Biological Molecules

Flashcards for topic 1 biological molecules

Triglyceride

Formed by the condensation of one molecule of glycerol and three molecules of fatty acids forming 3 ester bonds

Phospholipid

Formed by the condensation of one molecule of glycerol and two molecules of fatty acid held by two ester bonds a phosphate group is attached to the glycerol

Competitive inhibitor

A molecule that is the same/similar shape as the substrate binds to the active site prevents enzyme-substrate complexes from forming forms enzyme-inhibitor complex

Non-competitive inhibitor

A molecule that binds to an enzyme at the allosteric site causing the active site to change shape preventing enzyme-substrate complexes from forming forms enzyme-inhibitor complex

Primary structure

The sequence of amino acids on a polypeptide chain peptide bonds between amino acids

Induced-fit model

The enzyme active site is not initially complementary to the substrate the active site moulds around the substrate this puts tension on bonds lowers the activation energy

Secondary structure

The folding or coiling of polypeptide to create a β pleated sheet or an α helix held in place by hydrogen bonds

Tertiary structure

The further folding to create a unique 3D shape held in place by hydrogen, ionic and sometimes disulfide bonds

Quaternary structure

More than one polypeptide chain in a protein

Peptide bond

Covalent bond joining amino acids together in proteins C–N link between an amine and carboxyl group of two different amino acid molecules formed by a condensation reaction

Ester bond

–COO– chemical bond formed between glycerol and fatty acids

Hydrophilic

The ability to mix, interact or attract water e.g. head region on a phospholipid

Hydrophobic

The tendency to repel and not mix with water e.g. tail region on a phospholipid

Polypeptide

Polymer chain of a protein made up of amino acids bonded together by peptide bonds via condensation reactions

Amino acid

The monomer of a protein formed from C,H,O,N contains a carboxyl group, amine group, an H, a central carbon and an R group

Carboxyl group

COOH group made up of a C with hydroxyl (OH) and carbonyl (double-bonded O) group bonded to it found in amino acids and fatty acids

Amine group

NH2 group found on amino acids

R group on amino acids

The variable group the part of each of the 20 amino acids that is different

α helix

A secondary structure in proteins the polypeptide chain coiled up and held in place by hydrogen bonds

β pleated sheet

A secondary structure in proteins the polypeptide chain folded into pleated sheets held in place by hydrogen bonds

Hydrogen bonds

Weak bond forms between H and O in many biological molecules e.g. proteins, DNA, tRNA

Ionic bonds

A bond that forms between the R groups of different amino acids in the tertiary structure of proteins

Disulfide bonds

A strong covalent bond between two sulfur atoms in the R groups of different amino acids in the tertiary structure of proteins

Active site

Unique-shaped part of an enzyme that the substrate binds to

Activation energy

The minimum amount of energy required for a reaction to occur

Enzyme-substrate complex

Forms when an enzyme and substrate collide and bind resulting in a lowered activation energy

Denature

When the active site changes shape so the substrate can no longer bind and no enzyme-substrate complexes form

Enzyme-inhibitor complex

The structure that forms when an enzyme and inhibitor collide and bind prevents enzyme-substrate complexes from forming

Saturated fatty acid

A long hydrocarbon chain with a carboxyl group at one end only single bonds between carbon atoms

Unsaturated fatty acid

A long hydrocarbon chain with a carboxyl group at one end at least one double bond between carbon atoms

Polar molecule

A molecule that has an uneven distribution of charge

Phospholipid structure

A hydrophilic (polar) head that is attracted to water Two hydrophobic (non-polar) tails that repel water In a bilayer, phospholipids form two layers with heads on the outside and tails on the inside.

