Biology - C5

Enzymes, DNA structure and replication, protein synthesis, gene expression and mutations

Enzyme

Biological catalyst that speeds up chemical reactions in living organisms by lowering the activation energy. Reusable.

Substrate

Substance an enzyme acts on in a cellular reaction.

Active site

Where the substrate bonds to the enzyme (it is the same shape as the substrate).

Induced fit model

Model used to show the interaction between the substrate and enzyme - focus on how the enzyme changes shape to better fit the substrate.

Allosteric site

Area on the enzyme that is not the active site.

Anabolic

Substrates catalysed by enzymes to build complex molecules from simpler ones (two made into one).

Catabolic

Substrates catalysed by enzymes to make simple molecules from a complex one (one made into two).

Biochemical pathways

Multiple enzyme reactions done to break down a complex molecule into simpler products.

Rate of enzyme activity factors

Temperature, pH, substrate concentration, and enzyme concentration. RoEAF

Temperature

As it increases the kinetic energy of substrates and enzymes increases causing more frequent collisions, enhancing the rate of reaction. Too much can denature the enzyme so there is an optimum for enzyme activity.

Denatures

When the 3D structure of an enzyme deforms due to factors like extreme heat or incorrect pH.

pH

Affects the rate of reaction. Optimum is precise and different for each enzyme depending on the part of the body.

Concentration

More enzymes or substrates means the frequency of collision is higher, increasing the reaction rate.

Coenzyme

Organic non-protein needed for some enzyme reaction as they carry substrate to the enzyme. Can move between enzymes.

Cofactor

Inorganic non-protein that go in the active site and the substrate attaches to allow reaction. Often permanently bonds to enzyme.

Cofactor

Competitive inhibitor

Binds to enzymes active site to stop substrate. Substrate concentration will increase then increasing rate of reaction.

Non-competitive inhibitor

Binds to allosteric site of enzyme causing active site to deform so substrate can not bind. Not in competition with substrate so concentration increase has not affect.

Deoxyribonucleic acid

DNA stands for

DNA

Provides instructions for the formation of proteins.

Ribonucleic acid

RNA stands for

Double helix

Shape of DNA

Single strand

Shape of RNA

Nucleus

Where DNA is found.

Eukaryotic cells

Found in multicellular organisms and has a nucleus.

Prokaryotic cells

Single celled organisms like bacteria, has no nucleus so DNA is stored in the cytoplasm.

Cells

‘Building blocks of life’ - have different functions and shapes

Nucleus and cytoplasm

Where RNA is found

Nitrogenous bases

What does DNA have 4 types of?

Adenine

Nitrogenous base starting with A

Thymine

Nitrogenous base starting with T

Guanine

Nitrogenous base starting with G

Cytosine

Nitrogenous base starting with C

Thymine

Adenine’s base pair for DNA (two hydrogen bonds)

Cytosine

Guanine’s base pair for DNA (three hydrogen bonds)

Transfer

tRNA meaning

Messenger

mRNA meaning

Ribosome

rRNA meaning

Uracil

Nitrogenous base starting with U

Uracil

Adenine’s base pair for RNA instead of Thymine

Semi conservative

DNA replication is _ as half the old strand is maintained in the new strand.

Mutations

What is minimised because half the DNA strand is used in the new DNA.

Helicase enzyme

Unwinds the DNA forming the replication fork by breaking the hydrogen bonds between nucleotides (check)

RNA primase

Makes the RNA primer to start making another strand in DNA replication.

DNA polymerase

Attaches to primer and adds the rest of the complimentary base pairs during DNA replication.

DNA ligase

Joins gaps in new DNA strand (after primers removed) during replication.

Monomer

Molecules bonded together to form a polymer

Amino acids

Molecules that combine to form proteins.

Proteins

What are enzymes, haemoglobin, keratin and collagne all an example of?

Gene

Sequence of bases in DNA that code for proteins.

Amino acids

What do the triplets of nucleotides code for?

Transcription

When the gene sequences is copied onto mRNA in protein synthesis.

Translation

When mRNA is used by ribosomes to build proteins in protein synthesis.

RNA polymerase

Enzyme that unwinds and copies DNA during protein synthesis.

pre-mRNA

What the DNA is transcribe onto during protein synthesis (does not transcribe the promoter or terminator).

Introns

Non-coding regions removed in post transcription modification (splicing).

Mature mRNA

What pre-mRNA becomes after the introns are removed and the cap and tail added.

Ribosome

What mRNA goes to to start creating proteins.

tRNA

What brings the amino acid into the ribosome during protein synthesis.

Polypeptide chain

Chain of amino acids created during protein synthesis.

Codon

Group of 3 bases.

Peptide bonds

Bonds that form between amino acids during protein synthesis to create the polypeptide chain.

Transcribed

Environment and behaviour affects which and what genes are _

Gene expression

Process in which chosen genes are transcribed

Phenotypic expression

Observable characteristics or traits that result from an interaction of genes and environment.

Phenotype

What you see (traits).

Environmental factors

What are diet, temperature, O2 levels, etc

Gene regulation

Process used to control which and what genes get transcribed in the cell (expressed).

Energy conservation

Why is gene regulation a thing?

Chemical tags

How gene regulation is done by turning genes ‘off and on’ by binding to the DNA.

Transcription factors

Proteins that determine gene regulation by binding to the DNA.

Activators

Proteins that boost transcription by making it easier for RNA polymerase to bind to the promotor.

Repressors

Proteins that stop transcription by making it harder for RNA polymerase to bind to the promotor.

Promotor

Initiates the transcription of genes.

Gene

Segment of DNA that codes for a specific protein.

Exon

Coding region in mRNA.

Intron

Non-coding region in mRNA.

Pentose sugar

Main part of sugar-phosphate backbone.

Phosphate group

Small part of sugar-phosphate backbone.

Sugar-phosphate backbone

Holds nitrogenous base in the double helix.

Restriction enzymes

Protein that can cut DNA in a bacterial cell

restriction site

area of DNA that the active site of the restriction enzyme recognises

endonuclease

Another name for restriction enzymes

DNA sequence

Each restriction enzymes has a particular _ in the DNA that it cuts

restriction enzymes

the defence system of bacterial cells against harmful foreign DNA (viruses)

methylase enzyme

What the bacterial cell uses to protect its DNA from being cut by restriction enzymes

methyl group

What the methylase enzyme adds to the DNA to protect it

6-8

Amount of base pairs in the DNA sequence of a restriction site

Nucleotide

Organic molecule made of a nitrogenous base, a phosphate and pentose sugar

Mutation

A change in the sequence of bases in a DNA strand

DNA replication

When are mutations in DNA most likely to occur?

mutagen

An agent that causes induced genetic mutation

UV radiation, chemical exposure and heat

Things that can induce mutation (mutagens)

somatic

mutations that are not passed on - not in gametes

germ line

mutations that are passed onto offspring

point, block and chromosomal

Types of mutations

substitutions, insertions and deletions

types of point mutations

insertions and deletions

which point mutations are frame shift mutations

silent, missence and nonsense

types of substitution point mutations

point mutation

type of mutation where the nucleotide bases in the genome are affected