7.a Carbohydrate metabolism 1: glycolysis Flashcards
Carbohydrates are composed of A, B and C only.
Carbohydrates: composed of carbon, hydrogen and oxygen only
Carbohydrates: physiological or dietary requirement?
Physiological
What are oligosaccharides? What are dextrins?
Oligo = consists of multiple sugars
Dextrins = 40-50 linked together
What is the basic CH structure?
Cn(H2O)n
Difference glucose galactose in terms of chemical structure?
Hydroxylgroup (OH) at carbon 4 is upward facing with galactose instead of downward with glucose.
Difference fructose with glucose?
Fructose: double bonded O is at C2. Ring is now formed differently: 5-ring instead of 6. Two carbons outside of the ring.
Difference RNA with glucose?
RNA: five-ring structure. One carbon outside of the ring. Hydroxyl group missing compared to fructose and glucose.
Name four disaccharides
- Sucrose (saccharose) (glucose + fructose, alfa 1,4)
- Trehalose (2x glucose, alfa 1-1)
- Lactose (glucose + galactose, beta 1-4)
- Maltose - isomaltosesu (2x glucose, alfa 1-4)
See p.54
Alfa = same side linkage
Beta = opposing sites linkage
Difference in bonding in maltose vs isomaltose?
Maltose: alfa 1-4
Iso: alfa 1-6
Moelcules link together with x and break apart with x
Condensation
Hydrolysis (often with enzyme)
x and x have a branched strucure, caused by x linkage
Starch, glycogen, alfa 1-6 linkage
What two types of starch can you distinguish? What are differences in shape?
- Amylopectin
- Amylose
- branched with isomaltose structure
- linear
Which is easier to digest of the two plant starches? Why?
Amylopectin. More hydrogen bonds, surface area is larger.
What about the GE of the starches?
GE is basically same between amylopectin + amylose.
What is the GI-index? (glycaemic index)
How fast does sugar intake lead to rise in insulin. How fast is glucose released.
Which has a lower GI index of the starches?
Starch amylose = low GI (more difficult to digest)
Starch amylopectin = high GI (less difficult to digest)
What happens when you give mice HGI diet vs LGI?
More leptin (more adipose tissue, more leptin), more insulin resistance, higher insulin in high GI group. Glucose level is maintained.
Name four non-starch polysaccharides?
Cellulose: very prevalent in cell walls. Therefore not able to digest it. We have some bacteria that are able to.
Chitin: shield of insects. Very different amino bond.
Pectin: E.g. mandarins, apples. Cannot digest it.
Inulin: fructose polymer. If you only have a few = FOS. Cannot digest, but relatively simple to ferment. SCFA.
Hydrogen in breath = fermentation in colon, gas production. LDD = ?
LDD (low digestible diet): way more Hydrogen in breath.
What is glycogenolysis?
Glycogen synthesis?
glycogenolysis = Glycogen -> g-6-p
Synthesis = other way around
What is glycolysis?
And gluconeogenesis?
glyc = g-6-p to pyruvate
Other way around = gluconeogen.
What is ketogenesis?
Ketones -> acetyl-CoA
What is fatty acid synthesis/oxidation?
Oxidation = fatty acids -> acetyl-CoA
Synthesis = acetyl-CoA -> fatty acids
Glycolysis takes place in the…
Glycolysis takes place in the cytoplasm. From pyruvate on it enters the mitochondria.
When is lactate made? What is it a measure for?
When having a lot of pyruvate or mitochondria cannot be used properly: lactate is made. Excreted out of the body most of the time. Lactate = measure for how aerobic or anaerobic your exercise is.
What is the initial substrate for glycolysis? Where does it come from when?
Initial substrate for glycolysis is glucose-6-phosphate. Can be made from glycogen or glucose.
In the fed stage: formed by phosphorylation of glucose (an ATP-utilising reaction)
In the fasting state: liver + muscle form glucose-6-phosphate from glycogen.
Glycolysis very global: first step from glucose?
- the glucose (6C) needs to be charged with 2 ATP.
Glycolysis very global: 2nd step from glucose?
- Huge drop in energy: glucose is split into two trioses (2x 3C glucose) (Glyceraldehyde-3-p)
Glycolysis very global: last step from glucose?
Then, 2 NADH + 2 ATP + 2 ATP + 2 pyruvic acid is formed. (alles dubbel) p.59
So, 5 ATP yield from glycolysis.
-2 invest
+ 7 yield
