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Zahra biology paper 1 > immunity/transport across cell membranes > Flashcards

immunity/transport across cell membranes Flashcards

1
Q

Interphase

A

S phase – DNA replicates semi-conservatively leading to two sister chromatids
- G1 and G2 – Number of organelles and volume of cytoplasm increases;
ATP content increased

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2
Q

mitosis

A

parent cell divide to two genetically identical daughter cells

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3
Q

prophase

A
  • Chromosomes condense, becoming shorter and thicker = appear as two sister chromatids joined by a centromere
    Nuclear envelope breaks down and centrioles move to opposite poles forming spindle network
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4
Q

metaphase

A
  • Chromosomes align along equator
  • Spindle fibres attach to chromosomes by centromeres
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5
Q

Anaphase

A
  • Spindle fibres contract, pulling sister chromatids to opposite poles of the cell
  • Centromere divides
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6
Q

telephase

A
  • Chromosomes uncoil, becoming longer and thinner
  • Nuclear envelope reforms = two nuclei
  • Spindle fibres and centrioles break down
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7
Q

cytokinesis

A

division of cytoplasm to two new cells

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8
Q

importance of mitosis

A
  • Growth of multicellular organisms by increasing cell number
  • Repairing damaged tissues / replacing cells
  • Asexual reproduction
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9
Q

malignant

A

cancer spreads affects other tissues

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10
Q

benign

A

non cancerous

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11
Q

cancer treatment

A

Disrupt the cell cycle – cell division / mitosis slows – tumour growth slows
- Prevent DNA replication → prevent / slows down mitosis

  • Disrupts spindle activity / formation → chromosomes can’t attach to spindle by their
    centromere → sister chromatids can’t be pulled to opposite poles of the cells →
    prevent/slow mitosis
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12
Q

Prokaryotic cells replicate by binary fission

A

vCircular DNA and plasmids replicate
Cytoplasm expands as each DNA molecule moves to opposite poles of the cell

Cytoplasm divides = 2 daughter cells, each with a single copy of DNA and a variable number of plasmids

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13
Q

Viral replication

A

Viruses don’t undergo cell division because they are non-living
1. Attachment protein binds to complementary receptor protein on surface of host cell
2. Inject nucleic acid (DNA/RNA) into host cell
3. Infected host cell replicates the virus particles

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14
Q

Fluid-mosaic model of membrane structure

A
  • Molecules within membrane can move laterally (fluid) e.g. phospholipids
  • Mixture of phospholipids, proteins, glycoproteins and glycolipids
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15
Q

Phospholipid bilayer

A

Allows diffusion of lipid soluble substances and very small molecules

● Restricts movement of water soluble substances and larger molecules

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16
Q

channel protien

A

allow diffusion of water soluble substances

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17
Q

carrier proteins

A

● Allow diffusion of slightly larger substances (facilitated diffusion)
● Allow active transport of substances against a concentration gradient

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18
Q

Cholesterol

A

Restricts movement of other molecules making up membrane → decreases fluidity increases rigidity

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19
Q

phospholipid bilayer

A

fluid membrane can bend for vesicle formation and phagocytosis

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20
Q

glycoproteins

A

act as receptors involved in cell signalling

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21
Q

glycolipids

A

antigens for cell recognition

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22
Q

Adaptations of cells for transport

A

membrane folded increasing SA
more protein channels/ carries for facilitated diffusion

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23
Q

Simple diffusion

A

Net movement of lipid-soluble or very small substances
From an area of higher concentration to an area of lower conc. down a concentration gradient
Across the phospholipid bilayer

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24
Q

facilitated diffusion

A

Net movement of water-soluble or slightly larger substances down a concentration gradient
Through channel / carrier proteins
Which are specific / complementary to a substance → shape / charge of channel / carrier determines
which substances move

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25
Q

Factors affecting rate:

A

Conc. gradient

Number of channel/carrier proteins

Surface area of membrane

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26
Q

channel protien

A

Pore filled with water
May be gated → can open

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27
Q

carrier protien

A

Complementary substance attaches to
binding site
Protein changes shape
Substance released on side of lower conc.

