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AS AQA Biology - Burnley College (2023-24) > Cells 3.2 > Flashcards

Cells 3.2 Flashcards

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1
Q

Structure of eukaryotic cells (AO1)

What is a eukaryotic cell?

A

A cell with a nucleus AND membrane-bound organelles.

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2
Q

Structure of eukaryotic cells (AO1)

Describe the structure of the nucleus (2 marks).

A

1. Nuclear envelope and pores

OR double membrane and pores;

2. Chromosomes/chromatin

OR DNA wrapped around histones;

3. Nucleolus/nucleoli

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3
Q

Structure of eukaryotic cells (AO1)

Describe the function of the nucleus (2 marks).

A

1. Stores genetic information/material for polypeptides (production)

OR codes for proteins

OR codes for primary structure of polypeptides;

2. Site of (Semi-conservative) DNA replication;

3. Production of mRNA/tRNA

OR site of Transcription;

4. Production of rRNA/ribosomes;

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4
Q

Structure of eukaryotic cells (AO1)

Eukaryotic cells contain linear DNA which is bound to which protein?

A

Histones

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5
Q

Structure of eukaryotic cells (AO1)

Draw out and label the structure of a mitochondrion

A
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6
Q

Structure of eukaryotic cells (AO1)

Mitochondrial DNA is linear OR circular?

A

Circular

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7
Q

Structure of eukaryotic cells (AO1)

What size are mitochondrial ribosomes?

A

70S

This is smaller than cytoplasmic ribosomes which are 80S

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8
Q

Structure of eukaryotic cells (AO1)

What process takes place in the mitochondria

A

Aerobic respiration

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9
Q

Structure of eukaryotic cells (AO1)

What are the products of aerobic respiration?

A

Carbon dioxide, water AND ATP

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10
Q

Structure of eukaryotic cells (AO1)

The cristae provide a large _________ _________ so more ATP synthase can be embedded into the inner mitochondrial membrane.

A

surface area

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11
Q

Structure of eukaryotic cells (AO1)

Which organelle can be found on the outer surface membrane of the rough endoplasmic reticulum?

A

Ribosome

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12
Q

Structure of eukaryotic cells (AO1)

What is the function of the rough endoplasmic reticulum?

A

Provide a large surface area for the synthesis of proteins via ribosomes on their surface.

Packages proteins into vesicles to be transported to the Golgi apparatus

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13
Q

Structure of eukaryotic cells (AO1)

Why is the smooth endoplasmic reticulum ‘smooth’?

A

No ribosomes on its surface

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14
Q

Structure of eukaryotic cells (AO1)

What is the function of the smooth endoplasmic reticulum?

A
  1. Synthesise lipids and packages them into vesicles.
  2. Synthesise carbohydrates and packages them into vesicles.
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15
Q

Structure of eukaryotic cells (AO2)

A

1. Less phospholipids in rough
OR
More protein/glycoprotein in rough
OR
Presence of ribosomes in rough;

2. (More protein/glycoprotein/ribosomes)
Rough – production/transport of proteins;

3. (More phospholipid)
Smooth –production / modification / packaging / transport of lipids

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16
Q

Structure of eukaryotic cells (AO1)

What is the function of the Golgi apparatus?

A

1. Sorts, modifies and packages proteins into vesicles.

E.g. adds a carbohydrate to a protein to form a glycoprotein.

E.g. forms chylomicrons

2. Forms lysosomes

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17
Q

Structure of eukaryotic cells (AO1)

What is the name of enzyme contained by lysosomes?

A

Hydrolytic enzymes
(aka lysozymes)

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18
Q

Structure of eukaryotic cells (AO1)

Describe how lysosomes destroy pathogens or damaged organelles (2 marks).

A
  1. Lysosomes fuse with vesicle
  2. Release its hydrolytic enzymes
  3. Which breakdown pathogens AND/OR damaged and worn out organelles
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19
Q

Structure of eukaryotic cells (AO1)

What is the function of ribosomes?

A

Synthesise proteins

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20
Q

Structure of eukaryotic cells (AO1)

Ribosomes are made up of……..

A

ribsomal RNA (rRNA)

Protein sub-units

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21
Q

Structure of eukaryotic cells (AO1)

What size are cytoplasmic ribosomes?

A

80S

This is also the size of ribosomes on the rough ER

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22
Q

Structure of eukaryotic cells (AO1)

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 synthesis protein;
  3. Mitochondria produce ATP (for protein synthesis);
  4. Golgi apparatus modifies and packages protein;
  5. Vesicles transport protein

OR

  1. (Vesicles) fuse with cell(-surface) membrane;

Accept exocytosis at cell membrane

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23
Q

Structure of eukaryotic cells (AO1)

What is the name of the process when a vesicle fuses with the cell surface membrane to release its content?

A

Exocytosis

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24
Q

Structure of eukaryotic cells (AO1)

TRUE or FALSE

The nucleus can contain more than one nucleoli?

A

TRUE

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25
Q

Structure of eukaryotic cells (AO1)

DNA in the eukaryotic nucleus is linear OR circular?

A

Linear

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26
Q

Structure of eukaryotic cells (AO1)

The cell-surface membrane consists of a _________________.

A

Phospholipid bilayer

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27
Q

Structure of eukaryotic cells (AO1)

Name the main polymer that forms the cell wall in plants.

A

Cellulose

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28
Q

Structure of eukaryotic cells (AO1)

Name the main polymer that forms the cell wall in fungi.

A

Chitin

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29
Q

Structure of eukaryotic cells (AO1)

Draw out and label the structure of a chloroplast.

A

Chloroplasts also contain circular DNA, 70S ribosomes & starch grains.

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30
Q

Structure of eukaryotic cells (AO1)

The thylakoid membranes provide a large surface area for more ______________.

A

chlorophyll

this allows MORE light energy to be absorbed during photosynthesis

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31
Q

Structure of eukaryotic cells (AO1)

The synthesis of glucose as a result of photosynthesis takes place in which part of the chloroplast?

A

Stroma

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32
Q

Structure of eukaryotic cells (AO1)

Name the main polymer that forms the cell wall in algae.

A

Cellulose

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33
Q

Structure of eukaryotic cells (AO1)

Algae are unicellular eukaryotic organisms that can ________________ .

A

Photosynthesise

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34
Q

Structure of eukaryotic cells (AO1)

What is the function of the large permanent vacuole in plant cells?

A
  1. Provide support, making cells turgid.
  2. Store of sugars and amino acids
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35
Q

Structure of eukaryotic cells (AO2)

U. marinum cells ingest bacteria and digest them in the cytoplasm.

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

A

1. Lysosomes;

2. Fuse with vesicle;

3. (Releases) hydrolytic enzymes;

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36
Q

Structure of eukaryotic cells (AO2)

Give one feature of the chloroplast that allows protein to be synthesised inside the chloroplast and describe one difference between this feature in the chloroplast and similar features in the rest of the cell.

