carbohydrates Flashcards

Question

Glycoproteins are

Answer 1

- Proteins that have carbohydrates covalently attached - Most extracellular eukaryotic proteins have associated carbohydrate molecules - Carbohydrate content varies between 1-80% by mass

Answer 2

- Increases the proteins solubility - Influence protein folding and conformation - Protect it from degradation - Act as communication between cells

Answer 3

- Less commonly called mucopolysaccharides - Found in mucus and also synovial fluid around the joints - Un-branched polymers made from repeating units of hexuronic acid and an amino-sugar, which alternate through the chains - contain groups NH, OSO3-, COO- eg- hylaluronate, heparin, keratan sulphate

Answer 4

- Formed from GAGs covalently attaching to proteins - Macromolecules found on the surface of cells or in between cells in the extracellular matrix - Form part of many connective tissues in the body - COO- goes inside cell EG- Syndecan, Glypican

Answer 5

- Very similar to proteoglycans - Usually found on the outer plasma membrane and extra cellular matrix, - Also in blood and within cells in the secretory system (Golgi complex, secretory granules) - Some cytoplasmic and nuclear proteins are also glycoproteins

Answer 6

- Group of genetic disorders caused by the absence or malfunction of enzymes required for the breakdown of glycosaminoglycans - Over time the glycosoaminoglycans build up in connective tissue, blood and other cells of the body - This build up damages cellular architecture and function

Answer 7

- Severe dementia - Problems with the heart and any other endothelial structure as the glycosaminoglycans build up between the endothelial cells - Bones tend to be stunted and joints will be inflammed and become severely damaged - Hurler, Scheie, Hunter, Sanfilippo syndromes are all examples of mucopolysaccharidoses

Answer 8

- Severe developmental defects: - Stop developing at around 4 years - Death at around 10 years old - Clouding and degradation of the cornea - Arterial wall thickening - Dementia caused by, amongst other things: - Build up of CSF - Enlarged ventricular spaces Experimental therapies currently include: - Gene therapy - Enzyme replacement therapies

Answer 9

Starch - Cereals, potatoes, rice Glycogen - Meat (however when the animal dies enzyme activity in tissue degrades much of the glycogen stores) Cellulose and hemicellulose - Plant cell walls – we don’t digest this Oligosaccharides containing (α1→6) linked galactose - Peas, beans, lentils – not digested Lactose, sucrose, maltose - Milk, table sugar, beer Glucose, fructose - Fruit, honey

Answer 10

Mouth: - Salivary amylase hydrolyses (α1→4) bonds of starch Stomach: - No carbohydrate digestion Duodenum (first part of the small intestine): - Pancreatic amylase works as in mouth Jejunum (second part of small intestine): - Final digestion by mucosal cell-surface enzymes: - Isomaltase – hydrolyses (α1→6) bonds - Glucoamylase – removes Glc sequentially from non-reducing ends - Sucrase – hydrolyses sucrose - Lactase – hydrolyses lactose Main products are – Glc, Gal, Fru

Answer 11

- Glucose is absorbed through an indirect ATP-powered process - ATP-driven Na+ pump maintains low cellular [Na+], so glucose can continually be moved into the epithelial cells - This system continues to work even if glucose has to be moved into the epithelial cells against it’s concentration gradient (i.e. When blood glucose is high)

Answer 12

Galactose has a similar mode of absorption as glucose, utilising gradients to facilitate it’s transport

Answer 13

Fructose is slightly different, - Binds to the channel protein GLUT5 - Simply moves down it’s concentration gradient (high in gut lumen, low in blood)

Answer 14

Cannot be digested by the gut, but they do have a use - Increase faecal bulk and decrease transit time Lack of oligosaccharides in the diet can lead to poor health - Many western diets Polymers are broken down by gut bacteria - Yielding CH4 (methane) and H2 - Beans will also have the same effect!

