Test 3 Flashcards
(139 cards)
1
Q
Which general formula do carbohydrates derive their name from?
A
Cn(H2O)n
2
Q
What functions do carbohydrates have?
A
- Nutritional
- Structural
- Informational
- Osmotic pressure regulation
3
Q
Carbohydrate chemical characterization
A
- Poly hydroxy aldehydes
- Poly hydroxy ketones
Sugars with an aldehyde group are called aldoses
Sugars with a keto group are called ketoses
4
Q
Classification of carbohydrates
A
- Monosaccharides - one unit of carbohydrate
- Disaccharides - two units of carbohydrates
- Oligossacharides or Polysaccharides - multiple units of carbohydrates
5
Q
What are enantiomers?
A
Pairs of stereoisomers.
Basically, mirror images that can’t be overlapped.
Assigned the letter D or L at the start of their name
6
Q
What are D vs L designations based on?
A
Based on where the OH-group is. If its on the Left its an L- and if its on the right its a D-.
For sugars you look at c farthest from the aldehyde or keto group
7
Q
Important monosaccharides (according to the presentation)
A
- D-glyceraldehyde - simplest sugar
- D-glucose - most important in diet
- D-fructose - sweetest of all sugars
- D-galactose - part of milk sugar
- D-ribose - used in RNA
8
Q
Hemiacetal vs hemiketal
A
Hemiacetal - forms from alcohol and aldehyde
Hemiketal - forms from alcohol and ketone
9
Q
Carbohydrates in cyclic structures, a and b anomers.
A
a - when OH group is down compared to CH2OH (trans)
b - when OH group is up compared to CH2OH (cis)
10
Q
Glycosidic bonds
A
11
Q
Polysaccharides types and functions
A
Types:
- Homopolysaccharides - all 1 type of monomer e.g. glycogen, starch…
- Heteropolysaccharides - different types of monomers - e.g. peptidoglycans…
Functions:
- glucose storage
- structure
- information
- osmotic regulation
12
Q
Polysaccharide - glycogen
A
- like amylopectin but even more highly branched and more compact
- branches increase H2O-solubility
- many nonreducing ends, but only one reducing end
- ideal energy storage for glucose
- can become so concentrated that it precipitates or crystallizes into glycogen granules
13
Q
Polysaccharide - cellulose
A
- most abundant polysaccharide
- result in long fibers - for plant structure
- animals can’t digest it, except ruminats and termites that have bacteria in their intestines that can digest it.
- humans don’t digest it, and its often called “fiber”. It has no caloric value.
14
Q
What is the result of glycolysis?
A
2 pyruvate, 2 ATP and 2 NADH
15
Q
How many enzyme catalyzed reactions are there in glycolysis?
A
there are 10 enzyme - catalyzed reactions in glycolysis
(optional)
1. Hexokinase transfers a phosphate group from ATP to glucose, making it more chemically reactive.
-> making Glucose-6-phosphate
- irreversible
- Glucose-6-phosphate (aldose) is converted to
fructose 6-phosphate (ketose) by phosphohexose isomerase
- reversible
–> this step is critical for the next two.
