Lipids & Proteins : Biology WJEC AS

Lipid Functions

- Energy storage (x2 carb energy)
-Vital organ protection (kidneys- NOT LIVER)
-Oxidation of lipids produces metabolic water (camel humps)
-Leaf waterproofing/ reduces evaporation water loss
-Thermal Insulation (retains body heat)

Triglycerides (lipid)

(HYDROPHOBIC)
Glycerol backbone + 3 fatty acids (hydrocarbon chain with -COOH carboxylic group)

Triglyceride Bond

ESTER

Monounsaturated Fatty Acids

1 carbon double bond (not full number of hydrogen atoms)

Polyunsaturated Fatty Acids

2+ carbon double bonds (not full number of hydrogen atoms)

Phospholipids (lipid)

(HYDROPHILIC P HEAD & HYDROPHOBIC FATTY ACID TAILS)
Glycerol backbone + 2 fatty acids + phosphate group (P)

Phospholipid Function

-Main cell membrane component
-Form micelle (sphere) when mixed with water
-Liposomes (sphere)- healthy genes are inserted in lab

Cholesterol

A type of fat.
-Cell membrane component
-Produces hormones (steroids/reproductive)

LDL

Low Density Lipoprotein

HDL Function

(GOOD- from plant sources)
Removes fatty deposits from arteries. Takes to liver.

LDL Function

(BAD- from animal sources/saturated fats)
Brings fatty deposits to artery wall= atheroma!

Lipids Components

Carbon/Hydrogen/Oxygen

Amino Acid Structure

-Central Carbon + hydrogen
-Amino Group (NH2)
-Carboxylic Acid Group (-COOH)
-R/Side Group

Protein Structure

-When amino acids are joined by a condensation reaction
-DIPEPTIDE (two amino acids)
-POLYPEPTIDE (3+ amino acids)

Protein Function

-Enzymes (catalysts)
-WBC Antibodies
-Growth (new cell formation)
-Structural (myosin)

Hydrolysis of Proteins

= amino acids
- Add H2O and protease enzyme/boil with dilute acid

Primary Structure of Protein

Sequence of amino acids determined by DNA (joined by peptide bonds). Forms a linear polypeptide chain. NOT YET A PROTEIN!!

Secondary Structure of Protein

Polypeptide chain coils into ALPHA HELIX or BETA PLEATED SHEET.
(held by peptide + hydrogen bonds)

Tertiary Structure of Protein (example: enzymes)

Folding the secondary structure into a 3D/globular shape.
-Held by... peptide + hydrogen + ionic (R group charges) + disulphide (covalent bond between cysteine/S amino acids) + hydrophobic/philic interactions.

Quaternary Structure of Protein

When 2+ tertiary structure polypeptide chains join= COMPLEX PROTEIN!
-Held by... peptide + hydrogen + ionic (R group charges) + disulphide (covalent bond between cysteine/S amino acids) + hydrophobic/philic interactions.

Quaternary Protein Example - Haemoglobin

-GLOBULAR
((SOLUBLE))
4 Polypeptide Chains (2x ALPHA and 2x BETA)
-Prosthetic (non-protein) haem group... oxygen binds to Fe ion here = oxyhaemoglobin!

Quaternary Protein Example - Collagen

-FIBROUS
((INSOLUBLE))
3 Identical Polypeptide Chains (alpha helix)
-Every third amino avid is GLYCINE- small R group so twisted closely together

Protein TEST

Biuret Test--
Add biuret reagent.
POSITIVE= lilac
NEGATIVE= pale blue

Lipid TEST

Emulsion Test--
Add equal volumes of H2O and ethanol.
...mix...
POSITIVE= cloudy white
NEGATIVE= remains clear

Collagen Molecule

3x alpha helixes cross linked by hydrogen bonds~ twisted closely together.

Collagen Fibre

Many collagen molecules covalently bonded together.

Types of Proteins (EATS)

EATS
-Enzymes
-Antibodies
-Transport (carriers)
-Structural