Answer 15

``` Deficiencies may be genetic Can result from, - Severe intestinal infection - Other inflammation of the gut lining - Drugs injuring the gut wall - Surgical removal of the intestine ``` Characterised by abdominal distension (enlargement) and cramps

Answer 16

enzyme tests of intestinal secretions. | Usually checking for lactase, maltase or sucrase activity

Answer 17

- Most common disaccharidase deficiency - Most humans lose lactase activity after weaning - Western whites retain lactase activity into adulthood - Theory that this comes from cattle domestication 100,000 years ago

Answer 18

- Undigested lactose is broken down by gut bacteria causing gas build up and irritant acids - Lactose is osmotically active, thus drawing water from the gut into the lumen causing diarrhoea Symptoms can be avoided by, - Avoiding milk products (many non-western diets do) - Using milk products treated with fungal lactase - Supplementing diet with lactase

Answer 19

- Most common disaccharidase deficiency - Most humans lose lactase activity after weaning - Western whites retain lactase activity into adulthood - Theory that this comes from cattle domestication 100,000 years ago

Answer 20

- Undigested lactose is broken down by gut bacteria causing gas build up and irritant acids - Lactose is osmotically active, thus drawing water from the gut into the lumen causing diarrhoea

Answer 21

- Avoiding milk products (many non-western diets do) - Using milk products treated with fungal lactase - Supplementing diet with lactase

Answer 22

Glucose diffuses through the intestinal epithelium cells into the portal blood and on to the liver Glucose is immediately phosphorylated into glucose 6-phosphate by the hepatocytes (or any other cell glucose enters) Glucose 6-phosphate cannot diffuse out of the cell because GLUT transporters won’t recognise it - This effectively traps the glucose in the cell Enzyme catalyst, - Glucokinase (liver) - Hexokinase (other tissues)

Answer 23

High Vmax so low affinity for substrate High Vmax so very efficient enzyme this is the opposite for hexokinase

Answer 24

the liver doesn’t “grab” all of the glucose, so other tissues have it. Hexokinase does most of the work

Answer 25

liver “grabs” the Glucose. Hexokinase is also working abut glucokinase takes care of all the extra glucose.

Answer 26

it can phosphorylate all that glucose quickly, thus most absorbed glucose is trapped in the liver

Answer 27

even at low glucose tissues can “grab” glucose effectively

Answer 28

tissues are “easily satisfied”, so don’t keep “grabbing” glucose

Answer 29

converts glycogen to glucose-6-phosphate. glucose-6-phosphate is broken down into glucose by glucose-6-phosphotase. This process is called glycogenolysis.

Answer 30

there is no Glucose-6-Phosphate and so are not directly available for blood glucose. When doing exercise, glycogen is converted to G6P and through glycolysis this is converted to lactate. the lactate is then converted into blood sugar in the liver

Answer 31

- Glycogen does not form directly from Glucose monomers - Glycogenin begins the process by covalently binding Glc from uracil-diphosphate (UDP)-glucose to form chains of approx. 8 Glc residues - Then glycogen synthase takes over and extends the Glc chains

Answer 32

- Glycogen does not form directly from Glucose monomers - Glycogenin begins the process by covalently binding glucose from uracil-diphosphate (UDP)-glucose to form chains of approx. 8 glucose residues - Then glycogen synthase takes over and extends the glucose chains

Answer 33

The chains formed by glycogen synthase are then broken by glycogen-branching enzyme and re-attached via (α1→6) bonds to give branch points

Answer 34

- Glucose monomers are removed one at a time from the non-reducing ends as G-1-P - Following removal of terminal Glucose residues to release G-1-P, by glycogen phosphorylase, Glucose near the branch is removed in a 2-step process by de-branching enzyme - Transferase activity of de-branching enzyme removes a set of 3 Glucose residues and attaches them to the nearest non-reducing end via a (α1→4) bond - Glucosidase activity then removes the final Glucose by breaking a (α1→6) linkage to release free Glucose - This leaves an unbranched chain, which can be further degraded or built upon as needed

Answer 35

Liver (and kidney, intestine) glucose 6-phosphatase deficiency Symptoms: - high [liver glycogen] – maintains it’s normal structure - low [blood Glc] – fasting hypoglycaemia - This is because glycogen cannot be used as an energy source – all Glc must come from dietary carbohydrate - high [blood lactate] – lacticacidaemia - Because the lactate produced by skeletal muscle cannot be reconverted to Glc in the liver (this process requires glucose 6-phosphatase – see Cori cycle lectures)

Answer 36

Treatment: - Regular carbohydrate feeding – little and often - Every 3-4 hours throughout the day and night - Can be administered through a nasogastric tube and pump, but sudden death has occurred when the pump fails or the tube disconnects

Answer 37

