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Topic 2- Cells ms Flashcards

1
Q

U. marinum cells ingest bacteria and digest them in the cytoplasm. Describe the role of one named organelle in digesting these bacteria 3m

A

1.Lysosomes
2. Fuse with phagosome/vesicle
3. Releases hydrolytic enzymes

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2
Q

Give 2 structures found in all prokaryotic and eukaryotic cells

A

Cell-surface membrane
Ribosomes
Cytoplasm
DNA

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3
Q

Describe how a sample of chloroplasts is isolated from leaves 4m

A
  1. Break open cells and filter
  2. In an ice-cold, isotonic/same water potential, buffered/pH controlled solution
  3. Centrifuge/spin and remove nuclei/cell debris
  4. Spin at a higher speed, chloroplasts settle out
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4
Q

Outline the role of organelles in the production, transport and release of proteins from eukaryotic cells 4m

A
  1. DNA in nucleus is code for proteins
  2. Ribsomes/RER produce proteins
  3. Mitochondria produce ATP (for proteinsynthesis)
  4. Golgi apparatus package/modify
  5. Vesicles transport
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5
Q

Compare and contrast how an optical and TEM microscope work and their limitations

A
  1. TEM uses electrons and optical uses light
  2. TEM allows a greater resolution
  3. (so with TEM) smaller organelles can be observed/ greater detail in organelles
  4. TEM views dead cells only whereas optical can view live specimens
  5. TEM doesn’t show colour whereas O can
  6. TEM requires a thinner specimen
  7. TEM requires a more complex staining
  8. TEM focusses using magnets whereas O uses glass lenses
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6
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 microscope 4M

A

Add a drop of water to the (glass) slide
Obtain a thin section and place on slide / float on water
Stain with KI
Lower coverslip using mounted needle

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7
Q

Explain one way in which a plant cell is adapted for photosynthesis

A

Chloroplasts absorb light;
Q Do not accept chlorophyll as alternative to chloroplasts
Or
Large vacuole pushes chloroplasts to edge (of cell);
Or
Thin / permeable (cell) wall to absorb carbon dioxide;

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8
Q

What is the advantage of the mitochondria having a small width

A

short diffusion pathway / short pathway to the centre / large SA:V ratio
for faster, more diffusion;

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9
Q

How do microvilli help the absorption of the small intestine

A

Have a large surface area (for diffusion)

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10
Q

Explain why the biologist used a blender and then filtered the mixture
HOMOGENISATION+ CENTRIFUGATION

A
  1. Break open cells / homogenise / produce homogenate;
  2. Remove unbroken cells / larger debris;
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11
Q

2 structures found in a plant cell but not in an animal cell

A
  1. Chloroplasts / plastids
  2. Cell wall
  3. Cell vacuole
  4. Starch grains / amyloplasts;
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12
Q

Explain why it is important for the student to obtain a thin section of the tissue

A

Single layer of cells / few layers of cells;
So that light that can pass through / cells absorb light;

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13
Q

Suggest how the student could have used the slide of find the number of stomata per cm2

A

Method of determining area of field of view / area seen using microscope;
Count number of stomata in field of view;
Repeats and calculation of mean

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14
Q

The stomata on the leaves of pine trees are found in pits below the leaf surface. Explain how this helps to reduce water loss

A

Water vapour accumulates / increased humidity / reduced air movement
(around stomata);
Water potential / diffusion gradient reduced

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15
Q

Name the type of bond that joins amino acids together in a polypeptide

A

Peptide

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16
Q

Explain why there are lots of mitochondria in the cell

A

(Site of aerobic) respiration;
Release ATP / energy for active transport / transport against the concentration
gradient / protein synthesis / exocytosis;

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17
Q

Explain why the suspension was kept ice-cold
HOMOGENISATION

A

Reduces / prevents enzyme activity;

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18
Q

Explain why the suspension was isotonic
HOMOGENISATION

A

Prevents osmosis / no (net) movement of water / water does not enter
organelle / water does not leave organelle;
So organelle / named organelle is not damaged / does not burst / does
not shrivel;
Neutral

