Carbohydrates: Digestion/absorption Flashcards
Oligosaccharide aka
Disaccharide
Monosaccharides in Oligosaccharide vs polysaccharide
O = 2-20
P = more than 20
Glycoconjugates =
Linked to proteins or lipids
Glycoprotein
Or
Glycolipids
Glycoproteins =
More protein than sugar
Proteoglycans =
More sugar than protein
Where are glycoproteins bound
Membrane
Examples of proteoglycans
Mucins (mucus)
Lectins (cell to cell interactions)
Glycolipids example
Blood types
Trioses are ____ and examples are _______
The smallest sugars
Aldose and Ketose
Basic idea of enantiomers
Mirror images of one another
Connecting 4 different groups off the main carbon
the main carbon is called the chiral carbon
Most monosaccharides are in _ form
D
The most oxidized carbon in aldose and ketose
A = C1
K = C2
Which is more common, pentoses or hexoses
Hexoses
_______ are _____ that have the _______ molecular formula but _______
Isomers
Molecules
Same
Different arrangements of atoms
Interconverted just rotating a group on a single bond ______
Conformational isomers
α vs β
To make a disaccharide you take a _____ and a ____
α glucose
β glucose
When you make a disaccharide what is the product
H2O
Two glucose molecules connected by glycosidic bond
Disaccharide has what kind of ends and their characteristics
reducing end = 1 carbon next to 1 oxygen
NonReducing end = 1 carbon next 1 carbon
Amylose and amylopectin are examples of
Polysaccharides
Common polysaccharides
Cellulose
Starch = amylose, amylopectin
Glycogen
Sources of common polysaccharides
Cellulose = plants
Starch = plants
Glycogen = animals
Subunits of common polysaccharides
Cellulose = β-glucose
Starch and glycogen = α-glucose
Branches and shapes of common polysaccharides
Cellulose = no branches, parallel lines
Starches
amylose = no branches, top of hostess cupcakes
amylopectin = yes branches, 20ish subunits
Glycogen = yes branches, 10ish subunits
Amylose vs amylopectin bonds logic
Amylose shape is hostess cupcake, pretty basic so only 1-4 bonds
Amylopectin is branching so needs more variety, so 1-4, and 1-6
Starch and glycogen RE vs NRE
Only 1 RE
TONS of NRE going every which way!
How are cellulose fibrils connected
Hydrogen bonds
We cannot ______ carbs so we _______
Absorb long polymer
Use glycosidases to Hydrolyze/break them down
What breaks down carbs in mouth
And what does it break
α-amylase
Cleaves 1-4
α-amylase creates
α-dextrins which have a lot of α 1,6 glycosidic bonds
When you hear 1,6 think
Branching!!!
What does our stomach acid do to α-amylase
Inactivates it
____ releases _____ into the duodenum to ______
Pancreas
HCO3- (bicarbonate)
Neutralize it
Why do we want to neutralize the duodenum
So enzymes can be functional again
What is secreted in duodenum from pancreas
Bicarb and α-amylase
What is formed in small intestine due to cleavages
Maltose(disaccharide), isomaltose, maltotriose
When and where do sucrose and lactose get acted on
When they contact the brush border in the intestines
Bacteria in colon can do what and what do they get in return
Breakdown small sugars
They get energy in return
______ cleaves sucrose to ______
Sucrase
Glucose and fructose
_____ cleaves lactose to ____
Lactase
Glucose and galactose
When bacteria breakdown sugars what do they form
Gases and short chain FA
FA are what is used for energy
GLUT 1-4 are
Glucose facilitated
GLUT 5 is
Fructose facilitated
Which GLUT is insulin dependent
4
Where are all the GLUTs located
1 = most tissues
2 = liver, kidney, pancreatic β
3 = brain, placenta, fetal muscle
4 = skeletal/heart muscle, adipocytes
5 = small intestine
Which GLUT affects vmax
4
Cellulose in our diet goes out as
Fiber
GLUT 1 has a _____ km which means
Low
Takes glucose up readily
SGLT1 is ____ and needs ______and needs _____ to regulate sodium
Sodium glucose transporter
Sodium needs to come in with glucose
Na+/k+ ATPase
Why is GLUT2 not in intestines
Because it has a HIGH km and has a hard time brining in glucose
Where are SGLT1 and what do they do there
In kidney cells
For glucose reabsorption
SGLT1 transport glucose from ____ to ______ in
Lumen
Capillaries
