Integration of metabolism

Question 1

What are the effects of leptin and adiponectin ?

Answer 1

stops fatty acid synthesis, insulin secretion increases fatty acid oxidation and glucose uptake in muscle and heart

Question 2

What signaling molecule leptin and adiponectin increase ?

Answer 2

AMPK

Question 3

What are the advantages of LC MS/MS ?

Answer 3

LC-MS/MS allows for the detection of many metabolites simultaneously to provide a complex metabolic profile LC-MS/MS is exquisitely sensitive into femtogram (10-15g) range LC-MS/MS can be quantitative LC-MS/MS is fast because it requires little sample preparation

Question 4

What cycles do hepatic tumours suppress ?

Answer 4

Do not do TCA for energy, No peroxisomal activity No processing of fatty acids

Question 5

What cycles do hepatic tumours upregulate ?

Answer 5

Glycolysis & β-Oxidation (for ATP) PPP (for NADPH & Ribose-5-P) Citric Acid Cycle (DNA bases & AAs)

Question 6

What is the iKnife ?

Answer 6

Fine tipped cauterizing knife that uses a vacuum to suck tissue into LC MS/MS for immediate analysis

Question 7

What is the active form of vitamin D ?

Answer 7

1, 25-(OH)2D3 (1, 25, dihydroxy vitamin D)

Question 8

What is the precursor to active vitamin D ?

Answer 8

25-OH-vitamin D

Question 9

What is the difference between bilayers and membranes ?

Answer 9

Membranes are not synthetic, they are not uniform in their fatty acid composition, they contain proteins and cholesterol

Question 10

What are the phospholipases an where do they cleave ?

Answer 10

Phospholipase A1: Cleaves at ester bond of the first fatty acid Phospholipase A2: Cleaves at the ester bond of the second fatty acid
Phospholipase C: Cleaves at the PO bond releasing IP3
Phospholipase D: Cleaves at the PO bond releasing IP2

Question 11

What is the common prostoglandin precursor ?

Answer 11

Aracadonic acid (20:4Δ<sup>6,8,11,14)</sup>
It is cleaved by phospholipase A<sub>2</sub>

Aracadonic acid is then converted to prostoglandin H₂ (PGH₂) by Cyclo-Oxygenases (COX 1&2)

Question 12

What are the products of phospholipase C ?

Answer 12

Phosphadityl inositol 4,5-biphosphate (PIP₂) is converted to:

inositol 1,4,5- triphosphate (IP₃)
and
diacylglycerol (DAG)

Question 13

What are they 2 parts of taurochloric acid ?

Answer 13

Taurochloric acid is a bile salt consisting of a sterol derivitive and taurine (hydrophilic)

Question 14

What kinds of molecules easily pass through membranes?
Which ones need transporters ?

Answer 14

Ions and large uncharged polar molecules need transporters

Small uncharged polar molecules (urea, water, glycerol etc) and hydrophobic molecules (oxygen, CO2, nitrogen, benzene) can pass unaded. (Though they sometimes have transporters to increase speed)

Question 15

Compare and contrast: artificial phospholipid bilayers & natural membranes.

Answer 15

Artificial membranes are created spontaiously in vitro
They do not contain proteins, or cholesterol
Artificial membranes are symmetrical (inside and ourside) and do not contain flippase/flopase/scrabblase, so the phospholipids do not cross inside to outside

Question 16

How does the cell modify the structure of lipid bilayers to give them the properties of natural membranes?

Answer 16

The cell encorporates proteins for signalling, transport, and maintenance,

Cholesterol is added to increase fluidity, and create lipid rafts (with calveolin)

The fatty acids are adjusted to affect fludity and are not symmetrical between the inner and outer layers

Question 17

What is the functional role played by cholesterol in membrane structure?

Answer 17

Cholestol affects fluidity of the membrane

Cholesterol helps in the formation of lipid rafts by intercollating between the long unsaturated fatty acids in the raft. These rafts contain claveolin, which dimerize to cause endocytosis.

Question 18

What are the general charges inside and outside of a membrane ?

Answer 18

Typically, inside is negative,

Outside is neutral

Question 19

What are 6 common constituants of the outer (cytosolic) leaflet ?

Answer 19

Phosphodityl ethanolamine (PE)
Phophadityl choline (PC)
Sphingomyelin (SM)
Glycolipid
PS
Phosphatidylinositol (PI)

Question 20

What are 5 common phospholipids found on the inside of a membrane ?