- Phosphofructokinase (PFK-1) transfers a phosphate group from ATP to fructose-6-phosphate to yield
fructose-1,6-bisphosphate
-key step for regulation in glycolysis
(PFK-1 is an allosteric enzyme)
- irreversible
- Aldolase cleaves the sugar molecule into two different triose phosphates;
- glyceraldehyde-3-phosphate (aldose)
-Dihydroxyacetonephosphate (ketose)
- reversible
- Triose phosphate isomerase converts the ketose from last step into the Aldose (glyceraldehyde-3-phosphate)
-reversible
- Beginning of payoff phase:
Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) oxidise glyceraldehyde-3-phosphate to
1,3-bisphosphoglycerate (very high energy)+ NADH
-reversible
- ATP is generated by substrate level phosphorylation, transferring phosphate group from 1,3-bisphosphoglycerate, making it 3-phosphoglycerate
-reversible, but mostly to the right
- Phosphoglycerate mutase relocates the remaining phosphate group from C3 to C2, making it
2-Phosphoglycerate
-reversible
- important intermediate is generated; 2,3-BPG
= the major allosteric regulator of haemoglobin
- Enolase causes a double bond to form in the substrate by extracting a water molecule, yielding Phosphoenolpyruvate (PEP), a compound with a very high potential energy
-reversible
- Pyruvate kinase transfer the phosphate group from PEP to ADP forming pryuvate
- requires K+ and either Mg2+ or Mn2+
- irreversible
16
Q
Two stages of glycolysis
A
- Energy investment phase (preparatory)
- glucose molecule is inside cell, and must be kept there. –> produce glucose-phosphate, to destabilise the glucose and then split it
- Energy payoff phase
- oxidise the split molecule, generating ATP and NADH
17
Q
Regulation of glycolysis can occur via
A
a substrate limited - when concentrations of reactant and products in the cell are near equilibrium, then it is the availability of substrate which decides the rate of reaction
a enzyme limited - when the concentration of substrate and products are far away from the equilibrium, then it is activity of an enzyme that decides the rate of reaction. these reactions are the one which controls the flux of the overall pathway.
18
Q
Where does the glucogenesis occur?
A
Mainly in the liver, more limited in the kidney and small intestine under some conditions.
19
Q
The three irreversible steps that glucogenesis has to bypass
A
- Hexokianse
- Phosphofructokinase
- Pyruvate kinase
20
Q
The energy expense of gluconeogenesis
A
for 1 glucose produced:
4ATP + 2GTP + 2NADH
21
Q
Phosphorylation of enzymes and regulatory proteins in the liver by protein kinase A results in..?
A
- inhibition of glycolysis
- stimulation of gluconeogenesis
- making glucose available for release to the blood
22
Q
Enzymes that are phosphorylated by protein kinase A…
A
- Pyruvate kinase
- CREB
- Fructose-2,6-biphosphate
23
Q
Transport of Mitochondrial Matrix
A
24
Q
What is a Lipid?
A
Biological molecule that is insoluble in aqueous solutions and soluble in organic sollvents. Have relations to fatty acids as esters. Potentiality of utilization by living organisms.
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1. What is required for the activation of a
fatty acid?
2. What does one cycle of oxidation of a
fatty acid produce?
3. What does Acetyl CoA produce when
entering the cytric acid cycle?
1. 2 ATP
2. 1 NADH = 3 ATP
1 FADH2 = 2 ATP
3. 12 ATP
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Name 4 physiological functions of Lipids
1. They serve as structural components of
biological membranes
2. Provide energy reserves, predominantly in
the form of triacylglycerols
3. Both lipids and lipid derivatives serve as
vitamins and hormones
4. Lipophilic bile acids aid in lipids
solubilization
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Where are Ketone bodies formed?
Ketogenisis in the Mitochondria
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4 classes of Lipids
1 Simple lipids
2 Compound lipids
3 Derived lipids
4 Miscellaneous lipids
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How does Ketosis occur?
