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Biology Exam Questions > 2 Cells EQs > Flashcards

2 Cells EQs Flashcards

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1
Q

Compare bacterial cell and human cell (7 marks)

A
  1. Bacterial cell is much smaller than a human cell;
  2. Bacterial cell has a cell wall but human cell does not;
  3. Bacterial cell lacks a nucleus but human cell has a nucleus;
  4. Bacterial cell lacks membrane-bound organelles but human cell has membrane-bound organelles;
  5. Bacterial ribosomes smaller than human ribosomes
  6. Bacterial DNA is circular but human DNA is linear;
  7. Bacterial DNA has no proteins associated whereas human DNA is bound to histones
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2
Q

Give one piece of evidence that supports the theory that mitochondria evolved from prokaryotic cells (1 mark)

A

Circular DNA

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3
Q

Limitations of TEM (5 marks)

A
  1. can’t look at living material / must be in a vacuum
  2. specimen must be v thin
  3. artefacts present
  4. complex prep
  5. image not 3D
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4
Q

Describe and explain how centrifuging the culture allowed the scientists to obtain a cell-free liquid (3 marks)

A
  1. Large cells form 2. pellet.
  2. Supernatant can be removed
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5
Q

Describe how you could use cell fractionation to isolate chloroplasts from leaf tissue (3 marks)

A
  1. Break open cells and remove large debris.
  2. Solution is cold, isotonic and buffered.
  3. Second pellet is chloroplast
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6
Q

Explain why you need to push down hard on the cover slip but not push it sideways (2 marks)

A
  1. Push hard - spread/squash tissue
  2. Not push sideways - avoid breaking chromosomes
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7
Q

Name and describe five ways substances can move across the cell-surface membrane into a cell (5 marks)

A
  1. Simple diffusion of non-polar molecules down a conc gradient
  2. Facilitated diffusion down conc gradient via carrier/channel protein
  3. Osmosis of water down a conc gradient
  4. Active transport against a conc gradient via protein carrier using ATP
  5. Co-transport of 2 different substances using a carrier protein
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8
Q

The movement of Na+ out of the cell allows 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 by co-transport, brings glucose with it
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9
Q

Describe and explain two features you would expect to find in a cell specialised for absorption (2 marks)

A
  1. Folded membrane = large surface area
  2. Large number of carrier/channel proteins = fast rate of absorption
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10
Q

The movement of substances across cell membranes is affected by membrane structure. Describe how (5 marks)

A
  1. Phospholipid bilayer allows diffusion of non-polar substances
  2. Phospholipid bilayer prevents diffusion of polar substances
  3. Carrier proteins allows active transport
  4. Channel/carrier protein allow facilitated diffusion/co-transport
  5. Shape of channel/carrier proteins determines which substances move
  6. Number of channel/carrier determines how much movement
  7. Membrane surface area determines how much movement
  8. Cholesterol affects rigidity
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11
Q

Give two similarities in the movement of substances by diffusion and by osmosis (2 marks)

A
  1. High conc to low conc
  2. Passive
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12
Q

Contrast the processes of faciliatated diffusion and active transport (3 marks)

A
  1. FD involves channel or carrier proteins whereas AT only involves carrier proteins
  2. FD doesn’t use ATP whereas AT does
  3. FD takes place down a conc gradient whereas AT occurs against a conc gradient
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13
Q

Eukaryotic cells produce and release proteins.
Outline the role of organelles in the production, transport and release of proteins from
eukaryotic cells. (4 marks)

A
  1. DNA in nucleus is code for protein
  2. Ribosomes/rough endoplasmic reticulum produce protein
  3. Mitochondria produce ATP for protein synthesis
  4. Golgi apparatus package/modify
  5. Vesicles transport
  6. Vesicles fuse with membrane
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14
Q

Give one advantage of viewing a biological specimen using a transmission electron
microscope compared with using a scanning electron microscope. (1 mark)

A
  1. Higher resolution
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15
Q

Describe how you could make a temporary mount of a piece of plant tissue to observe the
position of starch grains in the cells when using an optical (light) microscope. (4 marks)

A
  1. Add drop of water to slide
  2. Obtain thin section (of plant tissue) and place on slide
  3. Stain with iodine in potassium iodide.
  4. Lower cover slip using mounted needle.
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16
Q

