Biological Molecules

Chapter 3

What ion is required for the hydrolysis of starch by an enzyme?

Chlorine (Cl-)

Pentose

5 carbons

Hexose

6 carbons

Describe ribose

ribose is a pentose monosaccharide, found as a pentose sugar in DNA (deoxyribose sugar)

Describe cellulose

Beta glucose (alternating molecules must be inverted otherwise hydroxyl groups are too far to bond), straight chained molecule, make hydrogen bonds > microfibril > macrofibril > fibres

Cellulose fibres

strong, insoluble, used to make cell walls, good for digestion

Fructose

hexose monosaccharide, occurs naturally in fruit

Sucrose

disaccharide, alpha glucose and fructose monomers, alpha non-reducing sugar, found in sugar cane ect

Maltose

2 alpha glucose monomers

Lactose

galactose + glucose monomers

Elements in carbohydrates

C, H, O

Elements in lipids

C, H, O

Elements in protein

C, H, O, N, S

Elements in nucleic acids

C, H, O, N, P (ATP is also a nucleic acid)

Biuret test method and positive result and what it tests for

Tests for - proteins. Method - add Biuret's solution to sample. Positive result - lilac colour

Benedict's test method and positive result and what it tests for (reducing)

Tests for - reducing sugars. Method - place sample in boiling tube (if solid, grind it up or blend in water), add equal amount Benedict's solution. Positive result - brick red colour

Why does the test for reducing sugars work?

Benedict's solution contains Cu2+ ions [copper(II) sulfate] that are blue. reducing sugars react with the copper ions reducing them to Cu+ ions [copper(I) sulfate] that are orange/red. the more reducing sugar present, the more precipitate formed meaning there are less Cu2+ in the solution therefore the precipitate is more brick red

Why does the test for non-reducing sugars work?

Hydrochloric acid needs to be added to hydrolyse the non-reducing sugar from disaccharide/polysaccharide to monosaccharides which are always reducing sugars

Emulsion test method and positive result and what it tests for

Tests for - lipids. Method - sample is mixed with ethanol, water is added, shaken. Positive result - cloudy emulsion

Iodine test method and positive result and what it tests for

Tests for - starch . Method - add iodine to sample. Positive result - blue/black colour

Benedict's test method and positive result and what it tests for (non-reducing)

Tests for - Non-reducing sugars. Method - boil sample with hydrochloric acid, add Benedict's solution and heat. Positive result - brick red colour

What is a phosphodiester bond?

The type of bond that links the nucleotides in DNA or RNA.

How does a phosphodiester bond connect nucleotides?

It joins the phosphate group of one nucleotide to the hydroxyl group on the sugar of another nucleotide.

Maltose

disaccharide, 2 alpha glucose monomers, alpha 1-4 glycosidic bond, reducing sugar, found in wheat/pears ect

Lactose

disaccharide, beta glucose and galactose monomers, beta 1-4 glycosidic bond, found in dairy products, reducing sugar

Functional role of nucleotides

nucleotides are the building blocks for nucleic acids and are essential for transferring information to new cells

Glycolipids

glycolipid is a molecule made of a lipid with a carbohydrate chain attached, found on the outer surface of the cell membrane. function = cell stability and function, cell surface receptors, cell-to-cell recognition, play role in immune response

Triglycerides

lipid that is made of 1 glycerol and 3 fatty acids. 3 ester bonds formed so 3 water molecules removed. insoluble in water

Triglycerides uses

energy storage, thermal insulation, cushioning, buoyancy, electrical insulation, respiratory substrate, energy source for respiration

Lipid properties

non-polar, insoluble in water, soluble in organic solvents like alcohol

what does cholesterol produce

vitamin D, steroid hormones, bile (helps in digestion, is made in liver)

saturated

no double C=C bond, solid at room temp

monounstaurated

1 double C=C bond, liquid at room temp

polyunstaturated

more than 1 double C=C bond, liquid at room temp

esterification

type of condensation reaction alcohol + acid --> ester + water

role of cholesterol

increase stability of the membrane, reduce fluidity of the membrane (regulate fluidity especially during temperature changes)

how do phospholipids form the bilayer of a plasma membrane

hydrophilic part forms hydrogen bonds with water, the medium in and out of plasma membrane is aqueous, hydrophobic nature of fatty acids result in them facing toward each other

melting point of lipids

less hydrogen atoms means more double C=C bonds, fatty acid chains bend, less uniformly packed, lower m.p.

why can lipids increase the buoyancy of aquatic animals

lipids/fats are less dense than water

phospholipid

a glycerol molecule, two fatty acids, and a phosphate group that is modified by an alcohol. The phosphate group is the negatively-charged polar head, which is hydrophilic. The fatty acid chains are the uncharged, nonpolar tails, which are hydrophobic

What are the charges of hydrophobic and hydrophilic parts?

