Topic 1: Biological Molecules

What is a protein?

A large and complex polymer molecule, made up of amino acids

What are the biological roles of proteins?

structural, catalytic, signalling, immunological

What is a structural protein?

The proteins that make up body tissue. E.g Muscle, skin, ligaments and hair

What is a catalytic protein?

Proteins that catalyse biochemical reactions. These are enzymes.

What is a signal protein?

A protein that delivers signals. E.g hormones and receptors

What is a immunological protein?

Antibodies

What are amino acids made up of?

amino group, carboxyl group, R group, Hydrogen

What is an amino group made up of?

NH2

What group of an amino acid defines it?

The R group as this is the only difference between each one

How do amino acids bond to make a dipeptide?

A condensation reaction between the amino group of one and the carboxyl group of another forms a peptide bond.

What is the primary structure of a protein?

sequence of amino acids, bonded with peptide bonds, in a polypeptide chain

What is the secondary structure of a protein?

The polypeptide chain folds and hydrogen bonds are formed between the peptide bonds. A beta pleated sheet or alpha helix is formed.

What is the tertiary structure of a protein?

The polypeptide chain folds again, interactions form between R groups , forming a specified 3D structure depending on the primary structure

What are the 4 interactions that can occur during tertiary structure formation?

ionic, hydrogen, disulfide bridges (only between cysteines) and hydrophobic interactions

What sections of the protein are hydrophobic interactions present in?

non polar sections

What is the quaternary structure of a protein?

two or more polypeptide chains joined and associated with the prosthetic (non protein e.g iron in haemoglobin) groups

What is the test for proteins?

Biuret test.

1) Add 2cm3 of food sample solution

2) Add 2cm3 of biuret

3)If protein present, will turn purple from blue

What is a fibrous protein?

Long, rope-like fibres with high tensile strength and are generally insoluble in water, formed from parallel polypeptide chains held together by cross-links

What are three examples of a fibrous protein

collagen - main component of connective tissue

keratin - Main component of hard structures

Silk - forms spider webs and silkworm cocoons

What is a globular protein?

A spherical shaped protein caused by tightly folded polypeptide chains with the hydrophilic groups on the outside, making them water soluble.

What are three types of globular proteins?

transport proteins, enzymes and hormones

What three factors can denature a protein?

Changes in pH, temperature and salt concentration

What happens to fibrous proteins when they are denatured?

They loose structural strength

What happens to globular proteins when they are denatured?

They become insoluble and inactive

What is a monomer?

Small molecules/units from which larger molecules are made

What is a polymer?

large molecules made from similar or identical monomers joined together

What are 3 examples of monomers?

Monosaccharides, amino acids and nucleotides

What are 3 examples of polymers?

carbohydrates, proteins, and nucleic acids

What is a monosaccharide?

simple sugar molecule

What is the general formula for monosaccharides

CnH2nOn

What are the two isomers of glucose?

alpha glucose and beta glucose

What are three monosaccharides

glucose, fructose, galactose

What is the difference between alpha and beta glucose?

In alpha glucose, the hydroxyl groups are horizontally opposite , in beta glucose they are diagonal

What are three examples of disaccharides?

sucrose, lactose, maltose

How are disaccharides formed?

A glycosidic bond forms between the hydroxyl groups of two monosaccharides in a condensation reaction.

How are disaccharides broken?

hydrolysis reaction

What is the bond formed in maltose?

alpha 1,4-glycosidic bond

Are sugars soluble or insoluble in water?

soluble

What is glucose used for?

It is the main respiratory substrate. Respiration breaks down glucose to make ATP

Where is lactose found?

milk

Where is sucrose found?

Translocated in plants

What is maltose the product of?

starch digestion

What are polysaccharides?

Large chains of monosaccharides

What are the two functions of polysaccharides?

energy storage (starch & glycogen) and structural support (cellulose)

Are polysaccharides soluble in water?

No, so they do not affect water potential

What is starch?

A large, coiled, branched polysaccharide that is the energy storage molecule in plant cells.

Starch is a mixture of what two polypeptides?

Amylose and amylopectin, both alpha glucose polymers

What is the structure of amylose?

A long, unbranched, spiral chain of alpha glucoses linked by alpha 1,4-glycosidic bonds.

What causes the helical shape of amylose?

hydrogen bonds between hydroxyl groups that project into the middle

What is the structure of amylopectin?

A long, branched chain of alpha glucose, with 1,4 glycosidic bonds (forms chain) and 1,6 glycosidic bonds (forms branches)

What is glycogen?

A highly branched polymer of alpha glucose, made up of 1,4 and 1,6 glycosidic bonds, that is the energy storage molecule in animal cells

What does the highly branched nature of glycogen allow for?

