Biochem: Dr. Blazyk Lectures Flashcards
What are the monomers of starch, sucrose, and lactose?
Glucose; glucose + fructose; glucose+galactose
What are most fats stored as?
Triacylglycerols (TAG)
What two macronutrients have essential components?
Fat and protein
What percentage of each macronutrient compose the energy reserves in the body?
Fat=80 (triglycerides in adipose), protein=15 (contractile proteins), carbs=<1% (glycogen)
What is the process of O2 reacting with macros to produce water, carbon dioxide, and ammonium (and energy)?
Oxidation reactions
How much energy is released as heat from oxidation reactions in cells? How much is conserved?
60% lost as heat, 40% conserved to produce energy and store energy
What are the three main precursors for anabolic pathways?
UDP-glucose, fatty acyl-CoA, Aminoacyl-tRNA
What macronutrients contribute to the citric acid cycle?
All three!
What are the intermediates for the Kreb’s cycle in order?
Acetyl-CoA, Citrate, Isocitrate, alpha-Ketoglutarate, Succinyl-CoA, Succinate, Fumarate, Malate, OAA
What are the enzymes of the CAC in order?
Citrate synthase, Aconitase, Isocitrate dehydrogenase, a-Ketoglutarate dehydrogenase, Succinyl-CoA synthetase, Succinate Dehydrogenase, Malate Dehydrogenase
What are the end products of the TCA Cycle?
2 CO2, 3 NADH, 1 FADH2, 1 GTP
Where are the products of the CAC used? Where is the CAC performed?
Oxidative Phosphorylation; inside the mitochondria inner membrane
If the ETC stops, what happens to the CAC? Why?
It stops; electron carriers (NADH/FADH2) stop being oxidized and cannot accept hydrogen/electrons from the CAC and the intermediate steps stop
What is the chain of electron movement in the ETC?
Com 1, Com 2, CoQ, Com 3, Cytochrome C, Complex 4
What complexes in the ETC pumps proteins into the cytoplasm to create a proton gradient?
Complex 1,2,4
What is complex 5? How does it work?
ATP Synthase; energy from proton gradient (4 protons) creates a conformational change and energy to phosphorylate ADP with Pi
What groups are involved in electron transport within the cytochromes?
Heme groups (Fe2+ to Fe3+)
What is the difference between heme of hemoglobin and cytochromes?
Iron stays in +2 state in hemoglobin and transfers between +2 and +3 in cytochromes
How many ATP is produced from 1 acetyl-CoA?
~10 ATP (3.5 from NADH, 1.5 from FADH2, 1 from GTP)
Where does glycolysis occur?
Cytoplasm
What does glycolysis generally produce?
Important intermediates for aerobic production
How can glycolysis produce ATP, anaerobic or aerobic?
Both
How many irreversible reactions and reversible reactions occur in glycolysis? Which regulate the entire process?
3 irreversible, 7 reversible;
Irreversible reactions bottleneck glycolysis
what are the three enzymes of the irreversible glycolysis?
Hexokinase, phosphofructo kinase 1, pyruvate kinase
What is the end product of glycolysis? 1 glucose=…
2 ATP, 2 pyruvate, 2 NADH
What enzyme is used in the anaerobic stage of glycolysis?
Lactate dehydrogenase (pyruvate -> lactate)
How is pyruvate used after aerobic glycolysis?
Pyruvate moves into matrix, binds with pyruvate dehydrogenase, and results in 2 Acetyl-CoA (links CAC)
How much ATP is produced aerobically with 1 glucose?
30-32 ATP
What causes the variation in the amount of ATP produced from glycolysis/CAC?
Which shuttle system transfers NADH into the mitochondria
Where does gluconeogenesis happen?
Kidney and Liver (80-90% in the liver)
Where do most of the precursors for gluconeogenesis come from?
Proteins via amino acids
What do gluconeogenesis and glycolysis share?
Reversible reactions enzymes of glycolysis
What are the irreversible reaction enzymes of gluconeogenesis?
Glucose-6-phosphatase, fructose 1,6-bisphosphatase, Pyruvate Carboxylase and PEP carboxykinase
What are the energy requirements of the irreversible reactions of gluconeogenesis?
