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Biology U3AOS1 (Protein Synthesis (Universal (the same triplet will code…
Biology U3AOS1
Protein Synthesis
Introns are then removed and they don't contain useful information for amino acids, leaving just the exons
A methyl cap is added to 5-prime end and a poly A tail is added to the 3-prime end
The template strand is used for building a messenger RNA molecule
This post transcription modification molecule then moves to a ribosome for translation
RNA polymerase unzips DNA and starts adding complementary RNA bases (A,U,C,G)
tRNA then is attached with the complementary anticodon and amino acid
Amino acid then breaks off to join the chain and the process is repeated until the STOP codon is reached
Universal
the same triplet will code for the same amino acid for almost all species
Degenerate/ Redundant
doesn't matter if there is a mutation as a single amino acid can be coded by more than one codon
Enzymes
Lock and key: the active site of an enzyme has a shape complementary to that of its substrate
Induced fit: entails a change in the active site of the enzyme to fit the substrate
Enzyme-substrate (E-S) complex: temporary compound produced by the bonding of an enzyme with its specific substrate, at the active site of the enzyme
Catabolism (exergonic) – releases useful energy from the breakdown of complex molecules
Every enzyme has an active site. Typically, a small pocket or cleft in an enzyme is an active site (has a 3-D shape), also known as the substrate binding site, which is essential for the enzyme to function.
Anabolism (endergonic) – complex molecules required by cells are synthesised from simpler building blocks, a process that requires an input of energy
Biological catalysts that speed up the rate of chemical reactions without themselves being used up in the reaction, they lower the activation energy
Factors
Temperature
increasing temperature, increases the amount of collisions between the enzymes and the substrate, therefore increases the rate of the reaction, if heated too much it will denature
pH
There is a particular pH for optimum activity for each enzyme. This is because the active sites of the enzyme can be disabled by the wrong pH.
Concentration
having an increase in enzyme concentration, increases the rate, but it will eventually plateau, if the substrate concentration increases, the rate increases, maximum rate therefore also plateaus
Inhibition
Cofactors
Cofactors may alter the shape of enzymes slightly to make the active sites functional or to complete the reactive site.
Reversible
Non-competitive inhibitors
Bind to the enzyme, but not at the active site. The substrate can bind but enzyme function is impaired (active site has changed shape). Bind at allosteric site.
Competitive inhibitor
Compete with the substrate for the active site
The inhibitor is temporarily bound to the enzyme, thereby preventing its function
Irreversible
The inhibitor is permanently bound to the enzyme, thereby causing it to be deactivated
Cellular Respiration
Krebs cycle
occurs in the matrix of the mitochondrion, inputs (2 pyruvate, 2ADP & Pi, 8NAD+, 2FAD) outputs (6 carbon dioxide, 2 ATP, 8NADH, 2 FADH2), ATP yield is 2
Electron transport chain
occurs on the cristae of a mitochondrion, inputs (6 oxygen, 32 ADP & Pi, NADH, FADH2), outputs (6 water, 32/34 ATP, NAD+, FAD+), ATP yield is 32 or 34
Glycolysis
occurs in the cytoplasm, inputs (1 glucose, 2ADP & Pi and 2NAD+) outputs (2 water, 2ATP, 2NADH, 2 pyruvate), ATP yield is 2
Aerobic respiration
can only proceed in the presence of oxygen
Endosymbiosis
a special kind of symbiotic relationship where one organism takes up permanent residence inside another organism
similar size, double membrane, circular DNA molecule, binary fission, own ribosomes, own RNA, own DNA
Purpose
To transfer chemical energy stored in glucose into chemical energy of ATP to be used by cells to stay alive
Anaerobic respiration
occurs when oxygen is not present, lactic acid fermentation (in animals), alcoholic fermentation (in plants)
Factors
Glucose Availability
If there is no glucose available, then all stages of cellular respiration will slow down. This is due to glucose being the main input of cellular respiration and therefore without it, cellular respiration cannot occur
Oxygen Concentration
