Exam 2 Flashcards
What is the fuel of the human body and every cell can metabolize it?
glucose
What 3 forms is glucose found in?
- monosaccharide
- disaccharide
- polysaccharide
What is the formula for a carbohydrate?
Cx(H2O)y
What are the 2 glucose disaccharides?
- sucrose
- lactose
What is sucrose made from?
glucose + fructose
What is lactose made from?
galactose + glucose
Starch is a ______saccharide
polysaccharide
What 2 polymers make up starch?
amylose + amylopectin
What is starch used for?
energy storage
Is starch made of more amylose or amylopectin?
amylopectin (75%)
Is amylose branch or unbranched?
unbranched
Is amylopectin branched or unbranched?
branched
What does starch breakdown into?
maltose
maltotriose
isomaltose
Maltose is a _____saccharide and Maltotriose is a ______saccharide
maltose: disaccharide
maltotriose: polysaccharide
Maltose and maltotriose have 1-4 linkages, why does isomaltose have a 1-6 linkage?
Amylopectin is branched and has a 1-6 linkage and that is where it comes from
What 2 types of enzymes break down carbohydrates?
- soluble enzymes
- anchored enzymes
What is an example of a soluble enzyme that breaks down carbs?
amylases
Where are amylases located?
saliva and intestines
What is an example of a anchored enzyme that breaks down carbs?
glycosidases
Where are glycosidases located?
intestines
How is monosaccharide glucose dealt with?
absorbed through intestine via SGLT-1
What are glycosidases anchored to?
microvilli in the intestines
What are the 3 types of microvilli-anchored enzymes?
- sucrase-isomaltase (alpha-glucosidase)
- maltase (alpha-glucosidase)
- lactase (beta-galactosidase)
Sucrase-isomaltase (alpha-glucosidase) splits __________ and ___________
sucrose and isomaltose
What is isomaltose made of?
2 glucose
Maltase (alpha-glucosidase) splits ________
maltose
What is maltose made of?
2 glucose
Lactase (beta-galactosidase) splits ________
lactose
Dietary glycogen is mainly ___________
amylopectin
Amylases mainly break down amylopectin or amylose?
amylopectin
Degrading amylose via amylase leaves you with what?
maltose and maltotriose
Degrading amylopectin via amylase leaves you with what?
glucose and limit dextrin
Degrading amylose and amylopectin with amylase then microvilli-anchored enzymes leaves you with…?
glucose
What causes lactase restriction?
loss of beta-galactose to break down beta (1-4) & (1-6) linkage in lactose
What are lactase tablets?
provides the body with the enzyme beta-galactosidase to break down lactose
Veggies are rich in _________ and________ which require alpha-galactosidases to break them down
Raffinose
Stachyose
What enzyme does Beano provide to help break Raffinose and Stachyose down in veggies?
alpha-galactosidases
What is sorbitol and why is it an issue?
in sugar free gum and cannot be broken down so bacteria in gut feed on it causing bloating
What is Lactulose and what does it do?
fructose + galactose
given as a laxative to decrease intestinal production of ammonia
What is considered a complex carb?
3 or more sugars
Glucose enters cells via _________ transport
facilitated (passive) transport
What are 3 glucose transporters?
- GLUT 1-3
- GLUT 4
- SGLT
Is GLUT 1-3 insulin sensitive or insensitive?
insensitive
Is GLUT 4 insulin sensitive or insensitive?
sensitive
Where is GLUT 4 found?
muscle and adipose cells
SGLT are driven by _____ gradient
Na2+
How is glucose retained in the cell?
hexokinase phosphorylates at position 6
Is the phosphorylation of glucose via hexokinase reversible or irreversible and why?
irreversible; coupled with ATP hydrolysis
Hexokinase I and III have ____________ kinetics
Michaelis-Menten kinetics (hyperbolic curve)
Why does Hexokinase I and III have Michaelis-Menten kinetics (hyperbolic curve)?
hexokinase in RBC are saturated with glucose so the [glucose] has little affect on hexokinase
- glucose-independent
Hexokinase IV is also known as ___________
glucokinase
Where is glucokinase found?
liver cells
Does glucokinase have high or low affinity for glucose and why?
low; glucokinase is almost never saturated with glucose so the [glucose] affects the activity a lot
What kind of kinetics does glucokinase have?
cooperatively kinetics
- glucose-dependent
What is the main signal to pancreas to secrete insulin?
glucose
Where is insulin stored?
granules in beta pancreas cells
How is insulin processed to become active?
C-peptide is cleaved off and B and A chain are connected
What is 2nM of glucose considered?
hypoglycemia (low)
What is >5mM of glucose considered?
hyperglycemia (high)
What secretes glucagon?
pancreatic alpha-cells
intestinal L-cells
What are the potentiators for insulin secretion?
amino acids
fatty acids
ketone bodies
What is the principal stimulus for glucagon production?
amino acids
What is the potentiator for glucagon secretion?
epinephrine
Insulin and glucagon secretion are __________ related
inversely
What is the glycemic index?
classifies how QUICKLY a food will affect the blood glucose level
How does constant consumption of high fructose corn syrup cause DMII?
pancreas becomes desensitized to glucose spikes and won’t secrete insulin
What sodium-dependent glucose transporter does the intestine use?
SGLT-1
What is the ratio of Na : glucose for SGLT-1 in intestines?
2Na : 1 glucose
What controls the flux of sodium through SGLT-1 and 2?
Na/K ATPase
What sodium-dependent glucose transporter does the kidney use?
SGLT-2
What is the ratio of Na : glucose for SGLT-2 in kidney?
1:1
How do anti-SGLT-2 medications work?
prevent hyperglycemia by blocking SGLT-2 so glucose cannot be absorbed
What two tissues in the body are exclusively fueled by glucose?
brain
red blood cells
Why is glucose stored as a complex carb?
free glucose is osmotically active and will enter RBC and cause them to burst
What is the definition of glycolysis?
the breakdown of glucose to extract energy from thr C-C bonds
What form of glycolysis creates the most energy?
oxidative phosphorylation (O2 present)
What kind of cells preform anaerobic glycolysis?
red blood cells (no mitochondria)
What is the start and end product of glycolysis?
glucose (C6)
pyruvate (C3)
What are the 2 phases of glycolysis?
- prep phase
- pay-off phase
Which phase in glycolysis cost energy and which gains energy?
prep phase: loss E
pay off: gain E
What’s the net cost of the prep phase of glycolysis?
2 ATP (2 dephosphorylation events)
What is the net gain of the pay-off phase of glycolysis?
4 ATP
2 NADH
2 H+
What enzymes in glycolysis perform DE-phosphorylations (ATP–>ADP)?
hexokinase
phosphofructokinase-1 (PFK-1)