Transport across the cell membrane-topic question probs note

the basic structure of all cell membranes

it is the same for organisms

components of the cell membrane

glycoprotein

carrie and channel proteins

glycoprotein

phospholipid bilayer

cholesterol

glycolipid

fluid mosaic model

fluid- the phospholipids move relative to each other

mosiac- the proteins dotted between phospholipids are of various shapes.

what does cholesterol do in the cell membrane

restricts movements of other molecules making up the membrane

surface area

increasing the surface area increases the rate of diffusion

if the cell membrane cannot withsatnd the pressure

then it will burst

a student put beetroot in a beaker of water and released pigment why

pigment diffuses out beetroo from high concentration to low concentration

why do we remove all the skin from beetroot

to ensure transport of substances from all surfaces

why do we blot the cylinder beetroot

to remove excess water

increasing the temperature on the effect on the permeability

The phospholipids increases increase in kinetic energy

phospholipids move more apart

breaking weak intermolecular forces

so membrane becomes more permeable

the transport mechanisms

active transport

facilitated diffusion

simple diffusion

co transport

osmosis

how does an enzyme catalyse a reacttion

the subtrate shape is complementary to the enzymes active site and binds to the active site

the active site then slightly changes shape , adding strain on the bonds of the substrate

lowering the activation energy

why does bacteria not need a mass transport system

because it has a high sa:v ratio

so diffusion is effiecient

detergent a hydrophobic head and hydrophilic tail, so suggest how it can remove bacteria from dishes

The detergent interacts with the hydrophobic core of the phospholipid bilyaer .

this then breaks the intermolecular forces between fatty acid tails

this disrupts the cell membrane making it more fluid and becomes more permeable

so the contents of the bacteria spill out

Explain the importance of the high percentage of proteins in the cell surface membrane of the small intenstine epitheleal cell

high numbrs of soidium potassium ion pump , to increase the rate of active transport of na+ ions into the blood

IMMUNITY

IMMUNITYYYYYY

antigens that the immune system would recognise as non self

transplant cells

toxins

cancer cells

pathogens

define an antigen

a molecule, normally a protein that triggers an immune response

what is antigen variability

variation in the shape and structure of an antigen caused by genetic variation

effect of antigen variability

more strains of the pathogen, less asy to make a vaccine

also, if the pathogen encounters the immune system, the B cells willn have a primary immune response because the aniti bodies are no longer complementary

phagocytosis of pathogens

1. pathogen releases chemicals which attract the phagocytes

2. phagocytes bind to the cell surface membrane of pathogen and surrounds it

3. the phagocyte forms a phagosome around the pathogen

4. the lysosome fuses with phagosome and releases lysozymes and hydrolytic enzymes to breakdown the pathogen into soluble particles

5. and release some by exocytosis

t lymphocytes response to foreign antigen

certain phagocytes process and present the antigens on their cell surface membrane

they become ANTIGEN PRESENTING CELLS

the T h lymphocytes bind to the APC antigens which then

stimulate further phagocytosis

stimulate the production of B cells

activate t cytotoxic cells, which make holes in the cell surface membrane

what is an antibody

a globular protein that is produced by B plasma cells in response to an antigen and binds to the specific complementary antigen.

antibody structure

4 polypeptide chains

2 heavy 2light

in a y shape, held by disulfide bridges

has constant region that is the same for all antibodies, but different variable regions, which bind to the antigen, forming antigen anbody complex they vary for each antibody

how are antibodies produced

B cells process and present antigens on their cell surface membrane

T helper cells bind to the antigen

then stimulates the production of B lymphocytes

B lymphocytes differentiate into plasma and memory cells

plasma cells then produce antibodies which have a complementary shape to the antigen, forming antigen antibody complex

what hppens when antigen antibody complex is formed

agglutination- clumping the bacteria, for easy phagocytosis

attracting the phagocytes to the bacteria

plasma and memory cells

plasma cells produce antibodies, which die in days, so it is a primary immune response

memory cells- divide rapidly by mitosis into memory cells and plasma cells, when encounters pathogen again. Plasma cells produce antibodies. This is a secondary immune response.

herd immunity

interrupting pathogen transmission to prevent the infection of unvaccinated people

vaccines protects individuals of a population from a disease

define immunity

the ability to resist infection caused by invading pathogens.

active and passive immunity

active immunity involves the presence of antigens, production of memory cells and long lasting

passive immunity- antibodies are brought form an outside source, it is short lasting, something that you may take every ten years.

structure of HIV

capsid

reverse transcriptase

attachment protein

lipid membrane

How does HIV replicate

Attaches to the CD4 receptor on the t helper cell

injects its RNA and reverse transcriptase into the host cell

the reverse transcriptase then uses RNA as a template, converts to viral DNA which is then inserted in the host cell chromosome.

the viral DNA is transcribed to viral mRNA,

viral mRNA is translated to viral proteins

viral particles assemble and burst out of the cell, destroying the t helper cell.

physical barriers against pathogens

skin AND acts as a physical barrier / contains sebum;

tears AND contains lysozymes to destroy pathogens;

stomach acid AND destroys pathogens in food;

hairs (in nose and ears) AND traps pathogens and dust;

msuucus AND traps pathogens and removes them by movement of cilia;;

suggest two enzymes lysosomes contain that can break down cell walls of engulfed bacteria

amylase and protease

hydrolyses carbohydrates to glucose

hydrlyses proteins to amino acids

explain the importance of phagocytosis in bringing abt a specific immune response in the human body

phagoctes becomes APC

the t helper cell binds to the antigen

t helper cell is activated

t cell helper cell start the cell mediated response

ues of monoclonal anitbodies

delivery of therapeutic medicine to cells

medical diagnosis( testing for sugar in glucose and pregnancy testing)

ELISA test

why doesnt antibiotics work on viruses

because many antibiotivcss work by weeeakening the cell walll and a irus have a protein coat not a murein cell wall, so it cannot work against it

describe the difference between non speciffic and specific immune response

specific respons: kills a particular pathogen, by recognising their specific antigen

non specific: traps all pathogens