Chapter 2

Question 1

Cell membranes are held together by …. interactions, about … nm thick

Answer 1

non-covalent, 5 nm
non-covalent = weak, no sharing of electrons

Question 2

Lipid bilayer = A %, membrane proteins = B%
Lipid bilayer: provides basic fluid structure. impermeable for C molecules

Answer 2

a = 50
b = 50
c = water-soluble

Question 3

Functions of membrane proteins

Answer 3

1. Transport
2. Receptor
3. Catalysis (e.g. ATP synthesis)
4. Structural (link cytoskeleton to extracellular matrix or
   other cell)
5. Cellular recognition

Question 4

Lipid molecules are amphiphilic = ?

Answer 4

Hydrophobic non-polar end
* Hydrophilic polar end

Question 5

Lipid bilayer consists of …. (75%), …. (5%) and …… (20%)

Answer 5

phospholipids
glycolipids
cholesterol

Question 6

What are liposomes?

Answer 6

Phospholipid membranes spontaneously
close to form a sealed compartment:
liposomes.
* It is the energetically most favorable
arrangement.

Question 7

Phospholipid molecules change places with their neighbors in a
monolayer very rapidly (107 times / s): true/false

Answer 7

true

Question 8

Are cholesterol molecules amphiphilic?

Answer 8

yes queen they are in the bilayer : heads to heads, tails to tails

Question 9

glycolipids: where and what do they do

Answer 9

Sugar-containing lipid molecules.
* Constitute 5% of total lipid molecules in the
outer monolayer.

Functions:
* Membrane protection
* Cell-recognition
* In nerve cells: membrane electrical propieties.

Question 10

cell membrane is symmetric with different phospholipid compositions in each of the bilayer leaflets:true/false

Answer 10

false

Question 11

Fluidity of a lipid bilayer depends on….. and ….

Answer 11

composition (fatty acid
composition and cholesterol amount)
and temperature

Question 12

Cholesterol makes the lipid bilayer stronger/weaker but less firm/fluid at normal body
temperature.

Answer 12

stronger, less fluid

Question 13

According to the fluid mosaic model of the membrane structure, membranes are
two-dimensional fluids in which protein are inserted into lipid bilayers.

Answer 13

okay

Question 14

Functions of cell membrane?

Answer 14

1. Diffusion barrier: regulates entry and exit of substances.
2. Vesicle transport (glandular secretions).
3. Cell identification: surface proteins allow identifying a cell.
4. Communication: proteins act as receptors for hormones.
5. Intercellular connections: cells can be in contact or linked by special
   complexes.

Question 15

ECF: has more A and B than intracellular fluid

Answer 15

A) K+
B) proteins

Question 16

Given enough time, virtually almost any molecule will diffuse across a proteinfree lipid bilayer down its concentration gradient: molecules move from more to
less concentration (downhill). True/false

Answer 16

True, but will take very long

Question 17

Rate of diffusion across membrane depends on…

Answer 17

• size of molecule
• polarity (more phobic, more easily)

Question 18

Lipid bilayers are essentially impermeable to

Answer 18

charged molecules (ions).

Question 19

Passive diffusion: depends on

Answer 19

concentration imbalance
Size molecule
Polarity

Question 20

Set the following molecules from fast diffusion - no doffusion through membrane

1. Large uncharged polar
2. small uncharged polar
3. ions
4. small nonpolar

Answer 20

4. small nonpolar
5. small uncharged polar
6. Large uncharged polar
7. ions

Question 21

Which 3 transport methods across membrane are there? passive or active?

Answer 21

1. simple passive diff (passive)
2. channels (passive)
3. transporters (can be active or passive)

Question 22

tonicity: ?

Answer 22

Osmolarity of the solution compared to
the plasma osmolarity

Question 23

what types of tonicity are there?

Answer 23

isotonic: same in & out
hypotonic: solution lower osm
hypertonic: solution higher osm

Question 24

differences channels and transporters?

Answer 24

channels: strictly passive, weaker interactions. faster transport rate,
transp: active or passive, undergo conformational changes

Question 25

ion channels are also highly ..... and ....

Answer 25

highly selective gated (most are close and open in response to stimulus)

Question 26

recall three types of stimuli for ion gate to open

Answer 26

1. voltage 2. mechanical stress 3. ligand binding (neurotransm, ion, nucleotide)

Question 27

two gradients control the movement of ions through cell membrane

Answer 27

1. conc gradient 2. ELECTROCHEMICAL GRADIENT.

Question 28

Typically, the inner surface of the plasma membrane is more A charged and the outer surface is more X charged.

Answer 28

A negatively X positively

Question 29

The combined influence of the concentration gradient and the electrical gradient on movement of a particular ion is referred to as its x gradient.

Answer 29

electrochemical

Question 30

ion channels are responsible for the electrical excitability of x cells

Answer 30

muscle

Question 31

ion channels mediate most forms of electrical signaling in the x system

Answer 31

nervous

Question 32

two other words for transporters?

Answer 32

carriers/permeases

Question 33

true or false: each transporter only binds and translocates a single solute type

Answer 33

true

Question 34

two steps for a transporter to get a molecule across?

Answer 34

1. recognition 2. conformational change

Question 35

Which 3 states does a transporter have?

Answer 35

1. outward-open 2. occluded 3. inward state

Question 36

which 3 types of active transporters are there?

Answer 36

1. uniport (one side to other side) 2. symport (simultanious transfer in same direction) 3. antiport (simultanious transfer in opposite direction)

Question 37

endocytosis: passive or active?

Answer 37

active

Question 38

What two main pathways for endocytosis are there?

Answer 38

1. Phagocytosis: Large particles 2. Pinocytosis: molecules and water

Question 39

Phagocytosis: - requires A through specific membrane receptors (B process) - It is a(n) passive/active and highly regulated process

Answer 39

A recognition b selective - active

Question 40

Phagocytosis: Once the phagosome is formed, it will fuse x * The content will be digested by .... enzymes.

Answer 40

x lysosomes. x lysosomal

Question 41

In mammals phagocytosis occurs in specialized cells, such as... Functions: defense against pathogens and cleaning cell debris.

Answer 41

- macrophages - monocytes - neutrophils - dendritic cells

Question 42

Pinocytosis: is a form of endocytosis involving X * In pinocytosis, the cell repeatedly takes in X from the surrounding environment using tiny vesicles. * Pinocytosis occurs in X cell types

Answer 42

X fluids containing small solutes. X fluid X many

Question 43

What subtypes of pinocytosis are there?

Answer 43

1. large: macropinocytosis 2. small (clathrin, caveolin and clathrin + caveolin dependent)

Question 44

Macropinocytosis: - A (requires receptor activation). - Requires reorganization of the B of the cytoskeleton. * A protrusion is used like an arm

Answer 44

A Selective B actin filaments

Question 45

Clathrin-dependent: X coat the vesicle to initiate endocytosis The vesicle with the cargo is transported into the cell and fuses with endosomes and lysosomes. X process: ligand-receptor Requires X

Answer 45

X Clathrin protein X selective X energy

Question 46

Caveolin-dependent endocytosis - Caveolae are small X - Endocytosis of X and X - In humans, this process occurs in cells lining the small intestine and is used primarily for absorption. * Require much X and the process is

Answer 46

X invaginations of the cell's plasma membrane. X fluids and solutes X energy. X Nonspecific.

Question 47

In what types of cells is exocytosis especially important?

Answer 47

- secretory cells - nerve cells