Metabolism

Question	Answer
What is catabolism?	Breakdown of complex molecules into smaller ones, releasing energy
What is anabolism?	Sythesis of new complex molecules from its smaller constituents, using energy
Why should we study metabolism?	Often the basis of disease - therefore we need to know how the body NORMALLY uses nutrients. In a disease state, metabolism can change (e.g. cancer)
The body needs to re-synthesise ____ from ____ to meet demand, as the body only has ____g - this is one fifth of the required amount during exercise.	ATP, ADP, 100
How is most ATP in the body synthesised?	Through oxidative phosphorylation in the mitochondria
Name 4 major oxidative pathways	1. glycolysis 2. fatty acid oxidation 3. TCA cycle (Krebs cycle) 4. Electron transport chain and oxidative phosphorylation
Glycolysis is an _________ process converting _________ to 2 x _________. It occurs in the ___________	anaerobic, glucose, pyruvate, cytoplasm
1. Glucose is _________ using ____ by __________ (or in the liver, ___________). This maintains a _______ _______.	phosphorylated, ATP, hexokinase, glucokinase, concentration gradient.
2. G-6-P is then converted to _________ __ ________ and then phosphorylated again using ____ by _____________________. This is the ____ _______ ____ of glycolysis.	Fructose 6 phosphate, ATP, phosphofructokinase, rate limiting step
3. The resulting ________ __ __ _________ splits into 2 x 3 carbon compounds, which undergo dephosphorylation to produce _________.	fructose 1,6 bisphosphate, pyruvate
How many ATP molecules are used and gained in glycolysis, and what is the resultant net gain?	2 used, 4 made = 2 gained
How many molecules of NAD+ are used in glycolysis, and at what stage?	2, in the conversion of the unstable 3 carbon compound to pyruvate.
Which enzyme converts phosphoenol pyruvate to pyruvate?	Pyruvate kinase
What inhibits the action of hexokinase?	G-6-P (it's own product)
What inhibits the action of phosphofructokinase?	ATP, Citrate and H+ (low pH) = (the products of oxidative phosphorylation)
What stimulates the action of phosphofructokinase?	AMP and Fructose 6 phosphate
What inhibits the action of pyruvate kinase?	ATP
How does ATP inhibit phosphofructokinase?	Lowers the affinity of PFK for fructose 6 phosphate
What does inhibiting PFK lead to?	Build up of G-6-P and therefore also inhibition of hexokinase
In the liver, there is _________ as well as hexokinase. It is not inhibited by a build up of ___ ___ ___ like hexokinase.	glucokinase, G-6-P
In muscles and tumours, most energy is gained through glycolysis, which is ________.	anaerobic
In anaerobic glycolysis in muscle and tumours, there needs to be a supply of NAD+ for formation of pyruvate. As there is no oxidative phosphorylation, where does it come from?	Pyruvate is converted to lactate, which also converts NADH to NAD+ which is used in the earlier stages of glycolysis.
What are 2 dangers in a build up of lactate?	1. Lactate is toxic - it must be broken down in the liver 2. It is acidic so causes fall in pH, which inhibits PFK
Tumours exist in a _______ environment, which activates __ __ __ __. This stimulates ______ _______ to grow and an increase in ___________ _______ so tumours can overcome the usual regulatory processes and survive.	hypoxic, HIF1, blood vessels, glycolytic enzymes
Apart from lactate, what is the other fate of pyruvate?	Acetyl CoA
What is an advantage and disadvantage of this?	Advantage = yields more ATP Disadvantage = requires O2
Where does aerobic respiration take place?	The mitochondria
Where does the TCA cycle take place?	Mitochondrial matrix
Pyruvate is converted to ________ ___ in the presence of ______. It is a __ carbon compound, and the by-products of the reaction are ______ and ______	Acetyl CoA, oxygen, 2, CO2, NADH
What does Acetyl CoA react with on its entry to the TCA cycle?	Oxaloacetate (4C)
What does this form?	Citrate (6C)
Citrate undergoes 3 main reactions: 1. a 5C compound is obtained by the loss of ____ and _____. 2. a 4C compound is obtained by the loss of ____ and _____. 3. The 4C compound is converted back to oxaloacetate, losing a molecule each of ____, _____ and _____.	CO2 and NADH, CO2 and NADH, GTP, NADH and FADH2
Which enzyme helps convert pyruvate to Acetyl CoA?	pyruvate dehydrogenase
