BCHM 4115 - Lectures 32-35

Hydrolysis of _ is crucial in the synthesis of PEP in gluconeogenesis?

Answer explanation

Write the complete equation for gluconeogenesis.

Answer explanation

What is the purpose of the Cori Cycle?

Answer explanation

The purpose of the Cori Cycle is to recycle lactate produced in muscles during anaerobic glycolysis back into glucose in the liver. During vigorous exercise, muscles experience low oxygen availability and convert pyruvate into lactate to regenerate NAD⁺, allowing glycolysis to continue producing ATP. Lactate is then transported through the blood to the liver, where it is converted back into pyruvate and then into glucose via gluconeogenesis. This newly synthesized glucose can be returned to the muscles for energy use, creating a metabolic loop that helps sustain muscle activity under anaerobic conditions. The cycle thus links the energy needs of muscle with the gluconeogenic capacity of the liver.

Tags

NGSS.HS-LS2-3

In gluconeogenesis, pyruvate cannot be directly converted back into phosphoenolpyruvate (PEP) because pyruvate kinase, a regulated enzyme in glycolysis, strongly favors the formation of pyruvate. What two enzymes and intermediate molecule are involved to facilitate the conversion of pyruvate to PEP?

Answer explanation

1. 1. pyruvate → oxaloacetate via pyruvate carboxylase

3. 2. oxaloacatete → PEP via PEP carboxykinase

Glycogen synthase catalyzes the formation of _ bonds while the branching enzyme catalyzes the formation of _ bonds.

Answer explanation

1st blank: α(1→4) glycosidic bonds

2nd blank: α(1→6) glycosidic bonds

What is glycogen phosphorylase and glycogen synthase regulated by?

Answer explanation

Tags

NGSS.HS-LS1-3

The four protein kinases involved in phosphorylating glycogen synthase are...

Answer explanation

1. Casein kinase, AMP dependent protein kinase, protein kinase A, and glycogen synthase kinase 3 (GSK3).

What is the enzyme that coverts fatty acids into fatty acyl-coA, and why is this conversion necessary?

Answer explanation

1. The enzyme responsible is acyl-CoA synthetase, which activates the fatty acid for degradation by attaching coenzyme A. This activation step is necessary for fatty acids of all sizes. However, the location of this process depends on the size of the fatty acid. For long-chain fatty acids, activation occurs in the cytosol, whereas short- and medium-chain fatty acids can be activated within the mitochondria.

Explain how the carnitine shuttle is able to transport fatty acyl-coA into the matrix.

Answer explanation

The carnitine transport system facilitates the movement of long-chain fatty acyl-CoAs into the mitochondrial matrix, where β-oxidation takes place. First, carnitine acyltransferase I (located on the outer mitochondrial membrane) replaces coenzyme A with carnitine, forming an O-acylcarnitine intermediate that can cross into the intermembrane space. This intermediate is then transported across the inner mitochondrial membrane via a translocase. Once inside the matrix, carnitine acyltransferase II removes the carnitine and reattaches a CoA group, regenerating fatty acyl-CoA.

What does serum albumin do in regards to transport?

Answer explanation

Serum albumin is the most abundant protein in blood plasma and plays a key role in transporting free fatty acids. It contains 11 distinct hydrophobic binding sites, where fatty acids released from adipocytes can bind for transport to their target tissues. This transport mechanism is essential because the nonpolar nature of fatty acids prevents them from freely floating in the polar environment of the blood plasma. By binding to albumin, the fatty acids are effectively shielded within the protein’s hydrophobic interior, allowing safe and efficient transport through the bloodstream.

Tags

NGSS.HS-LS1-1