1. Biological Energy Flashcards
What are the 2 main ways energy can be stored/transferred/released?
Describe ATP
1) Chemical bond formation: ATP/PCr/other P containing molecules/sugar stores. Releases stored energy.
2) Holding something away from equilibrium: PMF and chemiosmotic principle. Holding away from eq requires energy so letting it flow back releases stored energy.
Adenosine triphosphate: adenosine + ribose + 3 x P, made from phosphorylation of ADP and AMP, continually recycled (catabolism and anabolism). Get more eregry from ATP -> ADP than ADP -> AMP.
What is the ATP:AMP cellular ratio useful for?
Where does the ATP energy come from?
Cell senses how much energy is availble and can thus control the metabolic pathways that produce and use ATP.
Charge density (3 P have -ve charge so if hydrolyse the P-P bond, not as many -ve charges held close -> return to repulsion equilibrium), resonance (e- in structures produced can move around more freely), reaction held far from equilibrium (cellular conditions)
What does phosphocreatine do, and how is it synthesised?
What part of its synthesis is used in diagnosis?
List some other phosphate energy stores.
Acts as an ATP buffer. Synthesised by transfer of a P from ATP to creatine (reversible). Catalysed by creatine kinase. Important in tissues that have high fluctuating energy demands (muscle, brain) - allows quick ATP replenishment
Creatine kinase presence in blood = tissue damage.
Uridine triphosphate, guanosine triphosphate (interchangable with ATP, can be interconverted)
List some medium-long term energy stores.
Describe the relationship between energy storing and equilibrium.
Carbohydrate - glycogen (medium-term store in liver and muscle, synthesis/breakdown allosterically and resiprocally controlled, limited storage), Fat (mainly adipose tissue, high energy density, limitess storage)
Put energy in to hold something from equilibrium and release it again when allow it to reach equilibrium. So the further you move something from equilibrium, the more energy is stored in it. E.g. ATP reaction held far from eq.
Describe the PMF.
What is another name for this process?
A mitochondial electrochemical gradient across a membrane due to H+, giving a type of potential energy available for work in a cell. Occurs in oxidtative metabolism. ETC takes energy from e- and uses it to move H+ aross a membrane to create an electrochemical gradient (electro = + charge, chemical = H+ acidic), then letting it flow back down to equilibrium and using the energy to generate ATP. Coupling = describes linking to ATP generation.
Chemiosmosis (b/c linked to osmosis)
NB: all energy stores feed into ATP or PMF which can be used to power things in cell
Describe how the F1 F0 ATPase works.
How does a lysosome make use of this?
Converts ion gradients to ATP (and vice versa, thus ATPase/synthase). Two motors: electrical one in membrane powered by H+ flow and chemical one in cytosol powered by ATP. When one turns, so does the other. Electrical takes H+ gradient, converts it to rotational movement, which turns it into chemical energy making ATP.
H+ moves down -> across -> down. (Has to go across to make part of the motor rotate to drive ATP production).
Lysosome: ATPase can go both ways. Lysosomes use ATP to make H+ gradient to acidify contents = it’s enzymes are most active in acidic conditions.
This kind of ATPase also founf on golgi and other organelles
Why does the body extract energy from glucose in small chemical steps?
Describe the 2 ways of generating ATP?
Easier to capture energy if it’s in small manageable chunks.
1) Anaerobic: Substrate level phosphorylation - glycolosis breaks down glucose -> pyruvate -> lactic acid
2) Aerobic: Oxidative phosphorylation - pyruvate to mitochondria for Krebs and ETC
Describe glycolysis.
Describe TCA/Krebs.
Describe the ETC.
In cytoplasm. Consumes 2 ATP and produces 4 ATP and 2 NADH+. 2 x pyruvate from glycolysis used to make acetyl CoA for krebs or lactic acid.
In mitochondrial matrix. Takes pyruvate and extracts e-s for use in ETC. Produces CO2 and reduced cofactors (e- carriers) that carry e- to ETC.
In inner mitochondrial membrane. Couples reaction between an e- donor e.g. NADH/FADH and e- acceptor e.g. O2 to the transfer of H+ ions across a membrane, through a set of mediating biochemical reactions, generating a PMF (electrochemical gradient), and producing ATP. Final e- destination = O2.
How is energy used when breaking down/building biological molecules?
What are the two types of transport?
What are symporters and antiporters?
What is charge driven transport?
Breaking down = releases energy. Building (anabolism) = requires energy usually from ATP e.g. protein synthesis, DNA replication, hormone/steroid synthesis. Moving things into more ordered state away from entropy requires energy.
1) Passive: e.g. ion channel, often moving down own conc gradient
2) Active: uses ATP to move something across, can move against a conc grad
Symporters: transport 2 molecules at once in same direction
Antiporters: transport 2 molecules at once but in opposite directions. Can get 20 active transport: use ATP (B) to create conc gradient and use it to actively transport A (picture)
Can be linked to PMF - anything coupled to H+ can be transported. If e.g. make one side of membrane more +ve, -ve things flow towards it etc.
How is glucose moved against its concentration gradient?
How does the Na+/K+ pump work?
How does cotransport with the Na+/K+ pump and glucose work?
Active transport - glucose transporter: transport proteins in the membrane use ATP to move substances in/out of membrane against its conc gradient
Breaks down ATP -> ADP to pump 3 Na+ outside cell. 2 K+ are then transported into cell. Both are transported against a gradient. NB: Generates a Na+ and K+ gradient that can be coupled to transport of something else.
The pump is coupled with movement of glucose in to the cell, while allowing Na+ to enter (after being pumped out) through the coupled transport protein.
How is energy used for motility within muscles?
Muscle cells contain tubular myofibrils = repeating sarcomere sections composed of actin and myosin filaments that slide past each other during contraction and relaxation. ATP hydrolysis causes conformational changes in the proteins -> contraction. Myosin heads hydrolyse ATP and become reorientated and reenergised -> bind to actin forming crossbridges -> myosin heads rotate towards cente of sarcomere -> as myosin heads bind ATP the crossbridges detach from actin.
How is energy used to keep the body warm? (2 ways)
Shivering - uses muscles.
Non-shivering thermogenesis - uses H+ gradient in mitochondria but uncouples it from ATP production: lets H+ flow through thermogenin protein -> releases heat. (So turns PMF into heat). Particularly occurs in brown adipose tissue, imp for babies.
How do we control flux/reactions?
What is the cori cycle?
What 3 ways can regulatory enzymes be controlled?
Energetics e.g. reactions irreversible under certain conditions, compartments, enzyme regulation
Inter-organ metabolic coopertation: in muscle glucose -> lactic acid, then into blood to liver where convered back to glucose -> blood -> muscle again
Allostery - small molecule binds to enzyme (short term), Covalent modification - e.g. P addition to make it more/less active (short-term), Protein synthesis - hormones ctrl gene expression of enzyme protein (long-term)
