Non-ruminant carbohydrate digestion

What are the three disaccharides

Maltose, lactose, and sucrose

Glu + glu =

Maltose

Galactose + glucose =

Lactose

Glucose + fructose

Sucrose

Starch is made of ___% amylose and __% amylopectin

30, 70

Which is more digestible, amylose or amylopectin. Why?

Amylopectin because it has a1-6 bonds which causes branching

Where is glycogen stored in the animal? (mainly)

Liver and skeletal muscle

Which three species have salivary amylase?

Humans, pigs, and rodents

a-amylase hydrolyzes a1-4 bonds and requires _______

Calcium

Disaccharide digestion is primarily in the….. (be specific)

Microvilli of enterocyte

What are two specific transporters of carbs?

SGLT1 and GLUT

Na linked glucose transporter - takes energy

SGLT1

How does SGLT1 help glucose enter the enterocyte?

Glucose is bound to Na. Together, they are transported into the cell via the Na gradient. This gradient is maintained by the Na+/K+ pump, which moves Na out and K in AGAINST the gradient. This requires energy, which is why it’s an active process.

How does glucose pass from the enterocyte into the blood?

GLUT2

What transporter gets fructose into the enterocyte, which gets it out of the enterocyte into the blood?

GLUT5 in, GLUT2 out

Key hormone regulator of glucose absorption

Insulin

What cells release insulin?

Pancreatic beta cells

How does insulin help maintain blood glucose levels?

Insulin stimulates GLUT4 to move to the membrane which allows for glucose to transport into the cell via facilitated diffusion.

The synthesis of glycogen from glucose

Glycogenesis

The breakdown of glycogen

Glycogenolysis

The oxidation of glucose

Glycolysis

The production of glucose from noncarbohydrate intermediates

Gluconeogenesis

Production of 5-carbon monosaccharides and nicotinamide adenine dinucleotide phosphate (NADPH) 

Pentose phosphate pathway

The oxidation of pyruvate as acetyl-CoA to CO2 and H2O 

Tricarboxylic acid (TCA) cycle

Where does glycogenesis occur?

Cytosol (muscle, liver)

Where does glycogenolysis occur?

Cytosol (muscle, liver)

Once inside the cells, glucose is rapidly phosphorylated by _______ to form ___________. This cannot diffuse back out of the cells and is trapped in the cytosol, therefore maintaining the concentration gradient for glucose.

hexokinase, Glucose-6-phosphate

Glycogenesis (musle, liver) is used to store glucose as glycogen for future needs meaning it happens in a ___ state.

Fed

Glycolysis converts glucose to pyruvate in the cytosol. This happens in a ______ state.

Fasted

Glycolysis is regulated by _______ or glucokinase in the liver.

hexokinase

The TCA cycle occurs in the ______

mitochondria

The TCA cycle convert pyruvate to ________.

AcetylCoA

What are the reducing equivalents generated per turn of TCA?

3 NADH and 1 FADH2

The ETC uses the reducing power created from turns of the TCA cycle to produce ATP through _____________.

Oxidative Phosphorylation

When NADH is produced by glycolysis in the cytosol, it needs help getting into the mitochondria. There are two shuttles that help with this. What are they?

Glycerol 3-phosphate shuttle and malate-aspartate shuttle

Why does NADH produced by TCA cycle not need a shuttle?

TCA occurs in the mitochondria so its already there

The glycerol 3-phosphate shuttle system is used in __________. (what muscles)

Brain and skeletal

How does the glycerol 3-phosphate shuttle system work?

Hands electrons from NADH in the cytosol to FADH2 in the mitochondria. FADH2 feeds the ETC. This shuttle is less efficient, less ATP.

Where is the malate-aspartate shuttle used? (what tissues)

liver, kidney, and heart

Describe how the malate-aspartate shuttle system works.

Electrons are moved from the NADH in the cytosol to the NADH in the mitochondria. This process is reversible. Produces 3 ATP and is more efficient.

What happens during oxidative phosphorylation in the ETC?

NADH and FADH2 from the TCA cycle are coming in and the H+ is being translocated via oxidation. ADP is being phosphorylated. This creates ATP.

How much ATP comes from NADH vs. FADH2

3 from NADH and 2 from FADH