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Left RSFC Year 13 2022-24 > 2: Studying cells > Flashcards

2: Studying cells Flashcards

1
Q

What is the function of a ribosome?

A

Site of Protein synthesis;

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2
Q

What is the function of the Nucleus?

A

Contains genetic material / DNA;
Controls cell activity;

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3
Q

Describe the structure and function of the nucleus. [5]

A

Structure
1. Nuclear envelope and pores OR Double membrane and pores;
2. Chromosomes/chromatin OR DNA with histones;
3. Nucleolus/nucleoli;

Function
4. (Holds/stores) genetic information/material for polypeptides (production) OR (Is) code for polypeptides;
5. DNA replication (occurs);
6. Production of mRNA/tRNA OR Transcription (occurs);
7. Production of rRNA/ribosomes;

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4
Q

What is the function of the nucleolus?

A
  • Synthesise nucleotides
  • Synthesise cytoplasmic ribosomes (80s)
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5
Q

What is the function of a mitochondrion?

A

Site of aerobic respiration;
ATP production;
Site of Link/Krebs/ETC

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6
Q

What is the function of the Smooth Endoplasmic Reticulum?

A

Site of lipid synthesis;

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7
Q

What is the function of the Rough Endoplasmic reticulum?

A

Encrusted in Ribosomes;
Site of protein synthesis;
Transports and stores protein within the cell

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8
Q

What is the function of Golgi Apparatus? [2]

A

Modifies/packages/sorts proteins;
Produces vesicles;

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9
Q

What is the function of Lysosomes?

A

Contains hydrolytic enzymes;
Digests worn out organelles/autolysis;

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10
Q

What is the function of Cell surface membrane?

A

Made of a Phospholipid Bilayer;
Controls what enters the cell/ is selectively permeable;
Can be folded to increase SA;

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11
Q

What is the function of Chloroplasts?

A

Contain thylakoids, stacked into Granum;
Site of photosynthesis;

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12
Q

What is the function of a Capsule?

A

Protects cell from immune systems;
Aids bacteria sticking together;

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13
Q

What is the function of Plasmid?

A

Circular DNA;
Contains antibiotic resistance genes;
Contains fewer genes that are contantly transcribed;

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14
Q

What is the function of Cell Wall?

A

Provides rigid shape / structure;
Stops osmotic lysis;

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15
Q

What is the function of Flagellum?

A

Allows movement/propulsion;

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16
Q

Eukaryotic cells produce and release proteins. Outline the role of organelles in the production, transport and release of proteins from eukaryotic cells. [5]

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; OR Carbohydrate added/glycoprotein produced by Golgi apparatus;
    5 Vesicles transport OR Rough endoplasmic reticulum transports;
  4. (Vesicles) fuse with cell(-surface) membrane;
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17
Q

Compare & contrast Eukaryotic and Prokaryotic DNA [5]

A

Comparisons
1. Nucleotide structure is identical;
2. Nucleotides joined by phosphodiester bond;
OR Deoxyribose joined to phosphate (in sugar, phosphate backbone);
3. DNA in mitochondria / chloroplasts same / similar (structure) to DNA in prokaryotes;
Contrasts
4. Eukaryotic DNA is longer;
5. Eukaryotic DNA contain introns, prokaryotic DNA does not;
6. Eukaryotic DNA is linear, prokaryotic DNA is circular;
7. Eukaryotic DNA is associated with / bound to protein / histones, prokaryotic DNA is not;

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18
Q

State three differences between DNA in the nucleus of a plant cell and DNA in a prokaryotic cell. [3]

A

**Plant v prokaryote **
1. (Associated with) histones/proteins v no histones/proteins;
2. Linear v circular;
3. No plasmids v plasmids;
4. Introns v no introns;
5. Long(er) v short(er);

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19
Q

The structure of a cholera bacterium is different from the structure of an epithelial cell from the small intestine.