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19
Q

Explain why a TEM was used to view the amoeba cell’s structure

A
  1. High / better resolution;
  2. Shorter wavelength;
  3. To see internal structures / organelles / named organelles;
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20
Q

Advantage of using TEM instead of SEM

A

Higher resolution / higher (maximum) magnification / higher detail (of
image);
OR
Allows internal details / structures within (cells) to be seen / cross
section to be taken;

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21
Q

Advantage of using SEM instead of TEM

A

Thin sections do not need to be prepared / shows surface of specimen /
can have 3-D images;

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22
Q

Name the type of reaction that would break down these carbs into their monomers

A

Hydrolysis

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23
Q

Give a feature of starch and how it enables it to act as a storage molecule

A
  1. Coiled / helical / spiral;
    Feature = one mark
    Explanation = one mark
    Note: these are independent marking points
    These must be related for both marks but can be in reverse
    order
  2. (So) compact / tightly packed / can fit (lots) into a small space;
  3. Insoluble;
  4. (So) no osmotic effect / does not leave cell / does not affect water
    potential;
    Accept: prevents osmosis
  5. Large molecule / long chain;
  6. (So) does not leave cell / contains large number of glucose units;
  7. and 6. Accept: can’ t cross membranes
  8. Branched chains;
  9. (So) easy to remove glucose;
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24
Q

What is a tissue

A

(Group of) similar / identical cells / cells with a common origin;

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25
Q

Describe how to identify that starch was present

A

Add iodine / stain specific for starch to the slide / cells / tissue / add
iodine / stain specific for starch and examine under microscope;
Blue-black / blue / black / purple;

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26
Q

Describe 2 ways in which the molecule cellulose is similar to starch

A

Both are polymers / made of monomers;
Joined by condensation / molecules can be broken down by hydrolysis;
Both have 1-4 links;
Contain C(arbon), H(ydrogen) and O(xygen) / both made up of glucose;
Both insoluble;
Both contain glycosidic bonds;

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27
Q

Give a feature of a prokaryotic cell that is not found in a eukaryotic cell

A

plasmid / capsule / 70S ribosomes / smaller
ribosomes / complex cell wall / mesosome / no nucleus

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28
Q

Describe how a sample consisting of only chloroplasts can be obtained from homogenised plant tissue

A

use of differential centrifugation / or description;
first / low-spin pellet discarded / spin at low speed to remove cell
wall material / cell debris;
supernatant re-spun at higher speed / until pellet with chloroplasts is found;
method of identifying chloroplasts e.g. microscopy

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29
Q

Describe how the inner membrane of a mitochondria is adapted to its function

A

increased surface area;
for respiration / enzymes;
HIGHLY FOLDED- FORMS CRISTAE

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30
Q

Explain the advantages and limitations of using a TEM microscope to investigate cell structure

A

Advantages:
1 Small objects can be seen;
2 TEM has high resolution as wavelength of electrons shorter;
Accept better
Limitations:
3 Cannot look at living cells as cells must be in a vacuum / must cut section /
thin specimen;
4 Preparation may create artefact
5 Does not produce colour image;

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31
Q

Describe the principles and limitations of using a TEM to investigate cell structure

A

Principles:
1. Electrons pass through / enter (thin) specimen;
2. Denser parts absorb more electrons;
3. (So) denser parts appear darker;
4. Electrons have short wavelength so give high resolution;
Principles:
Allow maximum of 3 marks
Limitations:
5. Cannot look at living material / Must be in a vacuum;
6. Specimen must be (very) thin;
7. Artefacts present;
8. Complex staining method / complex / long preparation time;
9. Image not in 3D / only 2D images produced.

