Metabolism Flashcards
What are the three fates of pyruvate following glycolysis?
Enters the Kreb’s cycle as Acetyl CoA, concerted to lactate or ethanol
Where does the Kreb’s cycle take place?
In the matrix of the mitochondria
Where does oxidative phosphorylation take place?
In the inner membrane of the mitochondria
What is the name of the 15C compound that goes on to make cholesterol?
Farnesyl pyrophosphate (FPP)
Through which type of channels does K+ leave the cell during repolarisation?
Voltage gated potassium channels
Which of the following molecules can the brain use as fuel sources? Glucose, acetoacetate or fatty acids?
Acetoacetate
What is the main carbohydrate store of the body?
The liver
When muscle is respiring anaerobically, pyruvate is metabolised to which molecule?
Lactate
During times of prolonged fasting, what is produced?
Ketone bodies are produced from fatty acids
What is the isoelectric point?
The point at which the molecule has no charge
Which part of the zwitterion determines its chemical properties?
The R group.
Name the only achiral amino acid.
Glycine
Name some non-polar amino acids
Glycine and proline
Name some polar amino acids
Serine, Threonine, Tyrosine, Asparagine, cysteine
Name x2 basic amino acids and explain why they are basic?
Lysine and proline - are basic; they are always protonated
What is the name of the amino acid which forms disulphide bridges?
Cysteine
Name x1 hydrophilic amino acid
Glutamic acid
Name x1 hydrophobic amino acid
Valine
Which two amino acids are involved in sickle cell disease. What happens?
Glutamic acid switches to valine at position 6.
What is one way to separate proteins?
Electrophoresis
Sketch a trimeric peptide
Remember the NH2 and COOH terminals. x3 R groups on each amino acid
Can the peptide bond rotate?
No, but the central carbon in all amino acids can.
What is steric hindrance?
Molecular structure is too big for molecules to come close enough to react with one another.
Name x5 types of forces which pull a protein into shape
Covalent bonds, hydrogen bonding, Van der Waals, Ionic reactions, hydrophilic and hydrophobic bonds, steric hindrance
The Gibbs free energy for a single phosphoanhydride bond of ATP has a positive or negative value?
A negative value; ATP hydrolysis can couple energetically unfavourable reactions to more favourable ones.
What is the hydride ion (H-)?
H+ and 2 electrons.
Is glycolysis an aerobic or anaerobic process?
Anaerobic
What are the five co-factors in the pyruvate dehydrogenase complex?
TPP, Lipoamide, FAD, co-enzyme A and NAD+
What is substrate level phosphorylation and where is it seen?
When a phosphate is DIRECTLY added to ADP to form ATP - seen in glycolysis.
Is the first step of glycolysis - glucose to glucose-6-phosphate irreversible or reversible?
Irreversible
What is the name of the enzyme which catalyses the reaction from pyruvate to Acetyl CoA?
Pyruvate dehydrogenase
During which stage of the Kreb’s cycle is GTP produced from GDP?
Succinyl-CoA to Succinate
How many carbons are in a-ketoglutarate?
5C.
Before amino acids are entered as subtrates into the TCA cycle, what must first occur?
Transamination of amino acids.
Where does oxidative phosphorylation take place?
In the mitochondrial inner membrane
Describe the two steps in which oxidative phosphorylation can be split into?
- The translocation of protons from mitochondrial matrix to the intermembrane space.
- Protons flow back into the matrix from the intermembrane space coupled with ATP synthase to make ATP.
What is coenzyme Q also known as?
Ubiquinone
Describe the structure of ATP synthase.
F0 and F1 domains - F0 is membrane bound and contains a pore for protons to move through. F1 is made up of alpha, beta and gamma subunits.
What is the effect of oligomycin?
Binds to ATP Synthase stalk and blocks proton flow through
How does Cyanide block ATP production?
Cyanide binds with high affinity to Fe3+ in the cytochrome oxidase complex = blocks electron flow through the respiratory chain = inhibits proton pumping and ATP production.
What makes up the majority of the LDL?
Cholesterol esters
What is steric hindrance?
When a chemical reaction cannot occur due to the structure of that molecule.
Which is the largest human protein?
Titin
What is the free Gibbs energy for the hydrolysis of ATP?
-31kJ/mol
Crystallographic analysis of enzymes with and without substrate bound, support which model of enzyme function?
Induced fit theory
How does the activation energy of glucose combustion compare with glucose metabolism?
Glucose combustion = high activation energy
Glucose metabolism = low activation energy
Where does glycolysis take place?
Within the cytoplasm of the cell
How does Orlistat work
Reduces fat absorption by inhibiting gastric and pancreatic lipase.
What would Orlistat be used to treat?
Obesity.
Where does the majority of the energy used up by the body come from?
Fatty acid oxidation
The reaction from acetoacetate to acetone is a …… reaction
Decarboxylation
What is the predominant energy source during fasting?
Ketone bodies
Name the two enzymes required in fatty acid synthesis
Acetyl CoA decarboxylase
Fatty acid synthase
What is the overall reaction for lipogenesis?
Acetyl CoA (C2) + 7 Malonyl CoA (C3) + 14 NADPH +14 H+ > Palmitate (C16) + 7 CO2+ 6 H2O + 8 CoA-SH + 14 NADP+
De novo synthesis of fatty acids is limited to which x3 tissues/organs?
Liver, adipose tissue and lactating breast.
Name the enzyme which is mainly affected in fatty acid oxidation disorders
Dehydrogenases - MCADD - Medium chain Acyl Dehydrogenase deficiency. Autosomal recessive.
Why is Carnitine required in fatty acid oxidation?
Carnitine is required to move the Acyl CoA from the intermembrane space into the matrix.
A family of Acyl-CoA-dehydrogenases are required to catalyze the initial step in each cycle of β–oxidation.
True or false.
True.
Which species gets shorter by 2C in beta oxidation cycle - acetyl CoA or acyl CoA?
Acyl CoA
What are the three mechanisms the body will use during starvation?
Glycogen stores will be broken down to get glucose
Release free fatty acids from adipose tissue
Convert acetyl CoA to ketone bodies
Why do we need gluconeogenesis instead of relying on glycogen stores alone?
Glycogen stores are exhausted quickly (12-18hrs).
Is gluconeogenesis a direct reversal of glycolysis?
NO; Different enzymes are used.
Name x3 substances which make provide glucose during gluconeogenesis.
Lactate
Amino acids
Glycerol
Glycerol can be used to make which substance in the glycolytic pathway?
DHAP.
Name x2 ketogenic amino acids
Acetyl CoA and acetoacetyl CoA