A

Mark in pairs, 1 and 2 OR 3 and 4

  1. DNA;
  2. Is not associated with protein/histones but nuclear DNA is

OR is circular but nuclear DNA is linear

OR is shorter than nuclear DNA;

  1. Ribosomes;
  2. Are smaller (70S) than cytoplasmic ribosomes;
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37
Q

Structure of eukaryotic cells (AO1)

Outline the similarities in the structures of chloroplasts and mitochondria.

A

1. Both double membrane;
2. Both contain (circular) DNA;
3. Both contain ribosomes;

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38
Q

Structure of eukaryotic cells (AO1)

Outline the differences in the structures of chloroplasts and mitochondria.

A

4. Chloroplasts have thylakoids/grana whereas mitochondria have cristae;
5. Chloroplasts stroma whereas mitochondria matrix;
6. Chloroplasts pigments (chlorophyll) whereas no pigments in mitochondria;
7. Chloroplasts have starch grains whereas mitochondria have no starch grains;

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39
Q

Structure of eukaryotic cells (AO1)

A

D - Granum/grana/thylakoid(s);

E - starch / lipid;

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40
Q

Structure of eukaryotic cells (AO1)

A

B;

A;

E;

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41
Q

Structure of eukaryotic cells (AO2)

Human breast milk is produced and secreted by gland cells. These gland cells have adaptations that include many mitochondria and many Golgi vesicles. The milk contains a high concentration of protein.

Explain the role of these cell adaptations in the production and secretion of breast milk (2 marks).

A
  1. (Many mitochondria) release energy / ATP for movement of vesicles / synthesis of protein / active transport;
  2. (Many Golgi) vesicles transport protein / glycoprotein / milk to cell membrane / out of cell;
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42
Q

Structure of eukaryotic cells (AO1)

A
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43
Q

Structure of eukaryotic cells (AO1)

A

B Golgi (body / apparatus);

C Mitochondria / mitochondrion;

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44
Q

Structure of eukaryotic cells (AO1)

Name two structures present in plant cells that are not present in animal cells.

A
  1. Chloroplasts
  2. Cell wall
  3. Cell vacuole
  4. Starch grains
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45
Q

Structure of eukaryotic cells (AO1)

A

A stroma

B granum

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46
Q

Structure of eukaryotic cells (AO1)

A

W – chloroplast, photosynthesis;

Z – nucleus, contains DNA / chromosomes / holds genetic information of cell.

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47
Q

Structure of eukaryotic cells (AO1)

Identify X

A

Crista/cristae

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48
Q

Structure of eukaryotic cells (AO1)

A

L

H

N

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49
Q

Structure of eukaryotic cells (AO2)

A

Membrane-bound organelle(s)

OR Mitochondrion/mitochondria

OR Vesicle(s)/lysosomes

OR Rough endoplasmic reticulum

OR Nucleus/(double) nuclear membrane/pore(s)/ nuclear envelope;

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50
Q

Structure of eukaryotic cells (AO1)

Define a tissue

A

Similar specialised cells that perform a specific function

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51
Q

Structure of eukaryotic cells (AO1)

Define an organ

A

Different tissues that work together to perform a specific / vital function

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52
Q

Structure of eukaryotic cells (AO1)

Define an organ system

A

Different organs that work together to perform a specific / vital function

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53
Q

Structure of eukaryotic cells (AO1)

In complex multicellular organisms, eukaryotic cells become _____________ for specific functions.

A

specialised

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54
Q

Structure of prokaryotic cells and of viruses (AO1)

Prokaryotic cells are smaller OR larger than eurkaryotic cells

A

Smaller

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55
Q

Structure of prokaryotic cells and of viruses (AO1)

Define a prokarytic cell

A

Cells that DO NOT contain a nucleus or membrane-bound organelles

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56
Q

Structure of prokaryotic cells and of viruses (AO1)

Describe the structure of DNA in prokaryotic cells

A

no nucleus;

single circular DNA molecule that is free in the cytoplasm;

not associated with proteins/histones;

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57
Q

Structure of prokaryotic cells and of viruses (AO1)

By what process do prokarytic cells replicate their DNA

A

Semi-conservative replication

Meselson & Stahl used E.coli (a bacteria) for their experiments

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58
Q

Structure of prokaryotic cells and of viruses (AO1)

What is the name of the glycoprotein that makes up the prokaryote cell wall?

A

Murein

(aka peptidoglycan)

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59
Q

Structure of prokaryotic cells and of viruses (AO1)

What size are prokaryotic ribosomes?

A

70S

This is smaller than cytoplasmic ribosomes in a eukarytic cell

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60
Q

Structure of prokaryotic cells and of viruses (AO1)

What is the extra source of DNA called in a prokaryote

A

Plasmid(s)

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61
Q

Structure of prokaryotic cells and of viruses (AO1)

What genes are typically found in plasmids

A

Genes that benefit prokaryote survival
e.g., antibiotic resistance

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62
Q

Structure of prokaryotic cells and of viruses (AO1)

TRUE or FALSE

Prokaryotes can have more than one plasmid

A

TRUE

Prokaryotes have a variable number of plasmids

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63
Q

Structure of prokaryotic cells and of viruses (AO1)

What structure often surrounds the prokaryotic cell?

A

Capsule

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64
Q

Structure of prokaryotic cells and of viruses (AO1)

Give two structures found in all prokaryotic cells and in all eukaryotic cells.

A
  1. Cell(-surface) membrane;
  2. Ribosomes;
  3. Cytoplasm;
  4. DNA;
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65
Q

Structure of prokaryotic cells and of viruses (AO1)

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

A
  1. Circular DNA (molecule in cytoplasm);
  2. Murein cell wall

OR Peptidoglycan cell wall

  1. Smaller/70S ribosomes in cytoplasm;
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66
Q

Structure of prokaryotic cells and of viruses (AO1)

Name two features of HIV particles that are not found in bacteria.

A
  1. Capsid;
  2. Reverse transcriptase;
  3. RNA genome;

Accept ‘genetic material’ OR ‘genes’ for ‘genome’

  1. Envelope;
  2. Attachment proteins
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67
Q

Structure of prokaryotic cells and of viruses (AO1)

TRUE or FALSE:

All prokaryotic cells have one or more flagella.

A

FALSE

Some prokaryotes have NO flagella

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68
Q

Structure of prokaryotic cells and of viruses (AO1)

All prokaryotic cells have ___________ ribosomes than eukaryotic cells.

A

smaller

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69
Q

Structure of prokaryotic cells and of viruses (AO1)

A

Flagellum

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70
Q

Structure of prokaryotic cells and of viruses (AO1)

Name an organelle found in both a chloroplast and a prokaryotic cell.