Skeletal muscle phosphorylase deficiency Symptoms: - High [muscle glycogen] – maintains it’s correct structure - Weakness and cramps after exercise - No increase in [blood glucose] after exercise Most symptoms are not apparent in resting state, when muscles will use other energy sources (Glc and fatty acids from the blood) Usually becomes apparent in 20-30 year olds - Children do suffer the disease but may remember pain during adolescence and childhood

Answer 38

- Avoid strenuous activity - Make use of your “second wind” - Exercise briefly (anaerobically), wait for the pain to subside, continue to exercise (aerobically using oxidative phosphorylation of fatty acids)

Answer 39

- Avoid strenuous activity - Make use of your “second wind” - Exercise briefly (anaerobically), wait for the pain to subside, continue to exercise (aerobically using oxidative phosphorylation of fatty acids)

Answer 40

- evolved before atmospheric O2 was plentiful - occurs in cytosol – no complex organelles required It is therefore important to life and justifiably fills the central role in the metabolic pathways

Answer 41

For 1 Glucose passing through the preparatory phase: - 2 molecules of G-3-P formed to enter the payoff phase For each Glucose, 2 ATP are used in the preparatory phase and 4 ATP gained in the payoff phase Imagine a car – it won’t work even with all of the petrol it contains unless it has a battery (2 ATP’s act as this initial energy to “kick-start” the glycolysis pathway) Thus glycolysis gives a net gain of 2 ATP (and NADH) per Glc molecule

Answer 42

Catalyst – hexokinase Uses 1 ATP ΔG = -16.7 kJ/mol – essentially irreversible

Answer 43

Catalyst – phosphohexose isomerase | ΔG = 1.7 kJ/mol – proceeds either way due to low free energy

Answer 44

Catalyst – hexokinase Uses 1 ATP ΔG = -16.7 kJ/mol – essentially irreversible

Answer 45

Catalyst – phosphohexose isomerase | ΔG = 1.7 kJ/mol – proceeds either way due to low free energy

Answer 46

Catalyst – phosphofructokinase-1 (PFK-1) Uses 1 ATP ΔG = -14.2 kJ/mol – essentially irreversible 1st “committed” step of glycolysis, because G-6-P and F-6-P can be used in other pathways, but F-1,6-bisP is solely destined for glycolysis

Answer 47

Catalyst – fructose 1,6-bisphosphate aldolase (or aldolase for short) ΔG = 23.8 kJ/mol – under cellular conditions the actual free energy change is small so the reaction is readily reversible ``` This is the “splitting” part of glycolysis One Glucose (6 C’s) is converted to two different 3C triose sugars ```

Answer 48

Catalyst – triose phosphate isomerase ΔG = 7.5 kJ/mol – low, so readily reversible reaction Only G-3-P can participate in glycolysis, so the other 3 C sugar produced (dihydroxyacetone phosphate) is rapidly converted to G-3-P, thus yielding two G-3-P molecules for every one Glucose

Answer 49

Catalyst – glyceraldehyde 3-phosphate dehydrogenase *2 NADH’s are produced* ΔG = 6.3 kJ/mol – endergonic, but see later This is the first reaction in the “payoff” phase of glycolysis

Answer 50

"substrate-level” requires soluble enzymes and chemical intermediates, “respiration-linked” involves membrane bound enzymes and gradients of protons

Answer 51

Enzyme – phosphoglycerate kinase *2 ATP’s produced* ΔG = -18.5 kJ/mol – highly exergonic so spontaneous Steps 6 and 7 are an energy-coupled process, so the overall ΔG is -12.2 kJ/mol 1,3-bisPG is the reaction intermediate between this coupled process This is one of the substrate-level phosphorylation reactions in glycolysis (different than respiration-linked phosphorylation – see Citric Acid Cycle lectures)

Answer 52

Catalyst – phosphoglycerate mutase | ΔG = 4.4 kJ/mol – in cells this is even lower, so reaction is reversible

Answer 53

Catalyst – enolase | ΔG = 7.5 kJ/mol – again, in cells this is low, so reversible reaction can occur

Answer 54

Catalyst – pyruvate kinase *2 ATP’s produced* ΔG = -31.4 kJ/mol – highly exergonic, so reaction is spontaneous This final step produces pyruvate

Answer 55

- No NAD+ = no glycolysis - NAD+ limited in the cell – comes from niacin (essential vitamin) - Example opposite is for exercising muscle that produces lactate from the pyruvate, but pyruvate can have other fates - All of these fates will produce NAD+ to replenish the NAD+ required for reduction of various intermediate metabolites - This is termed redox balance

Answer 56

ANSWER: it depends on what you need at any given time The reactions that produce pyruvate from glucose are similar in most organisms What happens to pyruvate next, is variable: - Ethanol - Lactate - CO2

Answer 57

Yeast and several other microorganisms can generate ethanol from pyruvate 2-step process: - Pyruvate decarboxylase - Alcohol dehydrogenase This NAD+ then goes on to be recycled in glycolysis again (redox balance) under anaerobic conditions

Answer 58

In human cells lacking O2 - Vigorously exercising muscle - RBC’s – lack mitochondria (see later lectures as to why mitochondria are important) Pyruvate is reduced to lactate via fermentation Oxidation of NADH drives the reduction of pyruvate to lactate, which in turn replenishes stores of NAD+ for further glycolysis

Answer 59

- When we sprint, muscles don’t receive O2 fast enough to make ATP via oxidative phosphorylation - Instead ATP is made via substrate-level phosphorylation, producing lactate - Lactate is converted to Glucose in the liver by a process called gluconeogensis - The liver repays the oxygen debt run up by the muscles - This interaction between the liver and muscle is called the Cori cycle