Answer 20

Phosphatidylserine
Phosphaditylinositol
Phosphaditylinositol 4-Phosphate
Phosphatidylinositol 4,5 biphosphate
Phosphaditic acid

also PE

Question 21

What are the proteins that can change the inside/outside direction of a phospholipid ?

Answer 21

Flippase (outer to cytosolic leaflet)
Floppase (cytosolic to inner leaflet)
Scramblase (moves 2 phospholipids inopposite directions)

All are ATPases

Question 22

What can ‘flip-flop’ unassisted between membrane leaflets ?

Answer 22

Cholesterol

Question 23

Why are lipid rafts thicker than other parts of the membrane ?

Answer 23

The raft is composed of longer fatty acids that are interdigitated with cholesterol

Question 24

What is the role of lipid rafts in endocytosis ?

Answer 24

The lipid rafts contain the protein caveolin. When dimerized, they form a curve in the membrane, and eventually a trough called caveola. These pocket pinch off to form vesicles

Question 25

6 types of integral membrane

Answer 25

Type I: single domain spanning membrane, COO on inside Type II: single domain spanning membrane, NH3 in inside Type III: multiple domains spanning membrane, monomer Type V: multiple domains spanning membrane: multimer Type IV: lipid linked, anchored only by lipid Type VI: lipid linked, anchored by lipid and membrane spanning domain Note tha for type III and V, the most common number of membrane spanning domains is 7.

Question 26

What is a glycocalix and what is its role ?

Answer 26

It is a carbohydrate presented on the surface of a cell, for self-identification

Question 27

What exactly do we know about caveolin/caveolae? How are caveolae used by cell?

Answer 27

Calveolin dimerizes causing a curve in the surface of the membrane. These curves eventually form a caveola which pinches off and form a vesicle. This vesicle brings substrates from the intestitial fluid into the cell without allowing it to cross the membrane in a process called endocytosis.

Question 28

Red Blood Cells have a complex cytoskeletal architecture that makes the biconcave disc? What do think happens when there are mutations in any of the proteins depicted in Fig11-20 in Lehninger 6e (eg spectrin)

Answer 28

Spectrin is one of the major scaffolding proteins in red blood cells. It causes the biconcave shape found in human RBCs that maximise surface area and facilitate oxygen absorption. A mutation in spectrin may lead to a deformed cell, or cell death, as clevage of spectrin leads to apoptosis. Camels can alter the spectin on their RBCs to alternate between

Question 29

What is the glycerol - 3 - Phosphate bypass ?

Answer 29

It is a way of transferring the NADH reducing power from glycolysis without it crossing the inner mitochondrial membrane The NADH reduces Dihydroxyacetone phosphate into G3P, which in turn reduces FAD to FADH2. This is fed to complex Q

Question 30

How does the NADH from glycolysis power the electron transport chain ?

Answer 30

It doesnt It uses the G3P bypass or the malate-aspartate shuttle so that the NADH does not have to cross the inner mitochondrial membrane.

Question 31

What is the malate-aspartate shuttle ?

Answer 31

It is a way to bring the reducing power of NADH into the mitochondria Aspartate is converted to oxaloacetate, then reduced to malate by NADH. The malate is transported into the mitochondria where it reduces a different NAD molecule. This turns it back into oxaloacetate, whereupon it is converted back into aspartate and transported back outside the mitochondria Glutamate / α-ketogluterate are used to 'hold' the amino group to convert aspartate to oxaloacetate

Question 32

Compare AND contrast the two shuttles for mitochondrial entry of reducing equivalents (NADH) made in glycolysis.

Answer 32

Both the malate-asparte shuttle and G3P bypass are ways to move the reducing power of NADH from glycolysis without moving NAD or NAHD through the inner mitochondrial membrane The malate-aspartate shuttle reduces aspartate to malate and shuttles the malate across the membrane to regenerate NADH on the other side. It uses 2 separate pools of NAD/NADH The G3P bypass uses NADH to reduce dihydroxyacetone phosphate to G3P to reduce FAD to FADH2 on the outside of the IMM and feed into complex Q. This is faster, but does not include complex I, and therefore makes less ATP

Question 33

Why do NADH & FADH2 produce different amounts of ATP during ETC and Ox-Phos?

Answer 33

NADH is fed into complex I, which pumps 4 H+, before the electrons are transferred to complexes Q, 3, and 4. FADH2 is fed into complex II, then Q, 3, and 4. Complex II does not pump any protons

Question 34

Why do we have aquaporins if water can diffuse across the membrane by simple diffusion?

Answer 34

It speeds up the rate of diffusion. It also allows better control of diffusion, which is important in places like the kidney