Concentration of acetoacetate is very high and supply of oxaloacetate ( OAA - a TCA component) is insufficient, so acetoacetate is spontaneously decarboxylated to acetone
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Types of Simple Lipids
1 Natural fats and oils (triglycerides)
2. Waxes
(a) True waxes: cetyl alcohol esters of fatty
acids
(b) Cholesterol esters
(c) Vitamin A esters
(d) Vitamin D esters
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Types of Compound Lipids
1. Phospholipids and spingomyelin
2. Sphingolipids (also include glycolipids and
cerebrosides)
3. Sulfolipids
4. Lipoproteins
5. Lipopolysaccharides
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Types of derived lipids
1. Saturated & unsaturated fatty acids
2. Monoglycerides and diglycerides
3. Alcohols (b-carotenoid ring, e.g., vitamin A,
certain carotenoids)
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Types of Miscellaneous Lipids
1. Aliphatic hydrocarbons
2. Carotenoids
3. Squalene:
4. Vitamin E and K
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Fatty acids
Carbon atoms -
Saturated = only single bonds
Unsaturated = has double bonds
Essential fatty acids -
Cannot be synthesized by body
Must originate from Dietary source
Polyunsaturated fatty acids (linoleic,
linoleinic arachidonic)
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Activation of Fatty acids
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Signifigance of ketogenesis and ketogenolysis
1. Early stages of fasting, the use of ketone bodies by heart, and skeletal
muscle conserves glucose for support of the central nervous system. With more
prolonged starvation, the brain can take up more ketone bodies to spare glucose
consumption
2. High concentration of ketone bodies can induce ketonemia and ketonuria, and
even ketosis and acidosis
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Fatty acid Synthesis
Synthesized and degraded by different pathways
– from acetyl CoA
– in the cytosol
– intermediates are attached to the acyl
carrier protein (ACP)
– the activated donor is malonyl–ACP
– reduction uses NADPH + H+
– stops at C16 (palmitic acid)
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Reactions in Fatty acid reduction
1 Condensation - synthase combines
acetyl-ACP with malonyl-ACP to form
acetoacetyl-ACP (4C) and CO2
2 Reduction - converts a ketone to an
alcohol using NADPH
3 Dehydration - a trans
double bond is formed
4 Reduction - converts the double
bond to a single bond using
NADPH
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When is Fatty acid synthesis complete?
When palmitoyl ACP reacts with water to give palmitate and free ACP
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Types of polysaccharides
Homopolysaccharides
E.g. glycogen
heteropolysaccharides
E.g. peptidoglycans
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Functions of polysaccharide s
Glucose storage
Osmotic pressure
Information
Structure
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What is glycogen
Branched polymer of a 1->4 with glucose residues with 1->6 branches
Like amylopectin but highly branched
Branches increase H20 solubility
Many nonreducing ends but only 1 reducing end
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Glycogenolysis what is it
Breakdown of glucose to glycogen
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Where is glycogen stored and why
In the liver:The synthesis and breakdown are regulated to maintain blood glucose levels
In muscles:The synthesis and breakdown are regulated to meet the energy requirements of the muscle cell
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Glycogenylosis step 1
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Other facts about glycogenylosis step 1 reaction
It’s reversible
No investment of ATP needed and can enter glycolysis directly
The phosphorylated product (glucose 1-phosphate) can’t leave the cell
47
What is pyridoxal phosphate (prp)
A coenzyme that’s a derivative of pyridixine (vitamin B6).Vitamin B6 is required for the mobilization of glucose from glycogen
48
What happens during glycogenolysis
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What is the main product of glycogen breakdown
Glucose 1 phosphate
50
What happens during glycogenesis explained using words instead of the graph
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Epinephrine and glucagon stimulate.What are their functions
Muscles responsive to epinephrine and liver responsive to glucagon.Both signal a cascade of events leading to glycogen breakdown
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Fates of glucose 6 phosphate
53
The liver contains glucose 6 phosphatase.The muscles don’t.Why?
