plasma membranes

Question 1

what is meant my compartmentalisation

Answer 1

the formation of separate membrane bound areas in a cell

Question 2

what are membranes formed by

Answer 2

phospholipid bilayer

Question 3

what does a phospholipid consist of?

Answer 3

hydrophobic fatty acid tails - inside

hydrophilic phosphate heads - outside

Question 4

what was the fluid mosaic model and when was it

Answer 4

it was in 1972 by singer and Nicholson
this model describes how phospholipids are free to move within the layer relative to each other
giving the membrane flexibility

Question 5

what are intrinsic proteins

Answer 5

trans membrane proteins that are embedded through both layers of the membrane
they have hydrophobic r groups on their external surfaces

Question 6

give 2 examples of intrinsic proteins

Answer 6

channel proteins

carrier proteins

Question 7

what are channel proteins

Answer 7

passive movement of hydrophilic channel
polar molecules
ions down a concentration gradient

Question 8

what are carrier proteins

Answer 8

active transport
passive transport
protein usually changes shape

Question 9

what are glycoproteins

Answer 9

intrinsic proteins
embedded in membrane with attached carbohydrate chains
play a role in cell adhesion
and receptors in cell signalling when chemical binds to a receptor
receptors of neurotransmitters and hormones

Question 10

what are glycolipids

Answer 10

attached with carbohydrate chains
these molecules are called cell markers or antigens
peripheral proteins
hydrophilic R groups on their outer surfaces

Question 11

what is cholesterol

Answer 11

hydrophilic and phobic end
regulates the fluidity of membrane
cholesterol add stability to membranes without making them too rigid

Question 12

how does temperature affect membrane structure

Answer 12

when temperature is increased the phospholipids will have more kinetic energy and will move more
and the membrane will lose its structure
this will cause particles to across the membrane easier

Question 13

define diffusion?

Answer 13

is the net, or overall movement of particles from a region of higher concentration to a region of lower concentration
passive movement

Question 14

what affects the rate of diffusion

Answer 14

temperature - kinetic energy particles move faster

concentration difference - the bigger the difference between them faster rate of diffusion

Question 15

what 2 things affect diffusion across membranes

Answer 15

surface area- the larger the higher rate of diffusion

thickness of membrane- the thinner the exchange surface the higher the rate of diffusion

Question 16

define facilitated diffusion

Answer 16

diffusion across a membrane through protein channels
allows polar molecules and ions to pass
passive movement down a conc gradient

Question 17

what is meant by passive movement

Answer 17

no metabolic - ATP energy is required

Question 18

what is meant by active transport

Answer 18

movment of ions or molecules into or out of a cell from a region of low conc to a region of high conc
requires energy and carrier proteins

Question 19

describe the process of active transport in steps

Answer 19

1) the molecule or ion to be transported binds to the receptors of the carrier protein on the outside of the cell
2) on the inside ATP binds to the carrier protein and is hydrolysed into ADP and Phosphate
3) protein changes shape opening up the inside of the cell
4) molecule is released to the inside of the cell
5) phosphate molecule is released from the carrier protein and recombines with ADP to from ATP
6) carrier protein return to its original shape

Question 20

define bulk transport

Answer 20

another form of active transport

large molecules and whole cells are transported by bulk transport through channel or carrier protein

Question 21

define endocytosis

Answer 21

is the bulk transport of material into cells

Question 22

what are the 2 types of endocytosis

Answer 22

phagocytosis - for solids

pinocytosis - for liquids