32
Q

Describe and explain how cell fractionation and ultracentrifugation can be used to isolate mitochondria from a suspension of animal cells

A

Any five from:
1. Cell homogenisation to break open cells;
1. Accept suitable method of breaking open cells.
2. Filter to remove (large) debris / whole cells;
2. Reject removes cell walls.
3. Use isotonic solution to prevent damage to mitochondria / organelles;
3. Ignore to prevent damage to cells.
4. Keep cold to prevent / reduce damage by enzymes / use buffer to
prevent protein / enzyme denaturation;
5. Centrifuge (at lower speed / 1000 g) to separate nuclei / cell fragments /
heavy organelles;
5. Ignore incorrect numerical values.
6. Re-spin (supernatant / after nuclei / pellet removed) at higher speed to
get mitochondria in pellet / at bottom

33
Q

How are fatty acids and glycerol absorbed in the epithelial cell

A

Diffusion

34
Q

Explain the advantages of lipid droplet and micelle formation

A
  1. Droplets increase surface areas (for lipase / enzyme
    action);
  2. (So) faster hydrolysis / digestion (of triglycerides /
    lipids);
  3. Micelles carry fatty acids and glycerol /
    monoglycerides to / through membrane / to (intestinal
    epithelial) cell;
35
Q

Suggest how the Golgi Body/Apparatus is involved in the absorption of lipids

A
  1. Golgi (apparatus);
  2. Modifies / processes triglycerides;
  3. Combines triglycerides with proteins;
  4. Packaged for release / exocytosis
    OR
    Forms vesicles;
36
Q

Explain the role of independent segregation in meiosis

A

Allows different combinations of maternal and paternal chromosomes/alleles
Provides genetic variation

37
Q

What is an antigen?

A
  1. Foreign protein;
    Accept glycoprotein / glycolipid / polysaccharide
  2. (that) stimulates an immune response / production of antibody;
38
Q

What is an antibody

A
  1. A protein / immunoglobulin specific to an antigen;
  2. Produced by B cells
    OR
    Secreted by plasma cells;
39
Q

Contrast the structures of DNA and mRNA molecules to give 3 differences

A
  1. DNA double stranded/double helix and mRNA single-stranded;
    Contrast requires both parts of the statement
  2. DNA (very) long and RNA short;
    Accept ‛RNA shorter’ or ‛DNA bigger/longer’
  3. Thymine/T in DNA and uracil/U in RNA;
  4. Deoxyribose in DNA and ribose in RNA;
    R Deoxyribonucleic/ ribonucleic acid
    Ignore ref. to histones
    Ignore ref. to helix and straight chain alone
  5. DNA has base pairing and mRNA doesn’t/ DNA has
    hydrogen bonding and mRNA doesn’t;
  6. DNA has introns/non-coding sequences and mRNA doesn’t;
40
Q

What is a substitution mutation

A
  1. Replacement of a base by a different base (in DNA);
41
Q

Each antibody specifically binds to one of the proteins. Explain why

A
  1. Each protein has a different tertiary structure;
  2. (Each) antibody has a specific antigen / binding / variable region / site;
  3. So, (each antibody) forms different antigen-antibody complex
    OR
    (each antibody) only binds to complementary (protein);
42
Q

Describe how phagocytosis of a virus leads to the presentation of it antigens

A
  1. Phagosome / vesicle fuses with lysosome;
  2. (Virus) destroyed by lysozymes / hydrolytic enzymes;
  3. Peptides / antigen (from virus) are displayed on the cell membrane;
  4. Accept vacuole fuses with lysosome
  5. Reject virus fuses with lysosome
43
Q

Describe how the presentation of a virus antigen leads to the secretion of an antibody against this virus antigen

A
  1. Helper T cell / TH cell binds to the antigen (on the antigen-presenting
    cell / phagocyte);
  2. This helper T / TH cell stimulates a specific B cell;
  3. B cell clones
    OR
    B cell divides by mitosis;
  4. (Forms) plasma cells that release antibodies;
  5. and 2. ‘Helper’ is required once only.
  6. Accept ‘This (helper) T cell stimulates a competent B
    cell’
    ‘T cell stimulates B cell to undergo clonal selection’. This
    statement achieves mp2 and mp3.
44
Q

When HIV infects a human cell, the following events occur.
* A single-stranded length of HIV DNA is made.
* The human cell then makes a complementary strand to the HIV DNA.
The complementary strand is made in the same way as a new complementary
strand is made during semi-conservative replication of human DNA.
Describe how the complementary strand of HIV DNA is made.