Kidneys
The ___ of a transporter is inversely proportional to its affinity to its ____
KM
Substrte
GLUT 1 and 3 are really bad at what and why
Removing glucose from the blood quickly
Because they have a low KM, the slope change is minimal
What is significant about GLUT2 and its location
Liver, kidney, pancreatic β
It removes glucose from the blood quickly when the concentration is high
it is proportional to extracellular glucose concentration
Where are GLUT4 and what makes them move to where
Muscle and adipose
INTRACELLULAR vesicles
Insulin moves them to the outside of the cell onto the plasma membrane
So they can pump sugar into muscles
What 3 steps of glycolysis are regulated
Step 1 = hexokinase/glucokinase
Step 3 = phosphofructokinase 1
Step 10 = pyruvate kinase
What are the two phases of glycolysis
I = energy investment/energy input
II = energy generation/energy output
Which steps are ATP consuming and irreversible
1: glucose —hexokinase—->G6P
3: F6P ——phosphofructokinase1—->F16BP
G6P is a _____ to hexokinase
Allosteric inhibitor
Negative feedback
Which carbons get phosphates added to them at step 1
Carbon 6 gets a phosphate
Which carbons get a phosphate added to them at step 3
Carbon 1 gets a phosphate added
What inhibits step 3 and why
ATP inhibits step 3 because its saying “HEY we have a TON of ATP so stop making them”
Citrate also inhibits step 3 because its saying “HEY our citrate levels are HIGH, so our TCA cycle is well and full. Don’t make any more pyruvate please”
How does citrate inhibit PFK1 since the TCA is in mitochondria
It leaks out to cytosol
What do AMP and ADP signal in the energy investment phase of glycolysis and why
They tell PFK1 to rev up!!! Cuz they are the products when ATP get used. So they say we have low levels of ATP
______ cleaves F16BP into ______ and _____
Aldose - big al
G3P - glacier aldehyde
DHAP - don’t handle apparatus please
Which two products of Aldolase wants to look more like the other
DHAP wants to look like G3P
Before step 10 of glycolysis what is our ATP status
We’ve used 2 ATP and we’ve made 2 ATP
So net = 0
What steps are ATP generating and irreversible
Step 10
What inhibits pyruvate kinase
ATP
And
Acetyl CoA
What does acetyl CoA indicate for glycolysis
That we have enough energy and it can cool its jets
What activates pyruvate kinase
F16BP
What does substrate level phosphorylation mean?
ATP is made without using ETC and ATP synthase
Which is favored between 1,3BPG or 3PG
3PG
During glycolysis _____ are generated from _____ glucose molecule through ______
2 net ATP
Each
Subrtrate level phosophrylation
What doesn’t glycolysis use and what does that make it
Doesn’t us O2
ANAEROBIC
Which enzyme/step commits glucose to glycolysis
PFK-1
Step 3
How is glucose kept in a cell and how does it work
By Hexokinase or glucokinase turning it into G6P
G6P cannot cross plasma membrane easily
Hexokinase exists _____ and is inhibited by ____
In most tissues
G6P
Glucokinase exists in ____ and is inhibited by ____
Liver/pancreatic β cells
F6P
Hexokinase has a ____ km and that makes it _____
Low
Constitutive. Very efficient
What do high concentrations of G6P tell hexokinase
“Hey we have plenty of glucose for energy rn, don’t bring any more in from the blood”
Glucokinase has a ____ km and that makes it
High
Inducible. Which means it will only be active if we have high glucose concentration
How does the liver utilize glucose
It maintains the levels in the blood! Doesn’t use it for itself. Because our liver loves us
What is hexokinase IV
Another name for glucokinase
What triggers glucokinase to leave the nucleas and work
Glucose
What tells glucokinase to go back to the nucleas
F6P
How do you inactivate glucokinase
Attach it to regulator protein (RP) in nucleus
When our liver starts to form F6P what does that tell us
We are at capacity for storing glycogen at the G6P phase so it moves to the next phase, making F6P
What step is important for glycogen storage
G6P
If ____ isn’t around PFK-1 wont be active. It is the main regulator
PFK-2
When you have allosteric acitvators for F6P what does that do to KM
