divides/splits at metaphase/ anaphase;
27
Q

DNA helicase is important in DNA replication. Explain why. [2 marks]

A
  1. Separates/unwinds/unzips strands/helix / breaks H-bonds;
  2. (So) nucleotides can attach/are attracted / strands can act as templates;
28
Q

The oxygen dissociation curve of the fetus is to the left of that for its mother. Explain the advantage of this for the fetus. [2 marks]

A
  1. Higher affinity / loads more oxygen;
  2. At low/same/high partial pressure/pO2;
  3. Oxygen moves from mother/to fetus;
29
Q

After birth, fetal haemoglobin is replaced with adult haemoglobin. Use the graph to suggest the advantage of this to the baby. [2 marks]

A
  1. Low affinity / oxygen dissociates;

2. (Oxygen) to respiring tissues/muscles/cells

30
Q

Use the information provided and your knowledge of the founder effect to explain why Ellis-van Creveld syndrome occurs at a higher frequency in the Amish population than in people in America who are not Amish.[3 marks]

A
  1. Population formed by a small number of founders/people /30 people;
  2. (Founders show) less genetic diversity / small(er) gene pool / less variety of alleles;
  3. Individuals breed within group / do not breed with outsiders;
  4. High(er) chance of inheriting allele (than in non-Amish population);
31
Q

Abdominal pumping increases the efficiency of gas exchange between the tracheoles and muscle tissue of the insect. Explain why.[2 marks]

A
  1. More air/oxygen enters / air/oxygen enters quickly/quicker;
  2. (So) maintains/greater diffusion or concentration gradient;
32
Q

The insect opens its spiracles at a lower frequency in very dry conditions. Suggest one advantage of this. [1 mark]

A

Less/no water lost / (more) water retained;

33
Q

Removal of water from the tracheoles increases the rate of diffusion of oxygen between the tracheoles and muscle tissue. Suggest 3 reasons why.[3 marks]

A
  1. Greater surface area exposed to air;

2. Gases move/diffuse faster in air than through water; 3. Increases volume/amount of air;

34
Q

Describe how carbon dioxide in the air outside a leaf reaches mesophyll cells inside the leaf.[3 marks]

A
  1. (Carbon dioxide enters) via stomata;
  2. (Stomata opened by) guard cells;
  3. Diffuses through air spaces;
  4. Down diffusion gradient;
35
Q

Suggest how the faster rate of growth may increase profit for a farmer.[1 mark]

A

Beet ready quicker / less time required / allows land to be used again / harvested earlier;

36
Q

Describe and explain how selection will have affected the genetic diversity of sugar beet.

A
  1. (Diversity) reduced / fewer different alleles / less variation / smaller gene pool;
  2. As alleles have been chosen / rejected;
37
Q

Mitosis is important in the life of an organism. Give 4 reasons why.[4 marks]

A
  1. Growth / increase in cell number;
  2. Replace cells / repair tissue / organs /body;
  3. Genetically identical cells;
  4. Asexual reproduction /cloning;
38
Q

Explain why the biologist chose to examine 200 cells.

[1 mark]

A

(Ensures) representative (sample);

39
Q

what does having a low SD mean?[1 mark]

A

Low SD means results more reliable / repeatable;

40
Q

Farmers were offered grants by the government to plant hedges around their fields. Explain the effect planting hedges could have on the index of diversity for animals.[3 marks]

A
  1. Greater variety of plants;
  2. Another habitat / more habitats / places to live / niches;
  3. Another food source / more food types;
41
Q

Explain the difference in thickness between the pulmonary artery and the pulmonary vein.[1 mark]

A

High pressure / smoothes out blood flow / artery wall contains more collagen / muscle / elastic (fibres) / connective tissue;

42
Q

The thickness of the aorta wall changes all the time during each cardiac cycle. Explain why.[5 marks]

A
  1. (Aorta wall) stretches;
  2. Because ventricle/heart contracts / systole / pressure increases;
  3. (Aorta wall) recoils;
  4. Because ventricle relaxes / heart relaxes /diastole / pressure falls;
  5. Maintain smooth flow / pressure;
43
Q

Describe how tissue fluid is formed and how it is returned to the circulatory system. [6 marks]

