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A level Biology (Edmond)year 12 > CELLS-Cell membrane > Flashcards

CELLS-Cell membrane Flashcards

1
Q

why are membranes important? (6 marks)

A

-cell recognition
-separating organelles from cytoplasm
-separating cell content from outside
-provides surface for metabolic pathways
-regulating transport of materials in/out

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2
Q

what allows phospholipid to form bilayers which make up membranes in and around cells. ?

A

The phosphate group is hydrophilic (attracts water) and the fatty acid chains are hydrophobic (repel water).

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3
Q

what type of protein are channel/carrier proteins?

A

intrinsic protein

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4
Q

what do channel/carrier proteins do?

A

allow large molecules polar/ions to pass through

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5
Q

The arrangement of the bi-layer of phospholipids, integrated proteins, glycoproteins and glycolipids is known as the?

A

fluid-mosaic model
‘fluid’ - because the phospholipids are constantly moving
‘mosaic’ – proteins are scattered through the bilayer like tiles in a mosaic

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6
Q

what can peripheral proteins do?

A

can act as receptors and allow the cell to detect chemicals released from other cells so that they can respond

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7
Q

what are glycoproteins?

A

proteins with carbohydrates attached

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8
Q

what are glycolipids?

A

lipids with carbohydrates attached

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9
Q

what can a glycoprotein and glycolipids role be?

A

to act as antigens to supervise cellular recognition

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10
Q

what is cholesterol?

A

type of lipid that fits between phospholipids -binds to the tails of phospholipids so pack closer together

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11
Q

what can cholesterol do to cell membrane?

A

-give it stability
-has hydrophobic region so can act as a barrier to polar substances moving through the membrane

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12
Q

name 4 factors that can affect membrane permeability? and how does it affect it

A

-cholesterol, decreases fluidity and permeability
-unsaturated fats, increases fluidity and permeability
-saturated fats, decreases fluidity and permeability
-temp increases

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13
Q

what can solvents do to enzymes?

A

damage them by breaking the bonds

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14
Q

define diffusion? (a level)

A

Net, passive movement of particles from a higher concentration to a lower concentration until a dynamic equilibrium is reached.

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15
Q

what is simple diffusion? and give examples

A

is the movement of particles through the plasma membrane
e.g Small, non-polar or hydrophobic molecules like O2, CO2 & fatty acids.

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16
Q

What is facilitated diffusion?

A

Diffusion using carrier / channel proteins complementary to particular substances.
e.g large polar, hydrophilic, glucose, amino acids ect

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17
Q

describe the process carrier proteins do and what moves through it?

A

-Protein molecules in the membrane facilitate the movement of molecules.
-Large, polar or hydrophilic molecules like glucose & amino acids.

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18
Q

describe the process channel proteins do and what moves through it?

A

-Protein molecules form pores in the membrane to facilitate the movement of molecules.
-Charged or polar molecules like Cl-, Na+, K+, Ca2+.

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19
Q

What increases the rate of diffusion?

A

-Carrier / channel proteins
-concentration gradient
-Surface area
-Stirring
-temperature

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20
Q

What decreases the rate of diffusion?

A

-density
-distance
-size of molecules

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21
Q

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

A

Carrier / channel protein;
(Protein) specific / complementary to substance;
Substance moves down concentration gradient;

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22
Q

Explain why molecules of oxygen and carbon dioxide are able to diffuse across membranes [2].

A

Lipid / fatty acid part of membrane is non-polar / hydrophobic;
O2 & CO2 small / non-polar (molecules);
O2 / CO2 can diffuse through / dissolve in / get between molecules in this layer;
Down a concentration gradient;

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23
Q

Explain why the diffusion of chloride ions involves a membrane protein and the diffusion of oxygen does not [5].

A

Chloride ions water soluble/charged/polar;
Cannot cross (lipid) bilayer (of membrane);
Chloride ions transported by facilitated diffusion OR diffusion involving channel/carrier protein;
Oxygen not charged/non-polar;
(Oxygen) soluble in/can diffuse across (lipid) bilayer;

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24
Q

define active transport?

A

The movement of molecules or ions across a cell membrane from low to high concentration using ATP energy.

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25
Q

Explain the function of ATP hydrolase [2].

A

Releases energy when ATP converted to ADP + Pi;
Allows active transport of ions / ions to be moved against concentration gradient;

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26
Q

Explain how the movement of Na+ out of the cell allows the absorption of glucose into the cell lining the ileum [2].

A

Generates / maintains a concentration / diffusion gradient for Na+ from ileum into cell;
Na+ moving in by facilitated diffusion / co-transport, brings glucose with it;

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27
Q

what is co-transport?

A

when a protein can move two things across the membrane at the same time

28
Q

Explain how glucose is absorbed into the blood [3].

A

Na+ ions leave epithelial cell & enter the blood by active transport;
This creates a concentration gradient for Na+ to enter cell;
Na+ enters cell with glucose by facilitated diffusion;
Glucose diffuses into blood by facilitated diffusion;

29
Q

Describe & explain features of cells specialised for absorption [3].

A

Folded membrane / microvilli so large surface area;
Large number of co-transport / carrier / channel proteins so fast rate / for active transport / facilitated diffusion;Large number of mitochondria to make ATP / for aerobic respiration / to release energy for active transport;

30
Q

what affects active transport?

A

-Speed of carrier proteins
-Number of carrier proteins
-Rate of respiration

31
Q

define osmosis?

A

Net, passive movement of water molecules from a region of higher water potential to a region of lower water potential across a selectively permeable membrane.

