Lipids and Proteins spec

Question 1

What are the 2 groups of lipids

Answer 1

Triglycerides anf phospholipids

Question 2

What are lipids

Answer 2

varried group of substances that share the following characteristics:
contain carbon, hydrogen, and oxygen
insoluble in water
soluble in organic solvents

Question 3

How are triglycerides formed

Answer 3

by condensation reactions of one molecule of glycerol and three molecules of fatty acid

Question 4

what does a condensation reaction between glycerol and a fatty acid form
what bond

Answer 4

An ester bond (RCOOH)

Question 5

the R-group of a fatty acid can be what?

Answer 5

saturated or unsaturated

Question 6

Phospholipids what is substituted

Answer 6

one of the fatty acids of a triglyceride is substituted by a phosphate- containing group

Question 7

what is the emulsion test

Answer 7

-take a completly dry and greese free test tube
-to the sample add ethanol
-shake throughly to disolve any lipid in the sample
-add water and shake gently
-a milky-white emulsion indicates the presence of a lipid
-as a control, repeat the procedure using water instead of the sample, the final solution should remain clear

Question 8

Roles of lipids

Answer 8

-cell membranes
-source of energy
-waterproofing
-insulation
-protection

Question 9

Triglycerides structure

Answer 9

they have three fatty acids combined with glycerol
each fatty acid forms an ester bond with glycerol in a condensation reaction
hydrolyis therfore produces glycerol and three fatty acids

Question 10

Saturated triglyceride

Answer 10

there are no double bonds between carbon atoms
they tend to be solid as the chains can lie close together

Question 11

Unsaturated triglyceride- mono-unsaturated

Answer 11

single double bond between carbon atoms
tend to be oils- liquid due to the ‘kinks’ in the chain

Question 12

unsaturated triglyceride- polyunsaturated

Answer 12

if more than one double bond is present between carbon atoms
oils - liquid as the chains cant lie close together due to the ‘kinks’

Question 13

The structure of triglycerides relates to their properties which are:

Answer 13

-high ratio of energy-storing carbon-hydrogen bonds to carbon atoms so good source of energy
-low mass to energy ratio- good storage molecules- small
-large non- polar molecules, insoluble so storage doesn’t effect osmosis or water potential
-high ratio og hydrogen-oxygen atoms, sso they release water when oxidised so provide an important source of water especially for organisms livining in dry desert conditions

Question 14

Phospholipids

Answer 14

simillar to lipids except one fatty acid molecule is replaced bay a phosphate molecule
two parts to them a head and tail

Question 15

phospholipid head

Answer 15

hydrophillic (attracted to water but not fats)
polar part of the phospholipid

Question 16

Phospholipid tail

Answer 16

hydrophobic (oreintates itself away from water but mixes readily with fat)
non-polar part of the phospholipid

Question 17

The structure of phospholipids related to their properties

Answer 17

• polar molecules , hydrophillic phosphate head and a hydrophpbic tail- this creates a bi-layer acting as a hydrophobic barrier between the inside and outside of a cell
• hydrophillic head help to hold at the surface of the cell-surface membrane

Question 18

Proteins

Answer 18

very large molecules made up of amino acids

Question 19

Structure of an amino acid

Answer 19

basic monomer unit which combine to make a polymer called a polypeptide
polypeptides are then combined to form proteins
has a central carbon atom to which an amino group, carboxyl group (-COOH), hydrogen atom and a R group is all attached

Question 20

The formation of a peptide bond

Answer 20

condensation reaction between monomers of amino acids.
The water removal is made by combining an -OH from the carboxyl group of one amino acid and a -H from the amino group of another amino acid

Question 21

The primary structure of proteins

Answer 21

series of condensation reactions, amino acid monomers join together in a proccess called polymerisation this results in a long chain of amino acids called a polypeptide. The number, type and sequence of amino acids forms the primary structure of a protein.

Question 22

The secondary stdructure of a protein

Answer 22

the shapes which polypeptide chains form. Alpha helices and beta pleated sheets

Question 23

Tertiary structure of proteins

Answer 23

3D folded shapes by various bonding:
disulphide bridges- fairly strong so not easily broken
Ionic bonds formeed between any carboxyl and amino group that are not involved in forming peptide bonds. they are weaker so break more eaily
Hydrogen bonds- lots of them but easily broken

Question 24

Quaternary structure of proteins

Answer 24

the combination of different polypeptide chains
two or more chains

Question 25

Test for proteins

Answer 25

buiret test place solution in a test tube and add an eqaul volume of sodium hydroxide solution at room temperature add a few drops of very dilute copper ii sulphate and mix gently a purple colouration indicates the presence of peptide bonds and hence a protein. if no protein is present the solution will remain blue