Starting with some lettuce leaves, describe how you would obtain a sample of undamaged
chloroplasts. Use your knowledge of cell fractionation and ultracentrifugation to answer this question. (6 marks)

A
  1. Chop up
  2. Cold;
  3. Buffer solution;
  4. Isotonic / same water potential;
  5. Filter and centrifuge filtrate;
  6. Centrifuge supernatant;
  7. At higher speed;
  8. Chloroplasts in second pellet;
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17
Q

Describe the role of the spindle during mitosis (2 marks)

A
  1. Attachment of centromeres
  2. Separation of centromeres
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18
Q

Meiosis also occurs during the life cycle of organisms. What is the importance of meiosis? (2 marks)

A
  1. Halves chromosome number / haploid;
  2. Diploid / full number restored at fertilisation;
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19
Q

Describe how phospholipids are arranged in a plasma membrane. (2 marks)

A
  1. Bilayer
  2. Hydrophobic tails face inwards
  3. Hydrophilic head face outwards
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20
Q

Describe how the RER is involved in the production of enzymes. (2 marks)

A
  1. Has ribosomes;
  2. To make protein
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21
Q

Describe how the Golgi apparatus is involved in the secretion of enzymes. (1 mark)

A
  1. Golgi apparatus modifies protein
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22
Q

Name two structures in a eukaryotic cell that cannot be identified using an optical
microscope. (1 mark)

A

Mitochondria & ribosome

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23
Q

💫 Putting bee honey on a cut kills bacteria. Honey contains a high concentration of sugar.
Use your knowledge of water potential to suggest how putting honey on a cut kills
bacteria. (3 marks)

A
  1. Water potential in bacterial cells higher than in honey
  2. Water leaves bacteria by osmosis;
  3. Loss of water stops metabolic reactions.
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24
Q

The student cut a thin section of the tissue. Explain why it was important that the section was thin. (2 marks)

A
  1. allow more light to pass through
  2. enhance the visibility of cellular structures
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25
Q

Explain how the inner membrane is adapted to its function in a mitochondria (2 marks)

A
  1. increased surface area;
  2. for respiration / enzymes;
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26
Q

Name the process in which cells become adapted for different functions. (1 mark)

A

Differentiation / specialisation

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27
Q

Name two structures present in an epithelial cell from the small intestine that are
not present in a cholera bacterium. (2 marks)

A
  1. Nucleus
  2. (Smooth / rough) ER;
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28
Q

Describe the function of a chloroplast. (2 marks)

A
  1. Absorbs light;
  2. For photosynthesis;
  3. Produces sugars
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29
Q

What is the advantage to cells of having mitochondria? (2 marks)

A
  1. Able to respire aerobically;
  2. So make ATP
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30
Q

Give one process which occurs in the nucleus of a cell during interphase which is
necessary before cell division can take place. (1 mark)

A

replication of DNA

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31
Q

Suggest how a carrier protein actively transports a sodium ion into the cell in exchange for a hydrogen ion out of the cell (3 marks)

A
  1. co-transport
  2. Uses hydrolysis of ATP;
  3. Sodium ion and proton bind to the protein
  4. Protein changes shape
32
Q

Name two structures found in all bacteria that are not found in plant cells. (2 marks)

A
  1. Circular DNA
  2. Murein cell wall
33
Q

The resolution of an image obtained using an electron microscope is higher than the
resolution of an image obtained using an optical microscope.
Explain why. (1 mark)

A

Shorter wavelength between electrons

34
Q

Describe the role of one named organelle in digesting bacteria. (3 marks)

A
  1. Lysosomes;
  2. Fuse with vesicle
  3. Releases hydrolytic enzymes;
35
Q

💫 Suggest one explanation for the faster rate of plasmid replication in cells
growing in a culture with a high amino acid concentration. (2 marks)

A
  1. Amino acids used in protein synthesis
  2. So more enzymes for DNA/plasmid replication
36
Q

Why might an organelle not be visible in a microscope image? (1 mark)

A
  1. A section/slice so nucleus in another part of cell
    OR
  2. Nucleus not stained;
37
Q

Name an organelle found in both a chloroplast and a prokaryotic cell. (1 mark)

A

70S ribosome

38
Q

No organelles are visible in the cytoplasm of this red blood cell.
Suggest why. (1 mark)

A

Cytoplasm of red blood cell filled with haemoglobin.

