Biological molecules

What are the four types of biological molecules?

Carbohydrates, lipids, proteins, nucleic acids

What are all the biological molecules composed of? Carbohydrates and lipids are only composed of this.

Carbons, hydrogen, oxygen

What are proteins composed of?

Carbon, hydrogen, oxygen + nitrogen

What are nucleic acids composed of?

Carbon, hydrogen, oxygen +nitrogen+phosporous

What are monomers?

Smaller units from which larger molecules are made

What are the monomers of carbohydrates?

Called monosaccharides: e.g glucose, fructose and galactose

What are the monomers of proteins?

amino acids

What are the monomers of nucleic acids?

nucleotides

What are polymers?

Molecules made from a large number of monomers joined together

What is the process of monomers joining to form polymers called?

Polymerisation

What are the polymers of carbohydrates?

Called polysaccharides: e.g starch, cellulose, glycogen

What are the polymers of nucleic acids?

Polynucleotides

What are the polymers of protein?

polypeptides

What is a condensation reaction?

The removal of water to form a chemical bond between 2 molecules

What groups are removed in a condensation reaction?

Hydroxyl group (OH) and hydrogen (H)

What does a hydrolysis reaction require?

Energy supplied by ATP

How are most polymers made?

By condensation reaction

What is a hydrolysis reaction?

The addition of water to break a chemical bond between 2 molecules which releases energy. Breaks a covalent bond (e.g glycosidic, peptide, ester bond)

How are monomers joined together to form polymers? (What bonds)

By covalent bonds

what bonds are water made of?

Covalent bond between oxygen and hydrogen

What is a polar molecule?

a molecule with an uneven distribution of charge, (the electrons aren't shared equally in the covalent bonds) resulting in regions of partial positive (δ⁺) and partial negative (δ⁻) charge.

What is a hydrogen bonds?

a weak electrostatic attraction between a slightly positive hydrogen atom (δ⁺) of one polar molecule and a slightly negative atom (δ⁻) of another polar molecule

What are properties of hydrogen bonds?

Hydrogen bonds are induviduially weak but collectively they form a stronger attraction lattice that requires a lot of energy to break. - so high latent heat of vaporisation

what is the role water as a solvent?

Medium for metabolic reactions dissolves ions/minerals So organism absorbs ions/minerals

What is the role of water as a temperature buffer?

Water has a high specific heat capacity so a lot of energy is needed to raise temp of 1kg by 1 dgree

means its resistant to rapid changes in temp, and bc many organisms are made of water and live in water, allows body to remain at stable temp

What is the role of water a cooling mechanism?

It has a high specific heat herby heat of vaporisation so reports a lot of heat energy which comes from your body to evaporate. A lot of heat energy is used to evaporate a small amount of water bc high latent heat. Used to evaporate sweat which takes heat energy with it. So small water loss

What is the role of water as a habitat?

has a high specific heat capacity and high latent heat of vaorisation so it didn't change temp/evaporate easily. This provides a stable environments for many organisms to live in.

At low temps, water freezes into ice, water molecules a are held further apart in ice making it less dense than water so it floats.

This forms an insulating layer on the surface so water below doesn't freeze allowing organisms to move. Organisms also live on the ice

What is the role of water as a metabolite? (A molecule involved in metabolic reactions (reactions in a living cell/organism))

1. Hydrolysis reaction -using water to break down molecules

2. Condensation reaction - release water when joining molecule

3. Photosynthesis - use water a a raw material

What is the role of water as a transport medium?

Cohesion

Adhesion

Strong cohesion+adhesion helps water to flow through organisms carrying substances along with it

What is cohesion?

attraction between water molecules caused by hydrogen bonding between the molecules which results in water molecules sticking together to form a continuous column

What is adhesion?

Attraction between water molecules and the molecules of another material due to hydrogen bonding between water and polar surfaces Helps water to stick together via hydrogen surfaces such as the cell wall of a xylem cell

What is the general formula of carbohydrates?

Cx(H2O)y

What are other names for carbohydrates?

saccharides or sugars

What is a single sugar unit/carb known as?

A monosaccharide

What are examples of monosaccharides?

Glucose, fructose, ribose

What are 2 monosaccharides joined up together called?

a disaccharide

What are examples of disaccharides?

Lactose and sucrose

What are repeating units of monosaccharides called?

Polysaccharide

What are examples of polysaccharides?

