1.3 Cell Membranes and Transport

Question 1

what is the fluid mosaic model?

Answer 1

mosaic - the proteins are varied in shape and size and scattered throughout the lipid bilayer like a mosaic
fluid - the components are free to move along the membrane as in fluid

Question 2

What are the principle components of
the plasma membrane?

Answer 2

● Intracellular and extracellular proteins
● Glycoproteins
● Phospholipids
● Cholesterol

Question 3

what is the role of the cell surface membrane?

Answer 3

• boundary between living cell content and non-living surroundings
• controls the exchange of nutrients, respiratory gases and toxins

Question 4

role of extrinsic proteins?

Answer 4

● Receptors for hormones
● Act as antigens, enabling cell recognition
● Help cells adhere to each othe

Question 5

role of intrinsic proteins?

Answer 5

● Structural support
● Carry water-soluble molecules across the
phospholipid bilayer
● Form ion channels to enable active transport

Question 6

where are extrinsic proteins found?

Answer 6

embedded on the surface

Question 7

where are intrinsic proteins found?

Answer 7

they span the full width of the membrane

Question 8

describe the charges on the proteins

Answer 8

charged groups associates with polar hydrophilic heads
uncharged regions associate with inner hydrophobic tails

Question 9

what is the role of carrier proteins?

Answer 9

• receptors for hormones
  cell recognition and signalling
• antigens
• stabilize cell shape

Question 10

what is the role of cholesterol? (form of lipid)

Answer 10

gives stability and regulates the fluidity of the membrane

Question 11

what factors affect the permeability of the plasma membrane?

Answer 11

1. temperature
2. pH
3. Ethanol

Question 12

how does high temperature affect permeability?

Answer 12

high temp denatures proteins and melts the bilayer, which becomes more fluid so it increases the permeability
Freezing temps cause ice crystals which disrupt the membrane and increase permeability

Question 13

how does pH affect permeability?

Answer 13

extremes denature proteins so movement of molecules is affected

Question 14

how does ethanol affect permeability?

Answer 14

lipid soluble, so it can diffuse through the bilayer and dissolve it. denatures proteins
makes membranes porous= increases permeability

Question 15

who proposed the fluid mosaic model?

Answer 15

singer and nicholson

Question 16

what is the function of the phospholipid bilayer

Answer 16

to allow small (co2+o2) and non-polar vitamins to pass through

Question 17

what does the term lipid bilayer mean?

Answer 17

two layers of phospholipids

Question 18

name the hydrophobic parts

Answer 18

fatty acid tails

Question 19

state two roles of the plasma membrane

Answer 19

obtain oxygen and glucose
removes co2

Question 20

what is passive transport?

Answer 20

transport that does not need energy

Question 21

what is active transport?

Answer 21

transport that needs energy (ATP)

Question 22

what is diffusion?

Answer 22

passive movement of molecules from a region of relative high conc to one of relative low conc

Question 23

how does being small help molecules move?

Answer 23

higher kinetic energy molecules can pass between the phospholipid layer

Question 24

what is facilitated diffusion?

Answer 24

type of passive transport that allows substances to cross membranes with the assistance of special transport proteins

Question 25

what is the role of ion channels?

Answer 25

allows specific ions to pass through the protein channel

Question 26

what cannot pass through the membrane?

Answer 26

glucose, sodium ions, chloride ions

Question 27

what is the width of the plasma membrane?

Answer 27

7-8nm

Question 28

what is the role of cholesterol

Answer 28

regulates the fluidity of the membrane

Question 29

what is the role of carrier proteins?

Answer 29

bind to specific molecules - must be complementary

Question 30

what is a glycocalyx ?

Answer 30

A glycoprotein and glycolipid coating
surrounding the cell membrane of some
cells.

Question 31

State the factors that affect the rate of
diffusion.

Answer 31

● Temperature
● Steepness of concentration gradient
● Size of molecule
● Diffusion distance
● Surface area

Question 32

State the factors that affect the rate of
diffusion.

Answer 32

● Temperature
● Steepness of concentration gradient
● Size of molecule
● Diffusion distance
● Surface area

Question 33

define water potential?

Answer 33

A measure of the tendency of water
molecules to move from one area to
another.

Question 34

example of facilitated diffusion?

Answer 34

co-transport

Question 35

define active transport?

Answer 35

The movement of substances from a low
concentration to a higher concentration
(against the concentration gradient) through
carrier proteins with the use of energy in
the form of ATP

Question 36

How does cyanide affect active transport?

Answer 36

Cyanide inhibits cytochrome oxidase,
stopping the production of ATP. This
prevents active transport.

Question 37

What are the two mechanisms of bulk
transport?

Answer 37

endocytosis
exocytosis

Question 38

define endocytosis?

Answer 38

The bulk uptake of substances into a cell
by invagination of the membrane to form a
vesicle. Uses energy in the form of ATP

Question 39

State the two types of endocytosis

Answer 39

phagocytosis
pinocytosis

Question 40

What is pinocytosis?

Answer 40

The bulk uptake of liquids into the cell
using energy in the form of ATP

Question 41

What is phagocytosis?

Answer 41

The bulk uptake of solids into the cell
using energy in the form of ATP.

Question 42

Define exocytosis

Answer 42

The bulk transport of substances out of a
cell via a vesicle that fuses with the
plasma membrane. Uses energy in the
form of ATP.