Biochemistry - Metabolism Flashcards by Iuliana R

Pathways with metabolism site occurring in the mitochondria

Fatty acid oxidation (b-ox)
Acetyl CoA production
TCA cycle
Oxidative phosphorylation

How well did you know this?

Not at all

Perfectly

Pathways with metabolism site occurring in the cytoplasm

Glycolysis
FA synthesis
HMP shunt
Protein synthesis (RER)
Steroid synthesis (SER)
Cholesterol synthesis

How well did you know this?

Not at all

Perfectly

Pathways where metabolism occurs in both mitochondria and cytoplasm

HUGs take TWO (i.e., both)
Heme synthesis
Urea cycle
Gluconeogenesis

How well did you know this?

Not at all

Perfectly

Hexokinase

all tissues other than liver and b-cells of pancreas
Km and Vmax - lower (increased affinity, decreased capacity)
Not induced by insulin
Feedback inhibited by glucose 6-P

How well did you know this?

Not at all

Perfectly

Glucokinase

Liver and b-cells in pancreas
Km and Vmas - higher (decreased affinity, increased capacity)
Induced by insulin
Feedback inhibited by fructose 6-P

How well did you know this?

Not at all

Perfectly

First step of glycolysis?

Glucose to glucose 6-P

How well did you know this?

Not at all

Perfectly

Where is glucose stored at low concentrations? high concentrations?

Tissue (low) and liver (high)

How well did you know this?

Not at all

Perfectly

Rate limiting step of glycolysis?

PFK 1

How well did you know this?

Not at all

Perfectly

What is occurring in the fed state during regulation by F2,6BP?

Increase insulin, decreased cAMP, decreased protein kinase A, decreased FBPase 2, increased PFK 2, more glycolysis, less gluconeogenesis

How well did you know this?

Not at all

Perfectly

What is occurring in the fasting state during regulation by F2,6BP?

Increased glucagon, increased cAMP, increased protein kinase A, decreased PFK 2, increased FBPase 2, more gluconeogensis, less glycolysis

How well did you know this?

Not at all

Perfectly

What are the enzymes in the pyruvate dehydrogenase complex? what are their cofactors?

Pyruvate dehydrogenase - TPP (B1 thiamin)
Dihydrolipoyl transacetylase - lipoate, CoA
Dihydrolipoyl dehygrogenase - NAD+, FAD

How well did you know this?

Not at all

Perfectly

What happened when there is a pyruvate dehydrogenase complex deficiency?

Causes a buildup of pyruvate that gets shunted to lactate (via LDH) and alanine (via ALT)

How well did you know this?

Not at all

Perfectly

What is the conversion that the pyruvate dehydrogenase complex is apart of?

Pyruvate -> Acetly CoA

How well did you know this?

Not at all

Perfectly

How do you treat pyruvate dehydrogenase complex deficiency?

Increase intake of ketogenic nutrients (high fat content or increase lysine and leucine)

Lysine and Leucine - the onLy pureLy ketogenic amino acids

How well did you know this?

Not at all

Perfectly

Findings in pyruvate dehydrogenase complex deficiency?

neurologic defects, lactic acidosis, Increased serum alanine starting in infancy

How well did you know this?

Not at all

Perfectly

Pyruvate -> Acetyl CoA produces what products? and how many?

1 NADH

1 CO2

How well did you know this?

Not at all

Perfectly

Where do TCA cycle rxns occur?

Mitochondria

How well did you know this?

Not at all

Perfectly

What products and how many of each are produced by the TCA cycle?

3 NADH, 1FADH2, 2 CO2, 1 GTP per acetyl CoA = 10 ATP/acetyl CoA (2x everything per glucose)

What substrates are in the Krebs cycle?

Citrate Is Kreb’s Starting Substrate For Making Oxaloacetate

Citrate
Isocitrate
alpha-Ketoglutarate
Succinyl-CoA
Succinate
Fumarate
Malate 
Oxaloacetate

NADH electrons from glycolysis enter the mitochondria via what shuttle?

Malate-aspartate shuttle or glycerol 3-P shuttle

How many reactions occur in the Kreb’s cycle?

8 reactions

Where does the electron transport chain occur?

Inner membrane of the mitochondrion

How many types of electron carriers comprise the ETC?

