AQA A LEVEL BIO- BIOLOGICAL MOLECULES

What do all living organisms share that supports the theory of evolution?

The same biological molecules, indicating a common ancestry.

What is a monomer?

A simple, basic molecular unit from which larger molecules (polymers) are made.

Give three examples of monomers.

Monosaccharides, amino acids, nucleotides.

What is a polymer?

A large, complex molecule made up of repeating monomers joined together.

What is a condensation reaction?

A reaction that joins two monomers together, forming a chemical bond and eliminating a water molecule.

What is a hydrolysis reaction?

A reaction that separates two monomers by breaking a chemical bond and requires the addition of a water molecule.

What elements make up carbohydrates?

Carbon, Hydrogen, and Oxygen.

What are monosaccharides?

The simplest sugars, which are the monomers from which larger carbohydrates are made.

Name three examples of monosaccharides.

Glucose, Fructose, Galactose.

What forms a disaccharide?

Two monosaccharides join by a condensation reaction, forming a glycosidic bond.

What is maltose composed of?

Two glucose molecules.

What is sucrose composed of?

Glucose and Fructose.

What is lactose composed of?

Glucose and Galactose.

What are polysaccharides?

Carbohydrates formed when more than two monosaccharides join via condensation.

What is the primary function of starch?

Energy storage in plants.

Describe the structure of starch.

Made up of two polysaccharides of alpha glucose: amylose (unbranched) and amylopectin (branched).

What is glycogen's main function?

Main storage of energy in animals.

Describe the structure of glycogen

Polysaccharide of alpha glucose with branched chains every 10 monomers. C1-4 and C1-6 glycosidic bonds.

What is cellulose's primary function?

Provides structural strength in the cell wall of plants.

Describe the structure of cellulose

Polysaccharide of beta glucose monosaccharides joined together by C1-4 glycosidic bonds, in straight chains. Hydrogen bonds form between these chains forming a microfibril.

What is a reducing sugar?

A sugar that can donate electrons, e.g., Glucose, Fructose, Galactose, Maltose, Lactose.

What is a non-reducing sugar?

A sugar that cannot donate electrons, e.g., Sucrose.

What is the positive result for reducing sugars in Benedict's test?

Color change from blue to green, yellow, orange, or brick red.

What is the positive result for starch in the iodine test?

Color change from orange to blue/black.

What is the structure of triglycerides?

1 molecule of glycerol attached to 3 fatty acids.

What is the main function of triglycerides?

Energy storage, thermal insulation, buoyancy, and organ protection.

What are phospholipids composed of?

1 glycerol, 1 phosphate group, and 2 fatty acid tails.

What is the function of phospholipids in cell membranes?

Forms a lipid bilayer that acts as a barrier to water-soluble molecules.

What does amphipathic mean in relation to phospholipids?

Having both hydrophobic and hydrophilic regions.

What is the general structure of a fatty acid?

A fatty acid consists of a carboxyl group (COOH) and a hydrocarbon tail (R).

What distinguishes saturated fatty acids from unsaturated fatty acids?

Saturated fatty acids have no C=C bonds, while unsaturated fatty acids contain C=C bonds.

What is the test for lipids?

Add equal amounts of ethanol and sample, then add water; a positive result shows a white/milky emulsion.

What are amino acids?

Amino acids are the monomers from which proteins are made, containing C, H, N, and O.

How are peptides formed?

Peptides form when the carboxyl group of one amino acid reacts with the amine group of another via a condensation reaction.

What is the primary structure of a protein?

The primary structure is the sequence of amino acids linked together by peptide bonds.

What types of secondary structures can proteins have?

Proteins can have an alpha (α) helix or beta (β) sheet secondary structure.

What is the tertiary structure of a protein?

The tertiary structure is the 3D arrangement of polypeptide chains, formed by various bonds between R groups.

What is the quaternary structure of a protein?

The quaternary structure consists of one or more polypeptide chains interacting, held together by disulfide bridges.

What is the role of enzymes in biological reactions?

Enzymes are proteins that catalyze reactions by lowering their activation energy.

What is the lock and key model of enzyme action?

In the lock and key model, the enzyme's active site has a specific shape that fits a particular substrate.

What is the induced fit model of enzyme action?

In the induced fit model, the substrate binds to the active site, causing the enzyme to change shape to fit the substrate.