2 ATP and 2 GTP (to convert pyruvate to PEP since this is very energetically unfavorable)
What pathway generates five-carbon sugars?
Pentose Phosphate Pathway (pentose shunt/ hexose monophosphate pathway)
What are the two segments of the pentose shunt? Which are reversible and irreversible?
Oxidation segment (irrevers) and carbon-shuffling reactions (reversible)
What are the oxidative reactions of the pentose shunt?
G-6-P to 6-P Gluconoacetone (via Glucose 6-P Dehydrogenase)
6-P gluconate to ribulose 5-P (via 6-P Gluconate Dehydrogenase)
Both produce NADH + one other H+
How is glycogen used in the liver? Skeletal muscles?
Liver: used to correct low BG
Skeletal: used as energy in the absence of usable glucose
What is the activating step of glycogenesis?
Glucose 1-P to UDP-Glucose via UDP-glucose pyrophosphorylase (using UTP->PPi)
What enzyme makes glycogen “branching”?
Branching Enzyme via cleavages between monomers (1,4 links) and reconnecting them, forming a-1,6 bond
What enzyme converts G6P to glucose?
Glucose 6-phosphatase (hydrolysis)
What responds to low blood sugar?
Liver (gluconeogenesis/glycogen breakdown)
What do muscle cells do with G6P?
Insert it into glycolysis
What can remove glucose a1-6 branch where phosphatase can’t?
Glucan transferase (glycogenolysis) and debranching enzyme
What is the ratio of G1P and free glucose in glycogen breakdown?
~90% glucose from glycogen breakdown is G1P
Where does fatty acid oxidation occur?
In the mitochondrial matrix
What does FA oxidation produce?
Acetyl-CoA, NADH, FADH2
What processes does FA oxidation depend on to get its intermediates?
CAC and Oxidative Phosphorylation (and ETC) for ATP
T or F: FA odxidation can happen without O2 presence
False
What protein binds to FA’s and transports them to cells via blood flow?
Albumin
What reacts with a FA in the cytosol to allow it to pass into the mitochondrial matrix? What protein transports it across? What side chain is absolutely necessary?
Acyl-CoA Synthase; carnitine shuttle; CoA-S side chain
What cannot cross the inner membrane of mitochondria? How are FA’s transported then?
CoA; transferring CoA off/back on FA chain with carnitine shuttle in the mitochondrial membrane
What are the four steps of FA oxidation?
1) First dehydrogenation- AcylCoA Dehydrogen.
2) Hydration- Enoyl-CoA Hydratase
3) second dehydrogenation- 3-hydroxyacyl-CoA DH
4) Formation of Acetyl-CoA - Ketoacyl-CoA Thiolase
How many acetyl CoA molecules are produced from a 16-carbon Fatty Acid?
8 Acetyl-CoA
How many ATP molecules can 8 Acetyl CoA molecules produce? 7 NADH? 7 FADH2?
80
- 5
- 5
Why is energy stored as fat?
It can result in more ATP per unit weight than glucose (almost 3 times as many ATP units)
Where are ketone bodies synthesized?
Liver
What are ketone bodies exported for?
Fuel source for peripheral tissues
What are the physiological ketone bodies?
Acetoacetate; beta-Hydroxybutarate
What are the non-physiological ketone bodies?
Acetone (from acetoacetate)= BAD
Where does ketogenesis happen?
Mitochondrial matrix in the liver
What are the four steps of ketogenesis?
1) Acetoacetyl-CoA Formation
2) HMG-CoA formation
3) Acetoacetate Formation
4) Ketone body interchange
What are the four enzymes in ketogenesis?
1) 3-Ketoacyl-CoA thiolase
2) HMG-CoA synthase
3) HMG-CoA Lyase (
What are the advantages of ketone bodies compared to FAs?
More water soluble, easier vascular transport and cell contact
How are ketone bodies used by the cells to produce energy?
Generates Acetyl-CoA via breakdown and introduces it into CAC and ETC
1 ketone body = _____ Acetyl-CoA
2
In what cell types does FA biosynthesis occur? Where in the cell?
Mainly LIVER, lesser so adipocytes
Cytoplasm
What is the key regulatory enzyme of FA biosynth?