Plasma membrane

phospholipid bilayer cell surface membranes and organelle membranes

Reducing sugar

Sugars that can reduce Cu ions in Benedict’s reagent to Cu ions in the form of copper (I) oxide which forms a brick-red precipitate

Test for reducing sugar

Add Benedict's reagent heat observe green/yellow/orange/brick red precipitate

Triglyceride function

high ratio of C–H bonds to carbon atoms → lots of energy released when broken High hydrogen to oxygen ratio → release water when oxidised (metabolic water source) Large, non-polar → insoluble in water, doesn’t affect water potential Low mass to energy ratio → energy- rich storage molecule

Non reducing sugar

A sugar unable to reduce Cu glycosidic bond must be hydrolysed to expose the reducing group e.g. sucrose

Test for starch

Add iodine turns blue/black

Test for lipids

Add ethanol and shake to dissolve then add water white emulsion forms

Test for protein

Add biuret turns purple

Nucleotide

The monomer of DNA and RNA contains a pentose sugar, a phosphate group and a nitrogenous base

Nitrogenous base

Part of a nucleotide adenine, guanine, cytosine, thymine and uracil

DNA nucleotide

The monomer of DNA contains a deoxyribose sugar, a phosphate group and a nitrogenous base

Polynucleotide

DNA polymer many nucleotides joined together via a condensation reaction joined by phosphodiester bonds

Phosphodiester bond

Bond joining two adjacent nucleotides together formed via condensation reaction forms between a phosphate group and the pentose sugar

Complementary base pairs

The base pairs that align opposite each other and form hydrogen bonds adenine and thymine (in DNA) /uracil (in RNA) guanine and cytosine

Ribose

Pentose sugar found in RNA nucleotide and ATP

Uracil

Nitrogenous base found in RNA instead of thymine

DNA helicase

Enzyme that breaks hydrogen bonds between the two chains of DNA in a double helix causes the two strands to separate involved in DNA replication

Semi-conservative replication

Each new DNA molecule contains one original (parental) strand and one newly synthesised strand

DNA polymerase

Enzyme that joins together adjacent nucleotides

Metabolite Solvent

Water is involved in many reactions such as photosynthesis, hydrolysis, and condensation reactions Water is a good solvent meaning many substances dissolve in it polar (charged) molecules dissolve readily in water due to the fact water is polar

High specific heat capacity

A lot of energy is required to raise the temperature of the water because some of the heat energy is used to break the hydrogen bonds between water molecules important so water can act as a temperature buffer

Large latent heat of vaporisation

A lot of energy is required to convert water from its liquid state to a gaseous state this is due to the hydrogen bonds between molecules, as energy is needed to break these to turn it into a gas means water can provide a cooling effect

Strong cohesion

Water molecules ‘stick’ together due to hydrogen bonds results in water moving up the xylem as a continuous column of water provides surface tension, creating a habitat on the surface of the water for small invertebrates

ATP synthase

Enzyme that catalyses the synthesis of ATP from ADP + Pi

ATP hydrolase

Enzyme that catalyses the hydrolysis of ATP into ADP + Pi

Phosphorylation

The addition of a phosphate group to a molecule making the molecule more reactive/it gains energy

RNA nucleotide

monomer of RNA composed of a phosphate group, ribose and a nitrogenous base has the base uracil instead of thymine

Dipeptide

Two amino acids bonded together by a peptide bond formed by a condensation reaction

Structure of water

The oxygen atom is slightly negative the hydrogen atoms are slightly positive

Role of hydrogen ions

Determine the pH the more hydrogen ions, the more acidic the conditions are an important role in chemiosmosis in respiration and photosynthesis

Role of sodium ions in co-transport

Involved in co-transport for absorption of glucose and amino acids in the ileum

Role of iron ions

A compound of haemoglobin involved in oxygen transport

Ester bond

Describe how an ester bond form? A condensation reaction between glycerol and a fatty acid (RCOOH)

Arrangement of phospholipids in a cell- surface membrane

Hydrophobic (fatty acid) tails point away as they are repelled from water Hydrophilic (phosphate) heads point to and are attracted to water

DNA replication

Describe how DNA replication Helicase unwinds DNA double helix and breaks its hydrogen bonds new DNA nucleotides attracted to complementary base pairs on exposed template strand. join adjacent nucleotides.

Roles of inorganic ions in the body

Occur in cytoplasm and body fluids, in varying concentrations H ions: affect pH Fe ions: component of haemoglobin Na ions: involved in co-transport of glucose and amino acids PO ions: found in DNA and ATP (form phosphodiester bonds)

Properties of water

Metabolite solvent high heat capacity large latent heat of vaporisation strong cohesion between water molecules