Chapter 6 - Interactions between Cells and The Extracellular Environment

Question 1

Materials are transported in and out of a cell through the _____ _______

Answer 1

cell membrane

Question 2

What is vital for all cells to maintain?

Answer 2

constant/stable intracellular environment (homeostasis)

Question 3

The cell membrane is _____ _________.

Explain what this means

Answer 3

selectively permeable

only allows substances of certain sizes/charge in/out

Question 4

Explain why the cell membrane is selectively permeable

Answer 4

It is selectively permeable because it brings in molecules it needs and exclude molecules it does not need.

Question 5

What are the different ways substances can move across the cell membrane?

Answer 5

• passive transport
• active transport
• bulk transport

Question 6

What is another term for passive transport?

Answer 6

diffusion

Question 7

What are two examples of passive transport?

Answer 7

• simple diffusion
• facilitated diffusion

Question 8

What are two examples of active transport?

Answer 8

• primary active transport
• secondary active transport

Question 9

In passive transport, substances move from a ______ to _________ concentration.

Answer 9

higher
lower

Question 10

In which transport system across the cell membrane do NOT use energy?

Answer 10

passive transport

Question 11

In which transport system across the cell membrane USES energy?

Answer 11

active transport

Question 12

In active transport, substances move from a ______ to _________ concentration.

Answer 12

lower
higher

Question 13

Passive transport is ________ movement of substances from an area of high concentration to low concentration

Answer 13

spontaneous (natural)

Question 14

Define the concentration gradient

Answer 14

the concentration difference across a cell membrane

Question 15

Compare simple diffusion vs facilitated diffusion. Include examples

Answer 15

simple diffusion is for movement of small, non-polar and/or uncharges substances and move in/out the cell directly through the cell membrane (ex. o2, co2 (gases), steroids (fats)).

facilitated diffusion is for movement of large, polar, and/or charged substances and are repelled by the phospholipid bilayer (ex. Na+, Cl- (ions), glucose (large)). It requires facilitators to move substanecs in/out of the cell membrane (protein channels+carriers)

Question 16

Why are steroids allowed to travel straight through the cell membrane but not Na+

Answer 16

steroids are uncharged and nonpolar, meaning they use simple diffusion

Na+ is an ion with a positive charge, needing facilitated diffusion.

Question 17

What is a facilitator? Why are they important?

Answer 17

it helps move substances through the cell membrane (protein channels and protein carriers)

it helps move large, polar, and charged particles down the concentration gradient (high -> low)

Question 18

Compare the different facilitators in facilitated diffusion

Answer 18

protein channels

• embedded in cell membrane
• closed/open state (gate)
• move substances high -> low
• ex: Na+ channel, K+ channel, water channel

protein carriers

• embedded in cell membrane
• carrier physically attaches to substance being transported -> changes shape of protein carrier -> opens at opposite end -> releases substance
• ex: glucose carrier protein

Question 19

ion channels and protein carriers are mostly ______

Answer 19

specific (show specificity)

Question 20

In facilitated diffusion, which type of facilitator shows specificity?

Answer 20

protein carriers are more specific than ion channels because they have to bind to a substance

Question 21

ion channels and protein carriers can show ______ and _________

Answer 21

saturation and competition

Question 22

What does it mean when we say channels and carriers can show “competition”

Answer 22

some proteins (ion channels and protein carriers) can transport more than one molecule, which causes competition

Question 23

What is saturation and what happens to the rate of particle transport when saturation has been met?

Answer 23

when a molecules transport rate reaches its plateau

Question 24

Describe saturation and competition

Answer 24

The transport rate increases with increasing molecule concentration until all the carriers are in use -> transportation rates plateau -> saturation has been met

Some proteins are able to transport more than one molecule, which can cause a competition effect

The maximum transport rate is known as the transport maximum (Tm)

Question 25

If saturation is met after reaching a certain molecule concentration, what can you say about the number of channels and/or carriers present in the cell membrane?