A

(70S) Ribosome

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71
Q

Structure of prokaryotic cells and of viruses (AO1)

A
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72
Q

Structure of prokaryotic cells and of viruses (AO1)

A

Second box ticked

B – statements 1, 2 and 4

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73
Q

Structure of prokaryotic cells and of viruses (AO1)

A

W – (cell surface) membrane

X – cell wall

Y – capsule

Z – flagellum

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74
Q

Structure of prokaryotic cells and of viruses (AO1)

Viruses are ________ and non-living.

A

acellular

This means they need a host cell to surivive and reproduce

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75
Q

Structure of prokaryotic cells and of viruses (AO1)

TRUE or FALSE
Prokaryotes can have one or more flagella.

A

TRUE

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76
Q

Structure of prokaryotic cells and of viruses (AO1)

Draw out and label the key structures of a virus

A

Structures in red, funtion in black

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77
Q

Structure of prokaryotic cells and of viruses (AO1)

What is the function of the capsid in a virus?

A

Protects the viral genome (DNA or RNA)

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78
Q

Structure of prokaryotic cells and of viruses (AO1)

What is the function of the viral genome (DNA or RNA)?

A

Codes for (viral) protein

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79
Q

Structure of prokaryotic cells and of viruses (AO1)

RNA viruses (e.g. HIV) contain an enzyme that converts viral RNA into (c)DNA - what is the name of this enzyme?

A

Reverse transcriptase

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80
Q

Structure of prokaryotic cells and of viruses (AO1)

What is the function of viral attachment proteins?

A

Binds to receptors (on cell);

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81
Q

Structure of prokaryotic cells and of viruses (AO1)

TRUE or FALSE

Some viruses contain RNA as their genetic material

A

TRUE

These are called RNA viruses or retroviruses e.g. HIV

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82
Q

Structure of prokaryotic cells and of viruses (AO1)

A

Capsid and attachment protein

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83
Q

Methods of studying cells (AO1)

What are the principles of light (aka optical) microscopy?

A

A thin specimen is illuminated with light;

This light is focussed using a glass lens;

Magnified and view using the eye piece and objective lenses;

Specimens can be alive or dead;

Cellular structures like the nucleus can be stained with dyes to make them visible;

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84
Q

Methods of studying cells (AO1)

Explain why it is not possible to identify smaller organelles like mitochondria using an optical microscope (2 marks).

A
  1. Wavelength of light is (too) long;
  2. So has a lower resolution
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85
Q

Methods of studying cells (AO1)

A

A section/slice (so nucleus in another part of cell)

OR

(Nucleus) not stained;

A cell is 3D so slicing across the top or bottom may miss the nucleus

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86
Q

Methods of studying cells (AO1)

Identify organelles S and T

A

S = Vacuole

T = Chloroplast;

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87
Q

Methods of studying cells (AO1)

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

A

Higher resolution

OR

View internal structures;

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88
Q

Methods of studying cells (AO1)

A biologist separated cell components to investigate organelle activity. She prepared a suspension of the organelles in a solution that prevented damage to the organelles.

Describe three properties of this solution and explain how each property prevented damage to the organelles (3 marks).

A

1.   (Ice) cold to prevent/reduce enzyme activity;

2.   Buffered to prevent denaturing of enzyme/protein;

3.   Same water potential/ Ψ to prevent lysis/bursting (of organelle);

Accept: isotonic for same water potential.

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89
Q

Methods of studying cells (AO2)

Scientists investigated the role of a protein called CENP-W in mitosis. Their method involved cell fractionation and ultracentrifugation.

(a) The scientists began by lysing (breaking open) cells and organelles using a detergent that dissolves lipids in water.

Suggest how the detergent releases CENP-W from cells (2 marks).

A
  1. Cell surface membranes made from phospholipid bilyar;
  2. (Detergent) dissolves membranes / phospholipid (bilayer);
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90
Q

Methods of studying cells (AO2)

Explain how ultracentrifugation separates a protein involved in mitosis CENP-W from other molecules.

A
  1. Spin (liquid / supernatant) at (very) high speed;
  2. Molecules / CENP-W separates depending on (molecular) mass / size / density;

Densest molecules/organelles found at bottom of tube.

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91
Q

Methods of studying cells (AO1)

Contrast how an optical microscope and a transmission electron microscope work (3 marks).

A
  1. TEM use electrons whereas optical use light;
  2. TEM focuses using magnets whereas optical uses (glass) lenses;
  3. TEM allows a greater resolution;
  4. (So with TEM) smaller organelles / named cell structure (e.g. mitochondria) can be observed
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92
Q

Methods of studying cells (AO1)

Contrast the limitations of an optical microscope and a transmission electron microscope when studying cells (3 marks).

A
  1. TEM view only dead / dehydrated specimens whereas optical (can) view live specimens;
  2. TEM does not show colour whereas optical can;
  3. TEM requires thinner specimens;
  4. TEM requires a more complex/time consuming preparation;
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93
Q

Methods of studying cells (AO1)

During cell fraction explain why biologists use a blender and then filtered the mixture (2 marks).

A
  1. Break open cells / homogenise;
  2. Remove unbroken cells / larger debris;
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94
Q

Methods of studying cells (AO1)

Name the organelle that made up most of the first pellet after centrifuging at a lowest speed.

A

Nucleus / nuclei;

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95
Q

Methods of studying cells (AO1)

Describe how a sample of chloroplasts could be isolated from leaves (4 marks).

A
  1. Break open cells/tissue and filter

Accept homogenise and filter

  1. In cold, isotonic, buffered solution;
  2. Centrifuge/spin and remove nuclei/cell debris;
  3. (Centrifuge/spin) at high(er) speed, chloroplasts settle out;
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96
Q

Methods of studying cells (AO1)

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 (3 marks).

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

Allow any appropriate method that avoids trapping air bubbles

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97
Q

Methods of studying cells (AO1)

A student investigated the distribution of stomata on leaves from two species of plant. She removed small pieces from the lower surface of the leaves of each plant species. She mounted these pieces on separate microscope slides. She then counted the number of stomata in several parts of the epidermis on each piece of leaf tissue using an optical microscope.

The pieces of leaf tissue examined were very thin.

Explain why this was important.

A
  1. Single layer(s) of cells;
  2. So light can pass through;
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98
Q

Methods of studying cells (AO1)

A student investigated the distribution of stomata on leaves from two species of plant. She removed small pieces from the lower surface of the leaves of each plant species. She mounted these pieces on separate microscope slides. She then counted the number of stomata in several parts of the epidermis on each piece of leaf tissue using an optical microscope.

Give two reasons why it was important that the student counted the number of stomata in several parts of each piece of leaf tissue.

A
  1. Distribution may not be uniform

OR so it is a representative sample;

  1. To obtain a (reliable) mean;
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99
Q

Methods of studying cells (AO1)

Describe and explain how cell fractionation and ultracentrifugation can be used to isolate mitochondria from a suspension of animal cells (5 marks).

