Biology Exam Revision

What is the role of nucleic acids and proteins in maintaining life?

What is DNA

Deoxyribonucleic Acid, that carries inheritable genetic information to make proteins and i

What is a Cell

Cell is a basic organisational unit of life, all organisms make up cells, all cells come from pre-existing cells

Prokaryotic Cell

unicellular cell that are small, lack membrane bound nucleus and membrane bound organelles. Have a cell wall. Less complex

Eukaryote

cells that have membrane bound organelles, much bigger and complex and lack cell wall

Carbohydrate

type of biomacromolecule, used for energy source, storage, structural support and membrane structures

Lipid

Don't dissolve in water, solid lipids - fat liquid lipids - oils

Phospholipids

Made of a phosphate head and a triglyceride which has a glycerol and 3 fatty acid chains. head is negative charged, and has two fatty acid chains. Used in liposomes

Nucleic Acids

made of nucleotides which is monomer. Two type Deoxyribonucleic acid and Ribonucleic acid,

DNA

Deoxyribonucleic Acid, that carries genetic information that is inheritable and codes for specific order of amino acids that need to be joined to make proteins

RNA

ribonucleic Acid that has a ribose sugar and has uracil instead of thymine, rRNA, tRNA and mRNA, stored in nucleus found in cytoplasm

What is the bond between two nucleic Acids

Phosphodiester bond that is between the 3rd carbon and phosphate group

How do nucleotides join

Through condensation reaction, where two monomers join together to create a polymer while releasing a molecule

Genome

complete set of genes in cell or organisms, all same species have same genome, all cells in organisms have same genome

Proteome

Complete set of proteins expressed in cell or organisms at specific time, diff proteins expressed at different stages and genders, diff express in cell types

Why are cell functions different if same genome

different genes are turned on or off, and this can happen due to chemical tags which attach to DNA, prevent it from being read and turned into protein

Transcription

nucleus, mRNA made based on genetic code in DNA

Translation

ribosome, polypeptide created, based on genetic code in mRNA

Bond between bases

Hydrogen bonds

bonds between A and T

2 hydrogen bonds

Bonds G and C

3 hydrogen bonds

structure of DNA

negative phosphate group, deoxyribose sugar and nitrogenous base

How is DNA packaged

46 chromosomes of different nucleotide lengths, around histone protein

mRNA structure

linear molecule

rRNA

highly folded spherical molecule

tRNA

clover lead shaped, fold due to complementary base pairing

Purine

1 carbon ring bases a and g

pyrimidines

2 carbon rings bases t and c

short on how DNA turns into Proteins

DNA is copied in nucleus into mRNA
mRNA is modified and leaves nucleus and attaches to ribosome
ribosome makes protein based on mRNA codon, and amino acids brought to ribosome by tRNA

mRNA

carries genetic info to ribosome, tells ribosome which proteins made

tRNA

carries amino acid to ribosome

rRNA

makes up ribosome and creates bonds between amino acids on ribosome

central dogma

specific genes code for specific proteins

flanking region

DNA sequences that regulate transcription such as promotor and termination sequence

one gene structure

promotor, coding region, termination sequence

transcription direction

5 prime to 3 prime, nucleotides only attach to 3 prime end
phosphate of new one joins sugar of old one in chain

promotor region

binding site for RNA polymerase and also have specefic dna sequences that allow tf to bind

what are tf

turn transcription on or off

termination sequence

specific DNA sequence that stops transcription by telling RNA polymerase to detach

what strand does polymerase bind to

template strand

Explain steps of Transcription

1. RNA polymerase bind to promotor region of template strand at 3 end.

2. helicase unwinds DNA exposing bases of template strand

3. matching base pairing of RNA nucleotides against template strand

4. RNA polymerase continues moving in 3 prime to 5 prime direction along template strand creating growing RNA molecule that is 5 prime to 3 prime

5. termination sequence reached, RNA polymerase detaches, and pre Mrna formed
   

Codon

nucleotide triplet that codes for amino acid

redundant genetic code

one amino acid made by multiple codons

degeneracy

multiple codons code for one amino acids

start codon

AUG

exons

sections in genes which code for proteins

introns

non coding regions gene

post transcriptional process

introns spliced in mRNA using spliceosome

exons joined

5 prime cap and poly a tail 3 end for stable and prevent degrade

alternative splicing

some exons cut out, creates alternatives mRNA, allows one gene to code for multiple codons

how is amino acid trna brings determined

by specific anticodon on it

anticodon

found on trna and complementary to codon found on mrna

how does tRNA coil

has regions that pair with each other

stop codons

stop translation dont code for anything

Ribosomes

create pairing between mrna codon and trna anticodon and creates peptides bond between amino acids

