In: Biology
Fill in the blanks with the following terms:
Lactate NAD+ fermentation
NADH aerobic anaerobic acetyl CoA
When oxygen is available during glycolysis, the three-carbon
pyruvate may be oxidized to form:
(1) ___________________ + CO2, The coenzyme (2) _________________
is reduced to (3) ___________.
Under (4) _______________ conditions, pyruvate is reduced to (5)
_________________. In yeast, pyruvate forms ethanol in a process
known as (6) __________________.
Associate each of the following descriptions with pathways in
glycogen metabolism:
a. glycogenesis b. glycogenolysis
1. _____ breakdown of glycogen to glucose 2._____ activated by
glucagon
3. _____ starting material is glucose-6-phosphate 4._____ synthesis
of glycogen from glucose
5. _____ activated by insulin 6._____ UDP activates glucose
Gluconeogenesis: Glucose Synthesis
Associate each of the following descriptions:
a) gluconeogenesis b) pyruvate c) pyruvate kinase
d) pyruvate carboxylase e) Cori cycle
1. _____ an enzyme in glycolysis that cannot be used in
gluconeogenesis
2. _____ a typical non-carbohydrate source of carbon atoms for
glucose synthesis.
3. _____ a process whereby lactate produced in muscle is used for
glucose synthesis in the liver and used again by the muscle.
4. _____ the metabolic pathway that converts non-carbohydrate
sources to glucose.
5. _____ an enzyme used in gluconeogenesis that is not used in
glycolysis.
6. _____ a metabolic pathway that is activated when glycogen
reserves are depleted.
Match each of the following with the correct metabolic
pathway:
A. glycolysis B. glycogenolysis C. gluconeogenesis
D. glycogenesis E. fermentation
1. _____ conversion of pyruvate to alcohol
2. _____ breakdown of glucose to pyruvate
3. _____ formation of glycogen
4. _____ synthesis of glucose
5. _____ breakdown of glycogen to glucose
Answer: see below
When oxygen is available during glycolysis, the three-carbon pyruvate may be oxidized to form:
(1) Acetyl CoA + CO2, The coenzyme (2) NAD is reduced to (3) NADH . Under (4) __ Anaerobic conditions, pyruvate is reduced to (5) ___ Lactate In yeast, Pyruvate forms ethanol in a process known as (6) ______fermentation_____.
Associate each of the following descriptions with pathways in glycogen metabolism:
1. _Glycogenlysis__ breakdown of glycogen to glucose 2.__ glycogenolysis _ activated by glucagon
3. __ Glycogenesis___ starting material is glucose-6-phosphate 4.__ glycogenesis___ synthesis of glycogen from glucose
5. __ Glycogenesis___ activated by insulin 6.__Glycogenesis__ UDP activates glucose
Associate each of the following descriptions:
1. _Pyruvate kinase _ an enzyme in glycolysis that cannot be used in gluconeogenesis
2. _Pyruvate_ a typical non-carbohydrate source of carbon atoms for glucose synthesis.
3. __ Cori cycle ___ a process whereby lactate produced in muscle is used for glucose synthesis in the liver and used again by the muscle.
4. _ Gluconeogenesis the metabolic pathway that converts non-carbohydrate sources to glucose.
5. __Pyruvate carboxylase _ an enzyme used in gluconeogenesis that is not used in glycolysis.
6. _Gluconeogenesis __ a metabolic pathway that is activated when glycogen reserves are depleted.
Match each of the following with the correct metabolic pathway:
1. __ Fermentation ___ conversion of pyruvate to alcohol
2. __ Glycolysis ___ breakdown of glucose to pyruvate
3. ___ Glycogenesis __ formation of glycogen
4. ___ Gluconeogenesis __ synthesis of glucose
5. __ Glycogenolysis ___ breakdown of glycogen to glucose
Glycogen is a readily storage form of glucose. In simple word glycogen is a fuel reserve. It is a polymer of glucose residues, when energy is needed that can be broken down to yield glucose molecules. The two major sites of glycogen storage are the liver and skeletal muscle. Glycogen degradation and synthesis of glycogen is simple biochemical processes but regulation of these processes is complex.
Fermentation: It is an anaerobic respiration that occurs in the cytosol of yeast. It is also known as alcoholic fermentation. In this process, firstly sugars breakdown leads to the formation of pyruvate molecules which is known as glycolysis. Then the pyruvic acids get converted to ethanol and carbon dioxide and the regeneration of NAD+ from NADH. The net ATP yield of this fermentation is 2 molecules of ATP per mole of glucose.
The overall chemical formula for alcoholic fermentation is:
C3H3O3 (pyruvate) + NADH → C2H5OH (ethyl alcohol) + CO2 + NAD+
Glycolysis: Glycolysis is the first pathway in cellular respiration that happens in the cytoplasm. In glycolysis, glucose molecule and produces two molecules of pyruvate. This results in a net gain of two ATP molecules and two very high-energy NADH molecules. Glycolysis process can be summarized by the following equation:
C6H12O6 + 2 ADP + 2 Pi + 2 NAD+ → 2 CH3COCOO− (pyruvate) + 2 ATP + 2 NADH + 2 H2O + 2 H+
During pyruvate oxidation, pyruvate gets converted into acetyl-CoA by pyruvate dehydrogenase complex. This is also known as link reaction because it connects glycolysis and the Krebs cycle. The reaction is as follows:
2 Pyruvate + 2 NAD+ + 2CoA --> 2 Acetyl CoA + 2 CO2 + 2 NADH+
Glycogenesis: it is an anabolic process that involves the formation of glycogen from glucose. Glycogen is synthesis depends on the requirement of glucose and energy, when glucose levels as well as ATP are sufficiently high then insulin promotes glucose conversion for storage in liver and muscle cells. Glucose molecules are phosphorylated to glucose-6-phosphate and then converted to glucose-1-phosphate and UDP-glucose, and is added to glycogen chains for storage.
Glycogenolysis: it involves the degradation of stored glycogen in liver and muscle through catabolic reactions via the sequential removal of glucose monomers and it is catalyzed by the enzyme glycogen phosphorylase. Glycogenolysis is not simply the reverse process of glycogenesis. Different independent set of enzymes present in the cytosol that can catalyze the unidirectional steps of the pathway. Glycogen is degraded by breaking Glycosidic bonds to yield glucose 1–phosphate. Glycogenolysis takes place in muscle and liver cells in response to many hormonal for example glucagon, insulin, and epinephrine and neural signals.
Gluconeogenesis: this metabolic pathway involves synthesizing glucose from non-carbohydrate sources. Gluconeogenesis is not the exact reverse of glycolysis; some of the steps are similar in reverse direction. Gluconeogenesis is the main source of glycemia maintenance after glycogen stores are depleted during fasting. Gluconeogenesis is activated if energy is required. Gluconeogenesis is also stimulated by glucagon and inhibited by insulin.
Cori cycle: it involves anaerobic glycolysis to produce lactate in muscles during fasting or exercise and then lactate is transported to the liver and converted to glucose. After that glucose returns to the muscles can be metabolized back to lactate