39
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
  3. On inside and outside of membrane.
40
Q

Suggest and explain how two environmental variables could be changed to increase the growth rate of cells. (4 marks)

A
  1. Increased temperature;
  2. Increased enzyme activity;
  3. Increased concentration of oxygen;
  4. Increased respiration;
41
Q

Describe and explain what the student should have done when counting cells to make sure that the mitotic index he obtained for this root tip was
accurate (2 marks)

A
  1. Repeat count;
  2. To ensure figures are correct;
42
Q

When preparing the cells for observation the scientist placed them in a solution that had a slightly higher (less negative) water potential than the
cytoplasm. This did not cause the cells to burst but moved the
chromosomes further apart in order to reduce the overlapping of the chromosomes when observed with an optical microscope.
Suggest how this procedure moved the chromosomes apart. (2 marks)

A
  1. Water moves into the cytoplasm by osmosis;
  2. Cell/cytoplasm gets bigger;
43
Q

Describe the appearance and behaviour of chromosomes during mitosis (5 marks)

A

(During prophase)
1. Chromosomes condense
2. Chromosomes appear as two sister chromatids joined at the
centromere

(During metaphase)
3. Chromosomes line up on the equator of the cell;
4. Chromosomes attached to spindle fibres;
5. By their centromere;

(During anaphase)
6. The centromere splits
7. Sister chromatids are pulled to opposite poles

(During telophase)
8. Chromosomes become longer / thinner.

44
Q

Suggest how the increase in temperature of the water caused the release
of a red pigment. (2 marks)

A
  1. Damage to cell surface membrane;
  2. membrane proteins denature;
  3. Increased fluidity because damage to the phospholipid bilayer;
45
Q

Compare and contrast the processes by which water and inorganic ions
enter cells. (3 marks)

A
  1. Comparison: both move down concentration gradient;
  2. Comparison: both move through protein channels in membrane;
  3. Contrast: ions can move against a concentration gradient by active transport
46
Q

Another student compares the mitotic index in the roots of two different species.
Give two considerations within her method to ensure this comparison is valid. (2 marks)

A
  1. Roots/plant of the same age;
  2. Same distance from root tip;
47
Q

How to tell whether a cell is going through mitosis? (2 marks)

A
  1. The individual chromosomes are visible because they have condensed;
  2. Each chromosome is made up of two chromatids because DNA has replicated;
  3. The chromosomes are not arranged in homologous pairs, which they would be if it was meiosis;
48
Q

Suggest one way the structure of the chromosome could differ along its length to
result in the stain binding more in some areas. (1 mark)

A

Differences in base sequences

49
Q

A mixture of venoms from several snakes of the same species is used.
Suggest why. (2 marks)

A

May be different form of antigen/toxin
(within one species)

50
Q

During vaccination, each animal is initially injected with a small volume of venom.
Two weeks later, it is injected with a larger volume of venom.
Use your knowledge of the humoral immune response to explain this vaccination
programme. (3 marks)

A
  1. B cells specific to the venom reproduce by mitosis;
  2. B cells produce plasma cells and memory cells;
  3. The second dose produces antibodies in higher
    concentration and quickly
51
Q

Suggest why higher than normal concentrations of a protein could result in a tumour. (2 marks)

A
  1. Shortens interphase
  2. Faster cell cycle
  3. Resulting in a group of
    abnormal cells;
52
Q

Suggest how one antibody can be specific to tick protein and to alpha-gal. (2 marks)

A
  1. Part of tick protein and alpha-gal have a similar shape
  2. Antibody is complementary to both
53
Q

Suggest one advantage of the different percentage of cholesterol in red blood cells
compared with cells lining the ileum. (1 mark)

A

Red blood cells free in blood so cholesterol helps to maintain shape;

54
Q

E. coli has no cholesterol in its cell-surface membrane. Despite this, the cell maintains
a constant shape. Explain why. (2 marks)

A
  1. Cell unable to change shape;
  2. Because cell has a cell wall;
  3. Wall is made of murein;
55
Q

