What is the storage form of carbohydrate?
glycogen
Which is bigger, proglycogen or macroglycogen?
macroglycogen
Which form of glycogen is more sensitive to dietary carbohydrate?
proglycogen
Which form of glycogen is synthesized more rapidly following post exercise glycogen depletion?
proglycogen
When does post exercise synthesis of proglycogen reach a plateau?
after 24 hours
Which form of glycogen is synthesized slowly and constantly?
macroglyocgen
When does synthesis of macroglycogen occur?
for at least 48 hours post exercise
Which form of glycogen is responsible for carb loading?
macroglycogen
What is the storage form of glucose in animals?
glycogen
What bonds are most frequent in glycogen?
a1,4
What type of bonds are a1-4 and a1-6 bonds?
glycosidic bonds
What bond forms the branches of glycogen?
a1,6 bonds
How many bonds in glycogen are a1-6?
1 out of about 10
What is the purpose of branching in glycogen?
increases solubility and gives it more accessible surface area to “eat”
What is the first carbon in D-Glucose?
the one double bonded to O and single bonded to one H
What is the first carbon in a-D-Glucopyranose?
to the right and down to the O
Where does an a1-4 bond take place?
between the 1 carbon of a glucose and the 4 carbon of another
What are the two types of starch?
amylose and amylopectin
Is amylose branched or unbranched?
unbranched
What bond takes place in amylose?
a1-4
Is amylopectin branched or unbranched?
branched
What bonds take place in amylopectin?
a1-4 and a1-6
How often do we see an a1-6 bond in amylopectin?
every 30 a1-4 bonds
How much glycogen is stored in skeletal muscle?
400 grams
How much glycogen is stored in the liver?
100 grams
How much glycogen is stored in other cells?
small quantities
Where is glycogen stored in the cell?
cytosol
Why is glucose trapped in muscle?
it lacks the enzyme needed to release glucose
How much glucose is not fully accessible during exercise?
about 1600 kcal
What is the first step of glycogen synthesis initiation?
glucose is turned into glucose-6 phosphate
What is the second step of glycogen synthesis initiation?
glucose-6 phosphate is converted into glucose 1 phosphate
What is the third step of glycogen synthesis initiation?
glucose-1 phosphate is combined with UTP, forming UDP Glucose
What is used to initiate a chain of glycogen?
glycogenin
What is glycogenin?
a protein that starts the glycogen chain with the amino acid tyrosine
What enzyme initiates a glycogen chain?
glycogen initiator synthase
What enzyme adds glucose moleules to a glycogen chain?
glycogen synthase
What bond does glycogen synthase use to add a glucose molecule to a glycogen chain?
a1-4
Where does elongation of the glycogen chain take place?
cytosol
What enzyme is used in glycogen branching?
glucosyl 4:6 transferase
How does glucosyl 4:6 transferase work?
takes 5-8 carbon chains from the end and attaches them to another glucose molecule in the chain
What bond does glucosyl 4:6 transferase use?
a1-6
What are the advantages of branching in glycogen?
many ends, increases rates of synthesis and degradation, more soluble molecule
What enzyme degrades glycogen?
glycogen phosphorylase
What is the product of glycogen phosphorylase?
Glucose 1 phosphate
What enzyme converts glucose 1 phosphate to glucose 6 phosphate?
phosphoglucomate
Where does the glucose 6 phosphate from glycogen degradation go?
glycolysis and pentose phosphate pathway
What is the regulatory enzyme in glycolysis?
phosphofructokinase
When does glycogen phosphorylase become ineffective?
when there are four glucose molecules left prior to a branch point
What two enzymes are required to break down the end of the branches of glycogen?
glucosyl 4:4 transferase and amylo-a-1,6-glucosidase
What is the function of glucosyl 4:4 transferase?
removes the three glucose molecule prior to the last glucose of the branch
What is the function of amylo-a-1,6-glucosidase?
removes the last glucose of the branch
Why is calcium important for glycolysis?
calcium’s presence indicates muscle activity and a need to have glucose for glycolysis
What is the key enzyme responsible for the synthesis of glycogen?
glycogen synthase
Where is glycogen synthase bound?
to part of the glycogen protein complex
How is glycogen synthase released?
it is bound to part of the glycogen protein complex, when glycogen concentration decreases, it is released
What is gluconeogenesis?
synthesis of glucose from non-carbohydrate precursors
What is the pathway of gluconeogenesis?
pyruvate to glucose
What are the main entry points of gluconeogenesis?
pyruvate, oxaloacetate, and DHAP
What are the main non-carbohydrate precursors of gluconeogenesis?
lactic acid, amino acids, and glycerol
What parts of the body require glucose?
brain, red blood cells, testes, medulla of the kidney, cornea of the eye, and muscle
Can we reverse glycolysis?
no, energetically unfavorable
Where does gluconeogenesis take place?
liver and kidney
What % of gluconeogenesis takes place in the liver?
