Cellular respiration and metabolism WK3 Flashcards
What is cellular respiration. How is it achieved?
catabolic breakdown of nutrients into form usable by cells for their processes
-Achieved ATP production
-energy release
-60% lost as heat while 40% as ATP for cell activities
Explain the stages of metabolism
- Digestive enzyme breaks down macromols into absorbable forms
- Nutrients transported to cells (anabolised/catabolised)
- Catabolic pathways of (Krebs) cycle and oxidative phosphorylation
- Stages 2 and 3 (cellular resp)
Describe ATP structure and function. Explain energy in each phosphate group
-adenine, ribose, and 3xphosphate groups
-Important energy transfer mol.
-Stores energy from exergonic reactions-quickly release for physiological work
-Holds energy in covalent bonds
-2nd/3rd phosphate groups have high energy bonds
-Most energy transfers to/from ATP involve add/removal of 3rd
Differ requirements and functions of anabolism/catabolism
Anabolism-uses energy
-Requires enzyme- ATP synthase
-Hydrolysis of ATP
Catabolism-releases energy
-Requires enzyme-adenosine triphosphatase (ATPase)
-Enzyme breaks 3rd high-energy phosphate bond
-Separates ATP into ADP+phosphate+energy
What are the two mechanisms of ATP synthesis
- Substrate-level phosphorylation
- Oxidative phosphorylation
Describe substrate-level phosphorylation, where and how it occurs
-ATP formed from ADP+ phosphate group
-High-energy phosphate groups directly transfer to ADP from phosphorylated substrates
-Occurs in: Glycolysis, Krebs cycle
Describe carbohydrate metabolism
-Most dietary carbs burned as fuel within hours of absorption
-Most cells generate high-energy bonds from carbs
-Complete catabolism of one glucose molecule (each molecule produces gain of 36 ATP)
-Aerobic metabolism- energy production in the mitochondria requires oxygen
Describe glucose metabolism
-Starts in cytoplasm of cell w/glycolysis
-Can take place without O2 (anaerobic, fermentation)
-Each glucose broken down to 2 pyruvic acid molecules
-Pyruvic acid enters mitochondria
-CO2 removed from each molecules
-Remainder for to tricarboxylic acid (Krebs/citric acid cycle)
-Glycolysis uses 2 ATP molecules as energy to fuel this process
Describe glycolysis process
Final products;
-2x3-carbon molecules of pyruvic acid
-Converted to lactic acid if O2 not readily available
-Enter aerobic pathways if O2 readily available
- 2 NADH + H+ (reduced NAD+)
-Net gain of 2 ATP
3 major phases:
1. Sugar activation: glucose phosphorylated, uses 2 ATP molecules, anabolism stores energy
2. Sugar cleavage: split into 3-carbond fragments
3. Oxidation and ATP formation: removal of H, phosphate groups are attached
-Substrate level phosphorylation
Describe process of mitochondrial energy production
Oxidative phosphorylation
-Generates ATP
-Consumes oxygen
-Coenzymes required
Electron transports system
-Cytochromes pass H+ electrons on to oxygen
-Forms water
As occurs system generates ATP
Describe the krebs cycle (not the process)
-Some og energy from glucose is in ATP and NADH or lost as heat
-Most remain in pyruvate
-Doesn’t directly use O2
-Enzymatic pathway
-Use pyruvate to produce more ATP
-Removes H atoms from organic molecules and transfers to co-enzymes;
-NAD+ (nicotinamide adenine dinucleotide)
-DAF (flavin adenine dinucleotide)
-NAD+ and FAD gain electrons (gain energy-reduction)
○ NADH+
○ FADH2
Describe process of krebs cycle
1.Coenzyme A joins remaining 2 C molecules in pyruvate (forms acetyl-CoA
2.molecule enters Krebs cycle/citric acid cycle
3.The two C atoms combine with 4 carbon atoms (already present in cycle)
4.Broken down and H removed
5. Electrons transfer and passed along coenzymes (NAD+ and DAF)
6. Energy released performs enzymatic conversion of ADP to ATP
Describe process of substrate-level phosphorylation (after krebs)
1.High-energy phosphate group directly transferred from phosphorylated substrates to ADP
2. Phosphoryl (PO3)/phosphate added to ADP-converts ADP to ATP
3. Remaining 4 C atoms re-synthesised
4.Leads to another NAD in the cycle to form NADH and FAD, which forms FADH2
5. Results in 1 ATP, NADH, FADH2
6. Each cycle uses 1 pyruvate
7. At end of cycle: 4 ATP-2 from glycolysis and 2 from Krebs
Describe oxidative phosphorylation chemiosmotic mechanisms of ATP synthesis (electron transport chain)
-in mitochondria by e- transport proteins
-H atoms split into H+ and e- as they transfer from coenzymes to ETS
- e- shuttled along inner mitochondrial membrane, losing energy
-Released energy used to pump H into space between inner/outer mitochondrial membranes
-Inner membrane permeable to H only at channel proteins (ATP synthase)
-H flows through ATP synthase
-Energy captures and attaches phosphate groups to ADP
-NADH oxidised to NAD+-yields 2.5 ATPs
-FADH2 yield 1.5 ATPS when oxidised
Define process of electron transport chain
- Remaining energy from glucose released via ETC
- From Krebs cycle and glycolysis- 4 ATP, 2NADH, 2FADH2
- 2NADH and 2FADH2 work with enzymes-oxidation reduction takes place
- NADH and FADH2 (e- donors) contribute their e- to enzymes (e- acceptors) in cell membrane through electrochemical gradient
- Max number of ATP generated by ETS via chemiosmosis
- Gives cells total of 32-34 ATP
- Glycolysis occurs in cytoplasm
- Krebs cycle and electron transport in mitochondria (oxygen important for aerobic cellular respiration
9.Without, e- remain stagnant in ETC, halting production of ATP