Liver releases blood to be used up by the brain and muscles so it helps regulate glucose levels
The muscles retain glucose 6 phosphate for energy.Phosphorylated glucose not transported out of muscle cells
54
glycogen n + udp glucose=what in glycogenesis synthesis
glycogen n+1 + udp glucose
55
glycogen n + PI=what
glycogen n-1 + glucose 1 phosphate
56
Glucose 1-phosphate + UTP + H2O
UDP-glucose + 2Pi
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udp glucose and glycogen n becomes what
utp glucose and glycogen n+1
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what dooes the a 1,4 link become
a 1,6 link
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what is the regulatory enzyme and whats it regulated by.what happens in this process
glycogen synthase and phosphorylation.in it active a form converted to inactive b form
60
what regulates blood glucose levels and increases them
glycogen metabolism in the liver.this increases when carbs are eaten
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when does pp1 work best
when phosphorylase a is in the t state
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list of reactions for glycogenolysis
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what happens in the pentose phosphate pathway
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functions of the pentose phosphate pathway
NADPH production( reducing power carrier and role as cellular oxidants) and ribose synthesis( nucleic acids and nucleotides)
65
Demand for NADPH
biosynthetic pathways and detoxification
66
what are the 2 phases of the pentose pathway
67
describe the oxidative and nonoxidative pathways of the pentose pathway
oxidative produces nadph and is irreversible
non oxidative produces ribose 5 and is irreversible
68
describe the whole process of the oxidative stage of the phosphate pentose pathway
69
regulation of pentose phosphate pathway
glucose 6 phosphate is the enzyme.nadph is the inhibitor.however more demand for nadph increases enzyme activity
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pentose phosphate pathway regulation
1. Rapidly dividing cells require more ribose 5 phosphate than nadph
2.The need for nadph and ribose 5 phosphate is balanced
3.More nadph needed than ribose 5 phosphate.Fatty acid synthesis in adipose tissues
4.Cell needs both nadph and atp
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lactose synthesis (what is it).
lactose is synthesised by lactose synthase.enzyme is made of 2 proteins a and b.a is galactosyltransferase and found in many body tissues.b is a lactalbumin and b and a form a complex so lactose is formed
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function of the rumen
break down cellulose.Creates loss of gases (methane) and ruminants have to eructate (belch)
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animals with a rumen
cattle, sheep, goats, deer
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how do horses process grass without a rumen
They have a cecum (4 feet), large colon (10-12 feet), small colon (10-12 feet) and rectum (1 foot).Horses use microorganisms rather than enzymes for breaking down food
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cellulolytic bacteria
Produces cellulase -cleaves B1-4 linkages.Substrates are cellulose and hemicellulose.Best ph is 6-7.The microbes break down polysaccharides and sugars to produce vfa
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What is the Cori cycle.
A cycle thats costs 6p for every 2p made.Overall cost is 4p
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what regulates glucose levels when they are too high
pp1 which stimulates glycogen synthesis
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Complex lipids make up...
Membranes
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Lipid layers line up with..
Aliphatic tails inward
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Glycerophospholipids
- Glycerol is the alcohol
- Two are fatty acids
- Third is esterified to PO4^3- and choline
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Phosphotidylcholines
- also called "lecithins"
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Phosphatidylinositols (PI)
- Alcohol is inositol
- Serve as signaling or communication sites
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Cephalins
- another type of glycerophospholipds
- alcohol is ethanolamine or serine instead of choline
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Sphingolipids
- coating of nerve axons (myelin)
- alcohol portion is sphingosine (not glycerol)
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glycolipids
- contain carbohydrates
- also use sphingosine
- one type is cerebrosides
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Steroids
- a third major class of lipids
- they are all based on this structure
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Cholesterol
- most abundant steroid in the body
- cell membrane component
- raw material for steroids synthesis
- It exists in both free and esterified forms
- Esterifies with FA
- Necessary for human life
- Manufactured in the liver - body keeps a set amount
87
Lipoproteins
- classified by density
-- protein: lipid ratio
---> more protein, increased density
---> more lipid, decreased density
- transport cholesterol and fats
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The four classes of lipoproteins and where they are made
Four classes of lipoproteins:
- Chylomicrons
- VLDL - very low density lipoproteins
- LDL - low density lipoproteins (not good kind)
- HDL - high density lipoproteins (good kind)
They are made in the liver
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Typical values for cholesterol, HDL and LDL
Cholesterol:
- female: 157 - 167
- males: 150 - 174
HDL:
- females: 52 - 55
- males: 45
LDL:
- females: 100 - 106
- males: 97 - 116
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Lipoprotein lipase (LPL)
- enzymes anchored on the cell membranes in blood vessels
- releases glyceron and free fatty acids from chylomicrons and lipoproteins
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Triglycerides
- neutral fats
- made of 3 fatty acids and 1 glycerol
- 95% of dietary lipids (fats and oils)
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How much kcal/g does complete oxidation of fatty acids yield? And how much do proteins and carbohydrates yield?