A
  1. Cell homogenisation to break open cells;
  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 by enzymes / use buffer to prevent protein / enzyme denaturation;
  5. Centrifuge at lower speed to separate nuclei / cell fragments / heavy organelles;
  6. Re-spin (supernatant / after nuclei / pellet removed) at higher speed to get mitochondria in pellet / at bottom.
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100
Q

Methods of studying cells (AO1)

Describe the principles of using a transmission electron microscope to investigate cell structure
(3 marks).

A
  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;
101
Q

Methods of studying cells (AO1)

Describe the limitations of using a transmission electron microscope to investigate cell structure (3 marks).

A
  1. Cannot look at living material / Must be in a vacuum;
  2. Specimen must be (very) thin;
  3. Artefacts present;
  4. Complex staining method / complex / long preparation time;
  5. Image not in 3D / only 2D images produced.
102
Q

Methods of studying cells (AO1)

The scientists used a transmission electron microscope to study the structure of the amoeba. Explain why (2 marks).

A
  1. Shorter wavelength of electrons;
  2. So higher resolution;
  3. To see internal structures / organelles / named organelles (e.g. chloroplasts);
103
Q

Methods of studying cells (AO1)

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

A

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

104
Q

Methods of studying cells (AO1)

Describe how the student could use an eyepiece graticule to determine the mean diameter of stomata (3 marks).

A
  1. Calibrate eyepiece graticule against stage micrometer;
  2. Measure (each stoma) using eyepiece graticule;
  3. Take a number of measurements
    (to calculate a mean);
105
Q

Methods of studying cells (AO1)

Define resolution

A

The ability to distinguish between objects that are close together.

106
Q

Methods of studying cells (AO1)

Define magnification

A

The ability to make an object bigger (when using an optical or electron microscope)

107
Q

Methods of studying cells (AO1)

Describe the principles of using a scanning electron microscope to investigate cell structure (3 marks).

A
  1. Specimens are NOT sliced
  2. The electrons bounce off the SURFACE of the specimen.
  3. This produces a 3D image / shows the surface of a cell
108
Q

Methods of studying cells (AO2)

A

1. Nucleus;

2. Nucleolus/nucleoli

OR Nuclear membrane/envelope;

3. Mitochondria/chloroplast contain DNA;

109
Q

Structure of prokaryotic cells and of viruses (AO1)

Explain why viruses are described as acellular and non-living (2 marks).

A

*Mark point 1 (Acellular) *
no cell(-surface) membrane;

OR

Not made of cells;

Mark point 2 (Non-living)
Cannot (independently) move/respire/replicate/
excrete

OR

have no metabolism/metabolic
reactions;

OR
(Have) no nutrition;

110
Q

All cells arise from other cells (AO1)

TRUE or FALSE

Within multicellular organisms, all cells retain the ability to divide.

A

FALSE

Stem cells are the main cell type that can divide.

111
Q

All cells arise from other cells (AO1)

Eukaryotic cells that retain the ability to divide show a cell ______________.

A

cycle

112
Q

All cells arise from other cells (AO1)

DNA replication takes place during interphase OR mitosis in the cell cyle?

A

Interphase

During s-phase which stands for semi-conservative replication

113
Q

All cells arise from other cells (AO1)

Draw out and label the cell cycle

A
114
Q

All cells arise from other cells (AO1)

Fill in the missing words:

[1] is the part of the cell cycle in which a eukaryotic cell divides to produce two daughter cells, each with [2] copies of DNA produced by the parent cell during DNA replication.

A

[1] Mitosis
[2] identical

115
Q

All cells arise from other cells (AO1)

List the stages of mitosis in the correct sequence.

A

Prophase
Metaphase
Anaphase
Telophase

116
Q

All cells arise from other cells (AO1)

What is the name for the process where division of the cytoplasm occurs, producing two new cells.

A

cytokinesis

117
Q

All cells arise from other cells (AO1)

Explain why mitosis is important
(3 marks)

A
  • Growth of multicellular organisms
  • Replacement of cells and repair of tissues
  • Asexual reproduction
118
Q

All cells arise from other cells (AO1)

A

A, D, C, E, B

119
Q

All cells arise from other cells (AO1)

A

Prophase = C
Metaphase = A
Anaphase = D
Telophase = B

120
Q

All cells arise from other cells (AO1)

What are homologous chromosomes?

A

A pair of chromosomes which contain the same genes (but with different alleles)

This is what makes cells diploid (2n)

121
Q

All cells arise from other cells (AO1)

Draw out and label a pair of homologous chromosomes after semi-conservative replication.

A
122
Q

All cells arise from other cells (AO1)

What holds sister chromatids together after DNA replication

A

The centromere

123
Q

All cells arise from other cells (AO1)

Describe the structure of a chromosome

A

1. DNA is associated with histones;

2. (During mitosis/when visible) chromosome
consists of two (sister) chromatids joined at a
centromere;

124
Q

All cells arise from other cells (AO1)

Describe the appearance and behaviour of chromosomes during prophase

A

Chromosomes condense / coil / shorten / thicken / become visible;

(Chromosomes) appear as (two sister) chromatids joined at the centromere;

125
Q

All cells arise from other cells (AO1)

Describe the appearance and behaviour of chromosomes during metaphase

A

Chromosomes line up on the equator / centre of the cell;

(Chromosomes) attached to spindle fibres;

By their centromere;

126
Q

All cells arise from other cells (AO1)

Describe the appearance and behaviour of chromosomes during anaphase

A

The centromere splits / divides;

(Sister) chromatids / chromosomes are pulled to opposite poles / ends of the cell;

127
Q

All cells arise from other cells (AO1)

Describe the appearance and behaviour of chromosomes during telophase

A

Chromatids / chromosomes uncoil / unwind / become longer / thinner.

128
Q

All cells arise from other cells (AO1)

Describe what happens to the chromosomes in anaphase (2 marks)

A

Spindle fibres shorten and centromere splits;

Sister chromatids separate;

Sister chromatids pulled to opposite poles of the cell (by spindle fibres);

129
Q

All cells arise from other cells (AO1)

What is the name of the organelle that produces the spindle fibres?

A

centriole

There are two that move to opposite poles during prophase

130
Q

All cells arise from other cells (AO1)

A
  1. Chromosomes (are) becoming visible/distinct;
  2. Because (still) condensing;

Accept shorten or thicken for ‘condensed’

  1. Chromosomes (arranged) at random/not lined up;
  2. Because no spindle (activity);

OR

Because not attached to spindle fibres;

131
Q

All cells arise from other cells (AO1)

A

A

132
Q

All cells arise from other cells (Maths)

A

1.286

Rate is always DY / DX (time) (read off graph)

DY = 19 - 4 = 15 um
DX = 2500-1800 = 700 secs
min-1 (per minute), 700 / 60 = 11.67 mins

15 um / 11.67 mins = 1.286 um min-1

133
Q

All cells arise from other cells (AO1)

A
  1. The (individual) chromosomes are visible because they have condensed;

Accept ‘tightly coiled’ or ‘short and thick’ for condensed but do not accept ‘contracted’.