A
  1. (Complementary) nucleotides/bases pair
    OR
    A to T and C to G;
    Ignore ‘(DNA polymerase) forms base pairs/nucleotide pairs’
  2. DNA polymerase;
  3. Nucleotides join together (to form new strand)/phosphodiester bonds form;
    Ignore ‘(DNA polymerase) forms base pairs/nucleotide pairs’
    If clearly writing rote answer about DNA replication 2 max
    e.g. helicase or separating strands
45
Q

Give two structures a bacterial cell may have that a white blood cell does not have.

A
  1. Cell wall;
  2. Capsule / slime layer;
  3. Circular DNA;
    Reject “circular chromosome”
  4. Naked DNA / DNA without histones;
  5. Flagellum;
  6. Plasmid;
  7. Pilus;
  8. 70s / smaller ribosomes;
  9. Mesosome;
46
Q

Describe how bacteria are destroyed by phagocytes.

A
  1. (Phagocyte engulfs) to form vacuole / vesicle / phagosome;
    Accept surrounds bacteria with membrane
  2. Lysosome empties contents into vacuole / vesicle / phagosome;
    Accept joins / fuses
  3. (Releasing) enzymes that digest / hydrolyse bacteria;
    Ignore breakdown / destroy / lytic enzymes
47
Q

Explain one advantage of storing starch rather than glucose in potato cells

A

Feature of starch;
Consequence in terms of storage;
e.g.
Insoluble;
Therefore will not “wash” out of cell / affect water
potential / affect osmosis;
OR
Molecule coiled / branched;
Therefore large amount stored in small space / compact
OR
Does not affect water potential;
So no effect on entry of water (into cell);

48
Q

Describe how you could confirm that the granules contained starch

A

Granules) turn blue-black / dark blue / black / purple with iodine;

49
Q

Give 2 features which may be found in a prokaryotic cell which would not be found in this cell

A

Any two from:
Loop of DNA; Non-cellulose cell wall;
Plasmid; Capsule;
Flagellum; Mesosome;

50
Q

Give 2 structures in a eukaryotic cell that would not be identified using an optical microscope

A

Two of the following for one mark:
Mitochondrion / ribosome / endoplasmic reticulum / lysosome / cell-surface
membrane.

51
Q

Describe how you could use cell fractionation to isolate chloroplasts from the leaf

A
  1. How to break open cells and remove debris;
  2. Solution is cold / isotonic / buffered;
  3. Second pellet is chloroplast.
52
Q

Describe the appearance and behaviour of chromosomes during mitosis

A

(During prophase)
1. Chromosomes
coil / condense / shorten / thicken / become visible;
2. (Chromosomes) appear as (two sister) chromatids joined at the
centromere;
(During metaphase)
3. Chromosomes line up on the equator / centre of the cell;
4. (Chromosomes) attached to spindle fibres;
5. By their centromere;
(During anaphase)
6. The centromere splits / divides;
7. (Sister) chromatids / chromosomes are pulled to opposite poles /
ends of the cell / separate;
(During telophase)
8. Chromatids / chromosomes
uncoil / unwind / become longer / thinner.
No marks for naming the stages
Reject references to homologous chromosomes /
pairing of chromosomes
Ignore references to spindle formation during
prophase
5 max

53
Q

Describe 2 aseptic techniques she would have used when transferring a sample of broth culture on to an agar plate
Explain why each was important

A
  1. Keep lid on Petri dish
    OR
    Open lid of Petri dish as little as possible.
  2. To prevent unwanted bacteria contaminating the dish.
    OR
    L. monocytogenes may be dangerous / may get out.
    OR
  3. Wear gloves
    OR
    Wear mask
    OR
    Wash hands;
  4. To prevent contamination from bacteria on hands / mouth
    OR
    Prevent spread of bacteria outside the lab;
    OR
  5. Use sterile pipette
    OR
    Flame the loop
    OR
    Flame the neck of the container of the culture;
  6. To maintain a pure culture of bacteria
54
Q

Name the process by which bacterial cells divide

A

Binary fission

55
Q

Describe binary fission in bacteria.

