3. Cellular Respiration + Flashcards
1
Q
Cellular Respiration. Endergonic or Exergonic?
A
- overall an oxidative, exergonic process (ΔG = -686 kcal/mole)
2
Q
External vs. Internal Respiration
A
- External respiration: entry of air into lungs and gas exchange between alveoli and blood
- Internal respiration: exchange of gas between blood and cells + intracellular respiration processes
3
Q
Respiration Equation:
A
C6H12O6 + 6O2 —> 6CO2 + 6 H2O + energy
4
Q
Aerobic Respiration:
A
- in presence of O2 (glycolysis, pyruvate decarb, krebs cycle, oxidative phosphorylation), water is final product.
5
Q
Glycolysis
A
- decomposition of glucose into pyruvate in cytosol
- 2 ATP added, 2 NADH produced, 4 ATP produced, 2 pyruvate formed
- Net: 2ATP + 2 NADH + 2 pyruvate (+2 H2O, + 2 H+)
- ATP produced here via substrate-level-phosphorylation ( direct enzymatic transfer of Pi to ADP)
- PFK (enzyme) adds 2nd P, makes fructose 1,6-bisphosphate, this is irreversible and commits to glycolysis, major regulatory point.
6
Q
Pyruvate Decarboxylation
A
- at this point, we are in mitochondrial matrix
- pyruvate –> acetyl coA, producing 1 NADH and 1 CO2
- net: 2 NADH + 2 CO2
- catalyzed by PDC enzyme (pyruvate dehydrogenase complex)
7
Q
Krebs Cycle/Citric Acid Cycle/Tricarboxylic Acid Cycle
A
- fate of pyruvate from glycolysis
- in Krebs cycle, acetyl coA merges w/ oxaloacetate to form citrate, cycle goes w/ 7 intermediates.
- 3 NADH, 1 FADH2, 1 ATP (subs level pho), 2 CO2 produced per turn. (2 turns total for one glucose)
- Total for 1 glucose molecule: 6 NADH, 2 FADH2, 2 ATP (technically GTP), 4 CO2
- Place: mitochondrial matrix (like pyruvate decarbox)
- CO2 produced here is CO2 exhaled when animals breathe
8
Q
Electron Transport Chain (ETC)
A
- Place: inner membrane/cristae(folds that increase SA for more ETC action)
- Oxidative phosphorylation: ADP –> ATP from NADH and FADH2 via passing e- through various carrier proteins.
- NADH makes more energy than FADH2, more H+ pumped across per NADH (both are coenzymes), (3:2 yield)
- O2 if final e- acceptor - combines with native H+ to form H2O
- carriers extract energy from NADH and FADH2 while pumping protons into intermembrane space - ATP synthase uses this gradient (pH and electrical) to make ATP as it shuttles H+ back into inner matrix
- Coenzyme Q(CoQ)/Ubiquinone is a soluble carrier dissolved in membrane that can be fully reduced/oxidized
- Cytochrome C is a protein carrier in ETC, common in many living organisms, used for genetic relation. Cytochromes have nonprotein parts like iron (donat/accept e-, for redox)
9
Q
ATP Yield from 1 glucose
A
- not actual yield, mitochondrial efficacy varies.
- eukaryotes: 36 ATP
- prokaryotes: 38 ATP. More ATP because prok don’t have mitochonria so they don’t have to transfer pyruvate to mitochondrial matrix (costs ATP).
10
Q
Mitochondria
A
- outer membrane, intermembrane space (H+), inner membrane (oxid phosph.), mitochondrial matrix (krebs)
11
Q
Chemiosmosis in Mitochondria
A
- ATP generation from energy stored in form of proton concentration gradient across membrane.
- Krebs produces NADH/FADH2, they are oxidized (lose e-), H+ transported from matrix to intermembrane space, ph and electric charge gradient created, ATP synthase uses energy to create ATP by letting proton flow through the channel.
12
Q
ATP
A
- RNA nucleotide (due to ribose sugar)
- unstable because 3 phosphates in ATP are negatively charged and repel one another
- when one phosphate group removed via hydrolysis, more stable molecule ADP results
- change from less stable molecule to more stable always releases energy
- provides energy for all cells by transferring phosphate from ATP to another molecule
13
Q
Anaerobic Respiration
A
- Cytosol
- glycolysis + fermentation
- aerobic respiration regenerates NAD+ via O2, which is required for continuation of glycolysis, without O2, there would be no replenishing - NADH accumulates, cell would die w/ no new ATP, so fermentation occurs.
- Alcohol Fermentaion
- Lactic Acid Fermentation
14
Q
Alcohol Fermentation
A
- occurs in plants, fungi (yeasts), and bacteria (botulinum)
- pyruvate -> acetaldehyde + CO2, then acetaldehyde —> ethanol (and NADH -> NAD+)
- acetaldehyde is final e- acceptor (forming ethanol)
15
Q
Lactic Acid Fermentation
A
- occurs in human muscle cells, other microorganisms
- pyruvate -> lactate (NADH -> NAD+)
- lactate is transported to liver for conversion back to glucose once surplus ATP is available
16
Q
Facultative Anaerobes
A
- can use O2 when it’s present (more efficient) but switch to fermentation/anaerobic respiration if it isn’t
17
Q
Obligate Anaerobes
A
- cannot live in presence of oxygen
18
Q
Other Energy Sources
A
When glucose supply is low, body uses other energy sources, in priority of: others carbs, fats, and proteins. First converted to glucose or glucose intermediates, then degraded in glycolysis or CAC
19
Q
Alternate Energy Sources (other Carbohydrates)
A
- disaccharides are hydrolyzed into monosaccharides, most of which can be converted to glucose or glycolytic intermediates.
*** random: all cells capable of producing and storing glycogen but only muscle cells and especially liver cells have large amounts
20
Q
Insulin…..PFK enzyme.
A
- activates
- insulin means “hey, we got too much glucose around, so lets chew it up”
- glucagon inhibits PFK enzyme
21
Q
Alternate Energy Sources (Fats)
A
- fats store more energy than carbohydrates per C, their carbons are in a more reduced state
- fats are 10 cals/g, whereas carbs and protein are 4
- triglycerides in lumen of small intestine broken down via lipases into monoacylglycerides + fatty acids which are then absorbed into the enterocytes (cell lining of small intestine). There, they are reassembled into triglycerides and then (along with cholesterol/proteins/phospholipids) packaged into chylomicrons which move to lymph capillary for transport to rest of body where they are stored as adipose tissue.
- glycerol -> PGAL, enters glycolysis
- when fatty acid –> acetyl coA, every 2 carbon from fatty acid chain makes an acetyl coA. fatty acids in blood are carried by albumin
- fatty acids broken down via beta oxidation (mitochondrial matrix). 2 ATP spend activating entire chain. Saturated fatty acids produce 1 NADH and 1 FADH2 for every cut into 2 carbons. 18 C chain is 9 2C pieces but only cut 8 times, each cut is beta oxidation step. unsaturated fatty acids produce 1 less FADH2 for each double bond
- Fats more ATP yield than carbohydrates or proteins
22
Q
Alternate Energy Sources (Protein)
A
- least desirable source of energy, only when carbs and fats are unavailable.
- most amino acids are deaminated in liver, then converted to pyruvate or acetyl coA or other CAC intermediates, enter cellular respiration at these various points (varies by AA). Oxidative deamination removes ammonia molecule directly from AA. ammonia is toxic to vertebrates: fish excrete, insects and birds convert to uric acid, mammals convert to urea for excretion.