Explain why the data is described as processed results. (1 mark)

A

Calculations made from raw data

56
Q

HS virus infects nerve cells in the face. Explain why it infects only nerve cells. (3 marks)

A
  1. Outside of virus has antigens
  2. With complementary shape to receptor in membrane of cells;
  3. Receptor found only on membrane of nerve cells;
57
Q

Explain why a virus
can be described as inactive. (2 marks)

A
  1. No more cells infected
  2. Because virus is not replicating;
58
Q

Suggest one advantage of programmed cell death (1 mark)

A

Prevents replication of virus;

59
Q

Explain how this microRNA allows a virus to remain in the body for years. (4 mark)

A
  1. MicroRNA binds to cell’s mRNA by specific base pairing;
  2. So prevents mRNA being read by ribosomes;
  3. So prevents translation
  4. Proteins that cause cell death;
60
Q

Describe and explain one difference between a SEM and a TEM (2 marks)

A
  1. 3D with SEM, but 2D with TEM
  2. Because electrons bounce off using SEM
61
Q

What is a tumour? (2 marks)

A
  1. Abnormal cells
  2. Uncontrolled cell division;
62
Q

Describe how you would determine a reliable mitotic index (MI) from tissue observed
with an optical microscope. (3 marks)

A
  1. Count cells in mitosis in field of view
  2. Divide this by total number of cells in field of view;
  3. Repeat at least 5 times
63
Q

Describe how the composition of blood in the pulmonary artery of a fetus is different
from the composition of blood in the pulmonary artery of its mother.
Give one reason for this difference. (2 marks)

A
  1. Fetal blood has more oxygen
  2. Because gas exchange occurs in the placenta
64
Q

Explain how a fetus is protected against the pathogens that infect its mother during
pregnancy (3 marks)

A
  1. Antibodies from mother are
    complementary
  2. To antigens crossing the placenta;
  3. Giving passive immunity in fetus
65
Q

Explain why giving children more than one tetanus vaccination develops good
immunity against tetanus (2 marks)

A
  1. Production of more memory cells;
  2. So higher concentration of antibodies in blood
66
Q

Name the main biological molecule in cell membrane and cell wall? (2 marks)

A

membrane = phospholipids
wall = muerin

67
Q

Explain why the solution the biologist used was ice-cold, buffered and the same water
potential as the liver tissue (3 marks)

A
  1. Ice-cold – Slows enzyme activity to prevent digestion of organelles
  2. Buffered – Maintains pH so that enzymes are not denatured;
  3. Same water potential – Prevents osmosis so no shrinkage of organelles
68
Q

How can competitive inhibition slow cell division? (3 marks)

A
  1. Competes with substrate and binds at active site
  2. Fewer enzyme-substrate complexes;
  3. Fewer nucleotides available for DNA replication;
69
Q

Suggest why they recorded both percentage change and tumour volume. (2 marks)

A

Percentage change
1. To allow comparison as tumours may differ in size

Tumour volume
2. As tumours may differ in shape

70
Q

Mitosis is important in the life of an organism. Give two reasons why. (2 marks)

A
  1. Replace cells
  2. Genetically identical cells
71
Q

Suggest why the student soaked the root tips in hydrochloric acid (2 marks)

A
  1. To break down links between cell walls
  2. Allowing the stain to diffuse into the cells
72
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
    OR
    Reverse transcriptase makes DNA from RNA;
  4. Cell produces (viral) protein/capsid/enzymes;
  5. Virus assembled and released (from cell);
73
Q

Describe how the scientist would remove large organelles from this suspension of cell contents? (2 marks)

A
  1. Use centrifugation at increasing (sequence of) speed(s);
  2. Large/dense organelles (removed) in (first/early)
    pellet
74
Q

Give one feature of a chloroplast that allows protein to be synthesised (1 mark)

A

DNA

75
Q

What should happen before trying a drug on humans? (2 marks)

A
  1. Tested on other mammals to check for safety/side effects;
  2. Tested on (healthy) humans to check for safety/side effects;
  3. See if repeat doses stop the tumours regrowing
  4. Investigate different concentrations to
    find suitable/safe dosage;

Biology Exam Questions (5 decks)

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