Lecture 1 - Cell membranes (prior to class review)

Question 1

What are the different strategies for studying cell biology?

Answer 1

1) Biochemistry
2) Forward genetics
3) Reverse genetics
4) Imaging
5) Protein structure analysis
(BFRIP or RIP best friends)

Question 2

What are the different model systems used for cell biology?

Answer 2

1) Yeast
2) C. elegans
3) Mammalian cell culture
4) Xenopus
5) Mouse

Question 3

The basic structure common to all cells and almost all eukaryotic organelles is what?

Answer 3

lipid bilayer

Question 4

The lipid bilayer is composed primarily of ______ and more specifically _____.

Answer 4

1. Lipids

2. phospholipids (and cholesterol)

Question 5

What are some of the basic characteristics of the lipid bilayer?

Answer 5

1. Asymmetric
2. Will form spontaneously and seal spontaneously
3. Acts as a barrier to diffusion of charged molecules, most polar molecules and macromolecules
4. Animal cells maintain a negative membrane potential

Question 6

Among other activities, membrane proteins regulate _______ and maintain membrane _________.

Answer 6

1. transport

2. potential

Question 7

Where is phosphotidylinositol found in relation to the plasma membrane?

Answer 7

Found in cytosolic layer of membrane.

Question 8

The inositol ring is phosphorylated by what?

Answer 8

PI kinases to form PIPs.

Question 9

PI phosphorylation is important in many ________ _________ pathways.

Answer 9

intracellular signalling

Question 10

PI cleavage is accomplished by?

Answer 10

phospholipases

Question 11

What is a phospholipase?

Answer 11

An enzyme that hydrolyzes phospholipids into fatty acids and other lipophilic substances

Question 12

Polar or charged molecules are __________ and will interact with water.

Answer 12

Hydrophilic

Question 13

Non-polar molecules are _________ and are repelled by water.

Answer 13

Hydrophobic

Question 14

Lipids are ______ molecules.

Answer 14

Bi-polar

Question 15

Glycoproteins and glycolipids are oriented with the ________ groups on the cell _______.

Answer 15

1. glycosyl

2. exterior

Question 16

Charged lipids such as phosphotidylinositol occur in the _______ layer.

Answer 16

inner

Question 17

Transmembrane domains can be predicted from the ___________ ______.

Answer 17

hydropathy index

Question 18

What are hydrophobicity scales?

Answer 18

Values that define the relative hydrophobicity of amino acid residues. These scales are often used to predict the transmembrane alpha-helices of membrane proteins.

Question 19

What are the two different types of membrane proteins?

Answer 19

1. Integral membrane proteins

2. Peripheral membrane proteins

Question 20

What are the basic characteristics of integral membrane proteins?

Answer 20

1. Transmembrane (single pass or multi-pass)
2. Covalently linked to lipids on the cytosolic side
3. GPI anchor on the lumenal (extracellular side)
4. Solubilized by membrane disrupting agents.

Question 21

What are the basic characteristics of peripheral membrane proteins?

Answer 21

Associated with integral membrane proteins by non-covalent interactions
Solubilized by mild detergents, low or high pH, high or low ionic strength

Question 22

Integral membrane proteins are _______, meaning that they have polar ends and a hydrophobic transmembrane domain.

Answer 22

amphipathic

Question 23

The transmembrane domain of integral membrane proteins is typically composed of _____ ______ with mainly __________ amino acids or _____ _____.

Answer 23

1. Alpha-helices
2. hydrophobic
3. Beta Barrel

Question 24

Most molecules are brought into or taken out of cells by specific ________ that recognize only that molecule.

Answer 24

transporters (carriers)

Question 25

What are the steps for the identification of lac mutants?

Answer 25

1. Irradiate cells to make mutants 2. Place into full media (contains many sugars) (permissive) 3. Replica plate onto media with lactose as only sugar/Carbon source (certain colonies fail to grow) 4. Isolate colonies

Question 26

What E. coli mutants are unable to grow on lactose as sole carbon source?

Answer 26

Lac Z/Y mutants

Question 27

True or False? Both Lac Z and lac Y are required for utilization of lactose.

Answer 27

True

Question 28

What experiment was done was done to determine whether the lacZ/Y genes were involved in import or cleavage of the disaccharide lactose?

Answer 28

1. Add 14C carbon lactose to growth media 2. Wash away media 3. Measure radioactivity with cells

Question 29

What was the observation of the lactose experiment? (Mutant for Y/Z)

Answer 29

Lactose enters wt and lacZ mutant cells but does not enter lac Y mutant cells

Question 30

Lac Y is required for _______ of lactose into the cell.

Answer 30

transport

Question 31

It was later shown that _____ enters with lactose.

Answer 31

H+

Question 32

True or False? Lac Y also affects the uptake of sugars related to lactose.

Answer 32

False

Question 33

The lac Y protein has 12 predicted transmembrane ______ _______.

Answer 33

Alpha helices

Question 34

Ion channels and transporters are also important in all cells for maintenance of _________ and establishing ____ and __________ gradients.

Answer 34

1. Osmolarity 2. Ion 3. Electrochemical

Question 35

Animal cells are ______ charged.

Answer 35

Negatively

Question 36

The electrochemical gradient for a given ion is equivalent to?

Answer 36

The ion gradient plus the membrane electrical potential.

Question 37

The sodium-potassium ATPase transports 3 _____ out while bringing in 2 ________.

Answer 37

1. sodium | 2. potassium

Question 38

___ leak channels allow ___ to passively leave the cell.

Answer 38

K+ (bis)

Question 39

In a typical resting cell, ___ is near its electrochemical potential while ___ is far from equilibrium.

Answer 39

1. K+ | 2. Na+

Question 40

__ channels allow __ to exit the cell - toward its electrochemical eqb, partially offsetting the negative membrane potential.

Answer 40

Cl- (bis)