It lowers the km, making it more active
_____ ———PFK2———-> ______
F6P
F2,6bisP
What enhances PFK1 activity
F2,6bisP
What determines F2,6bisP levels
PFK2 and F2,6bisPase
Insulin is associated with
Phosphatases
If glucagon is high (when would that be?) what happens
When we’re fasting
Liver wants to put glucose out in our body
sooooo it inhibits glycolysis
How does our liver inhibit glycolysis
By phosphorylation get F26bisPase and making it active
F26bisPase turns F26P to F6P which then wants to go do gluconeogenesis
Why would our liver want to inhibit glycolysis
Because we want to be making sugar, not breaking it down
What does F26P do in liver vs adipose tissue
In liver it regulates glycolysis and gluconeogenesis
In adipose it regulates glycolysis
PFK2 in liver active vs inactive
INactive = phosphorylated
ACTIVE = dephosphorylated
F2,6bisPase in liver active vs inactive
INactive = dephosphorylated
ACTIVE = phosphorylated
IF fia talks about P she’s activated
A lactose intolerance would be determined by
A lactase deficiency
What enzyme decreases with age
Lactase
What inhibits pyruvate kinase
Alanine and ATP
Acetyl CoA
Long chain FA
What activates pyruvate kinase
F1,6bisP
Alanine indicates what about energy
We have enough so cool the jets on glycolysis
Glucagon signals what in the blood
Low blood sugar
Pyruvate kinase active vs inactive
INactive = phosphorylated
ACTIVE = dephosphorylated
What’s the first and second most enzyme deficiency
1st = G6PDH
2nd = pyruvate kinase deficiency
When you have a pyruvate kinase deficiency what is vulnerable
RBC
What levels are important to note for pyruvate deficiency, what happens to them
ATP decreases
2,3 bisphosophoglycerate increases
Pyruvate K deficiency is dominant or recessive
Autosomal recessive
With strenuous exercise what is O2 like
Anaerobic
During anaerobic conditions pyruvate makes
NAD+ and Lactate
Why is NAD+ important
It can be used for GAPDH
What’s the whole point of forming lactate
It regenerates NAD+ concentrations SOOO we can’t continue glycolysis at step 6
glyceraldehyde-3-phosphate ——GADPH—-> 1,3bisphophoglycerate
Enzyme used to turn pyruvate to lactate
Lactate dehydrogenase
Accumulation of pyruvate =
Hemolysis
Muscle cramping during strenuous exercise
If you’re in an aerobic condition what’s going on with pyruvate
It will continue on to be made into Acetly CoA
The Warburg effect is
Aerobic glycolysis in cancer
Even with O2 what do cancer cells do
Convert pyruvate to lactate
When cancer makes lactate why is this beneficial
Acidity helps cancers invade and escape our immune system
During Warburg effect ____ intermediary molecules can be used for ____ and cell growth
More
Anabolism
Galactose key enzymes
GALK
GALT
GALE
Deficiency in GALK, GALT, GALE lead to
Galactosemia = accumulation of galactose in your blood
GALK especially
Fructose enzymes
Fructokinase = rapid
Aldolase B = rate limiting
Fructokinase deficiency vs Aldolase B deficiency
F = benign
accumulation of fructose
AB = hereditary fructose intolerance
damages liver
reduced ATP/ADP ratio
trap pi in F1P form
Where is fructose mainly used
Liver
____ cannot be used for glycogen synthesis
Fructose
Why is fructose less regulated
It bypasses PFK1 rate limiting step
Why is consuming TONS of fructose bad?
Because we can’t regulate it (no rate limiting step)
Leads to fatty liver and hyperglycemia
Too much glucose can lead to
Glycosylation (HbA1C)
Glucose turning to fructose
Cataracts, retinopathy, peripheral neuropathy
Glycosylation
Excessive chemical attachment of glucose to proteins with out involvement of enzymes
Why does too much glucose lead to neural stuff/eye stuff
Certain cells lack/have low sorbitol dehydrogenase
Sooo they cant ???
Inducible vs constitutive enzymes. Give examples of each
Inducible = expressed under specific conditions. Can be turned on(induced) or turned off(repressed) in response to changes in our bodies concentration of the substrate
example = glucokinase
Con = always on no matter the substrate concentration
example = hexokinase
A few days on breast milk can lead to
Deficiency in GALK or GALT
