Cell signalling

Question 1

The plasma membrane is composed of ___ and ___ that are held together by _____ ____ interactions

Answer 1

The plasma membrane is composed of PHOSPHOLIPIDS and PROTEINS that are held together by NON-COVALENT HYDROPHOBIC interactions

Question 2

3 main characteristics of the plasma membrane

Answer 2

It is FLUID, DYNAMIC, and ASYMMETRICAL

Question 3

3 types of lipids in cell membrane

Answer 3

phospholipid
cholesterol
glycolipid

Question 4

What are used to lower LDL cholesterol and how?

Answer 4

STATINS are used to lower LDL cholesterol by INHIBITING the enzyme HGM-CoA reductase, which plays a role in the production of cholesterol in the liver

Question 5

What does CRAC stand for?

Answer 5

“Cholesterol Recognition Amino acid Consesus” sequence, present in some membrane proteins

Question 6

The first shell of lipid molecules, in direct contact with the membrane protein is termed the __ __

Answer 6

lipid annulus

Question 7

Predominant anion within the cell?

Answer 7

Cl-

Question 8

Percentage of genes in a typical genome which encode for membrane proteins

Answer 8

membrane proteins are encoded by more than 20% of the genes in typical genomes

Question 9

2 types of membrane proteins

Answer 9

1. transport and channel proteins (eg. ATPases)

2. receptors (eg. GPCRs)

Question 10

2 types of cellular transport and their definitions

Answer 10

1. Intercellular: transport BETWEEN CELLS and across membrane
2. Intracellular: WITHIN THE CELL across different compartments

Question 11

3 general classes of transport systems across membranes

Answer 11

1. uniport
2. symport
3. antiport
   note: symport and antiport are both forms of cotransport)

Question 12

channel proteins allow for what type of transport?

Answer 12

passive transport

Question 13

main difference between channel and carrier proteins?

Answer 13

carrier proteins bind to what is being transported, while channel proteins allow for diffusion

Question 14

Major differences between ion channels and ion transporters:

Answer 14

1. rate of flux through CHANNELS can be much greater than turnover number for a TRANSPORTER
2. Ion channels are NOT SATURABLE
3. Ion channels are GATED (open/closed in response to cellular events)

Question 15

Ions pass through gated ion channels only when what?

Answer 15

only when the channels are in OPEN CONFIGURATION

Question 16

2 types of ion gated channels

Answer 16

a) ligan gated: activate/inactivate depending on binding of extracellular ligands to the channel
b) voltage gated: opens when the membrane is depolarized

Question 17

Primary active transport

Answer 17

the energy released by ATP hydrolysis drives solute movement against an electrochemical gradient

Question 18

Secondary active transport

Answer 18

after a gradient of ion x (eg. Na+) has been established by primary transport, movement of x down its electrochemical gradient provides energy to drive cotransport of a second solute against its electrochemical gradient

Question 19

Active transport that uses 25% of energy at rest?

Answer 19

Na+ K+ ATPase

Question 20

what does Na+ K+ ATPase do?

Answer 20

couples the breakdown of ATP to the simultaneous movement of both Na+ and K+ against their electrochemical gradient (2 K+ in, 3 Na+ out)

Question 21

Active transport of glucose is driven by a ___ ___ that is generated and maintained by the _____

Answer 21

Active transport of glucose is driven by a Na+ GRADIENT that is generated and maintained by the Na+K+ATPase. THis is known as GLUCOSE SYMPORT.

Question 22

Describe glucose transport in intestinal epithelial cells

Answer 22

glucose is cotransported with Na+ across the plasma membrane into the epithelial cell. It moves through the cell to the basal surface, where it passes into the blood via GluT2, a passive glucose transporter

Question 23

What is the name of the basal glucose transporter molecule?

Answer 23

GluT2

Question 24

Na+K+ATPase pumps Na+ outward to maintain the gradient of Na+ that drives:

Answer 24

glucose uptake

Question 25

What are the main ways in which cells maintain a very low concentration of free Ca++ in the cytosol in the face of high concentrations of Ca++ in the ECF?