Answer 60

- In cells with access to O2 the pyruvate is oxidised to form acetyl coenzyme A (acetyl CoA) - This occurs within the mitochondria of cells - NADH formed in this reaction will later give up it’s hydride ion (:H-) to the respiratory chain.

Answer 61

- Brain - Nervous system - RBC’s - Testes - Embryonic tissues

Answer 62

needs 120 g of sugar a day out of the 160 g for the whole body

Answer 63

Approx. 20 g

Answer 64

190 g can be produced

Answer 65

it can be generated from other non-carbohydrate molecules | Usually occurs in the liver in response to hormonal controls

Answer 66

a reverse of glycolysis

Answer 67

are reversible. | Large –ve ΔG prevents these reactions being reversible

Answer 68

enzymes that catalyse a separate set of irreversible reactions This causes glycolysis and gluconeogenesis to be irreversible processes

Answer 69

(STEP 1) Glucose + ATP ---> Glucose-6-phosphate + ADP (STEP 3) Fructose-6-Phosphate + ATP ---> Frictose-1,6-bisphosphate + ADP (STEP 10) Phosphoenolpyruvate + ADP ---> Pyruvate + ATP

Answer 70

- Independent control of the glycolysis and gluconeogenesis pathways - Prevents them cancelling each other out - Utilise the cytosol (reactions C & D in steps 1 and 2) and also the mitochondria (reactions A & B in step 10)

Answer 71

ATP or Pyruvate the pyruvate gets converted to oxaloacetate and then back into PEP (phosphoenolpyruvate) - happens in the mitochondria

Answer 72

- Pyruvate enters mitochondria from cytoplasm and gets converted into oxaloacetate - Oxaloacetate gets converted into malate - Malate leaves mitochondria and gets converted to oxaloacetate - Oxaloacetate gets converted to PEP (phosphoenolpyruvate)

Answer 73

- pyruvate carboxylase - (m) malate dehydrogenase - (c) malate dehydrogenase - (c) PEP carboxykinase

Answer 74

- Lactate converts NAD+ into NADH to form pyruvate in cytoplasm - Pyruvate enters mitochondria and gets converted into oxaloacetate - Oxaloacetate gets converted into PEP in the Mitochondria - PEP moves into the cytoplasm

Answer 75

- lactate dehydrogenase - pyruvate carboxylase - (m) PEP carboxykinase

Answer 76

- Like the glycolysis reaction (3), it is a control point for gluconeogenesis as it is irreversible under cellular conditions - If it were a direct reversal of the glycolysis reaction, it would require phosphoryl group transfer from F-1,6-bisP to ADP, which is energetically unfavourable - Fructose 1,6-bisphosphatase catalyses

Answer 77

- Third bypass reaction is the final step in gluconeogenesis - Dephosphorylation of G-6-P to glucose - Reversing the 1st glycolysis reaction would require phosphoryl group transfer from G-6-P to ADP, which is energetically unfavourable - This reaction is straight forward hydrolysis of the G-6-P - Glucose 6-phosphatase is the catalyst

Answer 78

in the cytoplasm

Answer 79

- G-6-P, which is usually the end point for gluconeogensis - Ending the pathway here allows the cell to “trap” the glucose - This final step to make free Glc takes place in the lumen of the ER - It requires the G-6-P to be shuttled into the lumen and the Glc to be shuttled back out to the cytoplasm:

Answer 80

Fructose and galactose - Common dietary carbohydrates - The body does not have pathways for catabolism of either of these sugars - Most fructose is metabolised by the liver

Answer 81

- Uses 1 or 2 ATP for each fructose molecule converted - 2 enzymes catalyse the conversion of two glycolysis intermediates - Fructose 1-phosphate aldolase - Triose kinase

Answer 82

uses fructokinase and converts ATP into ADP | - irreversiable

Answer 83

glyceraldehyde and dihydroxyacetonephosphate - fructose-1-phosphate aldolase used - reversible

Answer 84

glyceraldehyde-3-phosphate - usestriose kinase to convert ATP to ADP - irreversiable

Answer 85

- G-1-P through a sugar-nucleotide derivative, UDP-galactose - UDP-glucose and UDP-galactose amounts remain unchanged as they are recycled, therefore the net product of this reaction is G-1-P

Answer 86

Produces NADPH for all organisms - LIVER – fatty acid synthesis, steroid synthesis and drug metabolism - MAMMARY GLAND – fatty acid synthesis - ADRENAL CORTEX – steroid synthesis - RED BLOOD CELLS – as an antioxidant ``` Produces pentoses (5-C sugars) - These are precursors of ATP, RNA and DNA ``` Metabolises the small amount of pentose's in the diet - Usually dietary pentose’s come from digestion of nucleotides

Answer 87

Oxidative, irreversible part - Generates NADPH - Converts G-6-P to a pentose phosphate Reversible, non-oxidative part - Interconverts G-6-P and pentose phosphate to form lots of different 3-, 4-, 5-, 6- and 7-C sugars

Answer 88

catabolic and anabolic pathways

Answer 89

NAD+ - an electron carrier

Answer 90

metabolism of dietary sugars in the redox reactions of glycolysis and the citric acid cycle

Answer 91

anabolism to convert simple precursors into things like fatty acids – NADP+ also acts as an antioxidant

Answer 92

differing specificities for NAD+ and NADP+ (two electron carriers) which stops NADP+ being used for metabolism and vice versa

Answer 93

reduced gluconeogenesis. | NAD+ gets reduced, particularly in the liver

Answer 94

gluconeogenesis. | So drinking inhibits gluconeogenesis

Answer 95