Complete oxidation: 9 kCal/g
Proteins and carbohydrates: 4 kCal/g
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Where do triaclyglycerols accumulate in mammals?
Mainly in the cytoplasm of adipose cells (fat cells).
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Triglyceride metabolism
- key concept - absorption
- triglyceride assimilation is key to the survival of the organism
- Dietary triglyceride must be hydrolyzed to fatty acids, monoglycerides, and glycerol before absorption
- Fatty acids must partition to the micellar phase for absorbtion
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Eicosanoids
Large group of autocoids with potents effects
Derived from metabolism of 20 carbon unsaturated fatty acids
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Lipolysis - monogastric and ruminant
- hydrolysis of triaclyglycerols by lipases
- mobilization of body triglycerides for use as energy
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Eicosanoids groups
1. The prostaglanids
2. Thromboxanes
3. Leukotrienes
4. HPETE (Hydroperoxyeicosatetraenoic
acids)
5.HETE (Hydroxyeicosatetraenoic acids)
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Triglyceride catabolism
- Hydrolysis of triglycerides yields
-- one glycerol
-- Three FFA
- glycerol is used for energy or gluconeogenesis
-- glyceron enters glycolytic pathways
- FFA are oxidized to CO2 and H2O
-- B-oxidation
-- takes place in mitochondria
-- FA's cannot be used for gluconeogenesis
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Eiscanoid hormones
Top left - Prostaglandin A2
Top right - Prostacylin (PGI2)
Bottom left - Thromboxane A2 (TXA2)
Bottom right - Leukotreine B4
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Adipocytes are...
the major storage site for triglycerides
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Pathways of arachidonic acid in biosynthesis
1. Phospholipase A2-mediated production from membrane phospholipids. Pathway is inhibited by glucocorticoids.
2. Phospholipase C
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Adipose tissue contains..
up to approximately 85% lipid
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Eicosinoid Pathway 1.
Produce of prostaglandin H synthase
(COX, cyclooxygenase) pathway
1. Thromboxane
2. prostaglandin E/PGE
prostaglandin F/PGF
prostaglandin D/PGD
3. Prostacylin (PGI2)
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Leptin
- protein hormone produced by adipocytes
-- larger cells = more leptin produced
- effects on many tissues
-- hypothalamus
---> regulates eating behavior
---> negative-feedback mechanism
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Eicosinoid Pathway 2.
Produce of lipoxygenase pathway
1.HPETEs
2.HETEs
3.leukotrienes
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Biosynthesis of triacylglycerols main pathways
Three main pathways for triacylglycerol biosynthesis are known:
- sn-glycerol-3-phosphate
- Dihydroxyacetone phosphate pathways
- Monoacylgycerol pathway
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Eicosanoid Hormones
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Flipases, EC and IC
- Selective translocation of PC to the ER lumen occurs. This becomes the plasma membrane
EC - rich in PC and SPH
IC - rich in PE and PS
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How is HMG-CoA reductase controlled in transcription, translation and posttranslational modifications?
Transcription - mRNA synthesis is inhibited by food cholesterol
Translation - HMG-CoA reductase synthesis is inhibited by non-ster derivatives of mevalonic acid
Posttranslational modification - increased level of cholesterol and/or mevalonic acid stimulates phosphorylation of HMG-CoA reductase --> enhancing degradation by proteases
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Biological significance of cholesterol
- an essential lipid constituent of cell membranes
- a precursor of steroid hormones and of bile acids
- intermediates of cholesterol biosynthesis are required to make vitamin D and for posttranslational modification of membrane proteins
- high plasma cholesterol promotes atherosclerosis
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Formation of Δ3 -Isopentenyl pyrophosphate
First its Melalonate, then with the help of mevalonate kinase and phosphomevalonate kinase it becomes 5-pyrophosphomevalonate. This with the help of pyrophosphomevalonate decarboxylase further becomes Δ3 -Isopentenyl pyrophosphate.
