Cells (transport Across Membranes, Immune System)

Question 1

Role of cholesterol in cell membrane

Answer 1

Restricts movement of other molecules
Stabilises it

Question 2

Function of cell membrane

Answer 2

Barrier between cells/ areas to maintain different concentrations on each side
Selectively/ partially permeable
Site of chemical reactions
Cell recognition (glycoproteins)
Cell signalling

Question 3

What do channel proteins transport

Answer 3

Small charged molecules
FD only
Specific

Question 4

What do carrier proteins transport

Answer 4

Large molecules
By FD and active transport and co transport
Specific

Question 5

Diffusion

Answer 5

Net movement of molecules from high to low concentration
Passive

Question 6

Facilitated diffusion

Answer 6

Passive
Movement of molecules across a cell membrane via a specific trans membrane protein, from high to low concentration

Question 7

Co transport gradients

Answer 7

One molecule goes down its gradient
The other goes against

Question 8

Co transport of glucose

Answer 8

Sodium ions actively transported out of epithelial cell into blood via carrier protein (sodium potassium pump)
Creates/ Maintains low concentration of sodium ions inside cell
So sodium ions move into the cell from the ileum via a carrier protein. Glucose is transported along with them in co transport via facilitated diffusion, against its concentration gradient
Glucose transported out of the cell into the blood down its concentration gradient via facilitated diffusion via a carrier protein

Question 9

Method for identifying the water potential of plant tissue

Answer 9

Prepare serial dilution of solute from a known concentration
Prepare cylinders of plant tissue
Weigh mass of each cylinder
Submerge cylinders in the range of solute concentrations for min 1hour
Reweigh cylinders
Calculate percentage change in mass
Plot solute concentration against percentage change in mass to form a calibration curve
Use calibration curve to estimate the water potential of plant tissue: when percentage change is zero

Question 10

Why are cylinders used

Answer 10

Similar surface area

Question 11

Why percentage change in mass

Answer 11

Allows for comparison of cylinders of different sizes

Question 12

Why use percentage change in mass of zero from calibration curve

Answer 12

SoLute and plant are isotonic

Question 13

Making dilution series from eg 1.2M NaCl and want 60cm3

Answer 13

Total volume/ known concentration x desired concentration = volume of known solute concentration

Question 14

Freezing temps affecting membrane permeability

Answer 14

Carrier proteins and channels lose their shape and open
Cell membrane damaged by ice crystals
Membrane very permeable

Question 15

Cold temps affect on membrane permeability

Answer 15

Low kinetic energy, phospholipids close together
Membrane is stuff
Least permeable

Question 16

Warm temps affect on membrane permeability

Answer 16

Phospholipids moving, more space between them so more permeable

Question 17

Hot temperatures affect on membrane permeability

Answer 17

Protein channels and carriers denature so are open
Phospholipid bilayer melts
Membrane very permeable

Question 18

Solvents effects on membrane permeability

Answer 18

Some solvents can dissolve the phospholipids in the cell membrane
Eg ethanol
Loses its structure
Increases permeability

Question 19

What do antigens allow the immune system to recognise

Answer 19

Pathogens
Cells from other organisms of the same species
Abnormal body cells
Toxins

Question 20

Pathogen

Answer 20

An organism that can cause communicable disease

Question 21

Antigens

Answer 21

Proteins (glycoproteins) on the surface cell membrane which initiates an immune response

Question 22

Cellular immune response

Answer 22

Lymphocytes
Phagocytes
T killer cells

Question 23

Immune response

Answer 23

Antigen of pathogen detected by phagocyte
Phagocyte presents antigen on its surface
T helper cells with complementary receptor binds to presented antigen
T helper cell releases cell signalling molecules that stimulate specific t killer and b cells
B cells with complementary antibody divide by mitosis and differentiate into plasma cells
Makes and secretes large amounts of antibodies
T cell and b cells divide to form memory cells

Question 24

Phagocytosis

Answer 24

Phagocyte recognises foreign antigen on pathogen
Engulfs pathogen into a phagocytic vacuole
Lysosomes fuse with the phagocytic vacuole
Lysosomes contain enzymes (lysozymes)
Which hydrolyse the pathogen

Question 25

T cells

Answer 25

Activated by antigens presented by phagocyte
T helper cells activate b cells and cytotoxic T cells
Cytotoxic T cells kill pathogens

Question 26

Antibodies

Answer 26

Proteins that bind to antigens to kill pathogens

Question 27

B cells

Answer 27

The b cell with the complementary antibody forms antigen-antibody complex
Activates/ selects right b cell
Selected b cell divides

Question 28

Clonal selection

Answer 28

Only the b cell that forms an antigen- antibody complex is selected to divide into plasma cells

Question 29

Plasma cells

Answer 29

Closes of selected b cell with complementary antibody to pathogens antigens
Make monoclonal antibodies
Agglutination (stick pathogens together)
So phagocytes can destroy many pathogens at once

Question 30

Humoral response

Answer 30

B cells
Plasma cells, monoclonal antibodies