Lipids ,cell Membranes

Question 1

What are lipids?

Answer 1

Hydrophobic compounds made up of C,H and O,insoluble in water but soluble in organic solvents e.g ethanol

Question 2

Two types of lipids?

Answer 2

Phospholipids and triglycerides

Question 3

Function of triglycerides?

Answer 3

Used for storage insulation and protection in fatty (adipose) tissue found under the skin they include fats +oils

Question 4

How are triglycerides formed?

Answer 4

When one glycerol molecule joins together with three fatty acid molecules via a condensation reaction

Question 5

each fatty acid forms an.. bond?

Answer 5

ester bond

Question 6

difference in the r group deterines

Answer 6

the differences in fats and oils

Question 7

the r group is a…

Answer 7

hydrocarbon chain which varies in length 4-22 c atoms

Question 8

saturated fatty acids?
mono-unsaturated fatty acids?
polyunsaturated fatty acids?

Answer 8

1. no double c=c bonds in the hydrocarbon chain
2. one double bond
3. more than 1 double c=c bond in the h-c chain

Question 9

How is the structure of triglycerides related to their properties

Answer 9

1. Have a high ratio of energy storing C-H bonds to C atoms therefore an excellent source of energy
2. They’re large non-polar molecules and insoluble in water so their storage doesn’t affect the water potential
3. High ration of H-O atoms triglycerides release water when oxidised therefore provide an important source of water

Question 10

What are phospholipids?
How’s re they formed?

Answer 10

• main components of the cell membrane
• similar to triglycerides but with a phosphate group in place of one fatty acid chain

Question 11

Phospholipids have a … head so..
phospholipids have a … tail so..
The phosphate group is …

Answer 11

Hydrophilic head - so attracts water molecules .
Hydrophobic tail - so orients itself away from water molecules but mixes readily with fat
Highly polar - so attracts water molecules

Question 12

When phospholipids are exposed to water they form either a ..?
In water they position themselves so that…?

Answer 12

Micelle or a bilayer
- hydrophobic heads are close to the water as possible and hydrophobic tails are away as possible

Question 13

How is the structure of phospholipids related to their properties?

Answer 13

• phospholipids are polar molecules so in aqueous solution can form bilayer within a cell surface membrane therefore a hydrophobic barrier is formed between inside and outside of the cell so water soluble substances cant easily pass through
• the hydrophilic phosphate heads of phospholipid molecules help to hold at the surface of cell-surface membranes
• can form glycolipids by combining with carbohydrates within the cell-surface membrane which are important in cell recognition
• phosphate group is highly polar so attrcats water molecules
• fattu acids are non-polar so repel water

Question 14

Importance of phospholipids in the cell surface membrane?

Answer 14

• makes cell selectively/partially permeable
• the smaller + less polar a substance the easier and faster it will diffuse across the the cell membrane
• allow lipid soluble substances to enter and leave the cell e.g vitamins
• prevent water soluble molecules entering and leaving the cell
• small molecules are able to pass through quickly
• charged particles unlikely to diffuse across the membrane even if they’re really small
  Makes cell flexible and self-sealing

Question 15

What are the components of the cell membrane?

Answer 15

Phospholipids, cholesterol , glycoproteins, glycolipids, Chanel proteins, carrier proteins, other proteins aswell

Question 16

What are the many functions of the cell-surface membrane?

Answer 16

• Divided cells into different compartments to make functions more efficient
• controls what enters and leaves
• recognise chemical substances from other cells
• fold in the cell membrane may form microvilli which increases SA for diffusion

Question 17

Extrinsic protein functions

Answer 17

• provide support and stability
• combine with carbohydrates to form glycoproteins and glycolipids which can act as chemical receptors
• cell recognition
• receptors sites for hormones
• protection

Question 18

Example of intrinsic protein
Function of intrinsic protein?

Answer 18

• carrier/Chanel protein
• act as hydrophilic press through which water soluble substances can pass
• sites of facilitated diffusion, co-transport and active transport
• can be enzymes

Question 19

What is a glycoprotein?
What is a glycolipids?

Answer 19

• proteins with attached carbohydrates chain
• lipids with attached carbohydrates chain

Question 20

State the function of glycoproteins?

Answer 20

Receptor molecules bind with hormones or neurotransmitters which can trigger chemical reactions within the cell
- e.g insulin, only some cells within the body have insulin receptors therdore insulin can be released to the entire body and only cells with insulin receptors will be triggered
- cell recognition - provide support and stability

Question 21

Function of cholesterol?

Answer 21

Control membrane fluidity - more cholesterol, less fluid therefore less permeable
Makes membrane stable at body temperature otherwise will burst

Question 22

FINISH