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28
Q

Osmosis

A

● Net diffusion of water
● From an area of high to low water potential (down a water potential gradient)
● Through a partially permeable membrane

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29
Q

Water potential

A

Pressure exerted by water molecules on
a membrane, measured in kPa
A measure of how likely they are to
move out of a solution
Maximum possible = pure (distilled)
water = 0 kPa
Increasing solute concentration
decreases water potential

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30
Q

effect of osmosis on cells

A

● Cytoplasm of cells has a relatively high concentration of sugars / salts
● Plant cells have a cell wall → prevents them from changing shape / bursting due to osmosis

31
Q

wp same as cells

A

no net movement of water

32
Q

wp higher than cells

A

Water moves into cell by
osmosis

Swell become turgid plant

Swell burst animal

33
Q

hypertonic

A

wp lower than cells water moves in. and cell shrivels

34
Q

isotonic

A

wp same as cells no net movement

35
Q

hypotonic

A

wp higher than cells water moves out cells swell and burst

36
Q

Active transport

A

● Movement of substances an area of lower to higher concentration (against a concentration gradient)
● Requires the hydrolysis of ATP and specific carrier proteins

37
Q

Factors affecting rate –

A

pH/temp number of carrier proteins, rate of respiration (ATP production)

38
Q

role of carrier protien

A
  1. Complementary substance binds to a specific carrier protein (on side of lower conc.)
  2. ATP binds and is hydrolysed into ADP + Pi, releasing energy
  3. This causes carrier protein to change shape → release substance on side of higher conc.
  4. Pi released → protein returns to original shape
39
Q

co transport

A

● Movement of two substances simultaneously via a co-transporter protein
● Movement of one substance against its concentration gradient is coupled with the movement of
another down its concentration gradient

40
Q

na co transport

A

NA+ actively transported from epithelial
cells to blood (by Na+/K+ pump)
Establishing a conc. gradient of Na+
(higher in lumen than epithelial cell)
Na+ enters epithelial cell down its
concentration gradient with glucose
against its concentration gradient
Via a co-transporter protein
Glucose moves down a conc. gradient
into blood via facilitated diffusion

41
Q

Dilution calculations

A

C1 x V1 = C2 x V2

42
Q

c1
v1

A

● C1 = concentration of stock solution
● V1 = volume of stock solution used to make new
concentration

43
Q

c2 v2

A

● C2 = concentration of solution you are making
● V2 = volume of new solution you are making

44
Q

Production of a calibration curve with which to identify the water potential of plant tissue

A

Create a series of dilutions using a 1 mol
dm-3 sucrose solution
Use scalpel / cork borer to cut potato into
identical cylinders
Blot dry with a paper towel and measure /
record initial mass of each piece
Immerse one chip in each solution and
leave for a set time (20-30 mins) in a
water bath at 30oC
Blot dry with a paper towel and measure /
record final mass of each piece

45
Q

Why calculate %
change in mass?

A

● Enables comparison / shows proportional change
● As plant tissue samples had different initial masses

46
Q

Why blot dry
before weighing?

A

Solution on surface will add to mass (only want to measure water taken up or lost)
Amount of solution on cube varies (so ensure same amount of solution on outside)

47
Q

increase in mass

A

Water moved into cells by osmosis
As water potential of solution higher than inside cells

48
Q

Decrease
in mass

A

● Water moved out of cells by osmosis
● As water potential of solution lower than inside cells

49
Q

No
change

A

● No net gain/loss of water by osmosis
● As water potential of solution = water potential of cells

50
Q

antigen

A
  • Molecules which, when recognised as non-self/foreign by the immune system, can
    stimulate an immune response and lead to the production of antibodies
  • Often proteins on the surface of cells
51
Q

what do antigens identify

A
  • Pathogens (disease causing organisms) e.g. viruses, fungi, bacteria
  • Cells from other organisms of the same species e.g. organ transplant, blood transfusion
  • Abnormal body cells e.g. cancerous cells / tumours
  • Toxins released from bacteria
52
Q

phagocytosis of pathogens

A
  1. Phagocyte recognises foreign antigens on the pathogen and binds to the antigen
  2. Phagocyte engulfs pathogen by surrounding it with its cell surface membrane / cytoplasm
  3. Pathogen contained in vacuole/vesicle/phagosome in cytoplasm of phagocyte
  4. Lysosome fuses with phagosome and releases lysozyme) into the
    phagosome
  5. These hydrolyse / digest the pathogen
  6. Phagocyte becomes antigen presenting and stimulates specific immune response
53
Q

t lymphocytes

A
  1. T lymphocytes recognises antigen presenting cells after phagocytosis (foreign antigen)
  2. Specific T helper cell with receptor complementary to specific antigen binds to it, becoming
    activated and dividing rapidly by mitosis to form clones which:
    a) Stimulate B cells for the humoral response
    b) Stimulate cytotoxic T cells to kill infected cells by producing perforin
    c) Stimulate phagocytes to engulf pathogens by phagocytosis
54
Q

