EK B1 Ch3 Metabolism I COPY Flashcards
phosphate groups on ATP
very hydrophilic donation of these groups can change conformation of proteins - phosphate groups of ATP contain phosphoanhydride bonds or phosphoric acids*** that are linked to an oxygen atom, reactivity is very similar to anhydrides
phosphoanhyride bonds
- hydrolysis is exothermic and spontaneous, can provide energy required for less energetically favorable reactions
delta H
change in enthalpy -negative for exothermic reactions
spontaneous reactions
delta G, change in Gibbs free energy is negative NOTE atp –> adp + Pi (gamma phosphate) has delta G <<<0 SO SPONANTEOUS AND NEGATIVE
oxidative phosphorlyation
occurs when oxidation reactions provide the energy for phosphorylation -requires the presence of oxygen as a final electron acceptor - in mitochodnria for ETC -energy comes from NADH, which is reduced form of nicotinamide adenine dinucleotide NAD+
substrate level phosphorylation
oxidation and phosphorylation are not coupled! ADP is simply one of several substrates in an enzyme-catalyzed reaction that results in transfer of a phosphate group to ADP - there are enzymes in both glycolysis and the citric acid cycle that catalyze substrate level phosphorylation
phosphorlyation
ATP is synthesized by teh addition of a phosphate group to adenosine diphosphate
acteyl-coa
coenzyme that transfres two carbons from pryvuate to 4-carbon oxaloacetic acid to begin the citric acid cycle (also known as Krebs cycle or TCA tricarboxylic acid cycle –> during this cycle two carbons are lost as CO2 and oxaloacetic acid is regernated
Each citric acid cycle….
-1 ATP, 3 NADH, 1 FADH2 - one GTP is converted to ATP via substrate level phosphorlation and 2 CO2** -one glucose model powers two turns of cycle, so really its 6 NADH, 2 ATP, 2 FADH2 only 2 NADH made per two glucose in glycolysis
beta- oxidation
produces 1 nadh per two carbon versus 3 NADH in TCA/KREBS/ ctric acid cycle
GTP in citric acid cycle
acts as phosphate donor to ADP to produce ATP, this process occurs via substrate level phosphorlyation just like glycolysis
NAD+ in TCA
regulation of TCA is tied to amount of NAD+ available, it is generated by the oxidation of NADH by the electron transport chain. If the ETC is inhibited, as when there is a lack of oxygen, NADH cannot be oxidized to NAD+. - in this case TCA is inhibited and the cell shifts its energy to anerobic respiration/pathways as a result TCA considered to be aerobic
NADH regulation in TCA
-citric acid cycle produces NADH! so if an excess of NADH builds up, the reactions slow down!
metabolism fats and proteins into TCA
-Acetyl-Coa not only substrate that can enter the TCA -some molecules can be modified to various TCA intermediates that can enter the cycle -amino acids come with carbon backbone, denamiated in liver -the deanimated product may be chemically converted to pyruvic acid or acetyl coa or it may enter TCA at various stages depending upon length of the carbon backbone
glutamic acid
5 c backbone can be converted into citric acid cycle intermediate alpha-ketoglutarate
to be used for energy.. amino acids
- must first be deanimated, after which they can enter the TCA as pyruvate or as one of the TCA intermediates -nuceltides must also be deaminated before entering the cycle as an intermediate -fats are converted to acetyl-CoA which can then enter the citric acid cycle
ETC (NADH)
NADH loses electrons, is oxidized to become NAD+ - oxygen gains electrons, is reduced to form water!
atp synthase
ex of oxidative phosphorylation
type 1 diabetes
- autoimmune disease where the immune system attacks the beta cells of the pancreas
glucogenoesis
Blueprint exam 4 details
Gluconeogenesis is a process that the body uses to create glucose from pyruvate. It occurs primarily in the liver and to some extent in the adrenal cortex, and its goal is to ensure an adequate supply of glucose (which can then be converted into energy, or stored as glycogen) throughout the tissues of the body. In particular, it can be important to replenish the stores of glycogen in muscle cells after they have been depleted by intense activity. It is upregulated by glucagon and by the presence of surplus pyruvate/acetyl-CoA.
Gluconeogenesis is not quite reverse glycolysis, although these two pathways do share some of the same enzymes and steps (although they occur in reverse). However, they also differ at some crucial stages. Glycolysis contains some steps that are highly exergonic and essentially irreversible under biological conditions, so gluconeogenesis needs to bypass those steps. Additionally, glycolysis and gluconeogenesis need to be separated in order to prevent a futile cycle in which glucose is broken down to pyruvate and then pyruvate is built back up into glucose.
Gluconeogenesis
Blueprint Exam 4 concept cont.
In particular, the final stage of glycolysis (phosphoenolpyruvate [PEP] → pyruvate) must be bypassed by gluconeogenesis.
Thus, why gluconeogenesis has a two-step pathway split up between the mitochondria and cytosol, in which pyruvate carboxylase converts pyruvate to oxaloacetate in the mitochondria by adding a COO- group.
Oxaloacetate is briefly converted to malate for transport out of the mitochondria, where it is then converted immediately back to oxaloacetate. At this point, in the cytosol, PEP carboxykinase converts oxaloacetate to PEP.