Glycogen,cellulose, and starch

What are functions of carbohydrates in living organisms

Source of energy-glucose is used in respiration to release ATP

Energy storage- stored as starch in plants or glycogen in animals

Structural - cellulose in plant cell (for strength)

What are properties of monosaccharides?

Soluble in water (hydrophilic) due to polar hydroxyl (OH-) groups Taste sweet Monomers that can join via glycosidic bonds to form disaccharides and polysaccharides

What are isomers?

Molecules that have the same molecular formula but different structural arrangements of atoms

What are the isomers of glucose?

alpha glucose and beta glucose

What is the symbol for glucose

C6H12O6

What type of sugar is a glucose molecule?

Hexose sugar (hexagonal shape)

What's the difference between alpha and beta glucose?

The orientation of the hydroxyl groups. In alpha glucose the OH group is below Carbon 1.

In beta glucose the Oh group is above Carbon 1

What are some examples of hexose sugars?

Glucose, fructose, galactose

what are examples of Pentose (5 carbon atoms) sugars?

deoxyribose and ribose

What are the key features of glucose?

Polar and soluble in water due to hydrogen bonds that form between the hydroxyl groups and water molecules. Means glucose is dissolved easily in the cytosol of the cell.

How do glucose molecules join?

Condensation reaction 2 alpha glucose molecules form a 1-4 glycosidic bond. One monosaccharide loses an OH group and one loses a H and so a water molecule is released.

This is a disaccharide

What type of bond is a glycosidic bond?

covalent bond

What does 1-4 glycosidic bond mean?

The two monosaccharides are joined at carbon atoms 1 and 4.

What are some examples of disaccharides?

Maltose, sucrose and lactose

What is maltose made of?

2 alpha glucose

What is lactose made of?

Alpha glucose+galactose

What is sucrose made of?

alpha glucose +fructose

Through what bonds do alpha glucose molecules join by?

Glycosidic bonds

What 2 polysaccharides do alpha glucose molecules join to form

Amylose and amylopectin collectively known as starch

What are the 2 polysaccharides of starch

Amylose and amylopectin

How is glucose made in plants?

photosynthesis

How is glucose stored in plants?

As starch

Is amylose branched or unbranched?

Unbranched

How is amylose formed?

Formed by condensation reactions between alpha glucose molecules joined together by 1-4 glycosidic bonds

What is the structure of amylose?

The angle of the 1-4 glycosidic bonds between each alpha glucose molecule means that this long chain of glucose twists naturally to form a helix which is further stabilised by hydrogen bonds. (Holds spiral shape)

What does the structure of amylose mean for it?

It's structure makes the polysaccharide more compact and much less soluble than the glucose molecules that make it

Why is amylose less soluble?

Because all the OH- (hydroxyl) groups are within the helix  so fewer hydroxyl groups are exposed to water so less hydrogen bonding between water molecules.

Why is glucose soluble?

It has many hydroxyl groups (OH-)

These groups are polar which allow it to form hydrogen bonds within water

How do hydrogen bonds allow glucose to dissolve?

The OH groups of glucose molecules are polar Which allow them to form Hydrogen bonds with water These hydrogen bonds overcome the intermolecular forces between glucose molecules Water molecules then surround the glucose allowing it to separate and dissolve

How is amylopectin formed?

Formed by condensation reactions between alpha glucose molecules joined together by 1-4 glycosidic bonds between molecules and 1-6 glycosidic bonds between branch points.

What is the structure of amylopectin mean?

It has a branched structure So its more soluble than amylose because more hydroxyl groups are exposed to water The OH- groups are polar so they can form hydrogen bonds with water These hydrogen bonds overcome the intermolecular forces between glucose molecules Water molecules then surround the glucose allowing it to separate and dissolve

What is the function of amylose?

It's a starch (glucose stored as starch) so can be broken down/hydrolysed to release glucose which can be broken down further to release energy. Slowly hydrolysed- provides sustained release of glucose

Why is amylose slowly hydrolysed/broken down?

Amylose is unbranched It coils into a compact helix So fewer ends are exposed for enzyme action Enzymes can only hydrolyse glycosidic bonds at the ends of the chains. With only 2 free ends the rate of hydrolysis is slower than a branched structure

What is the function of amylopectin

Starch can be broken down into glucose —energy Branched structure provides many free ends for rapid hydrolysis by enzymes. Quick release of glucose when energy is needed

What is glycogen?

