2B-Cell Membranes

Question 1

Cell membranes

Answer 1

• partially permeable and control which substances enter or leave the cell

Question 2

Fluid mosaic model

Answer 2

Phospholipids form a double bilayer, channel proteins, carrier proteins , glycolipids and glycoproteins, receptor proteins on cell surface membrane and cholesterol

Question 3

Phospholipids in cell membranes

Answer 3

Hydrophobic fatty acid tails face in so doesn’t allow large and water soluble substances (ions and polar molecules) but small non polar substances can diffuse across

Question 4

Cholesterol

Answer 4

A lipid that gives Membrane stability and bonds to hydrophobic fatty acid tails of phospholipids causing them to pack more closely together- makes more rigid -has hydrophobic regions barrier to polar substances and maintains cell shape

Question 5

Why blood cells have cholesterol

Answer 5

Membranes stability as free floating so maintains shape

Question 6

Temperature below zero affect on membranes

Answer 6

• phospholipids little energy so don’t move much. -close together so membrane rigid. -channel proteins and carrier denature increasing membranes permeability -ice crystals pierce membrane - permeability increases

Question 7

Temp of zero to 45

Answer 7

• phospholipids more mobile not tightly packed - partially permeable As temp increases phospholipids move more increasing permeability

Question 8

Temp of 45 above affect on membranes

Answer 8

Bilayer melts - increasing permeability - water inside cell expands puts pressure on membrane -proteins denature increasing permeability

Question 9

Simple diffusion

Answer 9

Passive process net movement of particles from an area of high conc to low conc across a partially permeable membrane down a conc gradient until equilibrium is established

Question 10

Factors affecting diffusion rate

Answer 10

1- conc gradient size. 2-thickness of exchange surface. 3- surface area

Question 11

Facilitated diffusion

Answer 11

Passive - net movement of particles from area of high concentration to low conc across a channel or carrier protein until equilibrium is reached

Question 12

What uses facilitated diffusion

Answer 12

Large and charged polar particles and ions

Question 13

Carrier proteins

Answer 13

1- Large molecule attaches to carrier protein in membrane 2- protein changes shape 3- releases molecule on opposite side f membrane

Question 14

Channel proteins

Answer 14

Pores in membranes for charge particles to diffuse through

Question 15

Factors affecting facilitated diffusion rate

Answer 15

1- conc gradient size. 2- number or channel or carrier proteins

Question 16

Osmosis

Answer 16

Net movement of water from an area of high water potential to low water potential across a partially permeable membrane until equilibrium is reached a passive process

Question 17

Pure water water potential

Answer 17

Zero

Question 18

Water potential of any water is

Answer 18

Zero or negative

Question 19

Water potential

Answer 19

Potential of water molecules to diffuse out or in of a solution

Question 20

How to lower Water potential

Answer 20

Add solutes

Question 21

The more negative water potential

Answer 21

More solutes in it

Question 22

Isotonic

Answer 22

Same water potential so won’t gain or lose any water as no net movement of water

Question 23

Hypotonic

Answer 23

Solutions with Higher water potential compared to inside of the cell so water enters

Question 24

Hypertonic

Answer 24

Solution with lower water potential than inside the cell so water leaves the cell net movement out

Question 25

Factors affects the rate of osmosis

Answer 25

1- water potential gradient 2- surface area 3- membrane thickness

Question 26

Active transport

Answer 26

Active process-energy to move particles across a membrane against a concentration gradient

Question 27

Carrier proteins in active transport

Answer 27

1- molecule attaches to it. 2-carrier protein shape changes and moves molecule across the membrane against the concentration gradient using energy from ATP.

Question 28

Co transporter proteins in active transport

Answer 28

1- bond 2 molecules to it and changes co-transporter proteins shape. 2-concentration gradient of one of the molecules used move the other against its own conc gradient using energy from ATP

Question 29

Co- transport and absorption of glucose

Answer 29

1- Na actively transported out of epithelial cells in ileum into blood by Na-k pump- conc gradient as high conc of Na in lumen of ileum than inside cell. 2-Na diffuse from lumen of ileum into epithelial cell down conc gradient via Na and glucose co transporter proteins so conc of glucose in cell decreases. 3- glucose diffuses into blood down conc gradient via protein channel via facilitated diffusion.

Question 30

Factors affecting Active transport

Answer 30

1-speed of individual carrier proteins 2- number of carrier proteins 3- rate of cell respiration and availability of ATP

Question 31

Antigens

Answer 31

Proteins molecules that generate an immune response found on body cells