103
Processes that determine the cholesterol balance
- intestinal uptake of dietary cholesterol
- de novo cholesterol synthesis
- synthesis of steroid hormones from cholesterol
- synthesis of bile acids from cholesterol, and their billary secretion
- bilary secretion of surpus cholesterol in unmodified form
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Formation of dimethylallyl pyrophosphate
Isopentenyl pyrophosphate becomes dimethylallyl pyrophosphate with the help of isomerase
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De novo synthesis of cholesterol, where is it? what is the equation?
Primary site: liver
Secondary sites: adrenal cortex, ovaries, testes
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Synthesis of farnesyl pyrophosphate
Geranyl pyrophosphate becomes Farnesyl pyrophosphate with the help of geranyltransferase
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Major roles of complex lipids
1. energy
2. membranes
3. hormones
4. cell-signaling
105
Lanosterol formation
2x farnesyl pyrophosphate becomes squalene with the help of squalene synthase. Squalene goes through cyclization and becomes lanosterol
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What in the liver parenchymal cell is involved in the synthesis of ketone bodies?
Mitochondrial HMG-CoA synthase
106
How many steps does the conversion of lanosterol to cholesterol require?
It requires 19 separate steps
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Conversion of HMG CoA to activated isoprenoids
HMG CoA reductase catalyzes mevalonic acid
Reaction catalyzed by the enzyme is the rate-limiting reaction.
The enzyme is the target of statins which inhibit the activity of HMG-CoA reductase.
(the statins can decrease total plasma cholesterol and LDL-cholesterol even by 50%)
107
De novo synthesis of cholesterol in short:
Stage 1: Forms HMG CoA
Stage 2: Forms activated 5 carbon intermediates (isoprenoids)
Stage 3: Six isoprenoids form squalene
Stage 4: Squalene + O2 form cholesterol
108
What is energy dissipation in the liver thought to contribute to
The 6p expended for every 2p produced causes weight loss
108
Fasting vs feeding cholesterol synthesis
Feeding promotes cholesterol synthesis
Fasting inhibits cholesterol synthesis
109
Regulation of Acetyl-CoA carboxylase
Global vs Local
Global:
+ insulin
- glucagon
- epinephrine
Local:
+ citrate
-Palmitoyl-CoA
-AMP
109
Types of bile acids/salts
Primary bile acids
- good emulsifying agent
- all OH on the same side
- pKa = 6
Conjugated bile salts
- amide bonds of glycine or taurine
- very good emulsifier
- pKa lower than bile acids
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Synthesis of bile salts
- Hydroxylation
- side chain cleavage
- conjugation
- secondary bile acids
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LDL receptor deficiency
- gene for LDL is on chromosome 19
- no gender difference
- Mutation is recessive
- 420 different mutations identified (dominant trait)
- activity 0 - 25% of normal
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Heterozygous FH vs Homozygous FH
Heterozygous FH:
- 1/500
- Hypercholesterolemia
Homozygous FH:
- 1/1 000 000
- Extremely high LDL - cholesterol
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Types of steroid hormones
* Glucocorticoids; cortisol is the major representative in most mammals
* Mineralocorticoids; aldosterone being the most prominent
* Androgens such as testosterone
* Estrogens, including estradiol and estrone
* Progestogens (also known as progestins) such as progesterone
113
Steroid hormones are derived from...
Cholesterol
114
Two important facts about steroid hormones
They are freely permeable to membranes so they are not stored in cells
They are not water soluble so they have to be carried in the blood complexed to specific binding globulins
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Functions of steroid hormones
- carbohydrate regulation (glucocorticoids)
- mineral balance (mineralocorticoids)
- reproductive functions (gonadal steroids)
also play roles in inflammatory responses, stress responses, bone
metabolism, cardiovascular fitness, behavior, cognition, and mood.
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