90%
What % of gluconeogenesis takes place in the kidney?
10%
What is needed to make gluconeogenesis favorable?
use alternative enzymes, couple the reactions to energy liberating reactions, and use ATP or the equivalent
What are the enzymes responsible for the irreversible reactions of glycolysis?
hexokinase, phosphofructokinase, and pyruvate kinase
Where do we find pyruvate carboxylase?
in the mitochondria of liver and kidney
What are the substrates of gluconeogenesis?
glycerol, lactic acid, and a-ketoacids
What is glycerol?
the backbone of triglycerides
What is lactic acid?
waste product of glycolysis
What are a-ketoacids?
pyruvate, OAA,a-keoglutarate
Where are a-keto-acids derived from?
glycogenic amino acids
What is the direct precursor to PEP?
OAA
Is glycerol fat?
no
Can glycerol be converted into glucose?
yes
Is glycerol a major source of making glucose?
no
What is a significant substrate for gluconeogenesis during exercise?
lactate
Where is lactate released from?
working muscle
What organ takes lactic acid to create glucose?
the liver
What is the Cori Cycle?
The muscle takes Glucose 6 Phosphate ->pyruvate ->lactate, which goes to the liver, -> pyruvate -> glucose, which goes to the blood stream
Does exercise raise or lower blood glucose?
lowers
What stimulates gluconeogenesis in the liver?
glucagon
Where is the carbonyl group on an alpha ketoacid?
alpha carbon
What are alpha ketoacids usually created from?
amino acids
What stimulates the conversion of amino acids into glucose?
starvation or low carb intake
Before an amino acids becomes glucose, what does it become first?
alpha ketoacid
What is the primary source of glucose from gluconeogenesis when at rest?
alpha ketoacids
Where do most alpha ketoacids come from?
the breakdown of amino acids
What are the non-essential glucogenic amino acids?
alanine, asparagine, aspartate, cysteine, glutamate, glutamine, glycine, proline, serine, tyrosine
What are the essential glucogenic amino acids?
arginine, histidine, isoleucine, methionine, phenylalanine, threonine, valine, tryptophan
What is the glucose-alanine cycle?
(in muscle) glycogen -> glucose 6 phosphate -> pyruvate -> (amino acids in, keto acids out) -> alanine (to the liver) -> pyruvate (NH3 ->Urea) -> glucose (to the blood stream)
When does the glucose alanine cycle take place?
primarily during exercise, when glycolysis is running fast
What is the difference between alanine and pyruvate?
the NH3 from alanine is removed and replaced by =O
What is ketosis usually in response to?
gluconeogenesis
What is ketosis?
an elevation in ketones in blood and urine
What can ketones be made into when oxidized?
ATP
What are ketones primarily created from?
fat
What does ketosis spare?
amino acids
What are some examples of common ketones?
acetoacetate, beta hydroxybutyrate, and acetone
What make ketone bodies?
acetyl CoA or things that can turn into acetyl CoA
What turns into acetyl CoA?
fat (through OHOT)
Can acetyl CoA turn into glucose?
no
What is the entry point into the Kreb’s cycle?
acetyl-CoA
Is fat burning increased or decreased in response to low carbohydrate?
increase
In ketosis, does the body use the ketones or glucose?
ketones
What diminishes gluconeogenesis?
ketosis
Where is insulin found?
beta cells of the pancreas
What does insulin do?
lowers blood sugar and stimulates glycogen formation
Does insulin inhibit or stimulate gluconeogenesis?
inhibits
Where is glucagon found?
alpha cells of the pancreas
What does glucagon do?
elevates blood sugar and stimulates glycogen breakdown
Does glucagon inhibit or stimulate gluconeogenesis?
stimulates
What is the cheerleader for glycolysis?
fructose 2,6 - bisphosphate
What does fructose 2,6-bisphosphate activate?
PFK in the liver
What does PFK in the liver do?
increases affinity for fructose 6 phosphate, decreases the inhibiting effect of ATP, and is an allosteric activator
Does eating fat stimulate fat synthesis?
no
What stimulates fat synthesis?
eating lots of sugar
What transport protein take glucose, fructose and galactose from the intestine to the liver?
GLUT2
Which transport protein in insulin dependent?
GLUT2
What transport protein takes glucose into muscle and adipose tissue?