  1. (Each) chromosome is made up of two chromatids because DNA has replicated;

Accept ‘sister chromatids’ for ‘two chromatids’.

  1. The chromosomes are not arranged in homologous pairs, which they would be if it was meiosis;
134
Q

All cells arise from other cells (AO1)

A

(D)CBEA.

135
Q

All cells arise from other cells (AO1)

What leads to the formation of tumours / cancers.

A

Uncontrolled cell division / mitosis / cell cycle

136
Q

All cells arise from other cells (AO1)

What is a tumour?

A
  1. Mass of cells/tissue

OR Abnormal cells/tissue;

  1. (As a result of) uncontrolled mitosis/cell division;
137
Q

All cells arise from other cells (AO1)

Many _____________ treatments are directed at controlling the rate of cell division.

A

cancer

138
Q

All cells arise from other cells (AO2)

A

1. 2 nuclei (in cells)

OR Cells (stopped) at telophase;

2. Cytokinesis prevented

OR Stopped cytoplasm dividing;

139
Q

All cells arise from other cells (AO1)

A
140
Q

All cells arise from other cells (AO1)

What is the name of the process by which prokaryotes divide?

A

Binary fission

141
Q

All cells arise from other cells (AO1)

Describe binary fission

A
  1. Replication of (circular) DNA;
  2. Replication of plasmids;
  3. Division of cytoplasm (to produce daughter cells);
142
Q

All cells arise from other cells (AO2)

A

Describe
1. (Trend of) slowing growth from before birth to 21 days

OR (Trend of) decreasing percentage undergoing mitosis from before birth to 21 days

OR (Trend of) decreasing percentage undergoing DNA replication from before birth to 21 days;

Explain
2. DNA replication happens before mitosis

OR Heart growth slowing until (fully) developed

OR These cells lost the ability to divide;

143
Q

All cells arise from other cells (AO2)

A
  1. No separation of chromatids/chromosomes/centromeres;

Accept anaphase prevented

  1. Chromatids/chromosomes all go to one pole/end/sides of cell/not pulled to opposite poles;
  2. Doubles chromosome number in cell OR one daughter cell gets no chromosomes or chromatids;
144
Q

All cells arise from other cells (AO1)

A

Centromere

145
Q

Transport across cell membranes (AO1)

Explain the arrangement of phospholipids in a cell-surface membrane (3 marks).

A

1. As a bilayer

2. Phospholipid both hydrophobic and hydrophilic OR Phospholipid polar

3. Triglycerides only hydrophobic
OR Fatty acid/triglyceride is non-polar;

4. Hydrophilic/phosphate group attracts water (to either side of bilayer)

OR Hydrophobic (fatty acid) tails point away/are repelled from water

146
Q

Transport across cell membranes (AO1)

Explain why the structure of a membrane is described as fluid-mosaic (2 marks).

A

Idea of molecules / named molecules moving (= Fluid);

Idea of both proteins and phospholipids (= Mosaic);

147
Q

Transport across cell membranes (AO1)

Draw out and label a diagram of the phospholipid bilayer (include different biological molecules)

A
148
Q

Transport across cell membranes (AO1)

What properties must a molecule possess to cross the cell surface membrane by simple diffusion

A

Lipid-soluble

AND/OR

Non-polar

e.g. hormones, oxygen & carbon dioxide

149
Q

Transport across cell membranes (AO1)

Explain why phospholipids can form a bilayer but triglycerides cannot (3 marks).

A

1. Phospholipid both hydrophobic and hydrophilic
OR
Phospholipid polar
OR
Phosphate group is charged;

2. Triglycerides only hydrophobic
OR Fatty acid/triglyceride is non-polar;

3. Hydrophilic/phosphate group attracts water (to either side of bilayer)

150
Q

Transport across cell membranes (AO1)

What transport process do channel proteins allow?

A

Facilitated diffusion

151
Q

Transport across cell membranes (AO1)

Receptors are embebbed into the cell surface membrane and have a specific and ___________ shape to only one molecule that binds.

A

complementary

152
Q

Transport across cell membranes (AO1)

Cholesterol role

A

Restricts the movement of other molecules making up the cell surface membrane;

153
Q

Transport across cell membranes (AO1)

A

Q

P

S

154
Q

Transport across cell membranes (AO2)

A

(Similarity)
Both have a phospholipid bilayer OR
Both have protein;

(Differences)
No channel/carrier proteins, whereas fluid mosaic does
OR
Protein layer outside (phospholipids), fluid mosaic is ‘dotted’;
Accept only one type of protein whereas fluid mosaic has many (types)
Cholesterol is not present whereas it is present in fluid mosaic;

155
Q

Transport across cell membranes (AO1)

Channel proteins have a specific __________ structure

A

tertiary

156
Q

Transport across cell membranes (AO1)

______________ have a specific tertiary structure and allow the transport of larger polar molecules (e.g. glucose) by facilitated diffusion and active transport.

A

Carrier proteins

157
Q

Transport across cell membranes (AO1)

TRUE or FALSE

Receptors have active sites

A

FALSE

Receptors have binding sites whereas only enzymes have active sites

158
Q

Transport across cell membranes (AO1)

Diffusion is a ____________ process – it does not require energy from ATP hydrolysis.

A

passive

159
Q

Transport across cell membranes (AO1)

Non-polar, lipid-soluble molecules like oxygen, carbon dioxide and hormones (e.g. oestrogen) can diffuse __________ a concentration gradient and cross the phospholipid bilayer.

A

DOWN

160
Q

Transport across cell membranes (AO1)

Explain how increasing temperature affects the rate of diffusion.

A

Increase kinetic energy therefore faster movement of molecules.

This leads to a faster rate of diffusion.

161
Q

Transport across cell membranes (AO1)

Explain how increasing surface area affects the rate of diffusion.

A

More cell surface membrane for molecules to pass through;

Therefore a faster rate of diffusion.

162
Q

Transport across cell membranes (AO1)

As a concentration gradient decreases, the rate of diffusion becomes ___________.

A

slower

163
Q

Transport across cell membranes (AO1)

The shorter the diffusion distance, the _______ the rate of diffusion.

A

faster

164
Q

Transport across cell membranes (AO1)

Facilitated diffusion is a passive process, it does not require ________.

A

ATP

165
Q

Transport across cell membranes (AO1)

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;
166
Q

Transport across cell membranes (AO1)

Pure water has the highest water potential and a value of _____ kpa.

A

0

(Zero)

167
Q

Transport across cell membranes (AO1)

Adding a solute (e.g. sucrose) makes the water potential of a solution _________.

A

negative

168
Q

Transport across cell membranes (AO1)

What is the name of the channel proteins required for the movement of polar water molecules by osmosis?

