Chapter 13 Flashcards
activation energy
the energy barrier before a molecule can undergo a chemical reaction that moves it to a lower energy/more stable state
what reduces activation energy in cells
enzymes
where is the energy generated from step-wise breakdown of sugar stored
high energy bonds in ATP and other activated carriers
3 stages of food breakdown (catabolism)
- Digestion in mouth and digestive organs
- Glycolysis
- Citric acid cycle and ETC
how does saliva help to digest food
salivary amylase breaks down complex sugars into simple sugars
salivary lipases break down fats
enzymes activated by acid in gut lumen to digest food
pepsin: breakdown of proteins to amino acids
gastric lipases: breakdown of TAG to glycerol and fatty acids
intestinal enzymes in food digestion process
amylases - breaks down starch into sugars
proteases (e.g. trypsin) - break down proteins by hydrolyzing peptide bonds
lipases - breaks down fats
nucleases - breaks down nucleic acids
in and out of glycolysis; net
In: 1 glucose, 2 ATP, 4ADPs, 2NAD+
Out: 2 pyruvate, 4 ATP, 2 NADH, 2ADP
Net: 1 Glucose, 2ADP, 2NAD+ -> 2 pyruvate, 2 ATP, 2NADH
glycolysis oxygen requirements
anaerobic, does not require O2
number of steps in glycolysis
10, each catalyzed by a different enzyme
investment phase of glycolysis
steps 1 and 3
consume 2 ATP
payoff phase of glycolysis
steps 6-10
produce 4 ATPs and 2 NADH
where does glycolysis occur
cytosol
glycolysis irreversible steps
1, 3, 10
glycolysis step 1
converts glucose to Glu-6-P
enzyme: hexokinase
traps glucose in cell
irreversible
glycolysis step 3
commitment to glycolysis
major regulatory step
enzyme: phosphofructokinase1 (pfk1)
regulated by insulin (promoter) and glucagon (inhibitor)
irreversible
glycolysis step 10
pyruvate synthesis
regulated by energy presence in cell
inhibited in energy rich conditions, promoted in energy poor conditions
glycolysis step 4
doubles number of molecules (splits 6C to 2 3C molecules)
glycolysis step 6
energy payoff begins
production of NADH
what steps of glycolysis produce ATP
7 and 10
substrate level phosphorylation
transfer of phosphate from substrate (sugar intermediate) to ADP to make ATP
Where does pyruvate go after glycolysis when O2 is available?
Actively transported to the mitochondria to be further oxidized
Where does NADH go after glycolysis if oxygen is available?
transported to the mitochondria to be used by the electron transport chain to replenish NAD+
where does pyruvate go if there is no O2 available?
fermentation (lactic acid in humans or ethanol in yeast)
main purpose of fermentation
regenerate NAD+ so glycolysis can continue
what does fermentation produce
NAD+
NO ATP
lactate OR
ethanol and CO2
pyruvate oxidation product
acetyl CoA (2C), CO2, and NADH
enzyme is pyruvate oxidation
pyruvate dehydrogenase complex (large 3 enzyme multi-subunit complex)
what is the purpose of the citric acid acycle
complete oxidation of AcetylCoA
waste product of TCA
2 CO2 per round
what is AcetylCoA first transferred to as the first step in the TCA cycle; forms what compound
added to oxaloacetate (4 carbons); forms citric acid/citrate
as citrate is oxidized, what products are released/produced
3NADH, 1FADH2, and 1GTP
how many steps/reactions are in the TCA cycle
8
what is regenerated at the end of the TCA cycle
oxaloacetate
does the TCA cycle use molecular O2
does not use it directly; but does require it to proceed since it replenishes NAD+ needed to proceed by accepting electrons at end of ETC
how many CO2 molecules are produced by the complete oxidation of 1 glucose molecule
6 CO2
(2 from pyruvate oxidation, and 2 from each acetylcoA)
6 carbon glucose produces 6 CO2 - all carbons detached in full oxidation
ATP per glucose
30
(7 from glycolysis, 3 from pyruvate oxidation (5-2 for transport of 2 NADH into mitochondria), 10 from TCA cycle)
how many NADH produced from one gluocse
10
(2 from glycolysis, 2 from pyruvate oxidation, 6 from TCA cycle)
