Bio Chap. 5

Front 1

Function of the membrane

Back 1

The membrane is the boundary between the cell and its environment
• it controls which substances can enter or exit the cell

Front 2

amphipathic

Back 2

a molecule that has both hydrophobic and hydrophilic region

1) Phospholipids
2) Proteins embedded in membrane

Front 3

The fluid mosaic of the cell membrane

Back 3

Fluidity
• The molecules of the membrane drift laterally across the plane
• allows the membrane to be permeable

Mosaic
• appearance created by proteins embedded in membrane

Front 4

What affects the fluidity of the membrane?
3

Back 4

1) Temperature decrease = fluidity decrease
• phospholipids pack closely together (like cold bacon grease)
2) Kinks of unsaturated fatty acids keep membrane liquid at room temp. vs. condensed saturated fats
3) Cholesterol keeps phospholipids further apart preventing solidification and stabilizes it at high temps

Front 5

2 types of proteins in the membrane based on location

Back 5

1) Integral proteins = transmembrane
2) Peripheral = attached to membrane or integral proteins on the cytosolic side

Front 6

Do all the proteins of the membrane move?

Back 6

No. Some are held in place because they are attached to the cytoskeleton or

Front 7

6 types of proteins based on function

Back 7

1) Transporter
2) Enzyme
3) Cell-surface receptor
4) Cell-to-cell recognition
5) Cell-to-cell adhesion
6) Attachment to the cytoskeleton

Front 8

Transport protein

Back 8

Since the membrane is selectively permeable, molecules that cannot pass through with ease need transport proteins.

2 types:
1) channels
2) carriers composed or proteins

Front 9

Aquaporins

Back 9

Transport proteins that transport water

Front 10

Enzyme proteins

Back 10

Act as catalysts for chemical reactions

Front 11

Cell-surface receptor proteins

Back 11

Detect chemical messages

Front 12

Cell-surface recognition
(identity marker proteins)

Back 12

Identify the cell to other cells

Front 13

Cell-to-cell adhesion proteins

Back 13

Glue cells to one another temporarily or more permanently

Front 14

Linking proteins

Back 14

Anchor surface proteins which intereact with other cells to the cytoskeleton

Front 15

Cell-to-cell recognition
Is important for...2
How do cells recognize one another?

Back 15

the ability of a cell to distinguish one cell from another

Important for:
1) building tissues
2) immunity's rejection of foreign cells

Glycoproteins: self recognition
Glycolipids: tissue recognition

Front 16

Selective permeability of the membrane:
What substance can pass through with ease?
Which need assistance?

Back 16

Can: Small, non-polar molecules
ex. O2, CO2, steroids

Can't: Large ionic or polar molecules
ex. sugar, amino acids

Front 17

Diffusion
Passive or active?
What causes it?

Back 17

• The movement of molecules into available space down the concentration gradient
• Passive transport
• heat causes molecules to move

Front 18

Concentration gradient
It stores...

Back 18

• High concentration to low concentration
• stores potential energy which is transformed into kinetic energy as molecules moves

Front 19

Passive transport vs. active transport

Back 19

Passive = moving down concentration gradient; requires no energy input
• spontaneous
• leads to homeostasis

Active = moving against concentration gradient; requires energy (ATP) and a carrier protein
• non-spontaneous
• ex. sodium-potassium pump

Front 20

Osmosis

Back 20

Water molecule diffusion

Front 21

Tonicity

Back 21

The ability of a cell to gain or lose water
• if solutes cannot move, water must
• water moves towards higher solute concentration - to where there is less water

Front 22

3 tonicities

Back 22

Hypertonic = high solute concentration
Hypotonic = low solute concentration
Isotonic = same solute concentration on both sides of membrane

Front 23

In an isotonic solution, does water stop moving?

Back 23

No! It continuously flows in and out of membrane at a constant rate, and so isotonic state does not change

Front 24

Tonicities of animal cells
If the environment is:

Back 24

Hypertonic: cell shrivels
Hypotonic: cell swells and bursts
Isotonic: Favorable

Front 25

Tonicities of plant cells
If the environment is:

Back 25

Hypertonic: plasmolysis = cell shrivels
Hypotonic: turgid = cell swells FAVORABLE
Isotonic: flaccid

Front 26

Facilitated diffusion

Back 26

Movement of molecules from greater to lesser concentration with the help of a transport protein
• molecules would need help if they are polar and/or too large to pass through selectively permeable membrane

Front 27

2 types of transport proteins

Back 27

1) Channel proteins:
• has a polar charged corridor that allows ions and polar molecules to pass through the membrane
• down concentration gradient
• ex. aquaporins

2) Carrier proteins
• binds to solute and carries it to the other side of the membrane
• substance can go from lesser to greater concentration

Front 28

Active transport / carrier protein mechanism
Ex. Sodium-Potassium Pump

Back 28

1) Permease, a carrier protein, maintains high concentrations of K+ in cell and Na+ out of cell
2) Permease picks up 3 Na+
3) ATP attaches to permease so it can turn around and release Na+
• when permease is facing out of cell it is in its high energy state
4) Permease picks up 2 K+
5) ATP releases and permease turns back around to low energy state

Front 29

What is the purpose of active transport?

Back 29

The work of the carrier protein builds a concentration gradient, which store potential energy that can be used to do work
• it charges the cell!