Chapter 1.4 : Cell structure and function pt. 2

Question 1

what is the main purpose of the plasma membrane an what characteristic does it exhibit

Answer 1

• its main purpose is to control the traffic into and out of the cell
• it exhibits selective permeability (regulates passages of substances )

Question 2

what is the plasma membrane composed of

Answer 2

a bilayer of phospholipids

Question 3

meaning of amphipathic

Answer 3

has a hydrophilic and hydrophobic region

Question 4

what is the membrane held together by

Answer 4

by hydrophobic interactions

Question 5

true or false, most lipids and proteins can shift laterally

Answer 5

true

Question 6

if the temperature decreases, what happens to the fluidity of the phospholipid membrane

Answer 6

they become packed together and the membrane solidifies

Question 7

suppose there is one membrane rich in phospholipids with unsaturated hydrocarbon tails and another membrane with saturated ones

which membrane is going to remain fluid for the longest if the temperature keeps decreasing

Answer 7

the membrane rich in unsaturated hydrocarbon tails

because unsaturated tails are kinked, it prevents packing enhancing membrane fluidity

Question 8

what is wedged in between phospholipids in the plasma membrane that acts as a fluidity buffer

Answer 8

cholesterol

Question 9

name two things fluidity had an effect on

Answer 9

• permeability
• ability of membrane proteins to move around

Question 10

differentiate the two types of membrane proteins

Answer 10

1. integral proteins
   - transmembrane: crosses the entire length
   - penetrate interior of lipid bilayer
2. peripheral proteins
   - not embedded in lipid bilayer

Question 11

integral proteins can sometimes have hydrophilic channels, what does it do

Answer 11

allows hydrophilic substances pass through

Question 12

how are membrane proteins held in place on the cytoplasmic side

Answer 12

attached to the cytoskeleton

Question 13

how are the membrane proteins held in place on the extracellular side

Answer 13

attached to fibres outside the cell

Question 14

what are the six major functions of membrane proteins

Answer 14

1. transport
2. enzymatic activity
3. signal transduction
4. cell-cell recognition
5. intercellular joining
6. attachment to cytoskeleton and extracellular matrix

Question 15

which is going to move through a membrane faster?
a hydrophobic/non polar substance or
a polar substance

Answer 15

the non polar substance crosses faster

Question 16

what are the two types of transport proteins

Answer 16

1. channel proteins
   hydrophilic channels
2. carrier proteins
   holds onto the substance then changes shape to shuttle them across the membrane

Question 17

differentiate passive and active transport

Answer 17

passive does not require energy input

active requires energy/help from atp

Question 18

how do you describe the solution if the concentration of non penetrating solutes inside the cells is higher than outside of the cell

Answer 18

hypertonic

Question 19

what does atp do

Answer 19

supplies the energy

Question 20

what is the name of the process that describes secretion of molecules by the fusion of vesicles from golgi

Answer 20

exocytosis

Question 21

what is the name of the process of that describe a cell taking in molecules by forming new vesicles from the plasma membrane

Answer 21

endocytosis

Question 22

differentiate phagocytosis and pinocytosis

Answer 22

phagocytosis is cell eating
pinocytosis is cell drinking