The main energy storage molecule in animals and fungi Stored in the liver and muscle cells Polymer/polysaccharide of alpha glucose monomers

How is glycogen formed?

Formed by condensation reactions between alpha glucose molecules joined by 1-4 glycosidic bonds and 1-6 glycosidic bonds between branch points

Why can large amounts of glycogen be stored?

It forms even more branches than amylopectin, so its more compact

Less space is needed to be stores so large amounts can be stored

Why can glycogen be broken down quickly?

The 1-6 glycosidic bonds between branch points give it a highly branched structure Giving it many free ends Allows enzymes to hydrolyse/break down glycogen rapidly releasing glucose quickly when energy is needed

Is glycogen soluble or insoluble?

insoluble because its very large and therefore does not tend to draw in water through osmosis

Why is glycogen being insoluble important?

It wont diffuse out of cells bc its very large so it maintains cells energy supply

Why is glycogen being able to rapidly break down important for animals?

Animals have a high metabolic rate So they need to release glucose rapidly for respiration

What is metabolic rate?

The rate at which all the chemical reactions take place in the body

How do starch and glycogen release glucose for respiration?

By hydrolysis reactions by enzymes requiring addition of water.

BTW hydrolysis breaks down glycogen with the addition of water. This doesn't mean glycogen is soluble bc it breaks down with water, glycogen can't dissolve...it js breaks down

What is cellulose?

The main component of plant cell walls

A polysaccharide

What's the difference between cellulose and starch+glycogen

Cellulose formed by condensation reactions between beta glucose molecules/monomers joined together by 1-4 glycosidic bonds.

What is the structure of cellulose?

The 1-4 glycosidic bonds link beta glucose molecules in an alternating orientation producing straight unbranched chains.

Why do alternate beta glucose molecules in cellulose have to turn 180 degrees/upside down?

In beta glucose, the OH- group on carbon 1 is above the ring.

To form 1-4 glycosidic bonds the hydroxyl groups on carbon 1 and carbon 4 must be lined up for condensation.

This alignment is only possible if every other glucose molecules rotate 180 degrees.

Function of cellulose?

Forms plant cell walls

Prevents cell from bursting and provides rigidity

Why is cellulose strong?

Straight chains of beta glucose molecules make hydrogen bonds between them forming microfibrils. Microfibrils join together forming microfibrils which combine to form cellulose fibres

Why can't humans digest cellulose?

Humans lack the enzyme cellulase so they can't break beta 1-4 glycosidic bonds

Why do humans need cellulose?

Bc it's indigestible, it acts as a dietary fibre adding bulk to gut contents and it also absorbs water, softening faeces.

So it prevents constipation

Bc it's indigestible it acts as a dietary fibre adding bulk to gut contents.

This slows movement of food through digestive tract

(Means sugars are absorbed more slowly which helps regulate blood glucose levels)

What is a reducing sugar?

any monosaccharide or some disaccharides (e.g maltose and lactose )that can donate electrons (or reduce another molecule)

What chemical is used to detect reducing sugars?

Benedict's regeant

What is the test for reducing sugar?

Benedict's test

How is the Benedict's test carried out?

1. Place the sample to be tested in a boiling tube. If it's not in liquid form, grind it up or blend in water.

2. add an equal volume of Benedict's regeant

3. Heat the mixture gently in a boiling water bath for 5 minutes

How does Benedict's test actually work?

Reducing sugars will react with the copper ions in the Benedict's regeant. This results in the addition of electrons to the blue Cu2+ ions.

What does the colour of the solution in Benedict's test depend on?

It depends on the concentration of the reducing sugar present.

The more reducing sugar present,the more precipitate formed + the less blue Cu2+ ions are left in the solution

What colour does the solution turn if it's a positive result in Benedict's test?

blue-green-yellow-medium-red

——>Increasing concentration of reducing sugar present.

What happens if you use Benedict's test on non-reduing sugars?

Non-reducing sugars don't react with benefits regeant + so the solution will remain blue after warming (negative result)

What is the most common non-reducing sugar?

Sucrose

When would sucrose (a non-reducing sugar) give a positive result for the Benedict's test and why?

If it's first boiled with dilute HCL when warmed with Benedict's solution.

Bc the sucrose has been hydrolysed into glucose and fructose which are both reducing sugars