The humoral response

A
  1. Clonal selection:
    a) Specific B cell binds to antigen presenting cell and is stimulated by helper T cells which
    releases cytokines
    b) Divides rapidly by mitosis to form clones (clonal expansion)
  2. Some become B plasma cells for the primary immune response – secrete large amounts of
    monoclonal antibody into blood
  3. Some become B memory cells for the secondary immune response
55
Q

Primary response

A

antigen enters body for the first time (role of plasma cells)
- Produces antibodies slower and at a lower concentration because
- Not many B cells available that can make the required antibody
- T helpers need to activate B plasma cells to make the antibodies (takes time)
- So infected individual will express symptoms

56
Q

Secondary response –

A

same antigen enters body again (role of memory cells)
- Produces antibodies faster and at a higher concentration because
- B and T memory cells present
- B memory cells undergo mitosis quicker / quicker clonal selection

57
Q

antibodies

A
  • Quaternary structured protein (immunoglobin)
  • Secreted by B lymphocytes
  • Binds specifically to antigens (monoclonal) forming an antigen-antibody complex
58
Q

antibodies - destroying pathogens

A

bind to two pathogens at a time
form antigen antibody complex
enables antibodies to clump pathogens together
phagocyte binds to antibodies phagocytose many pathogens at once

59
Q

vaccine

A

Injection of antigens
- From attenuated (dead or weakened) pathogens
- Stimulates the formation of memory cells
vaccine can lead to symptoms because pathogens may be alive so can reproduce and release toxins which can kill cells

60
Q

herd immunity

A

make it harder fir pathogen to spread as more people immune so fewer infected and susceptible

61
Q

active immunity

A

initial exposure to antigens
memory cells involved
slow
long term immunity
antibody produced and secreted by B plasma cells

62
Q

passive immunity

A

no exposure to antigen
no memory cells
fast
short term immunity
antibody introduced to Body from another organism

63
Q

vaccine ethics

A

tested on animals by humans animal central nervous system feels pain
expensive may not work
side effects
tested on humans so may put them under unnecessary risks

64
Q

antigen variability on disease

A

change in antigen shape not recognised by b memory cells so not immune and has to undergo primary immune response

65
Q

monoclonal antibodies

A

antibody produced from single group of genetically identical B cells
bond to specific complementary antigen have a binding site only 1 complementary antigen

66
Q

monoclonal antibodies useful in medicine

A

Only bind to specific target molecules / antigens because…
- Antibodies have a specific tertiary structure (binding site / variable region) that’s
complementary to a specific antigen which can bind/fit to the antibody

67
Q

antibody in ELISA

A

antibody to certain antigen diagnose disease or allergy
enzyme attaches to antibody reacts with substrate turning the solution a different colour

68
Q

replication of HIV in helper T cells

A
  1. HIV infects T helper cells
    - HIV attachment protein attaches to a receptor on the helper T-cell
    membrane
  2. Virus lipid envelope fuses with cell surface membrane and capsid released into cell which
    uncoats, releasing RNA and reverse transcriptase into cytoplasm
  3. Viral DNA is made from viral RNA
    - Reverse transcriptase produces a complementary viral DNA strand from viral RNA
    template
    - Double stranded DNA is made from this
  4. Viral DNA integrated into host cell’s DNA
  5. This remains latent for a long time in host cell until activated
  6. Host cell enzymes used to make viral proteins from viral DNA → viral
    proteins assembled with viral RNA to make a new virus
  7. New virus bud from cell (taking some of cell surface membrane as envelope)
  8. Eventually kills helper T cells
  9. Most host cells are infected and process repeat
69
Q

cold

A

reduce enzyme activity so organelles aren’t damaged

70
Q

isotonic

A

So water doesn’t move in or out of organelles by osmosis → so they don’t burst

71
Q

buffered

A

To keep pH constant → so enzymes don’t denature

72
Q

cell fractionation

A

Homogenise tissue using a blender
Disrupts cell membrane → breaks open cell
Releases contents / organelles
Keep in a cold, isotonic, buffered solution
Filter homogenate → remove large, unwanted debris
Ultracentrifugation → separate organelles in order of density / mass

73
Q

ultracentrifugation

A
  1. Centrifuge homogenate in a tube at a low speed
  2. Remove pellet of heaviest organelle and respin supernatant at a higher speed
  3. Repeat at increasing speeds until organelles separated out, each time pellet is made of
    lighter organelles

Zahra biology paper 1 (5 decks)

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