Answer 25

a) Ca++ is pumped out of the cytosol to the cell exterior | b) Ca++ is pumped into the intracellular, membrane enclosed organelles (eg. mito)

Question 26

Largest group of membrane receptors

Answer 26

GPCRs

Question 27

Molecules secreted by exocytosis may:

Answer 27

- adhere to the cell surface or incorporate into the extracellular surface - diffuse into the blood or body fluids as intercellular signal molecules (eg. extracellular vesicles, microvesicles, and exosomes) - be digestive enzymes

Question 28

pathway of a secreted protein

Answer 28

- protein synthesis on ribosomes on RER - Move from RER to Golgi by transport vesicles - in golgi, undergo protein modification, get sorted, concentrated and packed into secretory vesicles - secretory vesicles travel from Golgi and fuse with plasma membrane

Question 29

Exocytosis takes place by fusion of ___ ___ and ___ ___

Answer 29

secretory vesicles and plasma membrane

Question 30

3 types of extracelular vesicles:

Answer 30

- exosomes - microvesicles - appoptotic bodies

Question 31

What types of extracellular vesicles allow human cells to communicate with eachother?

Answer 31

exosomes

Question 32

The contents carried by the exosomes are derived from its ___ cell

Answer 32

parental

Question 33

endocytosis is divided into two types:

Answer 33

1. pinocytosis - ingestion of fluid or solutes via VESICLES | 2. phagocytosis - ingestion of large particles via VACUOLES

Question 34

t/f: endocytosis involves the fusion of two cytoplasmic faces

Answer 34

false. It involves the fusion of two non-cytoplasmic faces

Question 35

Endocytotic vesicles fuse with lysosomes to form ___ ___

Answer 35

secondary lysosomes

Question 36

formation of the receptor-coated pit

Answer 36

- proteins bind to receptors in invaginations of the membrane called COATED PITS - Coated pits concentrate receptors mediated for endocytosis in preferences to other receptors - Pits are coated on their cytosolic side with clathrin - adaptors link the membrane proteins with the clathrin that forms the outer layer of the coat - together with accesory molecules, the growing coated pit invaginates. Eventually, the membrane neck is severed to form a closed endocytic vesicle

Question 37

Clathrin recruitment depends on __ __

Answer 37

particle size

Question 38

two types of hormones

Answer 38

- steroid (traverse cell membranes) | - polypeptide (act through cell surface receptors)

Question 39

A ligand does not enter a cell, but generates ___ ___ that regulate physiological functions

Answer 39

second messengers

Question 40

Define ligand

Answer 40

A molecule that binds to a receptor (eg. adrenaline, sucrose)

Question 41

Define agonist

Answer 41

a ligand that binds to a receptor and alters the receptor-state resulting in a biological response. Conventionally increase receptor activity

Question 42

Inverse agonist

Answer 42

a ligand that binds to a receptor and reduces its activity

Question 43

Antagonist

Answer 43

a ligan that inhibits receptor activation by another ligand, generally an agonist

Question 44

2 types of G proteins

Answer 44

1. large heterotrimeric G-proteins - consist of 3 subunits (Ga, Gb, Gy) 2. small G proteins - monomeric

Question 45

G-proteins alternate between:

Answer 45

inactive guanosine diphosphate (GDP) and active guanosine triphosphate (GTP) bound state

Question 46

cAMP, IP3 and Ca++ are examples of

Answer 46

second messengers

Question 47

cAMP signal transduction system

Answer 47

- adrenaline binds to b-adrenergic receptor - Gs-protein activates adenylate cyclase, which increases cAMP - cAMP activates protein kinase

Question 48

What is the first step in taste desensitization?

Answer 48

phosphorylation

Question 49

Secretory ameloblasts produce many proteins in enamel, including:

Answer 49

amelogenin (AMEL), ameloblastin (AMBN), enamelin (ENAM)

Question 50

What plays a critical role in regulating the growth of initiall enamel crystals?

Answer 50

phosphorylation of a single serine residue (Ser-16) in AMEL (amelogenin)