CARBOHYDRATES Flashcards
what are the examples of compounds of carbohydrates
- starch
- sugars
- cellulose
- chitin
what are the general functions of carbohydrates
- structural components of DNA and RNA
- Serves as sources of energy e.g glucose
- serves are energy of storage e.g glycogen and satrch
- sparing the use of fats and proteins
what does the classification of carbohydrates based upon
- based on the size of base carbon chain
- based on the location of the C=O function group
- based on the number of sugar units
- based on the stereochemistry of the compound
how do we classify carbons accordding to the number of carbon in the molecule (Generic classification)
- Trioses (3 carbons)
- Tetroses( 4 carbons)
- Pentoses(5 carbons)
- Hexoses (6 carbons)
What distinguishes aldose from ketose in terms of their carbonyl group location?
Aldose derivatives have a terminal carbonyl group (O=CH-) at the end of their carbon chain, while ketose derivatives have a middle carbonyl group (O=C) linked to two other carbon atoms.
Describe the structure of the carbonyl group in aldose.
A carbonyl group is a functional group in organic chemistry characterize
The carbonyl group in aldose is an aldehyde functional group (O=CH-) located at the terminal carbon.
Where is the carbonyl group located in ketose?
In ketose, the carbonyl group is positioned between two other carbon atoms, forming a ketone group (O=C).
How does the position of the carbonyl group affect the classification of aldose and ketose
The location of the carbonyl group determines whether a sugar is classified as an aldose or a ketose. Aldoses have the carbonyl group at the end, while ketoses have it in the middle of their carbon backbone.
what are 3 major classes of carbohydrates
- monosaccharides
- disaccharides
- Polysaccharides
what are monosaccharides
simplest carbohydrates that cannot be further hydrolyzed and can contain 3 to 6 or more carbon atoms
what are the examples monosaccharides
- glucose
- fructose
- galactose
what are disaccharides
A disaccharide is a carbohydrate composed of two monosaccharides joined together by a glycosidic bond.
Which disaccharide is most abundant in blood?
sucrose
How can sucrose be hydrolyzed, and what products are obtained
Sucrose can be hydrolyzed into glucose and fructose
What disaccharide is present in milk, and what monosaccharides constitute it?
Lactose, composed of galactose and glucose, is the disaccharide present in milk
What are the products when maltose breaks down?
Maltose breaks down into two glucose molecules.
What are polysaccharides?
Polysaccharides are complex carbohydrates composed of many monosaccharides, typically ranging from 200 to 2500.
How do polysaccharides serve as energy storage components?
Polysaccharides, such as starch and glycogen, function as energy storage molecules in organisms
Provide an example of a structural polysaccharide and describe its role.
Cellulose is a structural polysaccharide and serves as an integral component of plant cell membranes.
How are CHO (carbohydrates) ingested in the form of starch and glycogen?
CHO are ingested as polymers, specifically starch and glycogen.
Which enzymes break down CHO during digestion, and what simpler sugars do they produce?
Salivary amylase breaks down CHO into dextrines and maltose, while pancreatic secretions break it down into glucose, lactose, galactose, and fructose.
Where are monosaccharides absorbed in the digestive tract, and how
Monosaccharides are absorbed across the walls of the duodenum and ileum through an active, energy-dependent, carrier-mediated transport system.
Which monosaccharides are absorbed at a greater rate: glucose, galactose, or fructose?
Glucose and galactose are absorbed at a greater rate than fructose.
How are monosaccharides transported to the liver after absorption?
Monosaccharides are transported by the portal vein to the live
What is the fate of glucose in the body?
Glucose is the only carbohydrate that can be directly used for energy or stored as glycogen
What must happen to galactose and fructose before they can be utilized?
Galactose and fructose must be converted to glucose before they can be used.
: Which carbohydrate is an integral component of plant cell membranes?
Cellulose is a structural polysaccharide found in plant cell walls
What is the primary site of monosaccharide absorption in the small intestine
The primary site of monosaccharide absorption is the duodenum and ileum
Why is glucose essential for energy metabolism?
Glucose is directly used for energy production and can be stored as glycogen for future use
What are the different fates of glucose in the body?
- Metabolized completely into carbon dioxide and water: This occurs during cellular respiration in the mitochondria, where glucose is broken down into carbon dioxide (CO₂) and water (H₂O) to produce energy (ATP).
