Test 3 Flashcards
Which general formula do carbohydrates derive their name from?
Cn(H2O)n
What functions do carbohydrates have?
- Nutritional
- Structural
- Informational
- Osmotic pressure regulation
Carbohydrate chemical characterization
- Poly hydroxy aldehydes
- Poly hydroxy ketones
Sugars with an aldehyde group are called aldoses
Sugars with a keto group are called ketoses
Classification of carbohydrates
- Monosaccharides - one unit of carbohydrate
- Disaccharides - two units of carbohydrates
- Oligossacharides or Polysaccharides - multiple units of carbohydrates
What are enantiomers?
Pairs of stereoisomers.
Basically, mirror images that can’t be overlapped.
Assigned the letter D or L at the start of their name
What are D vs L designations based on?
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
Important monosaccharides (according to the presentation)
- 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
Hemiacetal vs hemiketal
Hemiacetal - forms from alcohol and aldehyde
Hemiketal - forms from alcohol and ketone
Carbohydrates in cyclic structures, a and b anomers.
a - when OH group is down compared to CH2OH (trans)
b - when OH group is up compared to CH2OH (cis)
Glycosidic bonds
Polysaccharides types and functions
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
Polysaccharide - glycogen
- 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
Polysaccharide - cellulose
- 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.
What is the result of glycolysis?
2 pyruvate, 2 ATP and 2 NADH
How many enzyme catalyzed reactions are there in glycolysis?
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
Two stages of glycolysis
- 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
Regulation of glycolysis can occur via
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.
Where does the glucogenesis occur?
Mainly in the liver, more limited in the kidney and small intestine under some conditions.
The three irreversible steps that glucogenesis has to bypass
- Hexokianse
- Phosphofructokinase
- Pyruvate kinase
The energy expense of gluconeogenesis
for 1 glucose produced:
4ATP + 2GTP + 2NADH
Phosphorylation of enzymes and regulatory proteins in the liver by protein kinase A results in..?
- inhibition of glycolysis
- stimulation of gluconeogenesis
- making glucose available for release to the blood
Enzymes that are phosphorylated by protein kinase A…
- Pyruvate kinase
- CREB
- Fructose-2,6-biphosphate
Transport of Mitochondrial Matrix
What is a Lipid?
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.
- What is required for the activation of a
fatty acid? - What does one cycle of oxidation of a
fatty acid produce? - What does Acetyl CoA produce when
entering the cytric acid cycle?
- 2 ATP
- 1 NADH = 3 ATP
1 FADH2 = 2 ATP - 12 ATP
Name 4 physiological functions of Lipids
- They serve as structural components of
biological membranes - Provide energy reserves, predominantly in
the form of triacylglycerols - Both lipids and lipid derivatives serve as
vitamins and hormones - Lipophilic bile acids aid in lipids
solubilization
Where are Ketone bodies formed?
Ketogenisis in the Mitochondria
4 classes of Lipids
1 Simple lipids
2 Compound lipids
3 Derived lipids
4 Miscellaneous lipids
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
Types of Simple Lipids
1 Natural fats and oils (triglycerides)
- Waxes
(a) True waxes: cetyl alcohol esters of fatty
acids
(b) Cholesterol esters
(c) Vitamin A esters
(d) Vitamin D esters
Types of Compound Lipids
- Phospholipids and spingomyelin
- Sphingolipids (also include glycolipids and
cerebrosides) - Sulfolipids
- Lipoproteins
- Lipopolysaccharides
Types of derived lipids
- Saturated & unsaturated fatty acids
- Monoglycerides and diglycerides
- Alcohols (b-carotenoid ring, e.g., vitamin A,
certain carotenoids)
Types of Miscellaneous Lipids
- Aliphatic hydrocarbons
- Carotenoids
- Squalene:
- Vitamin E and K
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)
Activation of Fatty acids
Signifigance of ketogenesis and ketogenolysis
- 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 - High concentration of ketone bodies can induce ketonemia and ketonuria, and
even ketosis and acidosis
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)
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
When is Fatty acid synthesis complete?
When palmitoyl ACP reacts with water to give palmitate and free ACP
Types of polysaccharides
Homopolysaccharides
E.g. glycogen
heteropolysaccharides
E.g. peptidoglycans
Functions of polysaccharide s
Glucose storage
Osmotic pressure
Information
Structure
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
Glycogenolysis what is it
Breakdown of glucose to glycogen
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
Glycogenylosis step 1
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
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
What happens during glycogenolysis
What is the main product of glycogen breakdown
Glucose 1 phosphate
What happens during glycogenesis explained using words instead of the graph
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
Fates of glucose 6 phosphate
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
glycogen n + udp glucose=what in glycogenesis synthesis
glycogen n+1 + udp glucose
glycogen n + PI=what
glycogen n-1 + glucose 1 phosphate