Mono+Polymers, Carbs, Lipids, Proteins Flashcards
(27 cards)
Properties of lipids?
- Made of glycerol + fatty acids
- Insoluble in water, soluble in other solvents e.g. alcohol
- Long-term energy store
Functions of lipids?
- Source of energy
- Insulation
- Protection of organs
- Flexibility of cell membrane
- Waterproofing via waxy layer
Are triglycerides and phospholipids polymers?
No. They are not made up of similar monomers.
What are the two types of lipid?
Triglycerides and phospholipids.
Formation of triglycerides?
3 fatty acids (R-COOH) joined to 1 glycerol molecule. Joined in 3 condensation reactions with the loss of 3 water molecules. Form ester bonds; 3 ester bonds in 1 triglyceride.
What is the general formula for a fatty acid?
R-COOH. COOH is a carboxyl group, R is a long hydrocarbon chain.
Lipids emulsion test?
- Dissolve sample in ethanol (shake)
- Add water, mix
- Lipid present if white emulsion of fat droplets forms.
Difference between saturated and unsaturated fatty acids?
Saturated: no double bonds between carbon atoms. CnH2nO2, H always double C.
Unsaturated: double bonds between carbon atoms.
How to hydrolyse a lipid and what does it hydrolyse into?
Hydrolyses into glycerol and 3 fatty acids. Heat with acid or alkali and use enzyme lipase at its optimum temp. and pH.
What allows triglycerides to release twice as much energy as carbs during respiration?
They have 3 fatty acids and much longer chains of carbon-hydrogen bonds.
Why are triglycerides important for organisms in dry deserts?
They have a high ratio of hydrogen to oxygen atoms so they release ‘metabolic water’ when respired.
Are triglycerides polar or non-polar and what does this mean for them?
Non-polar or hydrophobic, meaning they are osmotically inactive and are ideal for storage.
Examples of where triglycerides are useful due to their insolubility?
Waxy cuticle of plant leaves and insects as insolubility helps to prevent water loss.
Formation of phospholipids?
1 glycerol, 2 fatty acid molecules and a phosphate group joined by a condensation reaction. Ester bonds.
Are phospholipids polar or non-polar?
They have a polar/hydrophilic head (contains phosphate group) and non-polar/hydrophobic tails (consists of long fatty acid chains).
What structures do phospholipids form in water?
A bilayer and a micelle. Hydrophobic tails face each other to avoid water, hydrophilic heads face outwards towards the water.
Compare and contrast triglycerides with phospholipids.
Both:
- are insoluble in water
- contain glycerol
- contain ester bonds
- contains C, H, O (but phospholipids also have P)
But:
- triglycerides have 3 fatty acids whereas phospholipids have 2 fatty acids + 1 phosphate group
- triglycerides are hydrophobic, but phospholipids have a hydrophilic head and hydrophobic tail
Globular vs. fibrous proteins? (Don’t have to know fibrous but good to recognise)
Globular:
- soluble with biochemical functions (enzymes, hormones, antibodies)
- highly folded polypeptide chain to produce a compact, complex tertiary structure
Fibrous:
- insoluble with structural functions (keratin in hair & nails)
Test for proteins?
- Add Biuret’s reagent to sample
- Colour change from blue to lilac indicates proteins present.
What are the monomers of proteins?
Amino acids.
Which elements do amino acids contain?
Carbon, hydrogen, oxygen, nitrogen, sometimes sulphur.
What is denaturing of a protein and how does it happen?
An irreversible alternation in the tertiary structure of a protein.
It occurs:
- when hydrogen/ionic bonds are broken
- due to high temps above the optimum or extreme pH changes.
Disulphide bonds are very strong and are much harder to break so are unaffected by these factors.
Describe the full structure of a protein.
Primary structure: specific sequence of amino acids in a polypeptide chain, giving the protein its shape.
Secondary structure: folding and coiling of the polypeptide chain due to hydrogen bonding between an anime group and an adjacent carboxyl group. Alpha helix or beta-pleated sheet.
Tertiary structure: further folding and coiling of the secondary structure due to hydrogen, ionic and disulphide bonds between R-groups. Tertiary structures are unique and specific, giving proteins many different roles. They also determine an enzyme’s active site.
Quaternary structure: more than one polypeptide chain held together by hydrogen, ionic and disulphide bonds.
Define monomer and polymer.
Monomer: small units which make up larger molecules.
Polymer: molecules made up of many much smaller units.
