Bio Chapter 3 - Metabolism Flashcards
Glycolysis
Glucose - > 2 molecules of pyruvate. Occurs in the cytosol. Net gain 2 ATP.
Anaerobic metabolism is the only energy source in the mammalian red blood cells.
Glycolysis/ Anaerobic respiration
Glucose + 2 Pi + 2 ADP + 2 NAD+ —> 2 pyruvate + 2 ATP + 2 NADH + 2H + + 2H20
Glycolysis step 1
Endergonic. Though coupled with ATP hydrolysis which is exergonic. Irreversible first step of the pathway. Uses a kinase to catalyze transfer of a phosphate group.
Glycolysis 3 part strategy
- Phosphorylates glucose, forming G6P
- Converts low energy phosphates to high energy phosphates
- High energy phosphates convert ADP to ATP
Glycolysis Step 2
Glucose -> Fructose
Aldohexose -> Ketohexose
Using Isomerase
Glycolysis Step 3,4
Add on another phosphate group by Kinase phosphofructokinase. F1,6,BisP lysis apart in a reverse aldol.
Dehydrogenase
NAD+, NADH, FAD, FADH2 Subclass of enzymes called oxidoreductases involved in oxid-reduc reactions.
Substrate level phosphorylation in glycolysis
Formation of ATP or GTP by direct transfer of a PO3 group. Step 6, break even point for ATP.
Mutase in glycolysis
Belongs to the class of enzymes isomers, Step 7.
Step 8 in glycolysis
Form a high energy molecule Phosphoenolpyruvate (PEP) in dehydration reaction.
Step 9 in glycolysis
PEP transfers PO3 group to ADP. Substrate level phosphorylation catalyzed by a kinase. Get (pyruvate + ATP) x2.
Step 5 Glycolysis
2NADH made from 2NAD+
to be sent to ETC
Fermentation
Pyruvate is reduced and NADH is oxidized.
Krebs/TCA/CAC Cycle outline
Occurs in the matrix of the mitochondria. Aerobic respiration. Pyruvate combines with Coenzyme A + NAD+ in an oxidative decarboxylation step.
Requires B1, B2, and B3 vitamins.
Acetyl Coenzyme A reaction
Pyruvate + Coenzyme A(HSCoA) + NAD+ -> Acetyle coenzyme A + CO2 + NADH
HSCoA is a dehydrogenase. Functional group = Thioester.
Krebs/TCA/CAC Cycle bottom line
TCA cycle dismantles acetyl groups converting them into CO2 and H+. The H+ goes into the ETC to produce ATP.
3 B Vitamins in Krebs/TCA/CAC Cycle
B1 Thiamine, B2 Riboflavin, and B3 Niacin
Krebs/TCA/CAC and enzymes exists where and what exception?
Matrix of the mitochondria. Succinic dehydrogenase is the exception in the inner mitochondrial membrane- site of ETC.
Krebs/TCA/CAC process in 3 steps
1) Acetyl CoA goes into the cycle and reacts with oxaloacetate to give citrate
2) 2 turns occur
3) Each turn gives 3 NADH, 1 FADH2, 1 GTP
Krebs/TCA/CAC intermediates
Porphoryins and even pyrimidine nucleotides for biosynthesis.
Krebs/TCA/CAC ATP synthesis
Substrate level phosphrylation when succinyl CoA synthase converts succinyl CoA to succinate.
Energy comes from hydrolysis of the thioester bond, exergonic reaction.
Alternative source of Acetyl CoA
Lipids can be oxidized into Acetyl CoA during beta oxidation and some aa can be made into Acetyl CoA.
ETC
90% of the ATP generation. Inner mitochondrial membrane. Complex series of oxida-reduc reactions.
NADH about 3 ATP
FADH2 about 2 ATP
ETC Complexes
Complex I accepts e- from NADH. FADH2 brings e- to Complex II.
As e- move down the ETC
Conformation changes in the inner membrane that allows for the H+ to be pumped into the intermembrane space from the matrix.
Oxidative phosphorylation. Increases pH on the inside and decreases it on the outside.
ATP synthase
1) Electrons add to O2 to form H20
2) ADP + Pi ->
Oxidative phosphorylation
Occurs in the inner portion of the mitochondria.
Basis of the chemiosomotic hypothesis
Ion gradients represent a high energy state which can be used to drive endergonic processes.
Oxidative phosphorylation by ETC. Electron transport leads to a proton gradient which flows back into the mitochondrion through ATPase, used to synthesize ATP.
