biological membranes 2.5

Question 1

2 ways proteins can be in the membrane

Answer 1

-Can be intrinsic/integral (span the entire membrane) • —Can be extrinsic (embedded in one half of the membrane

Question 2

What is the glycocalyx

Answer 2

Formed from glycolipids and glycoproteins outside of the membrane

Question 3

2 ways of diffusion

Answer 3

• simple diffusion

- facilitated diffusion

Question 4

factors affect rate of diffusion

Answer 4

• temperature
• diffusion distance
• surface area
• size of diffusing molecule
• concentration gradient

Question 5

Plant cells when water enters/leave

Answer 5

• plasmolysed —-flaccid

- turgid

Question 6

Animal cells when water enters/leaves

Answer 6

• cytolysis

- crenated

Question 7

Why cant plasmolysed cells metabolise?

Answer 7

Enzyme catalysed reactions need to be in solution

Question 8

What happens when temperature drops in terms of membrane fluidity and structure? (fatty acids and cholesterol)

Answer 8

Temperature drops

• saturated fatty acids become compressed
• unsaturated fatty acids kinks in their tails push adjacent phospholipid molecules away, maintaining fluidity
• cholesterol prevents phospholipids packing too closely therefore preventing reduction in fluidity and acting as a buffer

Question 9

What happens when temperature increases in terms of membrane fluidity? (fatty acids and cholesterol)

Answer 9

Temperature increases

• phospholipids have more kinetic energy o move around more making it more fluid and more permeable
• cholesterol buffers

Question 10

Effects of increased fluidity and movement of membrane due to temperature increase?

Answer 10

• membrane embedded proteins drift affecting the rates at which they catalyse reactions
• higher fluidity affects infolding of membrane in phagocytosis
• increase in fluidity changes ability for cells to signal each other

Question 11

Discuss proteins and temperature

Answer 11

Protein and temperature

• high temperatures cause atoms to vibrate breaking hydrogen bonds and ionic bonds in their structure so they unfold
• Tertiary structure changes shape, they denature
• cytoskeleton threads denature and membrane embedded proteins denature the plasma membrane falls apart, becoming more permeable due to hols forming
• rate of reaction slows if proteins/enzymes move or denture

Question 12

Effects of solvents on cell membrane

Answer 12

Organic solvents like acetone and ethanol damage cell membranes as they dissolve lipids

Question 13

2 types of bulk transport

Answer 13

• endocytosis

- exocytosis

Question 14

What is active transport

Answer 14

The movement of substances against their concentration gradient from an area of low concentration to an areas of high concentration across a cell membrane causing ATP and protein carriers

• ATP is hydrolysed
• releases energy
• energy released enables protein conformational change so they can move things against gradient

Question 15

2 types of endocytosis and what it is

Answer 15

Endocytosis is bringing large molecules into the cell by the plasma membrane surrounding and enclosing the particle, bringing it into the cell as a vesicle

• phagocytosis, the intake of solid matter
• pinoendocytosis, the intake of liquid matter

Question 16

What is exocytosis?

Answer 16

exocytosis I how large molecules are transported out of cells , a vesicle moves towards and fuses with the plasma membrane. This requires ATP to fuse the vesicles and to move the vesicles.
Every step the motor protein takes dragging the cargo along cytoskeleton threads, a molecule of ATP is hydrolysed