A

Formation 1. High blood / hydrostatic pressure / pressure filtration;

  1. Forces water / fluid out;
  2. Large proteins remain in capillary; Return 4. Low water potential in capillary / blood; 5. Due to (plasma) proteins;
  3. Water enters capillary / blood;
  4. (By) osmosis;
  5. Correct reference to lymph;
44
Q

In humans, substances move out of the capillaries to form tissue fluid. Describe how this tissue fluid is returned to the circulatory system. [6 marks]

A
  1. (Hydrostatic) pressure lower in capillary/blood / higher in tissues/tissue fluid;
  2. Water (returns);
  3. By osmosis;
  4. Water potential lower/more negative in blood/capillary / higher/less negative water potential in tissues / via water potential gradient;
  5. Due to protein (in blood);
  6. (Returns) via lymph (system/vessels);
45
Q

Biologists can also use protein structure to investigate the relationship between different species of crane. Explain why.[3 marks]

A
  1. More closely related (species) have more similarities in amino acid sequence/primary structure;
  2. In same protein / named protein e.g. albumin;
  3. Amino acid sequence is related to (DNA) base/triplet sequence;
46
Q

The number of species present is one way to measure biodiversity. Explain why an index of diversity may be a more useful measure of biodiversity.[2 marks]

A
  1. Also measures number of individuals in a species / different proportions of species;
  2. Some species may be present in low/high numbers;
47
Q

This test only detects the presence of HIV antibodies. Give two reasons why it cannot be used to find out if a person has AIDS. [2 marks]

A

(To diagnose AIDS, need to look for/at)

  1. (AIDS-related) symptoms;
  2. Number of helper T cells;
48
Q

A mother who was infected with HIV gave birth to a baby. The baby tested positive using this test. This does not prove the baby is infected with HIV. Explain why. [2 marks]

A
  1. Children receive (HIV) antibodies from their mothers/maternal antibodies;
  2. (So) solution will always turn blue/will always test positive (before 18 months)
49
Q

Before the cell was examined using the electron microscope, it was stained. This stain caused parts of the structure of the cell-surface membrane to appear as two dark lines.
Suggest an explanation for the appearance of the cell-surface membrane as two dark lines. [3 marks]

A
  1. Membrane has phospholipid bilayer;
  2. Stain binds to phosphate/glycerol;
  3. On inside and outside of membrane;
50
Q

Describe how substances move across cell-surface membranes by facilitated diffusion. [3 marks]

A
  1. Carrier/channel protein;
  2. (Protein) specific/complementary to substance;
  3. Substance moves down concentration gradient;
51
Q

Explain how the organic bases help to stabilise the structure of DNA. [2 marks]

A
  1. Hydrogen bonds between the base pairs holds two strands together;
  2. Many hydrogen bonds provides strength;
52
Q

Suggest one advantage of showing the genetic code as base sequences on mRNA, rather than triplets on DNA. [1 mark]

A

DNA has two strands each with a different (complementary) base sequence;

53
Q

Suggest the role of the mRNA stop codons. [2 marks]

A
  1. Stop translation;

2. Result in detachment of polypeptide chain from ribosome;

54
Q

Describe how vaccination can lead to protection against bacterial meningitis.[6 marks]

A
  1. Antigen/epitope on surface of N. meninigitidis / bacterium binds to surface protein / surface receptor on a (specific/single) B cell;
  2. (Activated) B cell divides by mitosis / produces clone; 3. (Division) stimulated by T cells;
  3. B cells/plasma cells release antibodies;
  4. (Some) B cells become memory cells;
  5. Memory cells produce plasma / antibodies faster;
55
Q

Penicillin has been the antibiotic of choice for the treatment of bacterial meningitis. Since the year 2000, strains of Neisseria meningitidis that are resistant to penicillin, sulfonamides and rifampin have been discovered in the UK. Describe how a population of Neisseria meningitidis (Nm) can become resistant to these antibiotics. [4 marks]

A
  1. Mutation;
  2. Results in Nm cell with allele for resistance to one antibiotic/to named antibiotic;
  3. (This) cell survives and passes the allele for resistance to offspring;
  4. Process repeated with different genes conferring resistance to each of the other (two) antibiotics;

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