Hydrophobic - uncharged (non-polar) - don't dissolve well. Hydrophilic - negatively (polar) - polar dissolve well in water. Oxygen - negative. Hydrogen - positive

phospholipids can form surfactants or bilayers

Surfactant - layer on the surface of water with the fatty acid tail sticking out. Bilayer - 2 layered sheets with fatty acids orientated towards each other

what does it mean when a lipid has both hydrophilic and hydrophobic properties?

the lipid is insoluble

sterol

example of a lipid found in both animals and plants, 4 carbon ring structure which is hydrophobic, hydroxyl group that is hydrophilic, insoluble, example of a sterol is cholesterol

biological roles of lipids

hormone production, electrical insulation, waterproofing (birds feathers), membrane formation ,hydrophobic barriers

Non-reducing sugars examples

sucrose

Reducing sugars examples

lactose, glucose, fructose, maltose

Reducing sugars definition

reducing agents in chemical reactions (donates electrons to other molecules). include all monosaccharides (e.g. glucose and fructose) and some disaccharides (e.g. lactose and maltose)

Non-reducing sugars definition

do not act as reducing agents in chemical reactions. include most disaccharides (e.g. sucrose) and simple polysaccharides

serial dilution

The concentration decreases by the same quantity between each test tube, used to compare against unknown concentrations

What is a colorimeter

measures light transmission through a substance . In this case we use a red light filter because the solution is blue - this is important as red light is absorbed by the blue solution whereas blue light would be reflected and not absorbed

How does a colorimeter work?

supernatant sits on top of the precipitate. The supernatant will be more blue if the glucose concentration is low, meaning there are more Cu2+ ions so there will be less transmission. High concentration > supernatant more red > less Cu+ > more transmission

COLORIMETER

centrifuge

spins really fast to separate the supernatant and precipitate from the solution

Fibrous protein

long thin insoluble molecule, unreactive, repeating primary structure (amino acid chains) cause a helical shape, does not contain prosthetic groups, main role is provide structure, examples include keratin, elastin, collagen

why are fibrous proteins insoluble?

they have a large number of hydrophobic R groups

why are fibrous proteins stong?

they have crosslinks due to hydrogen bonds

Keratin structure

fibrous protein found in nails, hair, scales. it can stretch and then return to its original shape/recoils after being deformed. very tough/strong due to disulphide bonds which make keratin less flexible

Elastin structure

fibrous protein found in the lungs, blood vessels lining. recoils after being deformed/stretch then is able to return to its original shape - they elongate but remain attached. very strong because of crosslinks and coiling (more crosslinks means the protein is stronger)

Collagen structure

fibrous protein found in skin, tendons, ligaments. it is flexible but cannot stretch. has 3 polypeptide chains which are crosslinked with hydrogen bonds forming a triple helix called tropocollagen. high tensile strength

Most common amino acids in collagen

Glycine (every third amino acid) (smallest), Proline, Hydroxyproline

Globular proteins

roughly spherical. compact. hydrophobic r groups move to centre and hydrophilic r groups move to water, the amino acids twists due to this interaction. soluble. roles - transport, hormones, enzymes. contain prosthetic groups - are conjugated proteins. Examples: insulin, catalase, haemoglobin

Haemoglobin structure

globular protein that can change shape, quaternary structure which has 2 a-globin and 2 B-globin polypeptide chains, there is a haem group in each subunit, conjugated protein

Haem group

contains Fe2+, it can reversibly combine with an oxygen molecule which forms oxyhaemoglobin

Importance of solubility for globular proteins

Can easily transport things in the body (i.e. haemoglobin transports oxygen through the bloodstream)

Scientific name for red blood cell

Erythrocyte

Conjugated proteins

globular protein that contains a prosthetic group

Prosthetic group

non-protein element in conjugated proteins

Insulin

globular protein with a specific fixed shape, produced in the pancreas, helps control blood glucose concentration, it is 2 polypeptide chains held together by 3 disulfide bridges

Catalase structure

globular protein, quaternary structure, conjugated, 4 haem groups (catalase breaks down harmful hydrogen peroxide)

what does polar mean?

unequal sharing of electrons as they are more attracted to 1 nucleus than the other

amino acid general structure

amine group, hydrogen, carboxyl group, alpha carbon, r-group

secondary structure

oxygen, hydrogen, nitrogen atoms of aa interact to form hydrogen bonds (not include R-group). location of hydrogen bond depend on aa sequence. forms alpha helix or beta-pleated sheet

primary structure

sequence of amino acids - polypeptide chain. number and order of aa determines the function of the protein

tertiary structure

coils and pleats fold. held together by hydrogen bonds, ionic bonds - stronger than hydrogen bond, disulphide bridges - covalent bonds bw r groups, hydrophobic and hydrophilic interactions - weak interactions bw polar and non-polar r groups.

quaternary structure

interaction of 2 or more individual proteins/polypeptide chains/subunits. chains do not have to be the same.

alpha helix

chain of aa coils into alpha helix - due to hydrogen bonds formed between oxygen from carboxyl group and hydrogen in amine group on an aa 4 aa ahead in the chain

beta pleated sheet

polypeptide chains lie parallel and are joined by hydrogen bonds. form sheet like structure. hydrogen bonds are strong enough to maintain shape but are easily broken by increase in temperature or change in pH

how is tertiary structure affected by heat

increase kinetic energy. bonds holding globular protein together break (not covalent bonds). complex shape of protein unravels. tertiary structure defines the active site of enzymes.

the breakdown of dipeptides and polypeptides

hydrolysis reaction breaks peptide bond