- lacticacidaemia (increased [blood lactate]) - hypoglycaemia (decreased [blood Glc]) And when untreated: confusion → loss of consciousness → death!

Answer 96

athletic dieting a drunken bum

Answer 97

lactate gets converted to pyruvate through NAD+ becoming NADH + H+

Answer 98

G-6-P dehydrogenase deficiency: - Genetic condition affecting 400 million people worldwide 1st step in the irreversible part of the P-P-P is catalysed by the enzyme G-6-P dehydrogenase G-6-P dehydrogenase deficiency causes low RBC NADPH levels This allows damaging free radicals and H2O2 to build up, which damages the RBC membranes The damaged RBC are then unable to suffer the extra trauma of infections, divicine toxin etc. Prevalence of this condition suggests it confers an evolutionary advantage As with sickle cell anaemia, ♀ carriers are resistant to the malaria parasite

Answer 99

Infection Certain antibiotics After eating fava beans (divicine) Haemolytic anaemia – RBC’s burst, which darkens the urine with the iron they contain

Answer 100

lots of PEP in muscle from lactate

Answer 101

- So, lactate → PEP → pyruvate (last step of glycolysis) - Pyruvate can enter the citric acid cycle - Thus, lactate formed in the exercising muscles of PEPCKmus mice ends up in the citric acid cycle, which in turn provides energy for most of the ATP needed for muscle function - This way the mice can keep on going and going and going...

Answer 102

tricarboxylic acid (TCA) cycle

Answer 103

common metabolic pathway for all “fuel” molecules (carbohydrate, fatty acids and amino acids)

Answer 104

mitochondrial matrix

Answer 105

Unlike glycolysis, which yields a small amount of energy (just 2 ATP’s), this cyclic pathway yields much more energy that is then passed on to another biochemical system (the electron transport chain), which produces large amounts of ATP. It also manages to be part of catabolic processes.

Answer 106

The cycle is a “gateway” to the aerobic metabolism of any molecule that can be transformed into an acetyl group or component of the cycle - Cycle does not produce ATP directly - It does not include O2 as a reactant - It removes e-’s and passes them on to form NADH and FADH2 - The cycle in collaboration with oxidative phosphorylation produces 90% of aerobic cell energy - It’s very efficient - Cyclical - Small number of citric acid cycle molecules can make loads of NADH and FADH2

Answer 107

Primitive metabolism is believed to have been similar to glycolysis Glycolysis (or something similar) yields no net oxidation of glucose (remember the NAD+/NADH redox recycling in glycolysis) It therefore can’t yield all of the potential energy that glucose contains, so through fermentations you get small amounts of ATP (only 2 mol ATP per Glc molecule) Thus, primitive organisms evolved ways of saving “some” of Glc’s potential energy

Answer 108

oxidise food molecules (e.g. Glc) further than was previously possible with the glycolysis reaction. This new use of O2 allowed the complete breakdown of high energy food molecules like Glucose. These O2 using organisms therefore had an evolutionary advantage.

Answer 109

- Primitive, anaerobic forms of metabolism are believed to have looked like glycolysis - The last part evolved to re-oxidise the NADH made earlier in the process - when you have O2 (acts as an electron) around, you can skip the last step altogether – NADH can pass it’s H ion through the terminal respiratory system to O2 to be re-oxidised to H2O

Answer 110

harvest electrons that could then be used to completely oxidise food molecules to CO2 and H2O

Answer 111

- Pyruvate from glycolysis and fatty acids are oxidised further to acetyl CoA in the mitochondrial matrix - Acetyl CoA sits in the centre of energy production for the cell as it allows different intermediates into the main energy producing pathway of the citric acid cycle

Answer 112

pyruvate and fatty acids- these get linked to Acetyl CoA in the mitochondria for citric acid cycle

Answer 113

- From pyruvate, through the action of the enzyme pyruvate dehydrogenase - Very complicated series of reactions involving - decarboxylation of the pyruvate molecule - then oxidation - followed by transfer of the CoA complex The decarboxylation step releases two electrons (in the form of 2 H ions), which can pass to O2 to produce more ATP through NADH intermediates

Answer 114

- massive - It contains tens of copies of each enzyme sub-unit (E1, E2, E3) Each sub-unit catalyses a different part of the reaction to convert pyruvate to acetyl CoA

Answer 115

catalyses the first decarboxylation of pyruvate

Answer 116

transfers the acetyl group to coenzyme A

Answer 117

recycles the lipoyllysine through the reduction of FAD, which is recyled by passing electrons to NAD+

Answer 118

So, from either carbohydrates or fatty acids we have ended up with acetyl CoA (C2), which enters the “black box” of the citric acid cycle - It’s a “black box” because the intermediate molecules that make up the cycle remain constant - Each turn, 2C’s enter (acetyl CoA) followed by removal of two different C’s as 2x CO2

Answer 119

oxidative decarboxylation and then removed again in substrate level phosphorylation. α-ketoglutarate dehydrogenase reaction is similar to pyruvate dehydrogenase

Answer 120

