AQA A Level Bio Biological Molecules

What is a monomer

A small repeating unit that can be joined together for form a larger one

What is a polymer

A larger unit made up of monomers

Name examples of monomers

Monosaccharide , amino acids , nucleotides

What is a condensation reaction

Two monomers are chemically bonded together , water is formed as a by product

What happens in a hydrolysis reaction

Two monomers are separated by breaking a chemical bond . Water is used up in this reaction .

Name examples of monosaccharides

Glucose , galactose and fructose

What is a disaccharide

A molecule made from 2 monosaccharides

How is a disaccharide formed

A condensation reaction between 2 monosaccharides

What makes up maltose

2 glucose molecules

What makes up sucrose

Glucose and fructose

What makes up lactose

Glucose and galactose

What is an isomer

A variation of a particular molecule . The formula stays the same , but structure is different

What are the isomers of glucose

Alpha and beta glucose

What is the difference between alpha and beta glucose

The hydroxyll group is in different positions

What is a polysaccharide

Multiple monosaccharides formed by condensation reactions

What is glycogen and what is it made out of

A polysaccharide made from multiple a glucose molecules

What is starch and what is it made out of

A polysaccharide made from multiple a glucose molecules

What is cellulose

A polysaccharide made from multiple b glucose molecules

What is the purpose of glycogen

It is an energy storage in animals

What is the purpose of starch

It is an energy storage in plants

What is the purpose of cellulose

A structural molecules for plants , espicially for cell wall

What is the structure of glycogen

Heavily branched , 1-4 glycosidic bonds branched with 1-6 glycosidic bonds

How is glycogen’s structure related to its function

It is insoluble so osmosis and cannot diffuse out of cells , Compact so lots can be stored in small spaces , highly branched to increase surface area for rapid hydrolysis to be acted on enzyme simultaneously

What is the structure of starch

Branched polymer of a glucose molecules , 1-4 glycosidic bonds and branched with 1-6 glycosidic bonds

How is starch structure related to its function

Insoluble so doesnt affect water potential , large so doesnt diffuse out of cells , compact so lots can be stored in small spac , hydrolysed to form a glucose so easily transported used for respiration , branched so large surface area for rapid hydrolysis so enzymes can act simultaneously.

What is the structure of cellulose

Straight lengths of b glucose bonded by 1-4 glycosidic bonds

How are monosaccharides in cellulose arranged

Alternative b glucose molecules are turned upside down

How is cellulose structure related to its function

Made up of b glucose so form long straight unbranched chains that are parallel , bonded by many hydrogen bonds which provides collective strength . Molecules are grouped together to form microfibrils which are grouped together to form fibres which provides more strength .

How to test for reducing sugar

1.Add benedicts reagent to sample

2.Heat for 5 minutes

If reducing sugar are present it will go blue to brick red

How to test for non reducing sugars

Use when a reducing sugar test is negative

1.Add hydrochloric acid to sample

2.Add sodium hydrogen carbonate to test

3.Add benedicts reagent

4.Heat for 5 minutes

If sugar is present it will turn blue to brick red

How to test for starch

1.Add iodine solution to sample

If starch present it will turn blue/black

How can we use a colorimeter to do a quantitative Benedict’s test

-Colorimeter measure the absorbance or transmission of light by a coloured solution

-More concentration solutions = more light absorbed/less light transmitted

-Compare to data table or calibration curve

What is the function of lipids

Energy source , Waterproofing , Insulation , Protection

What are the 2 groups of lipids

Triglycerides and phospholipids

What is the structure of a triglyceride

1 glycerol molecules and 3 fatty acids chains bonded by ester bonds

How is the structure of triglycerides related to its properties

-High ratio of energy storing C-H bonds so a good energy store

-Low mass to energy ratio so good storage molecule

-Large and non polar so insoluble in water and does not affect osmosis in cells

-High ratio of H-O atoms so release when water when oxidised to provide a source of water

What reactions occurs to form a triglyceride

A condensation reaction

What bond is between a fatty acid and glycerol

An ester bond

What can lipids be

Saturated or unsaturated

What is the difference between saturated and unsaturated

Saturated means no double bonds between carbon atoms whilst unsaturated means there are 1 or more double bonds between carbon atoms .

What does having a double bond do to the fatty acid chain

Adds a kink into it , so that it isnt straight

What is the difference in structure between triglyceride and phospholipid

-Phospholipid: 2 fatty acid chains + 1 phosphate group

-Triglyceride: 3 fatty acid chains

Describe the structure of a phospholipid

A hydrophobic tail which orients itself away from water but mixes readily with fat and and a hydrophilic head which interacts with water

What does hydrophobic mean

Water fearing - will not dissolve , repels wate

What does hydrophilic mean

Water loving - will dissolve in water

How do triglyceride reacts to water

They are hydrophobic - repel water

Describe the phospholipid bilayer arrangement

-Hydrophilic head point outwards into water

-Hydrophobic tail points inwards

How to identify lipids

1.Mix sample with ethanol

2. Mix with water and shake

3. If lipids are present white emulsion forms

What are the monomers of proteins

Amino acids

What are the elements make up proteins

C,H,O,N,S

What is the structure of an amino acid

What reaction causes two amino acids to bond together

A condensation reaction

What bonds holds amino acids together

Peptide

What is formed when two amino acids bond by condensation reaction

A dipeptide

What is formed when many amino acids bond by condensation reaction

A polypeptide

What is a functional protein

A protein which has a particular role

What is the primary structure of a protein

A sequence of amino acids

What is the secondary structure of a protein

The primary structure folded into either alpha helix or beta pleated sheets which is held together by hydrogen bonds

What is the tertiary structure of a protein

The 3D shape of a protein which determines how the protein interacts. It is held together by hydrogen , ionic and disulfide bonds.

What is the quaternary structure of a protein

Multiple polypeptide chains with the additional prosthetic groups.

How to test for proteins

1.Add biuret solution to sample

2.If proteins are present , sample will turn blue to purple

What are the two main types of proteins

Globular and fibrous