What are competitive enzyme inhibitors?

Competitive inhibitors have a similar shape to the substrate and bind to the enzyme's active site, preventing substrate binding.

What are non-competitive enzyme inhibitors?

Non-competitive inhibitors bind to a different site on the enzyme, changing the shape of the active site and preventing substrate binding.

How does substrate concentration affect enzyme activity?

Increasing substrate concentration increases the rate of reaction until all active sites are occupied.

How does enzyme concentration affect the rate of reaction?

Increasing enzyme concentration increases the rate of reaction until all substrates have formed enzyme-substrate complexes.

What effect does temperature have on enzyme activity?

As temperature increases, the rate of reaction increases until the optimum temperature is reached, after which activity decreases.

How does pH affect enzyme activity?

Each enzyme has an optimal pH; deviations reduce activity by altering the shape of the active site.

What is the function of DNA?

DNA (deoxyribonucleic acid) is a polymer that holds genetic information.

What is the function of RNA?

RNA (ribonucleic acid) transfers genetic information from DNA to ribosomes and makes up ribosomes alongside proteins.

What is the significance of the R group in amino acids?

The R group varies among the 20 different amino acids and determines the unique properties of each amino acid.

What is a dipeptide?

A dipeptide is formed when two amino acids are linked by a peptide bond.

What is a polypeptide?

A polypeptide is a chain of many amino acids linked by peptide bonds.

What bonds are involved in the tertiary structure of proteins?

Tertiary structure involves hydrogen bonds, ionic bonds, disulfide bridges, and hydrophobic interactions.

What happens to enzyme activity as the reaction progresses?

Initially, the rate of reaction is fast due to many substrates; it slows as substrates decrease and eventually stops when all substrates are used.

What are the two types of nucleic acids?

DNA and RNA

What three components make up a nucleotide?

A phosphate group, a pentose sugar, and a nitrogenous base

What sugar is found in DNA?

Deoxyribose

What sugar is found in RNA?

Ribose

What is the role of phosphodiester bonds in nucleic acids?

They bond nucleotides together between a phosphate and a pentose sugar.

What is the structure of DNA?

A double helix of two polynucleotide chains

What type of bond holds the base pairs together in DNA?

Hydrogen bonds

What is the process of DNA replication?

1) DNA helicase breaks hydrogen bonds between bases

2) Each strand acts as a template and free nucleotides are joined to exposed bases via complementary base pairing

3) DNA polymerase joins nucleotides together by reforming PHOSPHODIESTER bonds.

4) The new molecules consist of one strand from the original molecule and one newly synthesised one

What enzyme unwinds DNA during replication?

DNA helicase

What is semi-conservative replication?

A method of DNA replication where each new DNA molecule consists of one original strand and one new strand.

What is ATP?

Adenosine triphosphate, a nucleotide derivative used as an immediate energy source.

How is ATP synthesized?

Through a condensation reaction between ADP and a phosphate group, catalyzed by ATP synthase.

What happens during ATP hydrolysis?

ATP is broken down into ADP and a phosphate group, releasing energy.

What is the primary function of ATP in cells?

To provide immediate energy for cellular processes.

What is the structure of water?

Made of 2 hydrogen atoms and 1 oxygen atom, covalently bonded, with an unequal distribution of electrons.

What property of water allows it to support plant cells?

Strong cohesion between water molecules.

What is the role of hydrogen ions in biological systems?

They determine the pH of a substance and can affect enzyme function.

What is the role of iron ions in the body?

They are a component of hemoglobin and bind with oxygen to form oxyhemoglobin.

What is the function of sodium ions in cells?

They are involved in the co-transport of glucose and amino acids.

What is the role of phosphate ions?

They are components of DNA, RNA, and ATP.

What is the significance of the helical shape of DNA?

It allows for compact storage of genetic information.

What is the function of ATP hydrolase?

It catalyzes the hydrolysis of ATP to release energy.

What is the effect of water's high specific heat capacity?

It buffers changes in temperature, providing stability in biological systems.

What is the difference between condensation and hydrolysis reactions?

Condensation joins molecules and eliminates water, while hydrolysis breaks molecules apart using water.

What is the role of ATP in metabolic reactions?

It provides energy for essential processes in organisms.

Why must organisms produce large amounts of ATP?

ATP cannot be stored and only lasts a few seconds, requiring constant resynthesis.