4
FMN
Fe-S clusters
CoQ10
Cytochromes

Which of the electron carriers in the ETC are mobile?

CoQ10 and Cytochrome C

What occurs in Complex I: NADH Dehydrogenase of the ETC?

NADH transfers ions and electrons to FMN. The reduced FMNH2 forms, while NADH is deoxidized to NAD+, which returns to oxidative pathways such as TCA cycle oxidize more substrates Within complex I, the electrons are transferred to the Fe-S clusters and then to CoQ10

What occurs in Complex II: Succinate Dehydrogenase of the ETC?

Used when FADH2 is generated from the conversion of succinate -> fumarate in the TCA cycle Electrons from FADH2 are transferred to CoQ10 to yield QH2 This complex has a lower energy level than Complex I so FADH2 enters at a lower energy level here then NADH in complex I

What occurs in Complex III: Coenzyme Q10-Cytochrome c Reductase of the ETC?

The mobile carrier QH2 transfers electrons it has collected from NADH and FADH2 to an Fe-S cluster and then to cytochrome b, the first cytochrome in complex III From cut b, the electron is transferred to an Fe-S cluster and then to cut c1 and tgeb ti cut c. Each time an Fe3+ ion accepts an electron, it is reduced to Fe2+ and then oxidized back to Fe3+ as the electron is passed on along the chain. Cyt c is another mobile carrier, it moves the electron from complex III to complex IV

What occurs in Complex IV: Cytochrome c Oxidase of the ETC?

electrons are transferred from cytochrome c to cytochrome a, and then to cytochrome a3, the last cytochrome. In the final step of electron transport, electrons and hydrogen ions combine with oxygen (O2) to form water 4H+ + 4e- + O2 -> 2H20

What enzyme converts pyruvate to oxaloacetate in gluconeogenesis? Where does this occur?

Pyruvate carboxylase | Occurs in the mitochondria

What enzyme converts oxaloacetate to phosphoenolpyruvate (PEP)? Where does this occur?

PEP carboxykinase | Occurs in the cytosol

What enzyme converts fructose-1,6-BP to fructose 6-P in gluconeogenesis? Where does this occur?

Fructose 1,6-Bisphosphatase | Occurs in the cytosol

What enzyme converts Glucose 6-P to Glucose in gluconeogenesis? Where does this occur?

Glucose 6-phosphatase

What organ does gluconeogensis primarily occur in?

Liver

From what substrate to substrate is repeated in gluconeogenesis from glycolysis?

PEP to fructose 1,6-P

Odd-chain vs even-chain FAs as a glucose source

odd chain FAs cab enter TCA cycle, undergo gluconeogenesis and serve as a glucose source even chain FAs cannot produce new glucose, since they yield only acetyl CoA equivalents

What tissue cannot participate in gluconeogenesis and why?

Muscle bc it lacks glucose 6-phosphatase

What is the enzyme responsible for the oxidative reaction for the HMP shunt (pentose phosphate pathway)?

glucose 6-P dehydrogenase

What does the HMP shunt provide a source of?

NADPH from abundantly available glucose 6-P and ribose for nucleotide synthesis and glycolytic intermediates

Where does the HMP shunt occur?

Cytoplasm

What is NADPH necessary for?

It keeps glutathione reduced, which in turn detoxifies free radicles and peroxides

What does decreased NADPH in RBCs lead to?

Hemolytic anemia due to poor RBC defence against oxidizing agents

Essential fructosuria

defect in fructokinase autosomal recessive benign, asxs since fructose is not trapped in the cells fructose appears in blood and urine

Fructose intolerance

hereditary deficiency of aldolase B autosomal recessive Fructose-1-P accumulates, causing a decrease in available phosphate, which results in inhibition of glycogenolysis and gluconeogenesis Symptoms present following consumption of fruit, juice, or honey Sxs: hypoglycemia, jaundice, cirrhosis, vomiting Tx: decrease intake of both fructose and sucrose (glucose + fructose)

Galactokinase Deficiency

Hereditary deficiency of galactokinase Galactitol accumulates if galactose is present in diet Relatively mild condition autosomal recessive, metabolic dz Sxs: galactose appears in blood and urine, infantile cataracts. May initially present as failure to track objects or to develop a social smile