Describe how the structure of a cholera bacterium is different. [6]

A
  1. Cholera bacterium is prokaryote;
  2. Does not have a nucleus/nuclear envelope/ has DNA free in cytoplasm/has loop of DNA;

3 and 4 Any two from: [No membrane-bound organelles/no mitochondria / no golgi/no endoplasmic reticulum];
5 Small / 70s ribosomes only;
6 and 7 Any two from [Capsule/flagellum/plasmid / cell wall]

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20
Q

Name two structures found in all bacteria that are not found in plant cells. [2]

A
  1. Circular DNA (molecule in cytoplasm);
  2. Murein cell wall OR Peptidoglycan cell wall OR Glycoprotein cell wall;
  3. Small(er)/70S ribosomes (in cytoplasm);
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21
Q

Give one advantage of using a TEM rather than a SEM.

A
  1. Higher resolution;
  2. Allows internal details / structures within (cells) to be seen / cross section to be taken;
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22
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.

A

Electrons have a shorter wavelength

OR

Longer wavelength in light (rays);

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23
Q

Give one advantage of using a SEM rather than a TEM.

A
  • Thin sections do not need to be prepared
  • shows surface of specimen
  • 3-D images;
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24
Q

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

A

Advantages:
1 Small objects can be seen;
2 TEM has high resolution;
3 Electron wavelength is shorter;

Limitations:
4 Cannot look at living cells;
5 Must be in a vacuum;
6 Must cut section / thin specimen;
7 Preparation may create artefact;

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25
Q

Scientists isolated mitochondria from liver cells. They broke the cells open in an ice-cold, buffered isotonic solution. Explain why the solution was:
a) Isotonic
b) Ice cold
c) buffered

A

a) Prevents osmosis / no (net) movement of water So organelle/named organelle does not burst/shrivel;
b) Reduce/prevent enzyme activity so organelles are not digested / damaged;
c) Maintain a constant pH so proteins do not denature;

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26
Q

Describe and explain how cell fractionation and centrifugation can be used to isolate mitochondria from a suspension of animal cells. [6]

A
  1. Cell homogenisation to break open cells and release organelles;
  2. Filter to remove (large) debris/whole cells;
  3. Use isotonic solution to prevent osmotic damage to mitochondria / organelles;
  4. Keep cold to prevent/reduce damage to organelles by enzyme;
  5. Use buffer to maintain pH and prevent protein/enzyme denaturation;
  6. Use differential Centrifuge (at high speed/1000 g) to separate nuclei / cell fragments / heavy organelles;
  7. Re-spin (supernatant / after nuclei/pellet removed) at higher speed to get mitochondria in pellet/at bottom;
  8. Observe pellet with a microscope to identify mitochondria;
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27
Q

Describe the structure of a phospholipid molecule and explain how phospholipids are arranged in a plasma membrane (3 marks).

A
  1. Glycerol joined to two fatty acid tails Phosphate group joined to glycerol on opposite side. (joined by condensation reaction with ester bond).;
  2. Phospholipid has hydrophilic head (phosphate and glycerol) and hydrophobic tails (fatty acid chains)
  3. Arrange to form a phospholipid bilayer; (Hydrophilic head facing out. Hydrophobic fatty acid chains facing in)
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28
Q

Explain why a cell membrane may be described as a fluid-mosaic? [2]

A
  • The position of the molecules within the membrane is fluid – they are able to move around within the membrane.
  • Membrane is made up from a variety of different protein molecules arranged into a mosaic.
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29
Q

Explain the arrangement of phospholipids in a cell-surface membrane.

A
  • Bilayer OR Water is present inside and outside a cell;
  • Hydrophobic (fatty acid) tails point away/are repelled from water AND Hydrophilic (phosphate) heads point to/are in/are attracted to water;
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30
Q

Describe how an ester bond is formed in a phospholipid molecule. [2]

A
  1. Condensation (reaction) OR Loss of water;
  2. Between of glycerol and fatty acid;
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31
Q

Many different substances enter and leave a cell by crossing its cell surface membrane.

