Cell membrane

Question 1

What are the main functions of lipids?

Answer 1

1. Store energy
2. important structural components of cell membranes
3. Light absorption pigments
4. Thermal insulation (plants)

Question 2

What are the compounds of Triglycerides?

Answer 2

Glycerol & fatty acids

Question 3

What is a saturated fatty acid?

Answer 3

A fatty acid with all bonds saturated with hydrogen bonds (relatively straight & packed closely together) (ex butter)

Question 4

What is an unsaturated fatty acid?

Answer 4

one or more carbohydrates form double bonds (cause bends in molecule, preventing close packing) (ex oils)

Question 5

Saturation determines the … & … of lipids

Answer 5

fluidity & melting points

Question 6

Phospholipids are major components of all biological membranes. What are the Phospholipids components?

Answer 6

Start with a triglycerides —> one of the three fatty acids (repel water) is replaced by a phosphate group (attract water) —> creates charged molecule

Question 7

What does biological membranes contain?

Answer 7

Lipids, proteins & carbohydrates

Question 8

The fluidity is mainly affected by two factors, which?

Answer 8

1. Lipid composition - cholesterol & long-chain, saturated fatty acids are packed tightly together (less fluidity)
2. Temperature - fluidity decreases with lower temperature, many organisms replace saturated fatty acids with unsaturated ones in response to cold.

Question 9

There are three general types of membrane proteins, which are they?

Answer 9

1. Peripheral - surface of the membrane, low portion of animo acids, hydrophilic, not imbedded in bilayer.
2. Anchored - anchored to membrane through covalently attached lipids
3. Integral - part of protein imbedded in bilayer (hydrophobic domains)

Question 10

What is a glycolipid?

Answer 10

carbohydrate that is covalently bonded to a lipid

(Glycoprotein - one or short carbohydrate chain covalently bonded to a protein)
(Proteoglycans - more carbohydrates attached)

Question 11

Explain cell recognition

Answer 11

When one type of a cell specifically binds to another cell of a certain type

Question 12

Explain cell adhesion

Answer 12

The connection between two cells is strengthened.

*two types - homotypic (most common, cell binds to same molecule) & heterotypic (cell bind to different molecule, sperm/egg, algae)

Question 13

There are three types of cell junctions, which are they?

Answer 13

1. Tight junction: prevents substances to move through the space between cells
2. Desmosomes: holds neighbouring cells firmly together
3. Gap junctions: channels that run between membrane pores, allows substances to pass between cells (kanal)

Question 14

There’s both active and passive membrane transport - what’s the different?

Answer 14

The passive transport is not in need of any chemical energy to work. It is driven by the concentration gradient.

The active transport needs chemical energy to work.

Question 15

What are the three different states of osmosis?

Answer 15

1. Hypertonic - higher concentration of solution outside
   of the cell —> water is loss —> cell shrinks
2. Isotonic - both solutions have equal solute concentration
3. Hypotonic - Lower solute concentration inside of the cell —> water is gained —> cell expand (can lead to cell rupture (bursting)

Question 16

There are two types of gated ion channels, which are they?

Answer 16

1. Ligand gated channel- particular molecule (ligand) must bind to a part of the channel protein (gate will stay open as long as the ligand is bound to the channel protein)
2. Voltage gated channel - Change in polar of the membrane opens the gate (at resting potential the gate is glosed)

Question 17

What’s Aquaporins?

Answer 17

Water can cross membranes through specific protein channels

(Often ungated, usually always open)

Question 18

Explain what primary active transport is

Answer 18

Transport requires chemical energy in the form of ATP. Needs energy as it transports a substance against its concentrations gradient (low conc. —> high conc.)

Question 19

Three different types of primary active transports, which?

Answer 19

1. Uniporter - one substance in one direction
2. Symporter - two different substances in same directions
3. Antiporter - two different substances in opposite direction

Question 20

Explain what secondary active transport is

Answer 20

Transport driven by the ion concentration gradient formed by active transport