Additionally, the early stages of glycolysis (where phosphate groups are added to glucose) must be bypassed by gluconeogenesis. These are irreversible steps in glycolysis that involve the investment of ATP. Gluconeogenesis cannot simply reverse these steps, because doing so would mean creating ATP, which is the job of ATP synthase in the electron transport chain. Instead, gluconeogenesis bypasses these steps using enzymes that catalyze a simple hydrolysis reaction, splitting off a Pi from the carbohydrate.
breaking down fats….
Cause and effect:
- breaking down fats produces glycerol which can enter gluconeogenesis as DHAP
- proteins can break down into glucogenic amino acids which can enter gluconeogenesis as OAA, which is then converted to PEP by PEPCK
Q13 Blue print
Which specific class of enzymes is primarily responsible for the release of free glycerol from stored triglycerides?
- Lipase
Every enzyme you will ever see on the MCAT will fit under one of these labels. The test makers will not expect you to learn a bunch of random enzymes, but they will expect you to match an enzyme’s name to the clues given about its function, or vice versa. Luckily, most enzymes are named for exactly what they do (e.g., pyruvate decarboxylase) and for the substrate they act upon (e.g., DNA ligase).
Typically, only 10-15% of an individual’s energy comes from the metabolism of protein. A woman has a disorder that causes her body to preferentially degrade protein, leading her to obtain 85% of her energy from protein metabolism. What is a potential symptom of this disease?
A.Ketoacidosis
B.Organ failure
C. Low blood sugar
D.Decreased fat stores
A.
Ketoacidosis
Ketoacidosis is caused by an excess of ketone bodies, which are generated from the oxidation of fatty acids, not proteins.
B.
Organ failure
B is correct. If an individual were using proteins as her primary fuel, she would quickly run down her muscular protein stores and would be forced to degrade proteins from organs. This would cause organ failure. Under starvation conditions, muscular atrophy can be observed when both sugar and fat supplies have been depleted.
C.
Low blood sugar
If the body is burning proteins instead of sugar, if anything, hyperglycemia would result.
D.
Decreased fat stores
Fat stores should not become smaller because this individual is not drawing her energy from fat.
A. The solid line is ketone bodies, while the dashed line is fatty acids.
B.The solid line is glycogen, while the dashed line is glucose.
C.The solid line is ketone bodies, while the dashed line is glucose.
D.The solid line is insulin, while the dashed line is fatty acids.
The solid line is ketone bodies, while the dashed line is fatty acids.
This answer is incorrect
B.
The solid line is glycogen, while the dashed line is glucose.
This answer is incorrect
C.
The solid line is ketone bodies, while the dashed line is glucose.
C is correct. During starvation, as glucose (dashed line) supplies decline, fatty acid oxidation and ketone body (solid line) synthesis will take over to supply metabolic fuel.
D.
The solid line is insulin, while the dashed line is fatty acids.
This answer is incorrect
catabolic rxns
- Metabolism consists of two classes of chemical reactions: catabolic and anabolic
- Catabolic reactions break down larger molecules and release energy (exergonic)
anabolic rxns
Anabolic reactions build up from smaller molecules and require energy (endergonic)
Metabolic rxns are catabolic and anabolic…..
Reactions are often coupled to drive anabolic reactions
ATP is the short term energy currency in the cell
ATP hydrolysis yields ADP + Pi , –7.6 kcal/mol energy
Humans and other animals are heterotrophs: must consume energy from outside sources
Plants are autotrophs: make their own food via photosynthesis
ATP hydrolysis yields ………
ATP hydrolysis yields ADP + Pi , –7.6 kcal/mol energy
Metabolic- redox reactions….
Redox reactions transfer energy through electron transfer
Reduction and oxidation always occurs together
Reducing agent causes something else to be reduced. It is oxidized
Oxidizing agent causes something else to be oxidized. It is reduced
Redox is critical for cellular respiration
Reduction in Metabolism
Reduction is a gain of electrons (valence # is reduced, e.g., Fe3+ to Fe2+, NAD+ to NADH)
A reduced molecule gains energy when it gains an electron
Reduction often takes the form of hydride addition (H– = H+ + 2e)
NADH and FADH2 act as hydride donors (much like NaBH4 and LiAlH4 in orgo)
Oxidation in Metabolism
Oxidation is a loss of electrons (valence # is increased, e.g., NADH to NAD+)
An oxidized molecule loses energy when it loses an electron
Oxidation often means more bonds to oxygen
Examples: addition of –OH groups or conversion of C-O single bond to C=O bond
Reducing agent……
Reducing agent causes something else to be reduced. It is oxidized
Oxidizing agent
Oxidizing agent causes something else to be oxidized. It is reduced
Free energy
Free energy, ∆G, represents energy available to do work
∆Go = free energy change under “standard conditions”
Standard conditions = 25°C, 1 atm pressure, all solutions at concentration of 1M
These conditions are rarely met in real situations
Equilibrium constants reported in tables usually depend on ΔGo
They show whether products or reactants are favored when both start at 1M (unlikely)
ΔG = actual free energy change
ΔG= ΔG° + RT lnQ
ΔG =
ΔG = actual free energy change