``` condensation dehydration hydration oxidative decarboxylation (makes α-ketoglutarate) oxidative decarboxylation substrate level phosphorylation dehhydrogenation hydration (makes malate) dehydrogenation (makes oxaloacetate) ```

Answer 121

the citric acid cycle

Answer 122

controlled. Pyruvate dehydrogenase (PDH) is regulated by it’s immediate products and the end point of cellular respiration, ATP It’s regulated depending on the needs of the cell: - if cell has enough energy acetyl CoA, NADH and ATP send negative feedback to PDH. - if cell needs energy then pyruvate is sent to PDH and ADH goes to PDH

Answer 123

Both points are at non-reversible reactions (exergonic steps) First one – isocitrate dehydrogenase Second one – α-ketoglutarate dehydrogenase These control points allow re-direction of cellular resources

Answer 124

As with pyruvate dehydrogenase, this enzyme is allosterically controlled through ATP and NADH concentrations ATP and NADH will negatively regulate ADP positive regulates

Answer 125

Again, ATP and NADH negatively regulate | Also, succinyl CoA negatively regulates

Answer 126

citrate build up (isocitrate and citrate are interconvertable), which shuttles citrate into the cytoplasm causing phosphofructokinase to stop glycolysis.

Answer 127

α-ketoglutarate dehydrogenase is inactive, which switches it’s use to production of amino acids

Answer 128

amphibolic pathway, as it serves both catabolic and anabolic processes

Answer 129

When cellular energy needs are met through the citric acid cycle, it can produce the building blocks of nucleotide bases, heme groups and proteins One problem: this depletes the cell of citric acid cycle intermediates In exercising muscle the cells require ATP, which depletes the amount of oxaloacetate

Answer 130

when acetyl CoA is present, so a build up of acetly CoA triggers this reaction This is known as an anaplerotic reaction (Greek origin, meaning to “fill up”)