CoQ or Ubiqunione
Lipid soluble electron carrier. Receives e- from Complex II and Complex I and passes to Comp III.
Gluconeogenesis
Synthesis of glucose from noncarbohydrate precursors. E.g lactate, aa, or glycerol. Occurs in plants, animals fungi, bacteria, and microorgs.
Gluconeogenesis occurs during
Stavariont, Low carb diets, fasting, and intense exercise.
Occurs mainly in the liver and small amount in the cortex of kidney.
Gluconeogenesis begins in the
Mitochondria then goes to cytosol. Many reactions are the reverse of glucolysis.
Can fat be used in gluconeogenesis?
Most carbons in fat is not convertable into Actyl CoA. Glycerol backbone can be used.
Biotin is involved in adding CO2 to pyruvate to get oxaloactate.
Cori cycle
Gluconeogenesis is responsible for taking lactate produced during anaerobic metabolism and converting it into glucose in the liver.
Glycolysis vs gluconeogenesis
When ATP is needed, glucolysis is active; when there is little need for ATP, gluconeogenesis is more active.
Starvation
3 months before we die. Carbohydrates will exhaust within one day. The brain can not tolerate low glucose levels for a short time. The brain and RBC are dependent on this fuel.
First day of starvation
Decreased secretion of insulin and increase secretion of glucagon.
Triglycerides in adipose tissue and gluconeogenesis by the liver are the dominant processes. Muscle now shifts from glucose to fatty acids for fuel.
Beta oxidation of fatty acids halts the formation of Actyl CoA from pyruvate.
2-3 days of starvation
Large amounts of ketone bodies are formed by the liver are released into the blood. Used by the heart for fuel.
The brain uses acetoactate in place of glucose.
Ketone bodies
Made from Acteyl CoA. Since during starvation the TCA cycle is unable to oxidize the acetyl units formed from fatty acid breakdown.
After ketone depletion
Protein is used. Death results from loss of organ function.
DM compared to starvation
Glucose is not oxidized, thus fatty acids must be oxidized to compensate for the unavailable energy. Ketone bodies are formed, ketosis.
Prolonged ketosis
Acidosis. If blood pH is below 7.35
Pentose Phosphate pathway main
Anabolic. Two main pathways:
1) Provides NADPH- reductive biosynthesis of lipds
2) Provides Ribose 5 phosphate- nucleotide and nucleic acid biosynthesis
Penthose Phosphate pathway/Pentose Shunt or Hexose monophosphate pathway
All reactions occur in the cytosol.
Active in adipose tissue. NADPH is used to make fatty acids and steroids. Tissues such as the adrenals, liver, and adipose tissue have an abundance of enzymes of this pathway.
Glucose 6 phosphate has other routes than glycolysis.
Glyoxylate cycle
TCA/Kreb cycle modification in plants using acetate. enzymes of this cycle are found in organelles called glyoxysomes.
Allows seeds to grow in the dark/underground where photosynthesis is not possible.
Glyoxylate cycle main
Takes Actyl CoA into succinate for the synthesis of carbohydrate.
Glycogen
Storage form of glucose. Mainly found in liver and skeletal muscle. Most gluecose are alpha 1,4-glucosidic bonds. Branches are alpha 1,6 glycosidic bonds.
Glycogen branching
1) Makes polymers more compact
2) Makes polymers more H20 soluble
3) Produces more terminal glucose residues
Glycogenolysis
Breakdown of glycogen. Release of glycogen into the liver due to low levels of glucose into G6P. Raises glucose levels in blood.
In muscle, G6P enters glycolysis
directly rather than being delivered to the blood.
Glycogen is synthesize from ___ and store within __ as
G6P, liver and skeletal muscle, glycogen granules.
Excess Amino acids
Cannot be stored. Used as metabolic fuel.
NH2 is daminated and used to form urea.
Amino acids carbon skeletons can be broken down into
A) Actyl CoA B) Acetoacetyl CoA C) Pyruvate D) TCA cycle intermediates Fatty acids, ketone bodies, and glucose can be made from amino acids.
AA examples made into pyrvuate
Ser, Alan, Threon, Cyste
AA examples made into a ketoglutarate (TCA cycle intermediate)
Prol, Glutam
Phenylketouria (PKU)
Phenylalanine is made into aa tyrosine. In PKU, tyrosine is missing. Phenylalanine builds up in the blood and urea resulting mental retardation. Brain weight is below average and myelination of nerves is defective.
