Chapter 3- Aerobic Cellular respiration Flashcards
Aerobic cellular respiration
- phosphorylates ADP into ATP by breaking down glucose and moving electrons (oxidation and reduction reactions)
- breaks down glucose into 38 ATPs
- 4 catabolic processes:
1. Glycolysis
2. Pyruvate manipulations
3. Krebs cycle
4. Oxidative phosphorylation
Glycolysis
- glucose → 2ATP + 2NADH + 2pyruvate
- occurs in the cytosol
- anaerobic (does not require oxygen), it is used in fermentation also!
- extracts and uses high-energy electrons as glucose is broken down, to reduce NAD+ into NADH, which may travel to ETC for more ATP production.
Substrate-level phosphorylation
-transfers a phosphate group to ADP and generates ATP in glycolysis
GTP (Guanosine triphosphate)
-RNA nucleoside triphosphate like ATP
Flavin Adenine Dinucleotide (FAD)
-electron carrying coenzyme like NAD+
Fermentation
anaerobic pathway to oxidize NADH back to NAD⁺ so glycolysis can continue to make ATP.
Lactic acid fermentation
- regenerates NAD⁺ from NADH by reducing pyruvate into lactic acid.
- NADH transfers electron to pyruvate regenerating NAD+. This forms lactic acid/lactate
Cori Cycle
- converts lactate back to glucose when oxygen is available again.
- transports lactate from the myocyte (muslces) through the bloodstream to hepatocytes (liver cells).
- Lactate can then oxidize back into pyruvate which can form glucose through gluconeogensis.
Gluconeogensis
- creates new glucose from pyruvate
- energy investment of 6 ATP is required
- Glucose is broken down as oxygen is available again
Hepatocytes (liver cells)
- contain an enzyme that undoes hexokinase reaction of glycolysis
- Liver is the only organ that can release glucose into the bloodstream.
Alcohol fermentation
- it regenerates NAD+ for glycolysis to make 2 ATPs, similar to lactic acid ferm.
- However, electrons from NADH will not reduce the pyruvate
- Instead, pyruvate is decarboxylated to lose carbon as CO2.
- Left over molecule acetaldehyde will be reduced by NADH into ethanol, which oxidizes NAD+.
- Done by Yeast and produces ethanol found in alcohol.
Glycolysis (look at written notes for details)
-converts glucose into 2 pyruvates + 2ATP + NADH
Pyruvate manipulation (look at written notes for details)
-converts 2 pyruvates into 2CO2 + 2NADH + 2acetyl-CoA
Krebs Cycle (look at written notes for details)
-converts 2 acetyl CoA into 4CO2 + 6NADH + 2FADH + 2GTP
Oxidative phosphorylation (look at written notes for details)
-converts electron carries NADH and FADH into ATP and H2O
Obligate Aerobes
-only perform aerobic
respiration, need
oxygen to survive.
Obligate anaerobes
-only undergo anaerobic
respiration, will die in presence of oxygen
Facultative anaerobes
-can do aerobic, anaerobic respiration, or fermentation
-prefers aerobic respiration
because it generates the most ATP.
Microaerophiles
- only perform aerobic respiration
- but high amount of oxygen is harmful to them
Aerotolerant organisms
-only undergo
anaerobic respiration or fermentation, but
oxygen is not poisonous to them.
Alternative Sources of Energy Generation
- other types of carbohydrates, fats, and proteins can be modified to enter cellular respiration at various stages for energy generation.
- carbohydrates are the preferred energy source since they are easily catabolized and are high yield (4kcal/gram)
Glycogenolysis
-the release of glucose-6-phosphate from glycogen, a highly branched polysaccharide of glucose.
-Disaccharides
can undergo hydrolysis to release two carbohydrate monomers, which can enter glycolysis.
Glycogensis
-the conversion of glucose into glycogen to be stored in the liver when energy and fuel is sufficient.
Fats as source of energy generation
- present in the body as triglycerides
- Lipase enzyme digest fats into free fatty acids and alcohols through process of lipolysis.
- the digested parts are then absorbed by enterocytes in the small intestine and reform triglycerides.
Adipocytes
-cells that store fat (triglycerides)
-have hormone-sensitive lipase enzymes to help release triglycerides back into circulation as
lipoproteins or as free fatty acids bound by a
protein called albumin.
Chylomicrons
- are lipoprotein transport structures formed by the fusing of triglycerides with proteins, phospholipids, and cholesterol.
- They leave enterocytes and enter lacteals. (small lymphatic vessels that take fats to the rest of the body)
Low-density lipoproteins (LDLs)
-low density of proteins, unhealthy because they transport cholesterol to the peripheral tissues, causing vessel blockage.
High-density lipoproteins (HDLs)
-high density
of proteins, healthy because they bring
cholesterol to the liver to make bile.
Glycerol in the liver
-can be converted to enter glycolysis or make new glucose via gluconeogensis in the liver.
Free fatty acids
-undergo beta-oxidation to be
converted into acetyl-CoA.
-Beta-oxidation requires an initial investment of ATP, but then is continuously cleaved to yield two-carbon acetyl-CoA molecules (which can be used in the Krebs cycle for ATP generation) and electron carriers (NADH + FADH2 - produces more ATP).
Proteins as source of energy generation
- least desirable energy source bc the processes to get them into cellular respiration takes a lot of energy
- Catabolized when cells are starving due to unavailability of carbs and fats.
-They are broken down into amino acids, which must first undergo oxidative deamination
(removal of NH3 ) before being shuttled to various parts of cellular respiration.
-Ammonia (NH3 ) is toxic, so must be converted into uric acid or urea excreted from the body.
EX: humans convert ammonia into urea, which is excreted as
urine.