A
  1. Replication of (circular) DNA;
    Accept nucleoid
    Reject chromosome
    Reject mitosis
  2. Replication of plasmids;
  3. Division of cytoplasm (to produce daughter cells);
56
Q

Suggest and explain how two environmental variables could be changed
to increase the growth rate of these cells.

A

Principle of marking pairs: Named environmental variable; Correct effect
on growth rate;
Examples
1. Increased (concentration of) glucose;
2. Increased respiration;
3. Increased (concentration of) oxygen;
4. Increased respiration;
5. Increased temperature;
6. Increased enzyme activity;
7. Increased (concentration of) phosphate;
8. Increased ATP/DNA/RNA;
9. Increased (concentration of) nucleotides;
10. Increased DNA synthesis;

57
Q

Describe the role of the spindle fibres and the behaviour of the
chromosomes during each of these phases.
PROPHASE, METAPHASE, ANAPHASE

A

(In) prophase, chromosomes condense;
Accept chromatin for ‘chromosomes’ and for
‘condense’, shorten and thicken
3. (In) prophase OR metaphase, centromeres attach to spindle fibres;
4. (In) metaphase, chromosomes/pairs of chromatids at
equator/centre of spindle/cell;
5. (In) anaphase, centromeres divide;
6. (In) anaphase, chromatids (from each pair) pulled to (opposite)
poles/ends (of cell);
Accept for ‘chromatids’, chromosomes but reject
homologous chromosomes
7. (In) prophase/metaphase/anaphase, spindle fibres shorten;
If mark point 1 is not credited = 4 max
Do not carry forward error from 1.
Accept letters for stages as indicated in 1.
Accept for ‘shorten’, contract

57
Q

Name the fixed position occupied by a gene on a DNA molecule

A

Loci

58
Q

Explain why the student:
1. used only the first 5 mm from the tip of an onion root.
2. pressed down firmly on the cover slip.

A
  1. Where dividing cells are found / mitosis occurs;
    OR
    No dividing cells / mitosis in tissue further away / more than 5 mm
    from tip;
    OR
    To get (soft) tissue that will squash;
    OR
    Length that will fit under cover slip;
    Accept most dividing cells
  2. Single / thin layer of cells / spread out cells so light passes through
    (making cells / nuclei visible);
59
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.

A
  1. Examine large number of fields of view / many cells;
    Mark as pairs only
    Accept large number / 20 or more for many
  2. To ensure representative sample;
    Accept typical / reliable
    OR
  3. Repeat count;
  4. To ensure figures are correct;
    OR
  5. Method to deal with part cells shown at edge /count only whole cells;
  6. To standardise counting;
60
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.

A
  1. Water moves into the cells/cytoplasm by osmosis;
    Reject water moving into chromosomes/nucleus.
  2. Cell/cytoplasm gets bigger;
    Accept idea of cell/cytoplasm has greater
    volume/swells/expands.
61
Q

What is a homologous pair of chromosomes?

A

(Two chromosomes that) carry the same genes;
Reject ‘same alleles’
Accept ‘same loci’ (plural) or ‘genes for the same
characteristics’

62
Q

The scientists used a TEM to study the structure of the amoeba. Explain why

A
  1. High / better resolution;
  2. Shorter wavelength;
  3. To see internal structures / organelles / named organelles;
63
Q

Describe and explain how cell fractionation and ultracentrifugation can be used to isolate mitochondria from a suspension of animal cells

A
  1. Cell homogenisation to break open cells;
  2. Accept suitable method of breaking open cells.
  3. Filter to remove (large) debris / whole cells;
  4. Reject removes cell walls.
  5. Use isotonic solution to prevent damage to mitochondria / organelles;
  6. Ignore to prevent damage to cells.
  7. Keep cold to prevent / reduce damage by enzymes / use buffer to
    prevent protein / enzyme denaturation;
  8. Centrifuge (at lower speed / 1000 g) to separate nuclei / cell fragments /
    heavy organelles;
  9. Ignore incorrect numerical values.
  10. Re-spin (supernatant / after nuclei / pellet removed) at higher speed to
    get mitochondria in pellet / at bottom.
64
Q