Describe how substances can cross a cell surface membrane. [6]

A

1 (Simple / facilitated) diffusion from high to low concentration / down concentration gradient;
2 Small / non-polar / lipid-soluble molecules pass via phospholipids / bilayer;
OR
Large / polar / water-soluble molecules go through proteins;
3 Water moves by osmosis / from high water potential to low water potential / from less to more negative water potential;
4 Active transport is movement from low to high concentration / against concentration gradient;
5 Active transport / facilitated diffusion involves proteins / carriers;
6 Active transport requires energy / ATP;
7 Ref. to Na+ / glucose co-transport;

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32
Q

The movement of substances across cell membranes is affected by membrane structure.

Describe how. [6]

A
  • Phospholipid (bilayer) allows movement/diffusion of non-polar/lipid-soluble substances;
  • Phospholipid (bilayer) prevents movement/diffusion of polar/ charged/lipid-insoluble substances OR (Membrane) proteins allow polar/charged substances to cross the membrane/bilayer;
  • Carrier proteins allow active transport;
  • Channel/carrier proteins allow facilitated diffusion/co-transport;
  • Shape/charge of channel / carrier determines which substances move;
  • Number of channels/carriers determines how much movement;
  • Membrane surface area determines how much diffusion/movement;
  • Cholesterol affects fluidity/rigidity/permeability;
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33
Q

Name and describe five ways substances can move across the cell-surface membrane into a cell. [5]

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;
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34
Q

Compare and contrast the processes by which water and inorganic ions enter cells. [3]

A
  1. Comparison: both move down concentration gradient;
  2. Comparison: both move through (protein) channels in membrane;
    Accept aquaporins (for water) and ion channels
  3. Contrast: ions can move against a concentration gradient by active transport
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35
Q

Give two similarities in the movement of substances by diffusion and by osmosis [2]

A
  1. (Movement) down a gradient / from high concentration to low concentration;
  2. Passive / not active processes; OR Do not use energy from respiration / from ATP / from metabolism; OR Use energy from the solution;
36
Q

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

A
  1. Carrier / channel protein;
  2. (Protein) specific / complementary to substance;
  3. Substance moves down concentration gradient;
37
Q

Describe how you would use a 1.0 mol dm−3 solution of sucrose to produce 30 cm3 of a 0.15 mol dm−3 solution of sucrose.

A
  • Add 4.5 cm3 of (1.0 mol dm–3) solution to 25.5 cm3 (distilled) water.
  • Mix

M1V1= M2V2

38
Q

Explain the decrease in mass of potato tissue in the 0.40 mol dm−3 solution of sucrose. [2]

A
  1. Water potential of solution is less than / more negative than that of potato tissue; (Ψ as equivalent to water potential)
  2. Tissue loses water by osmosis.
39
Q

Describe how you would use the student’s results (dilution series and % change in mass) to find the water potential of the potato tissue. [3]

A
  1. Plot a graph with concentration on the x-axis and percentage change in mass on the y-axis;
  2. Find concentration where curve crosses the x-axis / where percentage change is zero;
  3. Use (another) resource to find water potential of sucrose concentration (where curve crosses x-axis).
40
Q

Describe the non-specific defence mechanisms the body may launch against pathogens (5 marks)

A

The process is called phagocytosis – No Mark
1. Pathogen is engulfed by the phagocyte.
2. Engulfed pathogen enters the cytoplasm of
the phagocyte in a vesicle;
3. Lysosomes fuse with vesicle releasing
digestive enzymes;
4. Lysosome enzymes break down the pathogen.
5. Waste materials are ejected from the cell by exocytosis;

41
Q

State two ways that pathogens cause disease.

A
  • Produce / secrete / release toxins
  • Damage/destroy cells / tissues / organs
42
Q

Describe how a phagocyte destroys a pathogen present in the blood. [3]

A
  1. Engulfs;
  2. Forming vesicle/phagosome and fuses with lysosome;
  3. Hydrolytic Enzymes digest/hydrolyse;
43
Q

Give two types of cell, other than pathogens, that can stimulate an immune response.