A

aquaporins

169
Q

Transport across cell membranes (AO1)

During osmosis, water moves from a [1] water potential to a [2] water potential, [3] a water potential gradient.

A

[1] high

[2] low

[3] down

170
Q

Transport across cell membranes (AO1)

Give two similarities in the movement of substances by diffusion and by osmosis.

A
  1. (Movement) down a gradient
  2. Passive processes;

OR Do not use energy from respiration / from ATP;

171
Q

Transport across cell membranes (AO2)

A

Concentration of sodium ions (outside cell);

As concentration increases so does the rate of (facilitated) diffusion;

172
Q

Transport across cell membranes (AO2)

A
  1. Between A and B - Movement through carrier proteins (accept channel proteins);

OR Facilitated diffusion;

  1. Between A and B - rate of uptake proportional to (external) concentration;
  2. Between C and D - all channel / carrier proteins in use / saturated / limiting;
173
Q

Transport across cell membranes (AO2)

A
  1. Rate of uptake is proportional / does not level off (so diffusion occurring);

Accept as one increases the other increases

  1. (Lipid-soluble molecules) diffuse through / are soluble in phospholipid (bilayer);
174
Q

Transport across cell membranes (AO1)

Active transport only involves [1] proteins.

It involves moving molecules [2] the concentration gradient from low to high.

This requires energy from [3].

A

[1] carrier

[2] AGAINST

[3] ATP hydrolysis

175
Q

Transport across cell membranes (AO2)

Sodium ions from salt (sodium chloride) are absorbed by cells lining the gut. Some of these cells have membranes with a carrier protein called NHE3.

NHE3 actively transports one sodium ion into the cell in exchange for one proton (hydrogen ion) out of the cell.

Use your knowledge of transport across cell membranes to suggest how NHE3 does this.

A
  1. Sodium ion and proton bind to the protein;
  2. Co-transport;
  3. Protein changes shape (to move sodium ion and / or proton across the membrane);
  4. Uses (hydrolysis of) ATP;
176
Q

Transport across cell membranes (AO1)

Cells involved in active transport contain higher numbers of which organelle. Explain why.

A

Mitochondria;

To produce ATP;

Energy from ATP hydrolysis;
(used to change shape of carrier protein)

move molecules against concentration gradient;

177
Q

Cell recognition and the immune system (AO1)

Each type of cell has specific molecules on its surface that identify it. These molecules include proteins and enable the immune system to identify:

A

pathogens;

cells from other organisms of the same species;

abnormal body cells;

toxins;

178
Q

Cell recognition and the immune system (AO1)

Define antigen

A

A foreign molecule / protein;

stimulates an immune response;

results in the production of a specific antibody;

179
Q

Cell recognition and the immune system (AO1)

Which organelle do phagocytes contain many of?

A

Lysosomes

180
Q

Cell recognition and the immune system (AO1)

Describe how a phagocyte destroys a pathogen present in the blood (3 marks).

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

Accept lysozymes for ‘enzymes’

181
Q

Cell recognition and the immune system (AO1)

Which cells stimulate an immune response.

A
  1. Pathogens e.g. bacteria / fungi
  2. Cells from organisms/transplants of the same species;
  3. Abnormal/cancer/tumour (cells);
  4. (Cells) infected by virus;
  5. Antigen-presenting cells
182
Q

Cell recognition and the immune system (AO1)

Describe how phagocytosis of a virus leads to presentation of its antigens (3 marks).

A
  1. Phagosome / vesicle fuses with lysosome;
  2. (Virus) destroyed by lysozymes / hydrolytic enzymes;
  3. Antigens (from virus) are displayed on the cell surface membrane;
183
Q

Cell recognition and the immune system (AO1)

Which immune cells contain receptors which bind to antigens on antigen-presenting cells during the cellular response?

A

T helper cells

184
Q

Cell recognition and the immune system (AO1)

What are the roles of a T helper cell?

A

1) Stimulates B cells to divide by mitosis

2) Stimulates phagocytes

3) Stimulates cytotoxic T cells

185
Q

Cell recognition and the immune system (AO1)

Upon stimulation, what chemicals do T helper cells release?

A

Cytokines

186
Q

Cell recognition and the immune system (AO1)

Which part of the T helper cell is specific and complementary to the shape of the antigen?

A

Receptor

187
Q

Cell recognition and the immune system (AO1)

Cytotoxic T cells destroy which cells?

A

Virally-infected cells;

Cancerous cells;

188
Q

Cell recognition and the immune system (AO1)

What is the name of the chemical contained by cytotoxic T cells that damages its target cells?

A

Perforin

189
Q

Cell recognition and the immune system (AO1)

The humoral response results in the production of ____________ .

A

Monoclonal antibodies

190
Q

Cell recognition and the immune system (AO1)

Upon stimulation, the B cells divide
by _____________ to produce clones.

A

mitosis

191
Q

Cell recognition and the immune system (AO1)

Describe how presentation of a virus antigen leads to the secretion of an antibody against this virus antigen (3 marks).

A
  1. Helper T cell cell binds to the antigen (on the antigen-presenting cell / phagocyte);
  2. This helper T cell stimulates a specific B cell;
  3. B cell clones

OR B cell divides by mitosis;

  1. (Forms) plasma cells that release antibodies;
192
Q

Cell recognition and the immune system (AO1)

What is the primary response.

A

Some B cells differentiate into plasma cells;

which produce and release large quantities of monoclonal antibodies (secreted into the blood);

193
Q

Cell recognition and the immune system (AO1)

What is the secondary response.

A

Some B cells become memory cells;

which persist in the blood;

help to mount a faster immune response upon re-infection;

194
Q

Cell recognition and the immune system (AO1)

Define monoclonal antibody

A

Same tertiary structure;

produced by identical/cloned plasma cells;

195
Q

Cell recognition and the immune system (AO1)

Monoclonal antibodies are an example of a ______________ protein

A

quaternary

196
Q

Cell recognition and the immune system (AO1)

The 4 polypeptide chains (2 heavy and 2 light) in an antibody are joined together by _______________.

A

disulphide bridges

197
Q

Cell recognition and the immune system (AO1)

A

‘X’ written at either or both ends of Y shape;

198
Q

Cell recognition and the immune system (AO1)

Describe and explain the role of antibodies in stimulating phagocytosis.

A
  1. Bind to antigen

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

  1. (Antibodies) cause clumping/agglutination

OR Attract phagocytes;

199
Q

Cell recognition and the immune system (AO1)

What is formed when an antibody binds to an antigen.

A

Antibody-antigen complex

200
Q

Cell recognition and the immune system (AO2)

NMO is a disease that leads to damage to nerve cells in the spinal cord.

A person with NMO produces anti-AQP4 antibody that attacks only these nerve cells.

Explain why the anti-AQP4 antibody only damages these cells (4 marks).