Fatty Acid Oxidation
Fatty acids can be oxidized to yield large quantities of ATP. Fatty acid oxidation (beta oxidation) occurs in the mitochondrial matrix. Start in the outer mitochondrial membrane and is oxidized in the matrix of the mitochondria.
Carnitine
Carries activated fatty acids across the mitochondria membrane. Gives us Actyl CoA, NADH, FADH2, Metabolic water.
Fatty Acid Synthesis
Cytosol. Fatty acids are made from Acetyl CoA. Apart of triglycerides and phosphotriglycerides.
Cholesterol
Synthesized from Acetyl CoA. Modulates the fluidity of eukaryotic cell membranes. Cholesterol is the precursor of steroid hormones like cortisol, progesterone, testosterone, and estradiol.
Steroids
Are nonhydrolyzable lipids.
Principle site for the synthesis of cholesterol
Liver
Cholesterol function
Also involved in the synthesis of bile acids. Assisting inthe absorption of dietary lipids in the intestine. Bile acids deprotonated to bile slats. Also emulsifies fats.
Too much cholesterol
Can be lethal. When cholesterol percentage in bile gets too high, precipitation occurs forming gallstones. It can block the entrance to the duodenum, losing the ability to digest fats. Bile pigments enter the blood and skin becomes jaundiced.
Also associated with heart disease.
Bilirubin
Pigment found in bile. It gives color to bile and stool. Bilirubin is excreted in bile and urine and is the main cause of jaundice. Bilirubin can be conjugated with glucuronic acid to become more water soluble. Has functions as an antioxidant.
The Urea Cycle
Central pathway in Nitrogen Metabolism. Catabolism and anabolism of aa is linked to TCA/Krebs cycle.
Urea Cycle premise
Most vertebrates, NH4+ is made into urea and excreted. NH3 is highly toxic. The cycle occurs mainly in the liver where urea is produced, then released into the blood
on it’s way to the kidneys to be excreted.
NH3 in the urea cycle
Carbamoylphosphate and requires 2 ATP molecules. This process requires ATP and does not produce it.
Enzymatic reactions in the Uric Cycle
A) a Mitochondrial reaction
B) others are cytosolic
Fumarate is produce in this cycle and is an intermediate in the TCA cycle and is returned there.
Hyperammonemia
Elevated NH4+
Can cause brain damage, coma, and death in infants
Different Nitrogenous Wastes in different classes
- Terrestrial animals and mature amphibians: Urea
- Fish and Marine: Ammonia
- Reptiles, birds, and Insects: Uric Acid
Photosynthesis equation
6Carbon dioxide + 6Water -(light)> Sugar + 6Oxygen
Photosynthesis chlorophyll
Green pigment located in chloroplasts which absorbs light energy. Chlorophyll resides in the thylakoid membranes.
Chlorophylls and carotenoids are the pigments that absorb light.
Photosynthetic reactions
Light Reaction: uses light for ATP production
Dark reaction: sugar making
Light Reaction
ATP, O2 and NADPH are made
Occurs in the grana (membranous bodies stacked)
H2) is split by sunlight releasing the O2(oxidative process).
Dark Reactions/ Calvin Benson Cycle
CO2 enters the stomates to produce 3 carbon PGAL. Carbon fixation occurs (in the stroma). Main enzyme Rubisco ( most abundant protein in nature).
6 molecules of CO2 per one molecule of glucose.
Photosynthesis highlights
Efficiency of 30%. Vital to life on Earth. Redox reaction which H+ gradient is formed across a membrane.
Chloroplasts and mitochondria
Endosymbionts
Small prokaryotic organisms that began to live inside large cells.
Electron paths photosynthesis
Noncyclic photphosphorylation and Cyclic photophosphorylation
Noncyclic photophosphorylation
e- that two ETC to prduce ATP and NADPH. Chemiososis same as in mitochondria. Light required.
NADPH from this path is sent to Calvin cycle.
Cyclic photophosphorylation
Consumes fair amount ATP. Only produces ATP.
Dark Reactions/ Calvin Benson Cycle summary
A) Carbon fixation occurs- sugar making B) ATP is used C) 6 turns D) NADPH is oxidized E) Rubisco is regenered. CO2 is attached to Rubisco. Being unstable it splits to 2 molecules of phosphoglycerate. Or. Phase 1: Carbon fixation Phase 2: Reduction Phase 3: Regen of ribulose