A
  1. (Cells from) other organisms/transplants;
  2. Abnormal/cancer/tumour (cells);
  3. (Cells) infected by virus;
44
Q

When a vaccine is given to a person, it leads to the production of antibodies against a disease-causing organism. Describe how. [6]

A
  1. Vaccine contains (specific) antigen from pathogen;
  2. Macrophage presents antigen on its surface;
  3. T (helper) cell with complementary receptor protein binds to antigen & becomes activated;
  4. T cell stimulates B cell by complementary receptor binding and releases cytokines;
  5. (With) complementary antibody on its surface;
  6. B cell divides to form clone secreting / producing same antibody;
  7. B cell secretes large amounts of (monoclonal) antibody;
45
Q

Explain how the humoral response leads to immunity. [3]

A
  1. B cells specific to the antigen reproduce by mitosis.
  2. B cells produce / differentiate into plasma and memory cells
  3. Second infection produces antibodies in larger quantities AND quicker. (More rapid & More extensive)
46
Q

Describe and explain the role of antibodies in stimulating phagocytosis. [2]

A
  • Bind to antigen OR Are markers (opsinisation);
  • (Antibodies) cause agglutination (clumping) OR Attract phagocytes;
47
Q

Describe the difference between active and passive immunity. [5]

A
  1. Active involves memory cells, passive does not;
  2. Active involves production of antibody by plasma cells/memory cells;
  3. Passive involves antibody introduced into body from outside/named source;
  4. Active long term, because antibody produced in response to antigen;
  5. Passive short term, because antibody (given) is broken down;
  6. Active (can) take time to develop/work, passive fast acting;
48
Q

State why some antibodies are referred to as monoclonal.

A

(Antibodies) produced from a single clone of B cells / plasma cells;
OR

(Antibodies) produced from the same B cell / plasma cell;

49
Q

What is the role of the disulfide bridge in forming the quaternary structure of an antibody?

A

Joins two (different) polypeptides;

50
Q

Tests using monoclonal antibodies are specific. Use your knowledge of protein structure to explain why. [3]

A
  • Specific) primary structure / order of amino acids;
  • (Specific) tertiary structure / shape;
  • (So) Only binds to / fits / complementary to one antigen;
51
Q

Describe the structure of the human immunodeficiency virus (HIV). [5]

A
  1. RNA (as genetic material);
  2. Reverse transcriptase;
  3. (Protein) capsomeres/capsid;
  4. (Phospho)lipid (viral) envelope OR Envelope made of membrane;
  5. Attachment proteins;
52
Q

Explain how HIV affects the production of antibodies when AIDS develops in a person. [3]

A
  1. Less/no antibody produced;
  2. (Because HIV) destroys helper T cells; Accept ‘reduces number’ for ‘destroys’
  3. (So) few/no B cells activated / stimulated OR (So) few/no B cells undergo mitosis/differentiate/form plasma cells;
53
Q

Describe how the human immunodeficiency virus (HIV) is replicated once inside helper T cells (TH cells). [4]

A
  1. RNA converted into DNA using reverse transcriptase;
  2. DNA incorporated/inserted into (helper T cell) DNA/chromosome/genome/nucleus;
  3. DNA transcribed into (HIV m)RNA;
  4. (HIV mRNA) translated into (new) HIV/viral proteins (for assembly into viral particles);
54
Q

Name two features of HIV particles that are not found in bacteria. Do not include attachment protein in your answer.

