TRANSPORT ACROSS THE CELL MEMBRANE

Question 1

what is the function of the cell?

Answer 1

ability to move ions and organic molecules across membranes selectively

Question 2

How do things move in/out PM?

Answer 2

Simple diffusion
Facilitated diffusion
Active Transport
(Endocytosis, Exocytosis)

Question 3

is the PM selectively permeable?

Answer 3

Allows controlled passage of substances & ions

Question 4

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

Answer 4

Macromolecules eg.DNA, RNA, protein

Solutes eg.Ions, metabolites, amino acids

Question 5

what is simple diffusion?

Answer 5

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

Question 6

what can move by simple diffusion?

Answer 6

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

Question 7

how is O2 transported by simple diffusion?

Answer 7

[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

Question 8

why is facilitated diffusion necessary?

Answer 8

Large and polar substances cannot cross PM

Question 9

what is used to allow facilitated diffusion to occur?

Answer 9

transport proteins

Question 10

what do transport proteins allow?

Answer 10

provide a path through the hydrophobic lipid bilayer facilitating the diffusion

Question 11

what type of gradient do uncharged molecules have?

Answer 11

conc gradient

Question 12

what type of gradient do ions have?

Answer 12

electrochemical gradient

Question 13

give an example of facilitated diffusion?

Answer 13

Glucose movement across the PM

Question 14

how is glucose transported across the PM?

Answer 14

Glucose conc is higher in blood than in RBC

Transport protein in required

Question 15

what are transport proteins?

Answer 15

integral membrane proteins containing trans-membrane segments

Question 16

what are the 2 main types of transport proteins?

Answer 16

Carrier proteins

Channel proteins

Question 17

what do carrier proteins do?

Answer 17

Facilitate traffic in either direction (inward/outward)

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

Question 18

how are carrier proteins categorised?

Answer 18

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

Question 19

what are the 3 types of carrier proteins?

Answer 19

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

Question 20

why doesn’t glucose move by simple diffusion?

Answer 20

Too large and too polar to diffuse across unaided

Question 21

how does glucose transport occur?

Answer 21

Erythrocytes: Glucose transporter GLUT 1 (uniport)

integral membrane protein

Question 22

Where are other glucose transporters located?

Answer 22

Liver & Muscle

Question 23

what do channel proteins do?

Answer 23

Form hydrophilic transmembrane channels

Allow specific solutes to pass PM/no change in shape

Question 24

what are the 3 types of channel protein?

Answer 24

Ion channels
Porins
Aquaporins

Question 25

what are ion channels?

Answer 25

Small pores lined with hydrophilic AA side chains

Question 26

what do ion channels allow?

Answer 26

Allow rapid passage of specific ions | Na+, K+, Ca2+, and Cl-

Question 27

are ion channels gated?

Answer 27

yes, pore opens/closes in response to stimulus

Question 28

what are the 3 kinds of ion channels?

Answer 28

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

Question 29

why are ion channels important?

Answer 29

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

Question 30

what do ion channels maintain+example?

Answer 30

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

Question 31

why is maintaining salt balance in the lungs important?

Answer 31

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

Question 32

what is active transport?

Answer 32

Movement of solutes against conc or electrochemical gradient | requires ATP

Question 33

what are the 3 major functions of active transport?

Answer 33

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

Question 34

what does active transport involve?

Answer 34

membrane proteins: pumps | transport system / exergonic reaction

Question 35

how do solutes move in active transport?

Answer 35

moved in one direction: unidirectional process

Question 36

what is a result of active transport?

Answer 36

a non-equilibrium steady state

Question 37

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

Answer 37

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

Question 38

what does the activation of ATPase allow?

Answer 38

K+ pumped inward & Na+ outward

Question 39

How are large materials transported across PM ?

Answer 39

Exocytosis and Endocytosis

Question 40

what is Exocytosis and Endocytosis involved in?

Answer 40

in the delivery, recycling and turnover of membrane proteins

Question 41

what is exocytosis?

Answer 41

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

Question 42

What kind substances released by exocytosis?

Answer 42

Peptides and protein hormones Enzymes Neurotransmitters

Question 43

what is endocytosis?

Answer 43

Process by which external materials are internalised by cells

Question 44

what happens in endocytosis?

Answer 44

A small segment of PM progressively folds inward | It pinches off to form an endocytic vesicle containing ingested substances or particles

Question 45

what is endocytosis important in?

Answer 45

Ingestion of nutrients by some organisms | Defence against microorganisms by WBC

Question 46

give examples of endocytosis

Answer 46

Phagocytosis ‘cellular eating | Pinocytosis ‘cellular drinking’

Question 47

what happens in phagocytosis?

Answer 47

Large and solid particles are ingested

Question 48

give examples of phagocytes

Answer 48

Macrophages | Neutrophils

Question 49

what is pinocytosis?

Answer 49

Liquids containing soluble molecules are taken up

Question 50

what happens in pinocytosis?

Answer 50

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