Answer 25

there is a limited number of channels/carriers

Question 26

T or F: The number of channels and carriers embedded in the cell membrane is constant throughout the life of the cell

Answer 26

False, they can be inserted or removed when needed The amount of carriers are determined by the need of the cell

Question 27

What type of carrier proteins transport glucose?

Answer 27

GLUT (1,2,3,4)

Question 28

Active transport requires some form of energy. List the 2 types of energy used in active transport.

Answer 28

direct ATP and indirect ATP (another form of E involving ATP; the energy needed to move molecules against their concentration gradient in secondary active transport is acquired by moving Na+ back into the cell)

Question 29

What words indicate a molecule is moving from a high to low concentration?

Answer 29

- moving down the concentration gradient - moving with the concentration gradient - moving with diffusion

Question 30

What words indicate a molecule is moving from a low to high concentration?

Answer 30

- moving up the concentration gradient - moving against the concentration gradient - moving against diffusion

Question 31

Compare passive and active transport (which way do substances move)

Answer 31

passive transport: high -> low active transport: low -> high

Question 32

There are 2 types of active transport: _________ active transport and ___________ active transport

Answer 32

primary active transport secondary active transport

Question 33

Primary active transport uses _______ ________ embedded in the cell membrane

Answer 33

protein pumps

Question 34

Describe how protein pumps work

Answer 34

protein pumps are used in PRIMARY active transport and require direct ATP to change the shape of a pump and open to the other side to release the substance (works kinda like a protein carrier, but needs ATP)

Question 35

What types of pumps are involved in primary active transport? Be specific

Answer 35

- Na+/K+ pump - Ca2+ pump

Question 36

The Na+/K+ pump is described as an ________ pump

Answer 36

exchange pump

Question 37

Summarize in words what is happening when a Na+/K+ is operating in the cell membrane and draw it out

Answer 37

The Na+/K+ pump using ATP to move 3Na+ out the cell and 2K+ into the cell and they both move against the concentration gradient (low -> high). ATP becomes converted into ADP + Pi

Question 38

Where is the Na+/K+ pump found?

Answer 38

in all body cells (ex. neurons, cardiac cells)

Question 39

Why is the Na+/K+ pump described as an exchange pump?

Answer 39

3Na+ are moving out of the cell in exchange for 2K+ moving in the cell

Question 40

Why does the cell become more negative inside as a result of the Na+/k+ pump operating?

Answer 40

There are more Na+ moving out of the cell, than there is K+ moving back in.

Question 41

What can cause the Na+/K+ pump to stop working?

Answer 41

- ATP production is altered - Presence of Na+/K+ pump inhibitors

Question 42

Describe secondary active transport

Answer 42

- movement of 2 substances simultaneously across cell membrane; 1 with diffusion (Na+) and 1 against diffusion (a different substance) - movement relies on primary active transport (the Na+/K+ pump); indirect use of ATP

Question 43

How does secondary active transport facilitate movement?

Answer 43

the energy needed to move molecules against their concentration gradient is acquired by moving Na+ back into the cell (Na+ was originally pumped out of the cell using ATP in primary active transport, the secondary active transport is also considered to be active transport)

Question 44

What are the different types of secondary active transport?

Answer 44

- co-transport/symport - counter-transport/antiport

Question 45

Compare co-transport/symport to counter-transport/antiport

Answer 45

co-transport/symport: both substances move in the SAME direction (both in or both out) ex: Na+/Glucose symporter K+/Cl- symporter counter-transport/antiport: both substances move simultaneously in the OPPOSITE direction ex: Na/Ca2+ Exchanger Na+/H+ Exchanger Cl-/HCO3- Exchanger

Question 46

How is ATP involved in secondary active transport?

Answer 46

1) high [Na+] outside 2) movement of Na+ by diffusion is the driving force for moving the second particle

Question 47

Bulk transport is the movement of relatively _______ macromolecules

Answer 47

large

Question 48

What are the different types of bulk transport? Describe them and give examples

Answer 48

endocytosis: movement into the cell; pinching to form a vesicle ex: protein, hormones, neurotransmitters exocytosis: movement out of the cell; intracellular vesicle fuses with plasma membrane ex: cholesterol