A
  1. (Anti-AQP4) antibody has a (specific) tertiary structure;
  2. Has binding site that only binds to / complementary to one antigen;
  3. Antigen to this antibody (only) found on these nerve cells;
  4. So, antibody (only) binds to / forms antigen-antibody complex with these nerve cells (causing damage);
201
Q

Cell recognition and the immune system (AO2)

Collagen is a protein produced by cells in joints, such as the knee.

Rheumatoid arthritis (RA) is an auto-immune disease. In an auto-immune disease, a person’s immune system attacks their own cells. RA causes pain, swelling and stiffness in the joints.

Scientists have found a virus that produces a protein very similar to human collagen.

Suggest how the immune response to this viral protein can result in the development of RA (2 marks).

A
  1. The antibody against virus (antigen) will bind to collagen;
  2. This results in the destruction of the (human) cells / collagen;
202
Q

Methods of studying cells (AO1)

A
  1. 3D with SEM, but 2D with TEM
    OR
    Only surface visible with SEM, but internal structures visible with TEM;
  2. Electrons bounce off using SEM
    OR
    Electrons pass through using TEM;
203
Q

Methods of studying cells (AO1)

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

Shorter wavelength between electrons;

OR

Longer wavelength in light rays;

204
Q

Methods of studying cells (AO1)

A student determined the size of a cell structure from a photograph obtained using a microscope.

He used a ruler and a calculator and gave the answer in μm.

Describe how the student determined the size of the structure (2 marks).

A
  1. Measure length of structure and divide by magnification;

Accept correct equation making reference to a measurement

  1. Correct conversion from measured length to µm e.g. ×1000 from mm;

OR

  1. Measure (length of structure) and divide by (image) length of scale bar;
  2. Multiply by actual length of scale bar;
205
Q

Structure of prokaryotic cells and of viruses (AO1)

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

A

No membrane-bound organelles

Circular DNA OR DNA free in cytoplasm

DNA not associated with proteins/histones

No introns

Murein/peptidoglycan (in) cell wall;

Only have smaller 70S ribosomes

206
Q

Transport across cell membranes (AO2)

A

1. Hydrophobic side next to/in/face fatty acids/tails
OR
Hydrophobic side next to/in/face hydrophobic part of phospholipid/bilayer;

2. Hydrophilic sides allow ion movement through membrane
OR
Hydrophilic sides form a channel;

207
Q

Structure of eukaryotic cells (AO1)

A

1. Magnification (figures) show A is bigger than B;
2. A has a nucleus whereas B has free circular DNA;
3. A has mitochondria whereas B does not;
4. A has Golgi body/endoplasmic reticulum whereas B does not;
5. A has no cell wall whereas B has a murein/peptidoglycan cell wall;
6. A has no capsule whereas B has a capsule;
7. A has DNA is bound to histones/proteins whereas B has DNA not associated with histones/proteins
OR
A has linear DNA whereas B has circular DNA;
8. has larger ribosomes;

208
Q

Cell recognition and the immune system (AO1)

What does a vaccine contain?

A

A dead / weakened / attenuated form of the pathogen

A specific antigen or antigens
e.g. an attachment protein on a virus

OFF-SPEC/AO2
mRNA that could be used by ribosomes to produce a specific antigen
e.g. an attachment protein on a virus

209
Q

Cell recognition and the immune system (AO1)

The primary response

After taking a vaccine, stimulation of B cells will lead to mitosis and differentiation into [1] and the production of a small quantity of [2]. [3] cells are also produced.

A

[1] plasma cells

[2] antibodies

[3] Memory

210
Q

Cell recognition and the immune system (AO1)

The secondary response

When a vaccinated person is infected with the actual pathogen, [1] cells will help produce a [2] concentration of antibodies AND [3].

A

[1] memory

[2] higher

[3] faster

211
Q

Cell recognition and the immune system (AO1)

Why do some patient’s receive boosters (a 2nd or 3rd dose of a vaccine)?

A

Produce more memory cells;

So higher concentration of antibodies produced;

At a faster rate;

212
Q

Cell recognition and the immune system (AO1)

What is herd immunity?

A

When the majority of the population is vaccinated;

Some unvaccinated individuals are also protected;

(this is because) vaccinated individuals are less likely to spread the pathogen to unvaccinated individuals;

213
Q

Cell recognition and the immune system (AO2)

Bacterial meningitis is a potentially fatal disease affecting the membranes around the brain. Neisseria meningitidis (Nm) is a leading cause of bacterial meningitis.

(a) In the UK, children are vaccinated against this disease. Describe how vaccination can lead to protection against bacterial meningitis
(6 marks).

A
  1. Antigen on surface of N. meninigitidis / bacterium binds to surface of T helper cell;
  2. T helper cell release cytokines / stimulate B cells;
  3. (Activated) B cell divides by mitosis;
  4. B cells differentiate into plasma cells which release antibodies;
  5. (Some) B cells become memory cells;
  6. Memory cells produce plasma cells / antibodies faster and at higher concentration;
214
Q

Cell recognition and the immune system (AO1)

What causes antigen variability?

A

random mutations

215
Q

Cell recognition and the immune system (AO1)

What are the consequences of antigen variability on antibody effectiveness?

A

Antigen tertiary structure changes shape;

Antibody binding sites / t cell receptors;

No longer complementary to antigen;

216
Q

Cell recognition and the immune system (AO1)

Vaccines may have negative __________ .

A

side effects

This is a common limitation of AO3 questions involving vaccines

217
Q

Cell recognition and the immune system (AO1)

New vaccines are typically developed and tested using animal models and cell cultures.

Explain why this is a limitation.

A

Even though antibodies may be produced, this does not mean it will have the same positive effect in humans.

218
Q

Cell recognition and the immune system (AO1)

What are the advantages of using animals during vaccine/drug research and development?

A

Stops human suffering through development of useful medicines.

219
Q

Cell recognition and the immune system (AO1)

When testing a new vaccine or drug, a vet closely observes the animals being used. Explain why.

A

A vet could stop the experiment to minimise any suffering;

The experiment may be repeated at lower concentration to reduce side effects

220
Q

Cell recognition and the immune system (AO1)

Give examples of active immunity

A

Natural infection with a pathogen;

Vaccine

221
Q

Cell recognition and the immune system (AO1)

Give examples of passive immunity

A

Maternal antibodies via breast feeding;

Antivenom
(contains antibodies against a specific pathogen)

222
Q

Cell recognition and the immune system (AO1)

Describe the difference between active and passive immunity (5 marks)

A

1. Active involves memory cells whereas passive does not;

2. Active involves production of antibody by plasma cells / memory cells whereas passive does not;

3. Passive involves antibody introduced into body from outside / named source (e.g. antivenom from horses);

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 whereas passive fast acting.

223
Q

Cell recognition and the immune system (AO2)

When a person is bitten by a venomous snake, the snake injects a toxin into the person. Antivenom is injected as treatment. Antivenom contains antibodies against the snake toxin. This treatment is an example of passive immunity.

