things to look over Flashcards
how does glucose get into cells
via GLUT transporters by fascilitated diffusion
what is the function of hexokinase
phosphorylates glucose
what is the function of phosphofructokinase
phosphorylates fructose-6-phosphate
what is the function of pyruvate kinases
converts phosphoenolypruvate to pyruvate
what is the function of NAD in glycolysis
- 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
what is the fate of pyruvate in anaerobic conditions
- alcoholic fermentation
- lactic acid formation in humans
what is the fate of pyruvate in aerobic conditions
- further oxidised in the citric acid cycle
where does the TCA cycle occur
mitochondria
how does pyruvate enter the mitochondrial matrix
- 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
once in the matrx how is pyruvate metabolised to Acetyl-CoA
- 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
what happens in the TCA cycle
- 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
where are the enzymes of the TCA cycle located
mitochondrial matrix apart from succinate dehydrogenase which is integrated in the inner mitochondrial membrane
what are the main features of the TCA cycle
- 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
high ATP
high NADP
high acetyl-CoA
plenty of energy
high ADP
high NAD+
lack of energy
for each molecule of glucose the net yield of molecules is …
4 ATP 10 NADH 10 H+ 2 FADH2 6 CO2
what is an effect of PDC deficiency ( pyruvate dehydrogenase complex )
- presents largely as a neurological disease in children
- poor muscle tone and lack of coordination
- respiratory problems
- retardation and seizures
- persistant lactic acidosis
what are the electrons from NADH and FADH2 used for
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
what is phosphoryl transfer potential
can be measured by the free energy change for the hydrolysis of ATP
what is electron transfer potential
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
what does a negative standard redox potential mean
- 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
what are cytochromes
proteins which contain haem groups as a functional co-factor
haem contains Fe(II) ion which can take up and release electrons
what is ATP synthase function
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.
what can inhibit oxidative phosphorylation
- cyanide, azide and CO inhibit transfer of electrons to O2
- no proton gradient can be formed
- no ATP can be synthesised
what is a nucleoside
base and sugar
what is a nucleotide
nucleoside and phosphate
what catalyses DNA replication
DNA polymerases
what unwinds the DNA in replication
helicase
what are the 3 types of DNA polymerases for eukaryotic cells
Pol I, II, III
Pol II synthesises all mRNA
what is transcription and translation used for
Transcription and translation take the information in DNA and use it to produce proteins.
what is transcription
Transcription is the process of copying a segment of DNA into RNA.
what is the process if transcription
- 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
what is the general transcription factor for all Pol II transcribed genes
TFIID
what is translation
Translation is the process of translating the sequence of a messenger RNA (mRNA) molecule to a sequence of amino acids during protein synthesis.
whats the process of translation
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
what is endotoxin shock
Endotoxic shock results from a severe, generalized inflammatory response induced by bloodstream infection with gram-negative bacteria.
what causes endotoxin shock
The lipid A portion of LPS (lipopolysaccharide)
what are FAS and FAS ligand
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
what happens in the ligation of Fas with FasL
activation of a caspase cascade that initiates apoptosis