Quicker glucose release as there are more points for enzymes to catalyse.

What are the features of starch and glycogen?

Coiled, so compact

Easily Hydrolysed

Insoluble in water, so don't affect water potential

Large, cannot leave the cell

What is cellulose?

A straight, unbranched polymer of beta glucose, made up of beta 1,4 glycosidic bonds, that forms plant cell walls

What is the structure of cellulose?

Microfibril (bundle of chains), formed by hydrogen bonds between adjacent chains

What do the hydrogen bonds between adjacent chains in cellulose do?

Makes the microfibrils strong, so gives structural support and strength

In beta glucose structures, how are the beta glucoses bonded?

By alternate glucoses being rotated 180°. One glucose is right side up, the next will be upside down and so on

How do enzymes act as catalysts?

They speed up reactions by lowering the activation

energy needed for a reaction to take place.

How do enzymes catalyse reactions?

They form enzyme-substrate complexes. Substrates bind to the active site of an enzyme.

How does the induced fit model show enzymes to work?

Active site forms as enzyme and substrate interact. The active site changes shape to be complementary to the substrate.

How does an enzyme join substrate molecules?

Brings substrate molecules closer together to

put stresses on bonds to join substrate

How does an enzyme break substrates?

Puts stresses on bonds to break substrate apart

What factors affect enzyme activity?

Temperature, pH, substrate concentration, enzyme concentration and inhibitors

How does enzyme concentration affect enzyme activity?

The more enzyme molecules there are, the more likely there are to be collisions between enzyme and substrate molecules, forming more enzyme-substrate complexes.

Why does enzyme activity eventually plateau after continuously increasing enzyme concentration?

All available substrates bind to enzyme active sites, so no more substrates are available, so no more ES complexes can form

Why does enzyme activity eventually plateau after continuously increasing substrate concentration?

All enzyme active sites become occupied, so the substrates can no longer bind to any more active sites, so no new RS complexes can form.

How does substrate concentration affect enzyme activity?

The more substrate molecules there are, the more likely there are to be collisions between enzyme and substrate molecules, forming more enzyme-substrate complexes

How does temperature affect enzyme activity?

As temp increases, kinetic energy in enzymes increases, so more collisions occur, so more ES complexes form. However after optimum temp is passed, bonds in the tertiary structure of the enzyme break, causing the enzyme to denature

How does PH affect enzyme activity?

Each enzyme has an optimal pH at which it can perform at its maximum rate. Too high or too low of a pH breaks the ionic and hydrogen bonds in the tertiary structure of the enzyme, so the enzyme denatures

How do competitive inhibitors affect enzyme activity?

They bind to the active site of enzymes, preventing ES complexes from forming, lowering activity but can be overcome by increasing substrate concentration

How do non competitive inhibitors affect enzyme activity?

Non-competitive inhibitors bind to the allosteric site and change the shape of the active site, substrates can no longer fit, so no ES complexes can form, but can be overcome by increasing enzyme concentration.

What is a competitive inhibitor?

a molecule that is a similar shape to substrates, complementary to active site, competes with the substrate to bind in the active site of an enzyme.

What is a non competitive inhibitor?

A molecule that binds to the enzymes allosteric site and changes the shape of the active site so substrates can no longer fit.

What are triglycerides made up of?

1 glycerol and 3 fatty acids

What is glycerol made up of?

3 carbons, 3 hydroxyl groups and 5 hydrogens

What is a saturated fatty acid?

One without carbon double bonds.

What is an unsaturated fatty acid?

One with carbon double bonds.

What is the general formula for a fatty acid?

R-COOH, where R is the hydrocarbon chain

What is a monounsaturated fatty acid?

fatty acid with one double bond

What is a polyunsaturated fatty acid?

fatty acid with two or more double bonds

What properties do double bonds change in fatty acids?

Lower melting point, Liquid at room temperature

Do oils have more unsaturated or saturated fatty acids?

unsaturated, liquid at room temperature

Do fats have more unsaturated or saturated fatty acids?

saturated, solid at room temperature

What three groups are fatty acids made up of?

Methyl group (CH3) , Hydrocarbon chain and carboxyl (COOH)

What bond forms between glycerol and fatty acids in a triglyceride?

An ester bond, formed by condensation between hydroxyl groups

What are the functions of triglycerides?

energy source, insulation, protection, water proofing and storage

How are triglycerides good at storage?

More energy per gram than carbohydrates, so more energy stored in less mass and they are insoluble in water so do not affect water potential

How are triglycerides good for insulation?

subcutaneous fat is a poor conductor of heat and they insulate neurones

How do triglycerides provide protection?

Provide a barrier around internal organs

How are triglycerides good for waterproofing?

Waxes in plants, oily secretions from mammals as they are hydrophobic