BIOLOGY A - (3.1.1 - 3.2) BIOLOGICAL MOLECULES

MONOMERS AND POLYMERS

MONOMERS AND POLYMERS

How to calculate the number of water molecules released in a polymer

(n-1) where n is the number of monosaccharides

Define monomers

Small, repeating subunits that form larger, complex polymers (monosaccharides)

Define Polymers

Molecules made from many monomers joined together

What happens during a condensation reaction

One water molecule is eliminated per glycosidic bond as two monomers are joined together. (Anabolic reaction)

What is the name of the bond formed in a condesation reaction

A glycosidic bond (One oxygen atom holding the two saccharides together)

What is hydrolysis

Opposite of a condensation reaction and is when water is added to break a chemical bond between two molecules (Catabolic reaction) Essentially electrolysis but with water and requires an enzyme***

Define carbohydrates

Molecules that only consist of carbon, hydrogen and oxygen which are large chains of sugar units called saccharides

Define monosaccharides

A singular monomer. Glucose is an example of a monosaccharide which contains 6 carbon atoms in each molecule and is the substrate for respiration making it very important

Define isomers

Molecules with the same chemical formula but arranged differently

Name the two isomers of glucose and their difference

Alpha (H on top) and Beta (H on bottom) glucose

What does fructose look like

50p coin with oxygen atom at the centre

Name 3 common monosaccharides

Glucose

Fructose

Galactose

Name 3 qualities of these monosaccharides

Sweet tasting

Soluble

Crystalline with general formula (CH₂O)n where “n” can carry any number from 3 - 7

Define disaccharide

Two monosaccharides joined together in a condensation reaction

What is maltose formed by

Condensation of two alpha glucose molecules which are held together by glycosidic bond

What is sucrose formed by

Condensation of alpha glucose and fructose

What is lactose formed by

Formed by condensation of alpha glucose and galactose

What is cellulose formed by

Condensation of two beta glucose molecules (Only thing in the world made from beta glucose)

What are sucrose and lactose both

Disaccharides / Simple sugars

What is cellulose

Polysaccharide / Complex sugar

What colour does glucose and Benedict’s solution go

Brick red/Orange

What colour does sucrose and Benedict’s go

Blue

Is glucose reducing or non reducing

Glucose is reducing because it gives the Cu²⁺ an electron which makes it Cu⁺ and “reduces” it. This causes the colour of the copper solution to change from blue to brick red/orange

Is sucrose reducing or non reducing

Sucrose is a non reducing sugar because it gives no electrons to the Cu²⁺ So₄^2- solution

Are monosaccharides reducing or non reducing sugars

Reducing sugars (ie glucose)

Are disaccharides reducing or non reducing sugars?

Non reducing sugars (ie sucrose)

Are lipids hydrophobic or hydrophilic

Lipids are hydrophobic

Are lipids soluble in water / ethanol

Water = NO (Float to top because of hydrophobia)

Ethanol = YES

Why do lipids not dissolve in water

To dissolve in water you need a charge and fats do not have a charge (non-polar) therefore they do not dissolve in water

What happens during a condensation reaction

During condensation, an enzyme is added to a solution which causes one monosaccharide gives up its hydroxyl group and the other gives up its hydrogen group which makes a H₂ O molecule. The remaining oxygen atom holds two monosaccharides together (Glycosidic bond)

What is starch and what are the two products that make it up

Starch is a polymer of alpha glucose

Amylose (Straight chained molecule) Stored as helix in plant to make it more compact

Amylopectin (Branched molecule)

Where is glycogen stored and why is it highly branched

Mammalian liver and muscles

Not many places where it can be stored since it is stored as granules so it must be highly branched to fit as much as possible in the limited space available

What is cellulose a polymer of

Beta glucose

Why does cellulose have a HIGH tensile strength

The cell wall is made from cellulose which needs to be strong to stop the cell bursting

Cellulose, unlike starch, is NOT a storage polymer

What is the name of the cell membrane

The cell SURFACE membrane

Why are amylose, glycogen and amylopectin all insoluble

So that there is no effect on the water potential/osmosis

No water goes in or out of cells

What kind of polymer is cellulose

Straight chained

How are the beta glucose monomers arranged in cellulose

They are inverted and form microfibrils (linear chains of B glucose monomers)

What charge does hydrogen have

Delta positive charge

What charge does oxygen have

Electronegative

What keeps the monomers of beta glucose together then

Electrostatic forces between the monomers

What are proteins polymers of

Amino acids

How are amino acids held together

Amino acids are held together by peptide bonds which are formed in condensation reactions. The peptide bonds form between the carboxyl group of one amino acid and the amino group of another

*LIPIDS*

LIPIDS

What are lipids

Fats and oils

What are fats

Solid at room temperature (eg butter)

