IB Chemistry Option B Biochemistry SL

The diverse functions of biological molecules depends on their

structures and shapes

Metabolic reactions take place in

highly controlled aqueous environments

Catabolism reactions involve

breakdown of substances

Anabolism reactions involve

synthesis of substances

Biopolymers are formed by

condensation reactions

Biopolymers are broken down by

hydrolysis reactions

Condensation involves the formation of a small molecule called

water

Examples of condensation reactions

amino acids to form proteins, sugars to form starch

Sucrose can be hydrolysed to form

glucose and fructose

Photosynthesis is the synthesis of

energy rich molecules

The reactant in photosynthesis are

carbon dioxide and water

The waste product of photosynthesis is

oxygen

The catalyst for photosynthesis is

light

The equation for photosynthesis

6CO₂ + 6H₂O -> C₆H₁₂O₆ + 6O₂

Respiration is a complex set of

metabolic processes providing energy for cells

Respiration is

exothermic

Amino acids contain which functional groups?

Amino, carboxyl

Proteins are polymers of

2-amino acids

Proteins are bonded by

amide links / peptide bonds

Amino acids are

amphoteric

Amino acids can exist as

zwitterions, cations and anions

The primary structure of a protein is

the sequence of amino acids

The secondary structure of a protein is

folding due to hydrogen bonding

The two secondary structures of proteins are

alpha helices and beta pleated sheets

Tertiary structure of a protein describes the

3D shape of the structure

The tertiary structure could be due to

hydrogen bonds, london dispersion forces, ionic attractions and disulfide bridges

Disulfide bridges are formed when

sulfur undergoes oxidation

The quaternary structure is the interactions of

seperate polypeptide chains to form a protein

Globular proteins have

Tertiary and quaternary structures folded into globular shapes

Globular proteins are soluble as

the hydrophobic chains tend to be in the centre

Fibrous proteins have

little or no tertiary structure, forming long polypeptide chains

Fibrous proteins contain bonding such as

cross links at regular intervals to form long fibres or sheets

Example(s) of fibrous protein

keratin (hair,) collagen (skin)

Example(s) of globular protein

Haemoglobin

A proteins 3D shape determines its

role or function in the body

Uses of proteins (4)

hormones,
structure,
enzymes,
energy

Enzymes are proteins that

catalyse biological reactions

Each enzyme is highly

specific for a particular reaction

Enzymes work by providing an

alternate pathway for a reaction with a lower activation energy

The active site is the part of the enzyme that

reacts with the substrate

The induced fit theory is that the site is not necessarily rigid but

can alter its shape for a better fit

At low substrate concentrations, the rate of reaction is proportional to

the concentration of the substrate

At high concentrations, the rate of reaction of an enzyme reaches a maximum because

all the enzyme active site are used up

Enzymes denature and stop working at 40 degrees celsius as

the weak bonds holding the tertiary structure break and the active site loses its shape

At different pH values the tertiary structure can be altered by

changes of the charge of amino acid residues affecting the bonds between them

Heavy metals can poison enzymes by

reacting with -SH groups, replacing the hydrogen with a heavy metal ion and altering the tertiary structure

Paper chromotography can be used to determine

the identity of amino acids

The first step of paper chromatography is: a small spot of the sample is placed near

bottom of a piece of chromotography paper

The second step of paper chromatography is: the paper is placed in a

solvent which rises up the paper due to capillary action

The third step of paper chromatography is: The sample spots move up the paper at

different rates

The fourth step of paper chromatography is: when the solvent reaches the top of the paper, it is removed from the container,

dried, and sprayed with an organic dye to develop the chromotogram by colouring the spots

The fifth step of paper chromatography is: the distance between the solvent front and the

origin line is measured

The sixth step of paper chromatography is: the distance between the

solute spot and the origin line is measured

The retention factor can be used to compare the

known values as all amino acids have a different Rf.

If the amino acids have the same Rf, the paper can be

turned 90 degrees and redone with a different solvent

The Rf value is calculated by

distance travelled by solute / distance travelled by solvent

At a low pH, the effect on amino acids is

the amino group is protonated

At high pH, the amino acids

carboxyl group will lose a proton

Amino acids can act as

buffers

The unique point at which an amino acid exists as a zwitterion is called the

isoelectric point

Gel electrophoresis is carried out on

polyacrylamide gel

In gel electrophoresis, amino acids

move at different rates toward the positive and negative electrodes, depending on the pH of the buffer

At its isoelectric point in gel electro., the amino acid

will not move as its charges are balanced

A zwitterion is an amino acid that has

no overall charge (but positively and negatively charged parts)

Because of the zwitterions, amino acids have high

melting points as they have strong ionic attractions

Zwitterions are soluble in

polar substances such as water (due to attractions between polar molecules and charges on zwitterion)

Fats yield more energy when oxidized because

they are more reduced than carbohydrates

Triglycerides are made up of

glycerol and three fatty acids

Triglycerides are made through

condensation

The bonds in triglycerides are called

ester links

Fatty acids can be

saturated, monounsaturated or polyunsaturated

Unsaturated fats have lower melting points because

the kink in the chain caused by C=C bond means molecules are unable to pack close together and london dispersion forces are weaker

The longer the saturated fat chain, the

higher the melting point

Phospholipids are made up of

glycerol, two fatty acids and a phosphate group

The phosphate group in phospholipids is also condensed to a

nitrogen containing alcohol

An example of a phospholipid is

lecithin (egg yolk)

Fats and oils are hydrolysed in the body to

glycerol and fatty acids by lipases (enzyme)

The addition of oxygen across the C=C bonds in fats causes

oxidative rancidity

The hydrolysis of the triesters is called

hydrolytic rancidity

Oxidative rancidity is a

free radical mechanism catalysed by light in the presence of enzymes

Rancid means that the fats "have gone off" causing a

disagreeable smell, texture or appearance

Alkaline hydrolysis of fatty acids produces

the salt of the fatty acid and is used in the manufacture of soap

Hydrolysis can occur in both

acidic or alkaline conditions, or catalysed by enzymes

The steroidal backbone is the

4 fused ring structure

Cholesterol is transported round the body by

low density lipoproteins and high density lipoproteins

LDL causes heart disease as

it carries cholesterol to the arteries and deposits it there

A major source of LDL is

saturated fats found in animal fats

HDL prevent heart disease by

removing cholesterol from the arteries and transporting it to the liver

The roles of lipids are (5)

-cell membranes (structural component)
-energy storage
-steroid hormones
-thermal and electrical insulation (protection of organs)
-transporters of lipid soluble vitamins

Lipids are soluble in

non-polar solvents (insoluble in water)

Iodine number is the

number of grams of iodine that can be consumed by 100g of fat

One mole of iodine reacts with

one mole of C=C bonds

As more iodine is added to unsaturated fat

purple colour of the iodine will stop disappearring

Lipids have higher energy than carbohydrates because

they contain proportionally less oxygen and therefore can be oxidized further, releasing more energy

The type of steroid that is sometimes abused is

anabolic steroids (build up muscle and are similar to testosterone)

Side effects of steroids include

Testicle shrinkage (M),
breast development (M),
voice deepening (F),
facial hair growth (F),
increased aggression (both),
high blood pressure (both)

Steroid uses

Oral contraceptive pills
Gout treatment
Hormone Replacement Therapy for menopause

Saturated fatty acids and trans-unsaturated fatty acids increase the amount of

LDL in the body, leading to heart disease

Carbohydrates have the general formula

Cx(H2O)y

Carbohydrates are oxygen-rich biomolecules, which play a central role in

metabolic reactions of energy transfer