Explain how the treatment with antivenom works and why it is essential to use passive immunity, rather than active immunity (2 marks).

A

Antivenom antibodies bind to the toxin/venom/antigen and causes its destruction;

Active immunity would be too slow/slower
OR
‘Passive immunity is faster

224
Q

Cell recognition and the immune system (AO2)

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.

A

1. B cells specific to the venom reproduce by mitosis;

2. B cells differentiate into plasma cells and memory cells;

3. The second dose produces antibodies (in secondary immune response) in higher concentration AND faster

225
Q

Cell recognition and the immune system (AO1)

Define monoclonal antibody

A

Same tertiary structure produced by identical plasma cells

226
Q

Cell recognition and the immune system (AO1)

What part of the monoclonal antibody makes it make it specific to a cell?

A

The antigen binding site

227
Q

Cell recognition and the immune system (AO1)

What can be attached to a monoclonal antibody?

A

therapeutic drugs (e.g. anti-cancer);

dye/stain/fluorescent marker;

228
Q

Cell recognition and the immune system (AO2)

The protein ZO-1 is found on the surface of ileum cells.

A scientist used an anti-ZO-1 monoclonal antibody to identify ileum cells in a sample of intestine observed using an optical microscope.

Suggest how the monoclonal antibody helped the scientist to identify ileum cells in the sample of intestine (4 marks).

A

1. ZO-1 is located in cell surface membrane;

2. Antibody is complementary (to ZO-1);

3. Binds/attaches to the ZO-1/protein;

Accept ‘forms antigen-antibody complex’

4. (Cells identified with) dye/stain/fluorescent marker linked to antibody;

229
Q

Cell recognition and the immune system (AO1)

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;

Accept ‘cancer cells’ as a specific cell

230
Q

Cell recognition and the immune system (AO1)

Describe the role of antibodies in producing a positive result in an ELISA test (4 marks).

A

1. First antibody binds/complementary (in shape) to antigen;

2. Second antibody with enzyme attached is added;

3. Second antibody binds to antigen;

4. Substrate/solution added and colour changes;

231
Q

Cell recognition and the immune system (AO1)

What is a false positive?

A

Test is positive but there is NO antigen / pathogen present

232
Q

Cell recognition and the immune system (AO1)

What is a false negative?

A

Test is negative but there IS antigen / pathogen present

233
Q

Cell recognition and the immune system (AO2)

A

1. Cancer/fused cells divide / replicate rapidly / uncontrollably;

Accept mitosis

2. B cells produce monoclonal antibody;

234
Q

Cell recognition and the immune system (AO1)

A

A = Attachment protein;

B = Capsid

235
Q

Cell recognition and the immune system (AO1)

Describe the structure of the human immunodeficiency virus (HIV) (4 marks).

A

1.   RNA genome / genetic material;
2.   Reverse transcriptase;
3.   Capsid;
4.   (Phospho)lipid (viral) envelope
5.   Attachment proteins;

236
Q

Cell recognition and the immune system (AO1)

What is the specific cell that HIV infects?

A

T helper cell

237
Q

Cell recognition and the immune system (AO1)

What does the HIV attachment protein bind to on the T helper cell?

A

receptor

Note: receptors are proteins with a specific tertiary structure

238
Q

Cell recognition and the immune system (AO1)

Describe how HIV is replicated
(4 marks)

A

1. Attachment proteins bind to receptors on helper T cell;

2. Nucleic acid/RNA enters cell;

3. Reverse transcriptase converts RNA to DNA;
(viral DNA inserted into host cell genome)

4. Viral protein/capsid/enzymes produced;

5. Virus (particles) assembled and released (from cell);

239
Q

Cell recognition and the immune system (AO1)

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

A

1. RNA converted into DNA using reverse transcriptase;

2. DNA 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 (e.g proteins)

5. For assembly into viral particles;

240
Q

Cell recognition and the immune system (AO1)

What happens to t helper cells infected with HIV?

A

Destroyed;

Number of cells decrease;

241
Q

Cell recognition and the immune system (AO1)

What condition develops when T helper cells falls below a critical threshold?

A

AIDS

Acquired Immunodeficiency Syndrome

242
Q

Cell recognition and the immune system (AO1)

TRUE or FALSE:

A virus with a double-stranded DNA genome requires reverse transcriptase.

A

FALSE

Virsues with a RNA genome (e.g. HIV) require reverse transcriptase

243
Q

Cell recognition and the immune system (AO1)

How can AIDS be diagnosed?

A

Lower / decreasing number of T helper cells;

Using ELISAs to measure the concentration of HIV antibodies / antigens;

244
Q

Cell recognition and the immune system (AO1)

Explain how HIV affects the production of antibodies when AIDS develops in a person (3 marks).

A

1. Less antibody produced;

2. Because HIV destroys / reduces number of helper T cells;

3. few/no B cells activated / stimulated
OR
(So) few/no B cells undergo mitosis/differentiate/form plasma cells;

245
Q

Cell recognition and the immune system (AO2)

In Europe, viruses have infected a large number of frogs of different species. The viruses are closely related and all belong to the Ranavirus group.

Previously, the viruses infected only one species of frog.

Suggest and explain how the viruses became able to infect other species of frog (2 marks).

A

1. Mutation in the viral DNA/RNA/genome/genetic material;

2. Altered tertiary structure of viral attachment protein;

Accept causes antigenic variability

3. Allows it/attachment protein/virus to bind to receptors of other species;

246
Q

Cell recognition and the immune system (AO1)

How do antibiotics work?

A

Preventing bacteria from synthesising murein cell walls;

Directly damaging murein cell wall;

(Some) inhibit binary fission by preventing DNA replication and protein synthesis;

247
Q

Cell recognition and the immune system (AO1)

Give one reason why antibiotics are not effective against viruses.

A

Do not have a cell wall/murein;

OR

Do not have bacterial structures/enzymes

OR

Do not have metabolic processes

248
Q

Cell recognition and the immune system (AO2)

Collagen is a protein produced by cells in joints, such as the knee.

Rheumatoid arthritis (RA) is an auto-immune disease. In an auto-immune disease, a person’s immune system attacks their own cells. RA causes pain, swelling and stiffness in the joints.

Scientists have found a virus that produces a protein very similar to human collagen.

Suggest how the immune response to this viral protein can result in the development of RA (2 marks).

A

1. The antibody against virus (antigen) will bind to collagen;

2. This results in the destruction of the (human) cells / collagen;

249
Q

Structure of prokaryotic cells and of viruses (AO1)

Describe one difference between the structure of DNA in a prokaryotic cell and in a eukaryotic cell.

A

(In prokaryotes)
Circular not linear
OR
Not associated with proteins/histones
OR
No introns;

AS AQA Biology - Burnley College (2023-24) (5 decks)

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