things to look over

Question 1

how does glucose get into cells

Answer 1

via GLUT transporters by fascilitated diffusion

Question 2

what is the function of hexokinase

Answer 2

phosphorylates glucose

Question 3

what is the function of phosphofructokinase

Answer 3

phosphorylates fructose-6-phosphate

Question 4

what is the function of pyruvate kinases

Answer 4

converts phosphoenolypruvate to pyruvate

Question 5

what is the function of NAD in glycolysis

Answer 5

• NAD+ is reduced to NADH + H+
• NAD+ is regenerated through oxidative metabolism of pyruvate
• NADH must be re-oxidised to let glycolysis continue
• when NAD+ is reduced to NADH + H+ an electron is donated

Question 6

what is the fate of pyruvate in anaerobic conditions

Answer 6

• alcoholic fermentation

- lactic acid formation in humans

Question 7

what is the fate of pyruvate in aerobic conditions

Answer 7

• further oxidised in the citric acid cycle

Question 8

where does the TCA cycle occur

Answer 8

mitochondria

Question 9

how does pyruvate enter the mitochondrial matrix

Answer 9

• H+ gradient from cytosol to matrix
• pyruvate transporter H+/pyruvate symport by fascilitated diffusion
• a similar process regulates ADP, ATP and inorganic phosphate (Pi) movement into and out of the mitochondia

Question 10

once in the matrx how is pyruvate metabolised to Acetyl-CoA

Answer 10

• the pyruvate dehydrogenase complex catalyses the oxidative decarboxylation of pyruvate to acetyl-CoA
• PDC consists of 3 enzymes and it is allosterically regulated by phosphorylation
• PDC activity determines glucose oxidation in a well oxygenated tissue
• The reaction is irreversible. Acetyl-CoA cannot be converted back to pyruvate

Question 11

what happens in the TCA cycle

Answer 11

• 2C unit (from acetyl-CoA) condenses with a 4C unit
• the resulting 6C unit is decarboxylated twice (yields 2XCO2)
• there are then 4 oxidation reactions which yields
  = 4 x (NADH + H+) and 1 x FADH2
• one GTP is formed (energy)
• the 4C unit is recreated

Question 12

where are the enzymes of the TCA cycle located

Answer 12

mitochondrial matrix apart from succinate dehydrogenase which is integrated in the inner mitochondrial membrane

Question 13

what are the main features of the TCA cycle

Answer 13

• All products of STAGE II metabolism can give rise to acetyl-CoA and as a result can be oxidised completely to CO2 via the TCA cycle
• All of the enzymes of the TCA cycle are associated with mitochondria
• Each turn of the TCA cycle involves the uptake of two carbon atoms in the form of acetyl-CoA and the release of two carbon atoms as CO2
• Each turn of the cycle results in the transfer of 3 pairs of electrons to NAD+ to form NADH + H+, and the transfer of 1 pair of electrons to reduce FAD to FADH2
• One substrate level phosphorylation reaction results in the formation of GTP from GDP and Pi

Question 14

high ATP
high NADP
high acetyl-CoA

Answer 14

plenty of energy

Question 15

high ADP

high NAD+

Answer 15

lack of energy

Question 16

for each molecule of glucose the net yield of molecules is …

Answer 16

4 ATP 
10 NADH
10 H+ 
2 FADH2
6 CO2

Question 17

what is an effect of PDC deficiency ( pyruvate dehydrogenase complex )

Answer 17

• presents largely as a neurological disease in children
• poor muscle tone and lack of coordination
• respiratory problems
• retardation and seizures
• persistant lactic acidosis

Question 18

what are the electrons from NADH and FADH2 used for

Answer 18

to reduce O2 and H2O

the energy is used to pump protons from the mitochondrial matrix to the intermembrane space

protons flow back across the membrane following their concentration gradient

energy of proton flow is used to phosphorylate ADP to ATP

Question 19

what is phosphoryl transfer potential

Answer 19

can be measured by the free energy change for the hydrolysis of ATP

Question 20

what is electron transfer potential

Answer 20

redox potential of a compound

• The standard redox potential E’o of a (reduced) substance X is a measure for how readily X donates an electron (in comparison with H2)
  X- —> X + e-

The standard free energy change is proportional to the change in standard redox potential and the number of electrons transferred

Question 21

what does a negative standard redox potential mean

Answer 21

• A negative E’o means that the reduced form of X has a lower affinity for electrons than H2, a positive E’o means the opposite

Question 22

what are cytochromes

Answer 22

proteins which contain haem groups as a functional co-factor

haem contains Fe(II) ion which can take up and release electrons

Question 23

what is ATP synthase function

Answer 23

The function of ATP synthase is to synthesize ATP from ADP and inorganic phosphate (Pi) in the F1 sector. This is possible due to energy derived from a gradient of protons which cross the inner mitochondrial membrane from the intermembrane space into the matrix through the Fo portion of the enzyme.

Question 24

what can inhibit oxidative phosphorylation

Answer 24

• cyanide, azide and CO inhibit transfer of electrons to O2
• no proton gradient can be formed
• no ATP can be synthesised

Question 25

what is a nucleoside

Answer 25

base and sugar

Question 26

what is a nucleotide

Answer 26

nucleoside and phosphate

Question 27

what catalyses DNA replication

Answer 27

DNA polymerases

Question 28

what unwinds the DNA in replication

Answer 28

helicase

Question 29

what are the 3 types of DNA polymerases for eukaryotic cells

Answer 29

Pol I, II, III

Pol II synthesises all mRNA

Question 30

what is transcription and translation used for

Answer 30

Transcription and translation take the information in DNA and use it to produce proteins.

Question 31

what is transcription

Answer 31

Transcription is the process of copying a segment of DNA into RNA.

Question 32

what is the process if transcription

Answer 32

• RNA polymerase binding. It detects the initiation sites on DNA and requires transcription factors
• DNA chain separation by unwinding the DNA
• Transcription initiation. Selection of first nucleotide of growing RNA. It requires additional general transcription factors
• Elongation. Addition of further nucleotides to the RNA chain and its synthesised in the 5’ to 3’ direction
• Termination - release of finished RNA
• Introns are spliced out before translation

Question 33

what is the general transcription factor for all Pol II transcribed genes

Answer 33

TFIID

Question 34

what is translation

Answer 34

Translation is the process of translating the sequence of a messenger RNA (mRNA) molecule to a sequence of amino acids during protein synthesis.

Question 35

whats the process of translation

Answer 35

Initiation

• GTP provides energy
• Ribosomal subunit binds to 5’ end of MRNA, moves along until start codon is found
• Initiator tRNA pairs to start codon
• large subunit joins assembly and initiator tRNA is located in P site

Elongation

• elongation factor brings aminoacyl-tRNA to site A
• GTP
• second elongation factor regenrates the first to pick up the next aminoacyl-tRNA

Peptidyl transferase catalyses peptide bind formation between amino acids in P and A sites

Termination

• occurs when A site of ribisome encounters a stop codon
• Finsihed protein cleaves off tRNA

Question 36

what is endotoxin shock

Answer 36

Endotoxic shock results from a severe, generalized inflammatory response induced by bloodstream infection with gram-negative bacteria.

Question 37

what causes endotoxin shock

Answer 37

The lipid A portion of LPS (lipopolysaccharide)

Question 38

what are FAS and FAS ligand

Answer 38

Fas and Fas Ligand (FasL) are two molecules involved in the regulation of cell death. They are part of the tumour necrosis factor receptor family

Question 39

what happens in the ligation of Fas with FasL

Answer 39

activation of a caspase cascade that initiates apoptosis