What is Normal and How is it Maintained?

Question 1

What does transport of substances downhill mean

Answer 1

transported down an electrochemical gradient
• requires no metabolic energy
• occurs by diffusion (simple or facilitated)

Question 2

What does transport of substances uphill mean

Answer 2

transported against an electrochemical gradient
• requires metabolic energy (direct or indirect)
• occurs by active transport (primary or secondary)

Question 3

What is the only form of transport that does not involve a protein carrier

Answer 3

Simple diffusion is the only form of transport

that does not involve a protein carrier

Question 4

Which forms of transport require a transport carrier ?

Answer 4

Facilitated diffusion, primary active transport,

and secondary active transport are all carrier mediated transport

Question 5

What of the 3 features carrier mediated transport

Answer 5

1) Saturation
2) Stereospecificity
3) Competition

Question 6

What is Saturation?

Answer 6

Saturation:
• saturability is based on the concept that carrier
proteins have a limited number of binding sites for
the solute

Question 7

What is Stereospecificity?

Answer 7

Stereospecificity:
• the binding sites for solute on the transport proteins
are stereospecific (i.e. recognizes specific isomers)
• e.g. Glucose transporter

Question 8

What is competition in terms of carrier mediated transport

Answer 8

Competition:

• transport proteins may recognize, bind, and
transport chemically-related solutes

• e.g. Glucose transporter recognizes and transports
D-galactose, thus making these binding sites
unavailable for glucose

Question 9

What are 5 things that Non-Electrolytes (Uncharged) net difusion depends on

Answer 9

Size of the concentration gradient

• Partition coefficient (K)
• Diffusion coefficient (D)
• Thickness of Cell Membrane
• Surface area

Question 10

What two additional variables does Electrolytes (Charged) require for net diffusion:

Answer 10

Electrolytes (Charged)
Net diffusion depends on two additional variables:

• Potential difference (can add to or negate the effects of
differences in concentrations)

• Diffusion potential (caused by diffusion of only a few ions)
- membrane must therefore be permeable to that ion
- does not cause changes in the concentration of ions in
bulk solution

Question 11

does facilitated diffusion require input of metabolic energy

Answer 11

• Requires no input of metabolic energy

Question 12

What was the difference between faciliated and simple diffusion

Answer 12

Unlike simple diffusion, facilitated diffusion uses a protein carrier