GLUT4
Is GLUT4 stimulated by insulin?
yes
What transport protein is stimulated by low energy charge?
GLUT4
What transport protein moves via facilitated diffusion?
GLUT4
What does it take for glucose to move from the blood to the muscle?
for the concentration of glucose to be lower in the muscle
What keeps glucose flowing into the muscle?
adding a phosphate to glucose in the muscle
When muscle glycogen is low, what gets converted to glycogen?
glucose 6 phosphate
Where does glucose go when muscle glucose and glycogen is full?
liver
Is glucokinase inhibited by its product?
no
What stimulates glucokinase?
stimulated by insulin
Where does synthesis of fatty acids take place?
liver, adipose tissue and kidney (to a lesser extent), mammary glands during lactation
Where does synthesis of fatty acid occur in the cells?
cytosol
What is the mechanism for the building of fatty acids?
incorporation of 2 carbon molecules (acetyl), NADPH provides reducing power, ATP is consumed
What two molecules are needed to start the process of fatty acid synthesis?
acetyl CoA (2 Cs), malonyl CoA (3 Cs)
What is malonyl made from?
acetyl
Where do acetyl and malonyl need to be for fatty acid synthesis?
cytosol
What are the 3 parts of the mechanism of fatty acid synthesis?
get acetyl to cytosol, make malonyl CoA, build the fatty acid (fatty acid synthase, CRDR)
What makes acetyl CoA?
oxidation of pyruvate
Where does oxidation of pyruvate take place?
mitochondria
When does oxidation of pyruvate take place?
when citrate levels are high
When do citrate levels elevate?
when Isocitrate Dehydrogenase is inhibited
What inhibits Isocitrate Dehydrogenase?
high levels of ATP
What does fatty acid synthesis require?
high ATP
What stimulates Acetyl CoA carboxylase?
citrate and insulin
What inhibits Acetyl CoA carboxylase?
malonyl CoA, Palmitol CoA (end product), and epinephrine
What is Acetyl CoA Carboxylase?
a protein
What increases the synthesis of Acetyl CoA Carboxylase?
High carb diets, low fat diets
What decreases the synthesis of Acetyl CoA Carboxylase?
high fat diets, fasting
What is fatty acid synthase?
a multienzyme complex
What is ACP?
Acyl Carrier Protein
What are the seven steps of ACP?
ACP grabs acetyl, ACP transfers acetyl to a holding site, ACP grabs malonyl, acetyl and malonyl combine (decarboxylation, 2+3=4), Ketone is converted into an alcohol (NADPH reduction), water is removed (double bond), molecule is reduced (NADPH)
Where does the growth on ACP stop?
16 carbons (Palmitate 16:0)
What are the four reactions of fatty acid synthase?
CRDR - condenses(+2C), reduces(NADPH), dehydrates, and reduces(NADPH)
Where is NADPH created?
pentose phosphate pathway
What is the source of reducing power in synthesis?
NADPH
What molecules are highly reduced?
fatty acids
What can palmitate be?
elongated and desaturated
What enzymes elongate?
elongases
What enzymes desaturate?
desaturases
Where do elongation and desaturation take place?
mitochondria and endoplasmic reticulum
At what carbon can humans not create a double bond?
beyond the 9th-10th
What are the important steps to fat synthesis?
eat sugar, rest, muscle hexokinase is inhibited by glucose 6 phosphate, liver glucokinase is stimulated by glucose and not inhibited by glucose 6 phosphate, liver runs glycolysis, ATP inhibits isocitrate dehydrogenase and stops TCA, citrate spills out and acetyl CoA is given back, Acetyl CoA into Malonyl CoA, fatty acid synthase adds malonyl CoAs(CRDR), Palmitate 16:0
What is the primary site of fructose disposal?
liver
What % of fructose is extracted by the liver on the first pass?
50%
What % fructose is extracted by the liver?
75%
What enzymes are essential for fructose metabolism in the liver?
fructokinase and triokinase
What does fructose skip?
the regulation of PFK
What conditions stimulate fatty acid synthesis?
high energy charge, lots of acetyl CoA, lots of NADH and FADH2, lots of citrate, lots of sugar (glucose and fructose), insulin
What are the key enzymes of fatty acid synthesis?
citrate lyase, acetyl CoA carboxylase, and fatty acid synthase (CRDR)
What is the product of the condensation step?
acetoactyl-ACP
What is the product of the 1st reduction step?
D-3-hydroxybutyryl-ACP
What is the product of the dehydration step?
crotonyl-ACP
What is the product of the 2nd reduction step?
butyryl-ACP