Acetyl-CoA Carboxylase (to make Malate CoA)
What kind of effector is ADP/AMP on PFK1?
Positive effector allosterically bound
What kind of effector is ATP on PFK1?
Negative effector allosterically bound
How can consistently high ATP levels in the liver affect PFK1? What is the molecule that bypasses this issue?
It can keep glycolysis from happening, which can result in both cell and systemic death
F2-6BP binds at the same time, but acts as a positive effector that is more potent than ATP’s action
What hormone is released in hypoglycemic conditions? Hyperglycemia?
Glucagon; Insulin
What spurs release of F2-6BP in the liver? Why?
Insulin; to increase rate of glycolysis and slow rate of glycogenesis
What enzymes participate in covalent modification via phosphorylation?
Phosphatase and Kinases
What is a free form protein? (In relation to covalent modifications via phosphorylation)
The one with the -OH group unbound by Pi
What is the effect of insulin on intracellular phosphatase?
Insulin activates them during hyperglycemia to activate glycogenesis
What is the effect of glucagon on intracellular kinases?
Activates kinases, phosphorylates enzymes, glycogenesis activated
How does genetic regulation differ from allosteric or covalent regulation?
It increases the physical number of enzymes active via transcription, and its effect is larger; MUCH slower than covalent/allosteric (hours to days vs. seconds to minutes)
(Insulin incr glycolysis enzyme production, glucagon is vise versa on glycogenesis and glycogenolysis)
What does is stimulated in the liver in well-fed conditions? What stimulates this?
Glycolysis, glucogenesis, Pentose Shunt, FA Synth, Cholesterol synth, Lipogenesis
Insulin
What is stimulated in adipose cells when the body is well-fed? What stimulates this?
Glycolysis, Pent Shunt, FA Synth, Cholesterol Synth, Lipogenesis
Insulin
What is stimulated in muscle cells when the body is well-fed? What stimulates this?
Glycogenesis (insulin)
Why is glycolysis activated/not activated in myocytes and liver/adipose cells under hyperglycemic conditions?
Muscle cells require glycogen reserves to be broken down when transferring from an inactive to an active state.
Liver/adipose use excess blood glucose for breakdown and energy production, whereas the muscle cells are more interested in storing the glucose for later use
What general type of hormone is insulin? Release of this molecule usually results in anabolism or catabolism?
Insulin is an anabolic hormone
Release favors the biosynthetic pathways to increase energy reserves (glycogen, ATP production via glycolysis, and FA Synthesis)
What is stimulated in adipocytes in a fasting state? What stimulates this?
Lipolysis to mobilize TAG reserves (MOSTLY EXPORTED)
Glucagon
What is stimulated in hepatocytes in a fasting state? What stimulates this?
Glycogenolysis, gluconeogenesis, B-oxidation, ketogenesis
Glucagon
What is the liver’s primary responsibility under fasting conditions?
Maintain glucose homeostasis
What is the primary source of glucose under fasting conditions in the liver?
Breakdown of glycogen
If no glycogen, gluconeogenesis takes over (not as good/fast)
What is the most abundant source of precursors for gluconeogenesis?
Proteins (amino acids) from muscle fibers
What is the liver’s primary source of glucose production in fasting? What is the primary energy source during fasting?
Glycogenolysis (and gluconeogenesis if this isnt available)
Fatty Acid Oxidation for energy (from adipose TAGs)
What is the role of Acetyl-CoA in fasting conditions?
1) generate only as much ATP as NEEDED for the body
2) use all excess A-CoA to generate ketones
What is stimulated in myocytes in a fasting state? What stimulates this?
Glycogenolysis ONLY VIA epinepherine and AMP/Ca2+
Glucagon does not mobilize glycogen in muscle cells
What is the main energy source for muscle cells in fasting state?
Fatty acids from adipocytes and ketones from the liver***
***REQUIRES sufficient oxygen and high mitochondrial density since ONLY aerobic ATP production can be used
What hormones are counterregulatory to insulin? What are their relationship?
Glucagon, epinephrine, cortisol, and growth hormone
They work together collectively against insulin action
Why is it important to have a variety of hormones to collectively work against insulin?
Muscle cells cannot use glucagon, so they need other chemical messengers to properly adapt to fasting statesq