where are fatty acids converted to acetylCoA
mitochondrial matrix
where does the citric acid cycle take place
mitochondrial matrix
where does pyruvate oxidation take place
mitochondrial matrix
does beta-oxidation require O2
requires to proceed but does not use it directly
process of releasing fatty acids from TAG and activating
uses water and ATP, couples fatty acid to HS-CoA to create fatty acyl CoA which enters beta oxidation
products of one round of beta oxidation
1FADH2, 1NADH, 1 acetylCoA
catabolic vs anabolic
catabolic break down and produce energy and building blocks
anabolic use building blocks and energy to synthesize new molecules
feedback regulation
allows cells to switch between anabolism and catabolism to adapt to changes in food availability or energy expenditure by inhibiting or activating an enzyme in pathway
gluconeogenesis
opposite of glycolysis
makes glucose from pyruvate
when does gluconeogenesis occur
when blood glucose levels are low (starving/fasting/exercise)
how does gluconeogenesis run irreversible glycolysis rxns in reverse
requires different enzymes to reverse or bypass irreversible steps
energy cost of gluconeogenesis
4ATP and 2GTP per glucose
where does gluconeogenesis happen
only in liver
phosphorylation as an enzyme regulator
phosphorylation can either increase or decrease protein activity depending on binding site and structure of protein
phosphorylation/dephosphorylation enzyme
protein kinases add phosphate group
phosphatase removes group
how does phosphorylation regulate protein activity
phosphate group covalently attaches to 1 or more amino acid side chains and causes conformational change
how is the enzyme pfk1 regulated
allosterically regulated by the binding of many substrates
activated by ADP/AMP/Pi
inhibited by ATP
enzyme that reverses step three of glycolysis (opposite of pfk1), and regulation
fructose 1,6-biphosphatase
activated by ATP
inhibited by ADP/AMP/Pi
G6P role as glycolysis regulator
inhibitor of pfk1, prevents the cell from making more than it needs and wasting energy
how do cells store excess glucose
glycogen, stored in granules in cytoplasm
first source of energy for cell in starvation
glycogen (gluconeogenesis is energetically costly)
which cells breakdown glycogen to export glucose to other cells as food
liver cells
which cells have glycogen for own needs but cannot export
muscle cells
effect of glycogen phosphorylase
causes glycogenolysis
break down to glycogen to G6P
inhibited by allosteric binding of G6P
glycogen synthetase enzyme
glycogenesis
production of glycogen from G6P
activated by binding of G6P
which glycogen enzyme is inhibited by binding of G6P
glycogen phosphorylase, high G6P indicates no more glycogen needs to be broken down
ATP inhibits which glycogen enzyme
glycogen phosphorylase
(enough energy, don’t need to make more G6P)
low G6P causes what
activation of glycogen phosphorylase
inhibition of glycogen synthetase
low ATP causes what
activation of glycogen phosphorylase
inhibition of glycogen synthetase
would high ATP favor glycogen breakdown or synthesis
synthesis; cell starts storing energy
effect of high insulin on glycogen enzymes
inhibits glycogen phosphorylase
activates glycogen synthetase
(because there is high glucose from the blood entering cells)
when does insulin secretion occur
after eating when blood glucose levels are high and cell can be storing energy
which stores more energy per weight: fat or glycogen
fats; glycogen stores a lot of water weight with it
How long can glycogen stores last
about a day
after a meal, what do cells do with the glucose
used for energy (glycolysis)
excess used to synthesize glycogen and fatty acids
what is the result of shorter term fasting (a day or less)
glycogen breakdown and beta oxidation of fatty acids
what is the result of starvation (long term fasting)
no more glycogen to break down- beta-oxidation and gluconeogenesis to create glucose needed for brain function