A
  1. Capsid;
  2. Reverse transcriptase;
  3. RNA genome;
  4. Envelope
55
Q

AO2 (More or Less)

Describe how a person infected with HIV will develop AIDS (if untreated) and die of secondary infections. [4]

A
  • High viral load leads to increased destruction of helper T/CD4 cells;
  • Less activation of B cells/cytotoxic T cells/phagocytes;
  • Less production of plasma cells/antibodies OR (With cytotoxic T cells) less able to kill virus infected cells;
  • (Less able to) destroy other microbes/pathogens OR (Less able to) destroy mutated/cancer cells;
56
Q

Describe the role of antibodies in producing a positive result in an ELISA test. [4]

A
  1. (First) antibody binds/attaches /complementary (in shape) to antigen;
  2. (Second) antibody with enzyme attached is added;
  3. (Second) antibody attaches to antigen;
  4. (Substrate/solution added) and colour changes;
57
Q

Describe the features of Prophase

A

Nuclear membrane begins to breakdown;
Centrioles move to poles of the cell;
Chromatin supercoils and condense into chromosomes;
Chromosomes appear as 2 sister chromatids joined by a centromere;

58
Q

Describe the features of Metaphase

A

Spidle fibres form;
Spindle fibres attach;
To the centromere of (each) chromosomes;
Chromosomes align at the equator;

59
Q

Describe the features of Anaphase

A

Spindle fibres shorten;
Centromere splits;
Sister chromatids are separated;
Chromatids pulled to opposite poles of the cell;

60
Q

Describe the features of Telophase

A

Nuclear membrane begins to reform;
Chromosomes unwind;
(2 distinct nuclei within one cell)

61
Q

What is a homologous pair of chromosomes?

A

Two chromosomes that carry the same genes in the same loci / location

62
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]

A

Description; Explanation;
E.g, 1. Examine large number of fields of view / many cells;
2. To ensure representative sample;

OR
3. Repeat count;
4. To ensure figures are correct;

OR

  1. Method to deal with part cells shown at edge /count only whole cells;
  2. To standardise counting;
63
Q

Meiosis results in cells that have the haploid number of chromosomes and show genetic variation. Explain how. [5]

A
  1. Homologous chromosomes pair up; or form a Bivalent
  2. maternal and paternal chromosomes are arranged in any order;
  3. Independent segregation;
  4. Crossing over;
  5. (Equal) Portions of chromatids are swapped between chromosomes;
  6. Produces new combination of alleles;
  7. Chromatids separated at meiosis II/ later;
64
Q

Describe the process of crossing over and explain how it increases genetic diversity [4]

A
  1. Homologous pairs of chromosomes associate / form a bivalent;
  2. Chiasma(ta) form;
  3. (Equal) lengths of (non-sister) chromatids / alleles are exchanged;
  4. Producing new combinations of alleles;
65
Q

Give two differences between mitosis and meiosis. [2]

A

Mitosis given first
1. One division, two divisions in meiosis;
2. (Daughter) cells genetically identical, daughter cells genetically different in meiosis;
3. Two cells produced, (usually) four cells produced in meiosis;
4. Diploid to diploid/haploid to haploid, diploid to haploid in meiosis;
5. Separation of homologous chromosomes only in meiosis;
6. Crossing over only in meiosis;
7. Independent segregation only in meiosis;

66
Q

When, during meiosis, do cells become haploid?

A

Meiosis 1

67
Q

When, during meiosis, does crossing over and independent segregation occur?

A

Meiosis 1

68
Q

When, during meiosis, do homologues become separated?

A

Meiosis 1

69
Q

When, during meiosis, do chromatids become separated to opposite poles?

A

Meiosis 2

70
Q

Describe how the process of meiosis results in haploid cells. Do not include descriptions of how genetic variation is produced in meiosis. [5]

A
  1. DNA replication (during late interphase);
  2. Two divisions;
  3. Separation of homologous chromosomes (in first division);
  4. Separation of (sister) chromatids (in second division);
  5. Produces 4 (haploid) cells/nuclei;
71
Q

Describe binary fission in bacteria. [3]

A
  1. Replication of (circular) DNA;
  2. Replication of plasmids;
  3. Division of cytoplasm (to produce daughter cells);
72
Q

What is a tumour?