Describe the principles and limitations of using a TEM to investigate cell structure

A

Principles:
1. Electrons pass through / enter (thin) specimen;
2. Denser parts absorb more electrons;
3. (So) denser parts appear darker;
4. Electrons have short wavelength so give high resolution;
Principles:
Allow maximum of 3 marks
Limitations:
5. Cannot look at living material / Must be in a vacuum;
6. Specimen must be (very) thin;
7. Artefacts present;
8. Complex staining method / complex / long preparation time;
9. Image not in 3D / only 2D images produced.

65
Q

Scientists use optical microscope and TEM to investigate cell structure. Explain the advantages and the limitation of using a TEM to investigate cell structure

A

Advantages:
1 Small objects can be seen;
2 TEM has high resolution as wavelength of electrons shorter;
Accept better
Limitations:
3 Cannot look at living cells as cells must be in a vacuum / must cut section /
thin specimen;
4 Preparation may create artefact
5 Does not produce colour image;

66
Q

The events that take place during interphase and mitosis lead to the production of 2 genetically identical cells. Explain how

A
  1. DNA replicated;
    Reject: DNA replication in the wrong stage
  2. (Involving) specific / accurate / complementary base-pairing;
    Accept: semi conservative replication
  3. (Ref to) two identical / sister chromatids;
  4. Each chromatid / moves / is separated to (opposite) poles / ends of cell
67
Q

Describe the function of the chloroplasts

A

Photosynthesis;
Uses light (energy);
To produce carbohydrates / starch / glucose / sugars / ATP /
reduced NADP;

68
Q

Give 2 other factors other than cost that should be considered when selecting an antibiotic to treat bacterial disease

A

side effects / allergic reactions / low toxicity to cells;
interaction with other drugs / effective in conditions of use / reasonably stable;
should only act on the problem bacteria / narrow spectrum;
how much resistance the bacteria have built up;

69
Q

Name a mutagenic agent

A

high energy radiation / ionising particles;
named particles / α, β, γ;
colchicine;
x rays / cosmic rays;
uv (light);
carcinogen / named carcinogen;
mustard gas / phenols / tar (qualified);

70
Q
A
  1. Microvilli provide a large / increased surface area;
  2. Many mitochondria produce ATP / release or provide energy
    (for active transport);
  3. Carrier proteins for active transport;
  4. Channel / carrier proteins for facilitated diffusion;
  5. Co-transport of sodium (ions) and glucose or symport / carrier
    protein for sodium (ions) and glucose;
  6. Membrane-bound enzymes digest disaccharides / produce
    glucose;
71
Q
A
  1. Phagocyte attracted to bacteria by chemicals / recognise antigens on
    bacteria as foreign;
  2. Engulf / ingest bacteria;
  3. Bacteria in vacuole / vesicle;
  4. Lysosome fuses with / empties enzymes into vacuole;
  5. Bacteria digested / hydrolysed;
72
Q
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;
    Accept any named membrane-bound organelle
  5. Bacterial ribosomes smaller than human ribosomes / bacteria have
    70S ribosomes whereas humans have 80S ribosomes;
  6. Bacterial DNA is circular but human DNA is linear;
  7. Bacterial DNA is ‘naked’ whereas human DNA is bound to histones /
    proteins
73
Q
A
  1. virus contains antigen;
  2. virus engulfed by phagocyte / macrophage;
  3. presents antigen to B-cell;
  4. memory cells / B-cell becomes activated;
  5. (divides to) form clones;
  6. by mitosis;
  7. plasma cells produce antibodies;
  8. antibodies specific to antigen;
  9. correct reference to T-cells / cytokines;
74
Q
A

Virus / fungus / protozoan;

75
Q
A

Biology Flashcards-ms (6 decks)

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