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 and heavily branched

What is starch made out of

Amylose and amylopectin

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

Highly branched for rapid glucose release

Compact so can be fit into small spaces

Insoluble so cannot affect water potential of cell

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 doesn’t affect water potential off cell so cell can’t burst

It is compact so can be stored in small spaces

Amylopectin has branches for rapid hydrolysis

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 forms 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 bond

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

What is the main role of globular proteins

Metabolic reactions

What are metabolic reactions

The sum of all reactions in the organism

What are anabolic reactions

Building up larger molecules

What are catabolic reactions

Breaking down molecules

What are enzymes

Biological catalysts that speed up chemical reactions

Name the energy that is required to start a reaction

Activation energy

How does an enzyme increase rate of reaction

Lowers activation energy

What is the induced fit model

The theory that the active site of an enzyme changes shape as the substrate binds to it . This is so that it can fit exactly to form an enzyme substrate complex .

Name the structure where the enzyme and substrate are bound together

Enzyme - substrate complex

Name the area on the enzyme and binds to and reacts with the substrate

Active site

The active site has a ____ shape to the substrate

Complementary

What determines the active site

The tertiary structure

What factors affect the rate of enzyme

Temperature , pH , enzyme and substrate concentration

How does temperature affect enzyme activity 

Increases kinetic energy = more successful collisions = more e-s complexes form

Too high temperature , bonds denature , active site changes shape and e-s complexes can’t form

How does pH affect enzyme activity

Enzymes have an optimum pH 

Below and above the optimum pH of an enzyme can cause the ionic bonds to break which alters the active site and e-s complexes can’t form so the enzymes denatured 

How does substrate concentration affect enzyme activity

Increases substrate concentration means more e-s complexes can form

This is limited as all active sites eventually become saturated so rate of reaction plateaus

No more e-s complexes can form

How does enzyme concentration affect enzyme activity

Increase in enzyme concentration means more active sites available and more e-s complexes can form

Further increase in enzyme concentration will not increase the reaction rate as all the active sites are full

What is a competitive inhibitor

Similar shape to substrate, bind active site

Effect reduced by increasing substrate concentration

What is Non - competitive inhibitors

Binds allosteric site , change enzyme shape

Effect not reduced by adding more substrates 

What are the two types of nucleic acid

RNA and DNA

What is the role of DNA

It carries genetic information

What is the role of RNA

It transfers genetic information from DNA to the ribosomes

Name the monomer of a nucleic acid

Nucleotide

What are the three components of a DNA nucleotide

Deoxyribose sugar , phosphate group , nitrogen - containing base

Name the four DNA bases

Adenine , Thymine , Cytosine , Guanine

What bonds join nucleotides in a single strand

Phosphodiester bond

What reaction joins phosphodiester bonds

Condensation reaction

Describe the structure of DNA

Double helix , Two antiparallel polynucleotide strands held together by hydrogen bonds between complementary base pairs

Which bases pairs together

A-T , C-G

What is the term called when the bases pair together

Complementary base pairing

Which bonds holds complementary base pairing together

Hydrogen bonds

How many hydrogen bonds between A-T and C-G

A-T = 2

C-G = 3

Why is complementary base pairing important

It ensures accurate DNA replication

What does antiparallel mean

One strand runs 5-3 and the other runs 3-5

What is the purpose of DNA replication

To produce identical DNA before cell division

What is semi conservative replication

New DNA molecules contain one original strand and one new strand

Summarise the entire process of DNA replication

DNA replication is semi-conservative. DNA helicase unwinds the double helix by breaking hydrogen bonds between bases, forming two template strands. Free DNA nucleotides are attracted to exposed bases via complementary base pairing (A–T, C–G). DNA polymerase joins adjacent nucleotides with phosphodiester bonds, forming the sugar–phosphate backbone . Each new DNA molecule contains one original strand and one newly synthesised strand.

What did the Meselson -Stahl experiment prove

Semi - conservative replication