How does it control entry to the TCA cycle?	Build up of NADH and Acetyl CoA causes production of a kinase which phosphosylates pyruvate dehydrogenase and makes it inactive
When a muscle in exercising, there is increased ____. This stimulates a _________ enzyme which activates __________ __________ and allows conversion of ________ to ______ ___.	Ca++, phosphatase, pyruvate dehydrogenase, pyruvate, Acetyl CoA
Which enzyme helps make citrate from acetyl CoA and oxaloacetate?	Citrate synthase
Which enzymes helps convert citrate into the 5C compound (alpha-ketogluterate)?	Isocitrate dehydrogenase
Which enzyme helps convert the 5C alpha ketogluterate into the 4C Succinyl CoA?	alpha ketogluterate dehydrogenase
What is beriberi and what does it do?	Deficiency of vitamin B1 (thiamine). Thiamine is a prosthetic group in pyruvate and alpha-ketogluterate dehydrogenase - lack of these causes difficulties in generating energy from glucose so causes cardiac and neurological symptoms
The FADH2 and NADH produced in the TCA cycle then goes to the ________ ___________ ________ to take part in the _________ __________ _________.	inner mitochondrial membrane, electron transport chain
NADH is oxidised by _____ ____________ to give _____ + ____ + ___. The ______ enter the chain at complex I and travel through complexes II, III and IV, gradually losing ______. They are then used in a reduction reaction to form _____ at complex IV.	NADH dehydrogenase, NAD+, H+, 2e-, electrons, energy, H2O
The FADH2 is oxidised by ________ ________ and the _______ enter the chain at complex II, taking the same course as those from NADH.	succinate dehydrogenase, electrons
As the electrons pass along the chain, their ______ allows ___ ions across the membrane into the ____________ _____. This creates an ____________ _______.	energy, H+, intermembrane space, electrochemical gradient
For each NADH molecule, ___ H+ ions are pumped out. For every FADH2 molecule, ___ H+ ions are pumped out.	10, 6
____ ______ molecules exist on the membrane, which are molecular motors. They have a channel which allows ____ ions into the matrix down the __________ _________. This movement causes a rotation of part of the protein, and the synthesis of ____ from ___ + ___.	ATP synthase, H+, electrochemical gradient, ATP, ADP + Pi
If the protein is uncoupled, ___ ions enter the matrix without synthesising ____. This generates _____ (used in newborns in brown fat molecules, as they cannot shiver).	H+, ATP, heat
What is the main regulator of the electron transport chain?	ATP - when there is excess, electron flow can be scaled down, but when there is need for ATP it can be increased.
What processes provide the energy for a 100m sprint? (4)	1. ATP stores in muscle 2. Glycolysis 3. Glycogenolysis 4. Creatine phosphate + ADP --> ATP + creatine
Why can creatine phosphate and glycolysis only be used for short bursts of exercise?	We only have small stores of creatine phosphate, and glycolysis produces lactate and therefore a fall in pH.
What substances provide energy while running a marathon?	Glycogen and fatty acids
In the fed state, where are most nutrients going?	1. From gut to liver 2. From liver to adipose stores 3. From liver to muscle 4. From liver to kidneys 5. From liver to brain
Which pathways are stimulated in the fed state? (3)	1. Glycolysis 2. Glycogenesis 3. Lipogenesis
Which pathways are inhibited in the fed state? (3)	1. Glycogenolysis 2. Lipolysis 3. Gluconeogenesis
Which molecules are abundant in the fed state?	1. Glycogen 2. Fatty acids
Which molecules are few in the fed state?	1. Glucose 2. Ketones
In starvation, where are most nutrients going?	1. From muscle to liver 2. From adipose stores to liver 3. From liver to brain 4. From liver to kidneys
Which pathways are stimulated in the starved state? (4)	1. Glycogenolysis 2. Gluconeogenesis 3. Lipolysis 4. Ketogenesis
What pathways are inhibited in the starved state? (3)	1. Glycolysis 2. Glycogenesis 3. Lipogenesis
Which molecules are abundant in the starved state? (2)	1. Glucose 2. Ketones
Which molecules are few in the starved state? (2)	1. Glycogen 2. Fatty acids

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	Created by Hannah Tribe about 10 years ago