Structural genes

code for proteins

Regulatory genes

code for proteins called transcription factors that regulate expression of structural genes

repressors

transcription factors that bind to DNA in promotor region prevents RNA polymerase to transcribe

Activators

bind to DNA in promotor region help RNA polymerase to assemble and enhance transcription

Regulation is not just on and off

Control of activity

Do eukaryotes have operators

No

how does regulation work of a cell from a sifferent cell

extracellular proteins like hormones bind to receptors which create signal that create transcription factor

describe bacterial DNA

one large circular DNA and multiple plasmid
no nucleus

no introns

transcription and translation happen at same time

what is operon

An operon is a cluster of genes under the control of a single promote

trp operon

regulated gene cluster that codes for enzyme subunits which produce trp

why is gene regulation important

to help save energy

parts of trp operon

promotor, operator and set of structural genes as well as upstream regulatory genes

regulatory proteins and types

coded by regulatory genes and regulate gene expression
tf - bind to promotor or operator regions to activate or repress expression

why is gene regulation important

different cells, evolution, response to environment

how does trp operon work

regulatory gene is constantly expressed and produces inactive repressor that on its own cant bind to operator, meaning gene cluster is expressed. when trp levels are high it binds to allosteric site of tf, making it bind to the switch on the operator preventing RNA polymerase to transcribe the genes.

Protein function remember TEACHERS

transport, enzymes, antibodies, contractile proteins, hormones, storage proteins, receptors, structural

what is a protein

type of biomacromolecule, monomer is amino acid and are long chain of amino acids

essential acids

9 amino acids body cant make so it has to consume it

structure of amino acid

amine group, variable group and carboxyl group
nh2, R, COOH

how do amino acids join

condensation polymerisation- two monomers join together creating a polymer releasing a molecule

how are amino acids joined

peptide bonds

primary structure of protein

specific order of amino acids in polypeptide chain

secondary structure protein

3D folding of regions of chain, due to different properties of R groups, held by h bonds

Alpha helices

spiral structures

beta sheets

folded pleats

random coils

just random coils

Tertiary structure

specific 3D folding of entire chain due to side chain interactions

Quaternary Structure

when protein is made of 2 or more polypeptide chains

secretory pathway

proteins made by cell that are secreted outside

Summary protein secretion

mRNA leaves nucleus, ribosomes on RER use mRNA to make protein, protein enters through lumen where it gets modified and packaged into vesicle which goes to Golgi. In Golgi it further gets modified and packaged into secretory vesicles. which travel to membrane and leave through exocytosis

transport vesicles

made by RER to transport proteins to Golgi made of phospholipids

Attenuation

method of reducing the expression of the trp operon in prokaryotic cells, blocks mRNA to be finished transcribing, relies on transcription and translation happening at same time

Leader region

between operator and gene cluster and has 4 regions, region one has two codons which code for trp,

attenuation high trp

ribosome does not have to stall at trp codons in region 1 and moves along to region 2 allowing region 3 and 4 to bind to create termination loop which is strong enough to pull rna polymerase from mRNA preventing it from being completed

attenuation low trp,

ribosome has to stall at trp codons in region 1 and allowing region 2 and 3 to bind to create anti termination loop which is not strong enough to pull rna polymerase from mRNA allowing mRNA to be completed

Insulin

hormone needed to regulate blood glucose leveles

Insulin production steps

1. isolate and amplify insulin gene

2. cut gene and put in plasmid

3. put plasmid in bacteira

4. grow bacteria

5. purify insulin

PCR

polymerase chain reaction

primers in PCR

short nucleotide sequences that are designed as flanking sequence of selected DNA

PCR steps and temperature

Denaturation - 94
Annealing - 55
DNA extension - 72

Denaturation PCR

Heat sample to denature hydrogen bonds between double stranded DNA and turn into single strand

Annealing PCR

primers bind to single stranded DNA

DNA extension

taq polymerase synthesizes complementary DNA strand based on original strand

Restriction Enzymes or endonucleases

found naturally in prokaryotes, defend against virus by digesting viral DNA

how restriction enzyme work

binds to recognition sequence and breaks phosphodiester bond in DNA backbone

what is recognition sequence

specific DNA sequence that are palindromic that restriction enzymes recognise and cut

Sticky ends

have overhangs that are very reactive and specefic