Lectures 1-5 Flashcards
What gives proteins charge?
Projecting side-chains can offer charge
Why are polypeptide chains flexible?
The peptide bond is essentially planar
There is a 40% double bond character around C-N
Which tertiary structure is preferred?
That of the lowest energy
What tells a protein where to go?
Its’ own specific sorting signal
What catalyses phosphorylation of proteins?
Kinase (PKA)
What catalyses dephosphorylation of proteins
Phosphatatse
What are the stages to growth factor signalling?
Activation of the tyrosine kinase receptor (dimerisation, phosphorylation) Cytoplasmic signallling (adaptor protein binds to phosphorylated receptor, Ras (G-protein) binds to adaptor)
What is the importance of UPR?
operates as a homeostatic response.
keeping the cell folding capacity in balance with its needs (limiting ER stress, decreasing unfolded protein production)
What is ERAD?
Endoplasmic Reticulum associated protein degreadation
What genes dictate proliferative control?
Oncogenes and tumour suppressor genes
Why would the cell cycle use checkpoints? (2)
To regulate proliferation
To maintain genomic integrity
Where are the major checkpoints found?
Middle of G1
Between G1 and S
Between G2 and M
What growth factors are involved in the checkpoint at G1?
none lmao tricked you
What does the G1 restriction point check for? What might happen?
The point at which the cell does not need extracellular signals to then divide.
checks for cell size (big enough to divide) and nutrient availability for daughter cells
If not it slips into G0 (quiescence), which is the state of most cells in the body
What is checked in metaphase?
connections between chromosomes and mitotic cpindles by the kineticore
What are kinases activated by?
cyclin
How does cyclin initiate mitosis?
build by in interphase, eventually forming maturation promoting factor (M-Cdk), initiating mitosis by phosphorylation
What is pRB?
The retinoblastoma protein
TS protein, binding to transcription regulators for genes for cell proliferation at the restriction point
What would inhibit pRB function?
specific growth factors, which activate Cdk’s, phosphorylating pRB
What happens when a receptor becomes oncogenic?
What might have the same effect?
Constant efficacy, deregulating cell proliferation
A mutated continuously active Ras protein
What are the yields of glycolysis?
2 pyruvate
2 ATP
2 NADH
glycolysis: how is glucose primed?
How many carbons does the product have?
in 2 phosphorylation steps and one isomerisation step to form fructose-1,6-bisphosphate
(6)
glycolysis: what is F-1,6-bp split into?
Glyceraldehyde 3-phosphate
eventually forms pyruvate (3C)
Which steps in glycolysis are irreversible?
hexokinase and phosphofructokinase (priming) pyruvate kinase (splitting)
anaerobic respiration: Why is lactate formed?
NAD+ must be regenerated to drive the glycolysis equilibrium forward and produce ATP
anaerobic respiration: How is lactate produced?
pyruvate is converted to lactate using lactate dehyrdrogenase
What causes Angina pectoris?
atherosclerosis blocks coronary arteries, reducing )2 supply to the heart, increasing lactate and hence leading to chest pains.
What intermediate in anaerobic respiration in RBC’s decreases their affinity for O2?
2,3-biphosphoglycerate
What happens in the Cori cycle?
Lactate from muscle tissue and alanine is converted to pyruvate, and then to glucose-6-phosphate in gluconeogenesis in the liver
What is required to form one glucose molecule in gluconeogenesis?
What is the net loss?
2 pyruvate 4ATP 2GTP 2NADH net loss: 2ATP, 2GTP
What is used to perform the Link’s reaction?
How many enzymes does it use?
Pyruvate dehydrogenase complex
3 enzymes
What happens at E1 of the pyruvate dehydrogenase complex?
Pyruvate undergoes oxidative decrarboxylation, adding TPP
What happens at E2 of the pyruvate dehydrogenase complex?
lipoamine transfers the acetyl group to CoA
What happens at E3 of the pyruvate dehydrogenase complex?
regeneration of lipoamine
What might remove some carbons from Acetyl CoA?
The formation of fatty acids
What are the subunits of cholesterol?
polar head group
rigid planar steriod ring structure
non-polar hydrocarbon tail
What does cholesterol do?
as 37 degrees it makes the membrane less fluid
This is because cholesterol is short and rigid, making membranes less permeable
What are transmembrane domains of proteins called?
hydrophobic amino acids orgnised into alpha-helical structures
(hydrophobic side-chains aare on the outside)
What are anchors?
integrins linking intracellular matrix to actin
what classes of membrane proteins are involved in facilitated diffusion?
channels
uniporter carrier proteins (has a binding site)
What comprises the net force driving charged solutes across the membranes?
concentration gradients
membrane voltage
(called the electrochemical gradient)
How is the Na+ electrochemical gradient maintained?
Na+ and K+ active transport, 3Na+ out against the concentration gradient, 2 K+ in against the concentration gradients
What is a coupled transporter?
one solute with the gradient, one solute against (antiport) (secondary AT)
CAN BE SYMPORT
What are ATP driven pumps?
primary active transport, straight up, normal AT
What does the Na+/glucose symporter do?
Na+ electrochemical gradient is used to drive the movement of glucose against its’ concentration gradient
What does the Na+/Ca2+ antiporter do?
moves 1 Ca2+ out for 3 Na+ in (Ca2+ against the concentration gradient)
What is the effect of the Na+/Ca2+ antiporter?
it reduces intracellular Ca2+ conc. reducing strength of cardiac muscle contraction
What is checked in G2?
the status of DNA replication from S phase
How does m-Cdk switch itself off?
initiating a process which leads to the destruction of cyclin.
Which cdk’s and cyclins are active at the restriction point?
cdk4 / cyclin D
cdk2 / cyclin (A/E)
which cdk’s and cyclins are active at the turn from G1 to S phase?
cdk 2 / cyclin (A/E)
cdk 1 / cyclin (A/B)
Which cdk’s and cyclins are active at the turn from G2 to M phase?
cdk 1 / cyclin (A/B)
What might inhibit a cdk?
INK and CIP inhibit cdk4
How does p53 work?
activates the transcription of p21, which inhibits cdk’s preventing transition into S phase, giving time for DNA to repair or apoptosis i think