If there is not enough oxygen available, then the cell will not be able to respire aerobically and will have to switch to anaerobic respiration which will actually increase the rate of ATP production
Temperature
If the temperature drops, then the rate of all chemical reactions that are catalysed by enzymes will be slowed down as the enzyme is no longer functioning at optimum temperature
Compensation point
the point reached in a plant when the rate of photosynthesis is equal to the rate of respiration
Lac operon
Bacteria only produce lactase when they are required to break down lactose
An operator is a short DNA segment that provides a binding site for a repressor
An operon is a group of linked structural genes with a common promotor and operator, that is transcribed as a single unit
lac Z, lac Y, and lac A are the three genes that metabolise lactose
A promotor (Plac) is a short DNA segment where RNA polymerase can attach
When lactose is absent, the repressor protein is active and binds to the operator, physically blocking RNA polymerase from attaching to the promoter. Transcription cannot start and the lac operon is repressed
the lac I gene is a regulator gene that encodes the repressor
When lactose is present, it binds to the repressor protein changing its shape and inactivating it so that it cannot bind to the operator. This means that RNA polymerase can attach to the promoter and start transcription of the structural genes
Photosynthesis
Endosymbiosis
a special kind of symbiotic relationship where one organism takes up permanent residence inside another organism
similar size, double membrane, circular DNA molecule, binary fission, own ribosomes, own RNA, own DNA
Light-dependent reaction
In the grana
Inputs: 12 water, sunlight
Outputs: 6 oxygen, 18 ATP, NADPH
Chloroplast
Thylakoids
light dependent stage of photosynthesis occurs here, stack of them is a granum or multiple grana
Ribosomes
make proteins (has mRNA and also DNA)
Stroma
fluid inside chloroplast, light independent stage occurs here, ribosomes and DNA are present in it
Light-independent reaction (Calvin Cycle)
In the stroma
Inputs: NADPH, 18 ATP, 6 carbon dioxide
Outputs: glucose, 6 water
Purpose
to create glucose for cellular respiration
Factors
Light intensity
increasing intensity can increase the rate until a maximum is reached
Temperature
there is an optimal temperature for each plant species. Enzymes catalyse the series of reactions in photosynthesis
CO2 Concentration
increasing the carbon dioxide concentration increases the rate until a maximum is reached
Wavelength of light
violet and red-light wavelengths can produce higher rates than yellow or green light
Plasma membranes
Hydrophobic: repelled by water
Hydrophilic: attracted to water
Made up of phospholipids (fatty acid tails - hydrophobic) & (phosphate heads - hydrophilic), protein channels and carrier proteins
Fluid mosaic model
a model which proposes that the plasma membrane and other intracellular membranes should be considered as two-dimensional fluids in which proteins are embedded
Diffusion
Osmosis
the net diffusion of free water molecules through a semi-permeable membrane from a region with a low solute concentration to a region with a high concentration
Facilitated diffusion
the passive net movement of larger molecules through a protein channel or carrier protein from a region with a high concentration of solute to a region with a low concentration of solute
Simple diffusion
the passive net movement of a substance from a region with a high concentration of solute to a region with a low concentration of solute
Active transport
the active net movement of a substance from a region with a low concentration of solute to a region with a high concentration of solute through a carrier protein
Bulk Transport
Exocytosis: molecules are exported out of the cell
Endocytosis: molecules are brought into a cell
Pinocytosis: cell engulfs a liquid object
Phagocytosis: cell engulfs a solid object
Nucleic Acids
DNA
Double helix
Every nucleotide has three parts: 5-carbon sugar, phosphate group and a nitrogenous base
Adenine, Thymine, Cytosine, Guanine
Genetic instructions for all body functions
RNA
Adenine, Uracil, Cytosine, Guanine
mRNA: copies portions of DNA (transcription) and transports them to a ribosome
Single-stranded
tRNA: brings amino acids to the ribosome, in response to the mRNA (translation)
rRNA: creates ribosomes in order for protein production to occur