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CTB > Cell signalling > Flashcards

Cell signalling Flashcards

1
Q

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

A

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

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2
Q

3 main characteristics of the plasma membrane

A

It is FLUID, DYNAMIC, and ASYMMETRICAL

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3
Q

3 types of lipids in cell membrane

A

phospholipid
cholesterol
glycolipid

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4
Q

What are used to lower LDL cholesterol and how?

A

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

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5
Q

What does CRAC stand for?

A

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

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6
Q

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

A

lipid annulus

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7
Q

Predominant anion within the cell?

A

Cl-

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8
Q

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

A

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

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9
Q

2 types of membrane proteins

A
  1. transport and channel proteins (eg. ATPases)

2. receptors (eg. GPCRs)

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10
Q

2 types of cellular transport and their definitions

A
  1. Intercellular: transport BETWEEN CELLS and across membrane
  2. Intracellular: WITHIN THE CELL across different compartments
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11
Q

3 general classes of transport systems across membranes

A
  1. uniport
  2. symport
  3. antiport
    note: symport and antiport are both forms of cotransport)
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12
Q

channel proteins allow for what type of transport?

A

passive transport

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13
Q

main difference between channel and carrier proteins?

A

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

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14
Q

Major differences between ion channels and ion transporters:

A
  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)
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15
Q

Ions pass through gated ion channels only when what?

A

only when the channels are in OPEN CONFIGURATION

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16
Q

2 types of ion gated channels

A

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

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17
Q

Primary active transport

A

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

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18
Q

Secondary active transport

A

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

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19
Q

Active transport that uses 25% of energy at rest?

A

Na+ K+ ATPase

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20
Q

what does Na+ K+ ATPase do?

A

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

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21
Q

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

A

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.

22
Q

Describe glucose transport in intestinal epithelial cells

A

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

23
Q

What is the name of the basal glucose transporter molecule?

A

GluT2

24
Q

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

A

glucose uptake

25
Q

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?

A

a) Ca++ is pumped out of the cytosol to the cell exterior

b) Ca++ is pumped into the intracellular, membrane enclosed organelles (eg. mito)

26
Q

Largest group of membrane receptors

A

GPCRs

27
Q

Molecules secreted by exocytosis may:

A
  • 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
28
Q

pathway of a secreted protein

A
  • 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
29
Q

Exocytosis takes place by fusion of ___ ___ and ___ ___

A

secretory vesicles and plasma membrane

30
Q

3 types of extracelular vesicles:

A
  • exosomes
  • microvesicles
  • appoptotic bodies
31
Q

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

A

exosomes

32
Q

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

A

parental

33
Q

endocytosis is divided into two types:

A
  1. pinocytosis - ingestion of fluid or solutes via VESICLES

2. phagocytosis - ingestion of large particles via VACUOLES

34
Q

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

A

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

35
Q

Endocytotic vesicles fuse with lysosomes to form ___ ___

A

secondary lysosomes

36
Q

formation of the receptor-coated pit

A
  • 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
37
Q

Clathrin recruitment depends on __ __

A

particle size

38
Q

two types of hormones

A
  • steroid (traverse cell membranes)

- polypeptide (act through cell surface receptors)

39
Q

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

A

second messengers

40
Q

Define ligand

A

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

41
Q

Define agonist

A

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

42
Q

Inverse agonist

A

a ligand that binds to a receptor and reduces its activity

43
Q

Antagonist

A

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

44
Q

2 types of G proteins

A
  1. large heterotrimeric G-proteins - consist of 3 subunits (Ga, Gb, Gy)
  2. small G proteins - monomeric
45
Q

G-proteins alternate between:

A

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

46
Q

cAMP, IP3 and Ca++ are examples of

A

second messengers

47
Q

cAMP signal transduction system

A
  • adrenaline binds to b-adrenergic receptor
  • Gs-protein activates adenylate cyclase, which increases cAMP
  • cAMP activates protein kinase
48
Q

What is the first step in taste desensitization?

A

phosphorylation

49
Q

Secretory ameloblasts produce many proteins in enamel, including:

A

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

50
Q

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

A

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

CTB (7 decks)

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