A
  1. Mass of cells/tissue OR Abnormal cells/tissue;
  2. Uncontrolled mitosis/cell division;
73
Q

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

Do not include details of how you would prepare the tissue observed with an optical microscope. [3]

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

OR

Select (fields of view) at random;

74
Q

Mitotic index formula

A

Number of cells with visible chromosomes (PMAT)(Divided by)
______________________________________________________
Total number of cells (Field of View)

75
Q

Pressing the coverslip downwards enabled the student to observe the stages of mitosis clearly.

Explain why.

A
  1. To create a single/thin layer of cells OR To spread out cells;
  2. So that light could pass through;
76
Q

Other students in the class followed the same method for the Root Tip Squash (RP2) practical, but calculated different mitotic indices.

Apart from student errors, suggest two explanations why.

A
  1. ( roots) are a different age OR grown in different conditions;

Accept suitable descriptions of conditions, eg in different temperatures

  1. (Root tips) from different plants/bulbs/species;
  2. Single field of view is not representative of a root tip

OR

(Other) students may have looked at more fields of view

OR

(Other) students may have calculated a mean;

  1. (Different fields of view are from) different parts of the root tip;

Reject different sized fields of view

Reject different number of cells (per field of view)

  1. Cells/roots undergo mitosis/cell division at different times/rates;
77
Q

Name the main polymer that forms the following cell walls.

Plant cell wall

Fungal cell wall

A

Plant cell wall = Cellulose

Fungal cell wall = Chitin

Pronounced KIY-TIN

78
Q

Determining the genome of the viruses could allow scientists to develop a vaccine.

Explain how. [2]

A
  1. (The scientists) could identify proteins (that derive from the genetic code) OR (The scientists) could identify the proteome;
  2. (They) could (then) identify potential antigens (to use in the vaccine);
79
Q

After a disease is diagnosed, monoclonal antibodies are used in some medical treatments.

Give one example of using monoclonal antibodies in a medical treatment.

A

Targets/binds/carries drug/medicine to specific cells/antigens/receptors

OR

Block antigens/receptors on cells;

80
Q

Describe and explain the role of antibodies in stimulating phagocytosis. [2]

A

1.   Bind to antigen OR Are markers;

Accept opsonin for ‘marker’

Accept form (antibody-antigen) complexes/are complementary to antigen

2.   (Antibodies) cause clumping/agglutination OR Attract phagocytes;

81
Q

What is an antigen? [2]

A
  1. Foreign protein; Accept glycoprotein / glycolipid / polysaccharide
  2. (that) stimulates an immune response / production of antibody;
82
Q

What is an antibody?

A
  1. A protein / immunoglobulin specific to an antigen;
  2. Produced by B cells OR Secreted by plasma cells;
83
Q

Give the two types of molecule from which a ribosome is made.

A

ribosomal RNA / ribosomal ribonucleic acid

and

ribosomal protein;

84
Q

The scientists measured the percentage change in tumour volume.

Suggest why they recorded both percentage change and tumour volume.

A

Percentage change: To allow comparison as tumours may differ in volume/size
**Tumour volume: ** (As) tumours may differ in length/width/shape OR
(As) volume is (best) indication of the number of cells in tumour;

85
Q

State 2 methods of delivering passive immunity

A
  • Antibodies from mother pass across the placenta to bind to specifically complementary antigens on pathogens that have also crossed the placenta
  • Through breast milk
  • Through plasma transfusion
  • Through ANTI-VENOM / ANTI-TOXIN injections
86
Q

Explain how a fetus is protected against a pathogen that infects its mother during pregnancy.

A
  • Antibodies have variable regions with specific tertiary structures
  • Complementary to antigens
  • Found on pathogen which has crossed the placenta
  • forms antigen-antibody complexes
87
Q

Explain why viruses are described as acellular and non-living. [2]

A
  1. no cell(-surface) membrane OR Not made of cells;
  2. (Non-living) have no metabolism/metabolic
    reactions;
    OR
    Cannot (independently) move / respire / replicate / excrete
    OR
    (Have) no nutrition;

MRSGREN

Left RSFC Year 13 2022-24 (10 decks)

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