32
Q

WATER POTENTIAL ():

A

The pressure (kPa) created by water molecules. It is the likelihood of water moving out of a solution.

33
Q

Lower water potential than cell.
so it is a what type of solution?

A

Hypertonic solution

34
Q

Same water potential than cell.
so it is a what type of solution?

A

ISOTONIC SOLUTION

35
Q

Higher water potential than cell.
so it is a what type of solution?

A

HYPOTONIC SOLUTION

36
Q

when a cell is shriveled we call it ? (plants/animals cells)

A

plasmolysed (plants)
crenated (amimal)

37
Q

what is a pathogen?

A

a microorganism that causes disease

38
Q

How do white blood cells fight infection?

A

Phagocytes engulf and destroy pathogens
Lymphocytes produce antibodies that disable pathogens

39
Q

What is the immune system?

A

The immune system is a group of cells, tissues, organs and mechanisms that defend an organism against pathogens and other foreign substances.

40
Q

what are the two types of Defence Mechanisms and what are they ?

A

-Non specific, Response is immediate and the same for all pathogens
e.g physical barriers (skin)
phagocytosis

-specific. Response is slower and specific to each pathogen
e.g cell-mediated response (T-lymphocytes)
humoral response (B lymphocytes)

41
Q

give me some examples of physical barriers?

A

-antimicrobial tears
-HCL acid in stomach
-mucus (produced by goblet cells)
-skin
-gut flora (bacteria in gut)
-platelets

42
Q

phagocytes are what type of cell and where are there made?

A

-wbc
-in bone marrow

43
Q

what are the two main types of phagocytes?

A

-neutrophils
-macrophages

44
Q

what can neutrophils do?

A

can rapidly engulf and destroy pathogens at the site of an infection

45
Q

what can macrophages do?

A

can destroy pathogen by phagocytosis same as neutrophils but also can antigen presentation cell

46
Q

what are cytokines?

A

is released when phagocyte engulfs a pathogen by the phagocyte
it signals to phagocytes and other immune cells to move to the site of infection and can also trigger inflammation and a fever.

47
Q

How do phagocytes detect invaders?

A

Chemicals released by pathogens, as well as chemicals released by body cells under attack, e.g. histamines,attract phagocytes

This response to chemical stimuli is known aschemotaxis
Phagocytes move towards the site of infection, where pathogens can be identified due to the presence of pathogenicantigens
Phagocytes have receptor proteins on their surface thatrecogniseantigensasnon-self

48
Q

describe the lymphocytes?

A

They play an important part in thespecificimmune response
They aresmallerthan phagocytes
They have alarge nucleusthat fills most of the cell
They are produced in thebone marrow before birth
There aretwo typesof lymphocytes (withdifferent modes of action). The two types of lymphocytes are:
T-lymphocytes (T cells)
B-lymphocytes (B cells)

49
Q

what are the two parts of Specific immune response?

A

-Cell-mediated response
-Humoral response

50
Q

what is cell-mediated response?

A

Involves specialised white blood cells called T-lymphocytes which target pathogens inside cells.

51
Q

what is the Humoral response?

A

Involves specialised white blood cells called B-lymphocytes which target pathogens by producing antibodies

52
Q

what are the two types of T-cells?

A

-T Helper Cell
-Cytotoxic T Cell

53
Q

define Cytotoxic T Cell?

A

Cell that destroys pathogenic cells by releasing chemicals into the invaded cell

54
Q

define T helper cell?

A

Cell that stimulates and recruits more cells to assist in the immune response

55
Q

describe the structure of antibodies?

A

-contains 4 poly peptide chains
two light, two heavy chains
-variable regions amino acid sequence
-2 antigen-binding sites
-hinge region
-2 disulphide bridges

56
Q

what is agglutination?

A

when antibodies can clump pathogens together

57
Q

what are the two types of immunity?

A

-passive
-active

58
Q

what is passive immunity?

A

immunity you get from being given antibodies made by a different organism
e.g mother(natural, breastmilk), vaccine(artificial)

59
Q

what is active immunity?

A

immunity when your immune system makes its own antibodies

60
Q

what are some ethical issues with vaccines?

A

-vaccines may be tested on animals
-humans in clinical trials
-who would be fist to receive it?

61
Q

why don’t vaccinations eliminate all diseases?

A

-people may have immunodeficiency so fail to induce immunity in some people
-antigenetic variability
-many different strains cant all be fought at once
-certain pathogens hide from the bodies immune system

62
Q

give me some ways people can get HIV?

A

-passed from mother to baby
-contaminated blood transfusions and organ transplants
-sharing needles
-sex without a condom

63
Q

what does HIV and AIDS stand for?

A

-human immunodeficiency virus
-acquired immune deficiency syndrome

64
Q

describe the structure of HIV (4marks)?

A

-has 2 RNA strands
-has 2 reverse transcriptase enzyme
-a capsid that is surrounding the RNA and enzyme
-lipid envelope surrounding the capsid
-attachment protein’s attached to lipid envelope

65
Q

How does HIV replicate?

A

-Attachment proteins on the HIV attach to receptors(SD4) on a helper T cell.
-HIV releases its RNA into the helper T cell.
-Reverse transcriptase converts this RNA into DNA.
-The viral DNA is inserted into the helper T cell’s genome.
-The helper T cell’s DNA is translated to make viral proteins.
-The proteins are used to assemble new HIV particles.
-Fully assembled HIV particles leave the cell in order to infect other cells.

A level Biology (Edmond)year 12 (4 decks)

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