AOS 1 - Biology Unit 3

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AOS 1 - Biology Unit 3 by Mind Map: AOS 1 - Biology Unit 3

1. Cell Theory: Cells are the basic unit of life All cells come from pre-existing cells

1.1. Living: M - Movement R - Respire S - Sensitive N - Nutrition G - Grows R - Reproduces E - Excrete W

1.2. Anaerobic - not oxygen conditions Aerobic - rich in oxygen

2. Plasma Membrane: Fluid Mosaic Model - the phospholipid bilayer is a complex structure that is fluid like, embedded with carbohydrates, proteins & lipids

2.1. What does the plasma membrane consists of: Phospholipids: Amphipathic - hydrophilic/hydrophobic Hydrophilic phosphate head Hydrophobic fatty acid tail

2.2. Protein Channels - facilitated diffusion/active transport Cholesterol - helps with membrane fluidity, the more cholesterol the more rigid the plasma membrane Carbohydrates/Sugars - identification

2.2.1. Diffusion: Simple Diffusion - particles travel passively (w/o energy) from an area of high solute concentration to low solute concentration, down its concentration gradient Active Transport - particles are travelling actively (w/ energy) against its concentration gradient (high solute concentration) Facilitated Diffusion - protein channels carrying the molecule across the plasma membrane to diffuse down its concentration gradient Osmosis - water is travelling from a place of low solute concentration to high solute concentration

3. Eukaryotes vs. Prokaryotes: Eukaryotes - multicellular/unicellular, membrane bound nucleus & organelles Prokaryotes - unicellular, no membrane bound nucleus nor organelles Circular DNA free floating Ribosomes - no membrane

3.1. Organelles: Animal Cell: Mitochondria Nucleus Ribosomes Golgi Apparatus - package proteins further to put into vesicles for exportation rER - package, transport & process proteins sER - lipid production Plant Cell: Vacuole Golgi Apparatus Ribosome - Site of protein translation - helps with protein synthesis Chloroplast - Site of photosynthesis sER rER

3.2. Cytosol vs. Cytoplasm: Cytosol - fluid Cytoplasm - fluid & the organelles

4. Proteins & Nucleic Acids Condensation Polymerisation - monomers are joined to form a polymer which releases water

4.1. Protein: Polymer - polypeptide chain Monomer - amino acid joined by peptide bond

4.1.1. Protein Structure: 1. Primary: sequence of amino acids 2. Secondary: interactions between hydrogen bonds of peptide bond Alpha helices - spiral Beta-pleated sheets - sheets 3. Tertiary: bonding/interactions between amino acid side chain / variable group / R group > Functional 3D shape 4. Quaternary: 2 or more poly peptide chains are joined together

4.1.2. Process of protein creation --> exportation: 1. DNA is copied by RNA polymerase to form mRNA, mRNA leaves the nucleus to travel to ribosomes studded onto our rough ER. 2. Polypeptide enters the rough ER, bending, folding and other modifications occur of the protein. 3. Small part of the rough ER pinches off with the protein and is transported via a vesicle to the Golgi apparatus 4. Vesicle travels to the golgi apparatus where it is further modified and packaged into a secretory vesicle 5. Secretory vesicle is transported to the cell membrane, fuses with the membrane and releases its contents via exocytosis

4.1.2.1. Cytosol Ribosomes - forms proteins that the cell itself uses Ribosomes studded onto the rER - forms proteins for extracellular use, exocytosed

4.1.3. Transcription: Producing our pre-mRNA from the DNA in cells > Initiation - start transcription > Elongation - making mRNA chain > Termination - ending transcription 1. Template strand DNA acts as the template for mRNA synthesis and DNA unwinds 2. RNA polymerase binds to the promoter region on the template strand 3. In 5'-3' direction, RNA polymerase extends the new complementary mRNA strand by adding RNA nitrogenous bases. 4. RNA polymerase replaces thymine with Uracil 5. Transcription is terminated when it reached STOP termination sequence on DNA 6. pre-mRNA is formed

4.1.3.1. Post-transcriptional Modification: 1. Splicing of introns: Spliceosomes cut introns and link the exons together Alternative splicing - exons can be rearranged in many different ways to form different proteins 2. 3' Poly-A-Tail: add adenine nucleotides to the end of the pre m-RNA, stabilises and minimises degradation of mRNA 3. 5' Methyl Guanine Cap: added for stability and protection

4.1.4. Translation: mRNA is read and the polypeptide chain is formed 1. mRNA attaches to the ribosomes - move along until it reaches START codon 2.mRNA codon feeds into the ribosome, tRNA brings MET and bind temporarily 3. tRNA brings specific amino acids to mRNA codon and bind temporarily via its anticodon 4. Amino acids are joined via condensation polymerisation to form peptide bonds 5. Process continues until STOP codon is reached and translation terminates. 6. Protein is released

4.1.4.1. Redundancy/Degeneracy - more than 1 codon for the same amino acid

4.2. Nucleic Acids: Polymer - DNA & RNA Monomer - Nucleotides

4.2.1. Nucleotide: 1. Ribose/Deoxyribose Sugar 2. Phosphate group 3. Nitrogenous Base DNA - Adenine (A), Thymine (T), Cytosine (C), Guanine (G) A - T & C - G RNA - Adenine (A), Uracil (U), Cytosine (C), Guanine (G)

4.2.1.1. Triplet - 3 letter code of the DNA Anticodon - 3 x bases on the tRNA complementary to the codon Codon - 3 x bases on the mRNA that code for the amino acid

4.2.2. Antiparallel - DNA chain 5'-3' whilst the other side is 3'-5' DNA - double stranded, double helix structure Chromosomes -> Histones RNA - single stranded, straight chained

4.2.3. DNA Replication - when a new cell is formed and it has to be replicated Semi-Conservative - the new DNA molecule contains one new and one old DNA strand 1. DNA strand unzips via DNA helicase > creating replication fork 2. Replication occur is catalysed by DNA polymerase, attaching the nucleotides to the replication strand, added from the 3' end 3. Lagging strand replicated in okazaki fragments and then they are joined together by DNA ligase

4.2.4. RNA x 3 types: 1. mRNA - messenger RNA: carries genetic messages to the ribosomes where it is translated into a particular protein 2. tRNA - transfer RNA: carries specific amino acids to the ribosome with the mRNA chain to build the polypeptide 3. rRNA - ribosomal RNA: makes up the ribosome

5. Gene Structure & Regulation Gene Regulation - process in which the expression of genes are activates or inactivated Operon - group of linked structural genes that are controlled by a promoter and an operator

5.1. Structural vs. Regulatory Genes: Structural genes - code for functional proteins (ones that are used in the body) Regulatory genes - code for factors, transcription & translation enzymes & molecules Master regulatory genes - control embryonic development

5.2. Upstream factors: Promoter Region - RNA polymerase first attaches to Operator: certain factors (activating/deactivating) bind to and regulate expression What can bind to the operator? Repressor - stop or slow down transcription Enhancer - increase transcription rate

5.3. Downstream Factors: Termination site - where the RNA polymerase stops transcribing

5.4. LAC Operon: prokaryotes codes for the enzyme that breaks down lactose 1. Lactose Absent Regulatory gene is producing a transcription factor that represses the transcription of the LAC operon, by binding to it and preventing RNA polymerase from transcribing lac z,y & a 2. Lactose Present: Lactose binds to the repressor, changing its shape until it is not longer able to bind to the operon and hence RNA polymerase can transcribe pre-mRNA