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IMS > TRANSPORT ACROSS THE CELL MEMBRANE > Flashcards

TRANSPORT ACROSS THE CELL MEMBRANE Flashcards

1
Q

what is the function of the cell?

A

ability to move ions and organic molecules across membranes selectively

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2
Q

How do things move in/out PM?

A

Simple diffusion
Facilitated diffusion
Active Transport
(Endocytosis, Exocytosis)

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3
Q

is the PM selectively permeable?

A

Allows controlled passage of substances & ions

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4
Q

what kind of things are transported in/out of the cell?

A

Macromolecules eg.DNA, RNA, protein

Solutes eg.Ions, metabolites, amino acids

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5
Q

what is simple diffusion?

A

Unaided net movement of solute molecules through the lipid bilayer from [high] to [low]

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6
Q

what can move by simple diffusion?

A

Small non-polar molecules move across PM: O2, Co2

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7
Q

how is O2 transported by simple diffusion?

A

[O2] is high in lungs and [O2] is low in RBCs

O2 is taken up by RBCs in circulatory system and released in body tissues

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8
Q

why is facilitated diffusion necessary?

A

Large and polar substances cannot cross PM

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9
Q

what is used to allow facilitated diffusion to occur?

A

transport proteins

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10
Q

what do transport proteins allow?

A

provide a path through the hydrophobic lipid bilayer facilitating the diffusion

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11
Q

what type of gradient do uncharged molecules have?

A

conc gradient

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12
Q

what type of gradient do ions have?

A

electrochemical gradient

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13
Q

give an example of facilitated diffusion?

A

Glucose movement across the PM

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14
Q

how is glucose transported across the PM?

A

Glucose conc is higher in blood than in RBC

Transport protein in required

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15
Q

what are transport proteins?

A

integral membrane proteins containing trans-membrane segments

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16
Q

what are the 2 main types of transport proteins?

A

Carrier proteins

Channel proteins

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17
Q

what do carrier proteins do?

A

Facilitate traffic in either direction (inward/outward)

Bind one/more solute molecules on one side of the PM, then undergo a conformational change

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18
Q

how are carrier proteins categorised?

A

based on the number of solutes transported and the direction they move

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19
Q

what are the 3 types of carrier proteins?

A

Uniport: Single solute
Symport: 2 solutes / simultaneously
Antiport: 2 solutes / opposite directions

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20
Q

why doesn’t glucose move by simple diffusion?

A

Too large and too polar to diffuse across unaided

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21
Q

how does glucose transport occur?

A

Erythrocytes: Glucose transporter GLUT 1 (uniport)

integral membrane protein

22
Q

Where are other glucose transporters located?

A

Liver & Muscle

23
Q

what do channel proteins do?

A

Form hydrophilic transmembrane channels

Allow specific solutes to pass PM/no change in shape

24
Q

what are the 3 types of channel protein?

A

Ion channels
Porins
Aquaporins

25
Q

what are ion channels?

A

Small pores lined with hydrophilic AA side chains

26
Q

what do ion channels allow?

A

Allow rapid passage of specific ions

Na+, K+, Ca2+, and Cl-

27
Q

are ion channels gated?

A

yes, pore opens/closes in response to stimulus

28
Q

what are the 3 kinds of ion channels?

A

Voltage gated: change in memb potential
Ligand gated: binding of specific molecules
Mechano-sensitive: mechanical forces

29
Q

why are ion channels important?

A

Play a vital role in cellular communication via regulation of ions passage across memb

30
Q

what do ion channels maintain+example?

A

maintain salt balance in cells

eg. a specific Cl- ion channel maintains conc in lung epithelial cells (airways)

31
Q

why is maintaining salt balance in the lungs important?

A

Defects: excessive mucus build up in lungs -> Cystic Fibrosis

32
Q

what is active transport?

A

Movement of solutes against conc or electrochemical gradient

requires ATP

33
Q

what are the 3 major functions of active transport?

A

Uptake of nutrients when conc higher inside cell
Secretory products & waste materials removed
Enables cells maintain intracellular conc inorganic ions

34
Q

what does active transport involve?

A

membrane proteins: pumps

transport system / exergonic reaction

35
Q

how do solutes move in active transport?

A

moved in one direction: unidirectional process

36
Q

what is a result of active transport?

A

a non-equilibrium steady state

37
Q

what is the role of Na+/K+ pump present on PM?

A

Maintains electrochemical ion gradients
increase [ K+] [ Na+] =inside
decrease[K+] increase[Na+] =outside

38
Q

what does the activation of ATPase allow?

A

K+ pumped inward & Na+ outward

39
Q

How are large materials transported across PM ?

A

Exocytosis and Endocytosis

40
Q

what is Exocytosis and Endocytosis involved in?

A

in the delivery, recycling and turnover of membrane proteins

41
Q

what is exocytosis?

A

Process by which the contents of secretory granules (intracellular molecules) are released to the exterior of the cell
Vesicle fuse with PM in releasing process

42
Q

What kind substances released by exocytosis?

A

Peptides and protein hormones
Enzymes
Neurotransmitters

43
Q

what is endocytosis?

A

Process by which external materials are internalised by cells

44
Q

what happens in endocytosis?

A

A small segment of PM progressively folds inward

It pinches off to form an endocytic vesicle containing ingested substances or particles

45
Q

what is endocytosis important in?

A

Ingestion of nutrients by some organisms

Defence against microorganisms by WBC

46
Q

give examples of endocytosis

A

Phagocytosis ‘cellular eating

Pinocytosis ‘cellular drinking’

47
Q

what happens in phagocytosis?

A

Large and solid particles are ingested

48
Q

give examples of phagocytes

A

Macrophages

Neutrophils

49
Q

what is pinocytosis?

A

Liquids containing soluble molecules are taken up

50
Q

what happens in pinocytosis?

A

Nonspecific in the substances that it transports
An invagination into the cell
Pinching off inside the cell to form coated vesicles (clathrin)

IMS (52 decks)

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