3.5 proteins: biological molecules & cell membranes

glycerol

3 fatty acids

what does glycerol and 3 fatty acid form?

(H2O released due to condensation) Triglyceride and 3H2O

ester bond

In a triglyercide after a condensation reaction

saturated fatty acid

CnH2nO2

• single carbon to carbon bonds

• mainly solid at room temps

• straight, good storage in animals

unsaturated fatty acid

• one or more double bonds between carbon to carbon

• mainly liquid at room temps

• not straight (eg, oil)

phospholid formation

roles of lipids in biological organisms

phosphorus: biological membranes, electrical impulses (myelin sheath)

Triglyceride: Energy reserves, thermal insulation, organ protection (kidneys) and metabolic water (water releases)

Wax: waterproofing reduces water loss

LDL (low density lipoproteins

• a diet of LDL can affect the coronary arteries with antheroma, due to fatty deposits reducing blood flow therefore oxygen towards heart

• when food is digest and absorbed in the small

• intestines, lipids and proteins combine to make lipoproteins

• if diet is high in saturated fats, this will form LDL, leads to heart disease/attack = antheromas in coronary arteries

• BAD cholesterol

HDL (high density lipoproteins)

• diet high un unsaturated fats causes the body to make more high density lipoproteins

• HDL carries harmful fats to the line to be broken down and disposed of

• GOOD cholesterol

testing for lipids

1) mix sample with ethanol (orange-brown with the equal amount of water ratio

2) shake so lipids will be dissolved

POS will be milky cloudy white emulsion

NEG will be clear

3 uses of lipids

energy store, thermal insulation, electrical insulation of nerves, buoyancy, waterproofing and protection of delicate organs (kidney)

what part of a phospholipid is hydrophobic and hydrophillic?

hydrophobic - fatty acid tails (non polar)

hydrophillic - phosphate heads (polar)

explain the compounds needed to form a phospholipid

Glycerol, two fatty acid tails and a phosphate group (PO4-)

explain the role of HDL

high density lipoproteins remove cholesterol from the blood

why are lipids a good biological molecule for storing energy?

they can store lots of energy in one molecule - twice as much as carbs

Acetic acid is non-polar, what other molecules will be attracted to it?

other non polar molecules such as the fatty acid tails of a phospholipid

describe the structure of a fatty acid tail

Carboxylic acid group, bonded to repeated CH groups, ends with a CH3 group.

explain how phospholipids are arranged to from a cell membrane

bilayer - phosphate heads pointing outwards towards the polar water inside and outside the the cell.

fatty acid tails facing inwards away from the polar environment

describe the structure of an unsaturated fatty acid tail

contains 1 or more C=C double bonds

maximum number of hydrogen attached to it

what part of the phospholipid is hydrophillic

the glyercol and phosphate group

explain the role of LDL

deposits cholesterol in the arteries, this narrows them and therefore reduced blood flow

examples of lipids

triglyceride, cholesterol, phospholipid and steroid hormone

formula of gylcerol

C3H8O3

describe the properties of a saturated fat

They are solids at room temperature due to the close packing of the fatty acid tails which causes strong forces of attraction, which require more energy to overcome.

describe the structure of a saturated fatty acid tail

It contains only C-C single bonds, so it has the maximum number of hydrogen atoms bound to it.

function of the cholesterol in the cell membrane

makes the CM stable and fluid

name the bond between a glycerol and fatty acid tails

ester bond

describe the properties of unsaturated fats

They are liquids at room

temperature due to the kink in the fatty acid tail which means the tails cannot pack as close together, weakening the forces of attraction.