What are oils

Liquid at room temperature (eg oil)

What is a triglyceride made of

3 Fatty acids + Glycerol molecule

What functional group do fatty acids have

Carboxyl functional group

What type of bond is the bond between the glycerol molecule and the fatty acids

An ester bond

Why is the reaction of glycerol and a fatty acid not a polymer

Because the repeating units are not regular (there are multiple combinations of fatty acids)

Name the 3 types of fatty acids and their properties

Saturated fatty acid

Mono saturated fatty acid (one C=C double bond)

Poly-unsaturated fatty acid (two or more C=C double bonds)

What are good fats

Polyunsaturated fats

Monounsaturated fats

What are some bad fats

Saturated fatty acids (Bad Cholesterol)

Trans fats

What is a phospholipid

Glycerol molecule + Phosphate group + 2 fatty acids

What is the phosphate group and why does this make it hydrophilic

PO₄ ^{3 -}

The phosphate group has a charge which attracts it to the water in an attempt to dissolve

What is a phospholipid bi - layer

A layer formed by the phosphate ‘heads’ which are hydrophilic as they are charged and fatty acids hanging out like ‘tails’ as they are hydrophobic

Why does this arrangement work

It allows the charged phosphate heads to be exposed to the water and reduces the non polar fatty acids contact with water

Is there water in the cytoplasm

YES

Why is there cholesterol in the phospholipid bi layer

To regulate the membrane fluidity - preventing it becoming too rigid or soft

Also makes the membrane impermeable to small molecules which keeps cells internal conditions normal

How does glucose get through the phospholipid bilayer

Carrier proteins transport it

(In muscle cells at rest there are less carrier proteins visible as the muscle requires less glucose)

What is the role of channel proteins in the phospholipid bi layer

These form hydrophilic pores which allow specific ions to pass through the membrane

What is DNA made from

A base - A,C,G,T

A sugar - Deoxyribose

A phosphate group

PROTEINS

PROTEINS

What four elements are amino acids made from

Carbon, hydrogen, nitrogen and oxygen

What is the amine group formula

NH₂ 

What is the carboxyl functional group formula

COOH

What is the term for two amino acids joined together by a peptide bond

A dipeptide

When does this dipeptide chain become a protein

When it folds

How are folded amino acid chains joined together

Via bonds

What are the 4 bonds that hold these dipeptide chains together

Hydrogen bonds (oxygen attracted to hydrogen)

Ionic Bonds (Electrostatic forces between negatively and positively charged R - groups)

Hydrophilic/Phobic interactions

Disulphide bonds (Proper covalent bonds)

What types of proteins are made from the strong disulphide bond

Strength proteins such as collagen and keratin

What is an INTRA disulphide bond

Bond formed within one polypeptide

What is an INTER disulphide bond

Bond between two different chains

What is the primary structure of a protein

The order and sequence of amino acids (only bond at this point is peptide bonds)

What is the secondary structure of a protein

Protein starts to fold into ALPHA helix (very coiled) or BETA pleated sheet (stretched coil)

Hydrogen bonds are only present at this point

What is the tertiary structure of a protein

3D shape of polypeptide but with 1 polypeptide chain

Quaternary structure

Two or more polypeptide chains wound together

Give 3 examples of quaternary proteins

Haemoglobin

Antibodies

Keratin/Collagen

What makes strength proteins such as keratin and collagen (contained in hair and nails) so strong

Because it has disulphide bridges

ENZYMES

ENZYMES

What does catabolic mean

Breaks down

What does anabolic mean (ie steroids)

Builds up

What is the name of the structure formed by a substrate and its enzyme

The enzyme substrate complex

What do intracellular enzymes do

Stay inside the cell or attached to the membrane of the cell

We are heterotrophs so we ingest food and break it down into smaller soluble components like glucose

What do extracellular enzymes do

Live outside of cells

Fungi and bacteria use these enzymes to feed (saprotrophic feeding)

Saprotrophs secrete enzymes onto the food which is then digested

What is a metabolic pathway

A biological recipe for turning a substrate into a product which involves multiple enzymes working together

What is the induces fit model of the enzyme model

The induced fit model is just an extension of the regular lock and key model that suggests that the enzymes active site is not fixed and instead moulds around the substrate for a better fit using “hinges”

What do catabolic pathways do

They break down large molecules into smaller ones in a series of reactions

• Aerobic respiration

What do anabolic pathways do

Build up larger molecules from smaller ones in a series of reactions

• Photosynthesis

What must and enzyme and substrate be for the reaction to work

They must be specific to eachother

What 3 things are enzymes affected by

pH

Temperature

Enzyme and substrate concentration

When is saturation point reached

When all active sites are occupied by a substrate

What is the optimum conditions

The optimum conditions is the conditions at which the enzyme works best. This is where the most collisions take place