Block B Flashcards
What is the first law of thermodynamics
Energy can neither be created nor destroyed (law of conservation of energy)
What is the second law of thermodynamics
The universe tends towards disorder (law of entropy)
What is entropy and what are the energy levels with high entropy vs low entropy
The degree of randomness in any system
High entropy = low energy level
Low entropy = high energy level
What increases the entropy and why
Heat because it increases the random motion of molecules
What is kinetic energy
Movement
What is potential energy
Stored energy
What is the enthalpy of a molecule
The total energy contained within the molecule / total heat content
What changes a molecules enthalpy
The conversion to a different structure during a chemical reaction, symbolised as ΔH
What is anabolism
Building molecules and consuming energy
What is catabolism
Breaking down molecules and releasing energy
What is hydrolysis
A chemical reaction where a water molecule is used to break a bond in a compound
What is phosphorylation
The attachment of a phosphate to a molecule
What is hydrogenation
A chemical reaction where hydrogen H4 is added to a compound
What are the 5 stages in an enzyme catalysed reaction
1 - substrates enter the active site
2 - substrates are held in the active site by weak interactions
3 - substrates are converted to products
4 - products are released
5 - active site is available for new substrates
What are the 2 mechanisms of enzymes
Lock and key - the shape of the active site is specific to the substrate and is a fixed shape
Induced fit - shape of the active site is flexible and changes shape to fit the substrate more snugly after binding
What type of bond is there between nucleotides
Covalent bonds
Examples of energy intermediates
ATP and NADH
What is entropy
The degree of disorder of a system
When a physical system becomes more disordered, the entropy _____
Increases
What is the role of cofactors
Stabilising the enzyme or substrate
Facilitating the reaction by acting as electron carriers or by transferring groups like hydrogen, phosphate or acetyl
What are inorganic cofactors
Metal ions, eg. Magnesium, iron, zinc
Can be permanently bound to the enzyme or can assist the reaction temporarily
What are organic cofactors
Coenzymes - bind loosely and temporarily to the enzyme
Prosthetic groups - bind covalently and permanently
The classification of enzymes by the reaction catalysed
Oxidoreductases
Oxidation and reduction reactions eg dehydrogenases
The classification of enzymes by the reaction catalysed
Transferases
Transfer a chemical group from one substrate to another eg kinases
The classification of enzymes by the reaction catalysed
Hydrolases
Hydrolysis (water splits the bond) of C-O, C-N, O-P, C-S bonds eg esterases, proteases, phosphatases
The classification of enzymes by the reaction catalysed
Lysases
Addition across a carbon-carbon double bond eg dehydratases, hydratases, decarboxylases
The classification of enzymes by the reaction catalysed
Isomerases
Intramolecular rearrangements
The classification of enzymes by the reaction catalysed
Synthetases
Formation of bonds between 2 substrates
The 6 factors affecting enzyme activity
pH
Temperature
Concentration of enzyme
Concentration of substrate
Inhibitors and activators
Covalent modification of enzyme
What is the specific activity of an enzyme and what does it give a measurement of
The activity of an enzyme per mg of total protein (expressed in μmol min-1mg-1)
Measures the purity of the enzyme
What are the 3 most important parts of metabolism
Energy - sometimes released, sometimes required
Carbon skeletons - building blocks
Reducing equivalents - electrons are sometimes released, sometimes required
What is the most common type of reaction in food breakdown (in regards to redox)
Oxidation
3 General principles of metabolism
Flow through metabolic pathways is unidirectional and therefore irreversible
The first step of the pathway is often the rate limiting step
Flow through pathways is regulated
What are the 3 energy storages forms in the body
Glycogen
Protein
Tryglycerides
What are the 5 circulating fuels in the body
Glucose
Lactose
Amino acids
Free fatty acids
Ketone bodies
What are the 3 key metabolic intermediates
Glucose-6-phosphate
Pyruvate
Acetyl-CoA
What is gene regulation of enzyme activity in metabolic pathways
The cell switches the genes that code for specific enzymes on and off
Long term control, slow
What is feedback regulation of enzyme pathways (2 types)
Feedback inhibition - end product of a pathway interacts with and “turns off” an enzyme earlier in the pathway, preventing a cell from synthesising more product than is needed (negative feedback)
Feedback activation - the end product speeds up production of further product (positive feedback)
What is allosteric regulation of enzyme pathways
When a regulatory molecule binds to a site on the enzyme that is not the active site, changing the active sites shape affecting enzyme activity
Non-competitive
Can either inhibit or activate
3 reasons for the importance of enzyme localisation
Enzymes are localised to the specific parts of the cell where their substrates are abundant, increasing efficiency
Isolation of certain enzymes in particular regions or organelles, it prevents unwanted reactions occurring in the wrong context
Allows for precise regulation of metabolic pathways
Are mitochondria inherited maternally or paternally
Maternally
____-_________ organelle (contains own ___, which is ______). Mitochondrial ___ (mtDNA) encodes ~___% of mitochondrial proteins.
Semi-autonomous
DNA
Circular
DNA
2.5
What are cristae and the functions
The folds of the inner membrane of mitochondria
where ATP synthesis takes place by oxidative phosphorylation
Where the electron transport chain occurs
What is the mitochondrial matrix and its functions
The compartment enclosed by the inner membrane
Gel like substance
Contains enzymes, mtDNA, metabolic intermediates
Site of the citric acid cycle producing NADH, FADH2 and CO2 which donate electrons to the electron transport chain
What are the 4 stages in cellular respiration - where does each stage occur, what are the products of each stage, anaerobic or aerobic
Glycolysis - cytoplasm, 2 ATP, 2 NADH, 2 pyruvate, anaerobic
The breaking down of pyruvate to an acetyl group - mitochondrial matrix, 1 NADH, 1 CO2, 1 Acetyl CoA, aerobic
Citric acid cycle - mitochondrial matrix, 3 NADH, 1 FADH2, 1 ATP, 2 CO2, aerobic
Oxidative phosphorylation - electron transport chain in the inner mitochondrial membrane, chemiosmosis, 28-32 ATP, H2O, NAD+ and FAD+, aerobic
What are the steps in the electron transport chain
Complex I accepts electrons from NADH - some energy pumps H+ protons into the intermembrane space, then electrons are transferred to ubiquinone (coenzyme Q)
Complex II accepts electrons from FADH - electrons are then transferred to ubiquinone (coenzyme Q)
From Coenzyme Q, electrons travel to complex III - some energy pumps H+ protons into the intermembrane space, then electrons are transferred to cytochrome C
From Cytochrome C, electrons are transferred to Complex IV - some energy pumps H+ protons into the intermembrane space, electrons are transferred to oxygen and water is produced
What complexes in the electron transport chain pump H+ protons into the intermembrane space
Complex I, Complex III, Complex IV
Explain chemiosmosis
Due to the electron transport chain pumping out H+ protons, this creates an electrochemical gradient.
Protons then flow back into the mitochondrial matrix through ATP synthase, an enzyme on the inner mitochondrial membrane, to synthesise ATP
This flow of protons provides the energy needed to convert ADP+Pi into ATP
