BIOL 101 - Biological Chemistry: Carbohydrates Review & Metabolism

This assignment provides a comprehensive review of carbohydrate metabolism, covering key concepts such as glycolysis, the citric acid cycle, and the electron transport chain. It requires students to describe various sugars using appropriate terminology, including aldose vs. ketose, number of carbons, and stereochemistry. The assignment also delves into the functions and structures of various carbohydrates, including ribose, glucose, fructose, and others, in relation to homeostasis. Furthermore, it examines the roles of glucagon and insulin in glucose regulation, the dual function of the debranching enzyme, and the process of gluconeogenesis, including the formation of phosphoenolpyruvate from pyruvate. The assignment also provides insights into the energy output, initial substrates, and end products of glycolysis, the citric acid cycle, and the electron transport chain. The student's response includes detailed descriptions of each of these processes, providing a thorough understanding of the topic.

BIOLOGICAL CHEMISTRY
[Author Name(s), First M. Last, Omit Titles and Degrees]
[Institutional Affiliation(s)]

Carbohydrates Review & Metabolism
Answer the following questions using complete sentences. Be sure to thoroughly answer each question, and submit by
Monday, April 13th at 1:00pm.
You must submit your work as a doc, docx, or pdf.
Glycolysis & Carbohydrate Review
1) Describe the sugars below using the terminology that you have learned in class. Your description should include
the type of sugar (aldose vs ketose), number of carbons (in ring and general) and when appropriate
stereochemistry (D vs L and /or α vs β) (4pts)
A)
B)
C)
D)
D-Xylose
It has five carbon atoms
It is aldose-ketose-isomerase.
β -D-Ribose
It has one carbon atom
Belongs to Aldose group
D-Ribose
It belongs to aldose groups
It has one carbon atom
D-fructose
It belongs to ketoses group
It has 6 carbon atoms

2) There are a variety of carbohydrates that are critical to homeostasis. Describe the function and general structure
of each of the carbohydrates in the table (4pts).
Sugar Physiologic Importance/Source
D- Ribose
It is responsible for the improvement of cellular process in the event of dysfunction
of mitochondrion.
D-Glucose It acts as essential source of energy for the organisms through anaerobic or aerobic
respiration or fermentation
D- Fructose It acts as an agent of sweetening.
Lactose It acts source of energy for the body. Obtained from milk.

Sucrose It acts as source of energy for the body
Starch It is converted into glucose so that it can be used as energy source.
Glycogen
Heparin Used in the reduction of blood clotting ability.

3) Describe the energy output and initial substrates and end products of glycolysis, the citric acid cycle, and the
electron transport chain (3pts).
Glycolysis
Glycolysis refe4rs to a process in which one molecule of glucose( substrate) is broken down so as to give two forms of
molecules of pyruvate( pyruvic acid). Usually it will take place in a multi-step pathway of metabolism which takes place
in the plant cell, animal cell as well as other micro-organisms cells (Murzin et al.2017).
The citric acid cycle
The citric acid cycle (CAC) is usually refered to as the Krebs cycle [or the TCA cycle (tricarboxylic acid cycle). It is actually a
series of reaction chemically which has its concepts exploited by nearly all the living or aerobic organisms. The substrate
which may be proteins, fats or carbohydrates is oxidized so as to give carbon dioxide and adenosine triphosphate (ATP)
as the end product.
Electron transport chain

An electron transport chain refers to a series of electron transfer which is usually complex from the donors of the
electron to the acceptors of the electron through redox reaction and has this particular transfer of electron with the
proton transfer across the membrane. In short it is the last component of respiration aerobically which uses substrate
(oxygen) which is later reduced in the endpoint as water.
Glycogenolysis & Gluconeogenesis
1) Describe the role of glucagon and insulin in glucose regulation. Be sure to describe in what state of
hunger/satiety each would be produced (3pts).
Roles: Glucagon and insulin help in the regulation of blood sugar level. Insulin assist cells in the absorption of glucose
hence the sugar level is reduced and the cells are provided with the glucose for energy. When the level of the blood
sugar are too low, there will be release of the glucagon which instructs liver to have its stored glucose released hence
the sugar level rises.
Functioning states: When one is satisfied, the process of digestion of the carbohydrates leads to their conversion into
glucose. This glucose is released into the bloodstream hence rise in the level of blood sugar. It is this increase in the
blood sugar or glucose level which will trigger the pancreas into production of insulin. Insulin will thus instructs the body
cells to take in glucose hence the blood glucose level will reduce significantly.
After four to six hours, the processes of digestion are completed and one is hungry again. The level of glucose in the
body goes down. This will trigger pancreas into releasing of glucagon. The hormone will trigger the muscle and liver cells
to convert the glycogen stored in them back into glucose which will be later released into the blood streams for cells to
use as energy source.
2) Describe the dual function of the debranching enzyme and explain why both functions are necessary (3pts).
A debranching enzyme refers to a molecule responsible for the facilitation of the glycogen breakdown. It is this glycogen
which is usually regarded as the glucose store in the body. This facilitation is achieved through activities of glucosidase
and glucosyltransferase. Prior to the catabolism activities of phosphorylase, the following two functions are performed
by the debranching enzyme.
Glucosyltransferase or 4-α-D-glucanotransferase transfers the three residues of glucose to a nearby branch from the
four-residue glycogen branch. This is very crucial since it will lead to the exposure of the single residue of glucose which
is joined to the chain of the glucose through linkage known as an α -1,6 glycosidic.
Glucosidase or what is commonly refered to as Amylo-α-1,6-glucosidase will cleave the alpha-1,6 linkage remaining
hence leading to the production of linear chain of glycogen and glucose.
It is important to note that the above two or dual functions are very important since failure to have a proper breakdown
of glycogen will lead to Glycogen storage disease type III which is deadly.

3) In gluconeogenesis there are a variety of steps that require energy input to proceed. Describe the formation
of phosphonoenolpyruvate from pyruvate using the image below. Be sure to discuss the changes in each
product, what substrates are included and the enzyme necessary for each reaction. (3pts)
In gluconeogenesis the first step is usually refered to as carboxylation of pyruvate. This leads to the formation of
oxaloacetate. The processes are characterized by the expenditure of energy specifically one molecule of ATP.
The oxaloacetate will then be decarboxylated and later phosphorylated so that it can give rise to
phosphoenolpyruvate (Lorillière et al.2019). This process is also characterized by the expenditure of
phosphoryl-transfer potential of GTP at higher levels. All these activities occur in the mitochondrion.
This can be summarized in the equation as shown below:
It is important to note that the first bit of the reaction is under the catalyst action of pyruvate carboxylase. The
subsequent catalysis is done by phosphoenolpyruvate carboxykinase. The entire process can be summarized as
shown in the equation below:

REFRENCES
Lorillière, M., Dumoulin, R., L’enfant, M., Rambourdin, A., Thery, V., Nauton, L., ... & Hecquet, L. (2019).
Evolved Thermostable Transketolase for Stereoselective Two-Carbon Elongation of Non-
Phosphorylated Aldoses to Naturally Rare Ketoses. ACS Catalysis, 9(6), 4754-4763.
Murzin, D. Y., Murzina, E. V., Aho, A., Kazakova, M. A., Selyutin, A. G., Kubicka, D., ... & Simakova, I. L.
(2017). Aldose to ketose interconversion: galactose and arabinose isomerization over heterogeneous
catalysts. Catalysis Science & Technology, 7(22), 5321-5331.