- Stored in the liver as glycogen: Excess glucose is converted into glycogen and stored primarily in the liver and skeletal muscles. Glycogen serves as a readily available energy reserve.
- Conversion to keto acids, amino acids, or protein: Glucose can be used for biosynthesis, contributing to the production of molecules like amino acids, proteins, and keto acids
What is glycolysis, and what does it involve?
Glycolysis is the metabolic pathway where glucose is broken down into smaller molecules. Key points:
~It occurs in the cytoplasm of cells.
~Glucose is converted into two molecules of pyruvate or lactate.
~ATP and NADH are produced during glycolysis.
What is glycogenesis, and where does it occur?
Glycogenesis is the process of converting glucose into glycogen for storage.
~It mainly occurs in the liver and skeletal muscles.
~Enzymes add glucose molecules to an existing glycogen chain.
~Glycogen serves as a short-term energy reserve
what is the difference between glycogenolysis and gluconeogenesis
glucogenolysis is a process by which glycogen breaks down into glucose while gluconeogenesis is a production of glucose from non-carbohydrate sources
what two major pancreatic hormones control blood glucose levels
- insulin
- glucagon
what glands plays a role in blood glucose control
adrenal grans and thyroid gland
What is the role of insulin in glucose metabolism?
Insulin, produced by the β-cells of the pancreatic islets of Langerhans, has several effects on glucose metabolism:Increases glycogenesis:
1. It promotes the conversion of glucose into glycogen for storage in the liver and muscles.
2. Enhances glycolysis: Insulin facilitates the breakdown of glucose into pyruvate or lactate.
3. Stimulates lipogenesis: It encourages the synthesis of fatty acids and triglycerides.
4. Decreases glycogenolysis: Insulin inhibits the breakdown of glycogen into glucose.
5.Reduces gluconeogenesis: It suppresses the production of new glucose from non-carbohydrate sources.
6. Inhibits proteolysis: Insulin prevents protein breakdown.
7. Suppresses lipolysis: It decreases the release of fatty acids from adipose tissue.
Where is insulin secreted, and what is its primary function?
Insulin is secreted by the β-cells of the pancreatic islets of Langerhans. Its primary function is to regulate blood glucose levels by promoting glucose uptake, storage, and utilization.
eplain glycogenesis and glycolysis: glucose →glycogen→pyruvate→ acetyl-CoA
Glycogenesis is the process of converting glucose into glycogen for storage.
Steps:
Glucose → Glycogen: Excess glucose is transformed into glycogen primarily in the liver and skeletal muscles.
Purpose: Glycogen serves as a readily available energy reserve.
Glycolysis is the breakdown of glucose into smaller molecules.
Steps:
Glucose → Pyruvate: Glucose is metabolized through a series of biochemical reactions, resulting in the production of pyruvate or lactate.
Energy Production: Glycolysis generates ATP and NADH.
Acetyl-CoA Connection: Pyruvate can further enter the citric acid cycle (Krebs cycle) to produce acetyl-CoA, a key molecule for energy production
what is lipogenesis
Lipogenesis is the process of producing lipid or fat to store biochemical energy for later metabolic use
What is the source of glucagon in the body?
Glucagon is secreted by the alpha cells of the islets of Langerhans in the pancreas.
When is glucagon released
Glucagon is released during stress and fasting states.
What is the primary function of glucagon?
Glucagon acts as a hyperglycemic agent, meaning it increases blood glucose levels.
How does glucagon affect glycogenolysis?
Glucagon stimulates glycogenolysis, leading to the breakdown of stored glycogen into glucose.
Describe the role of glucagon in gluconeogenesis
Glucagon promotes gluconeogenesis, where fatty acids are converted into acetyl-CoA, which can further form ketones, and proteins are broken down into amino acids that contribute to glucose production.
explain this in details “gluconeogenesis: fatty acids → acetyl-CoA → ketone, proteins → amino acids
Fatty Acids: These are primarily derived from stored triglycerides in adipose tissue
Fatty Acids → Acetyl-CoA:
Fatty acids undergo β-oxidation in mitochondria, producing acetyl-CoA.
Acetyl-CoA can enter the citric acid cycle (Krebs cycle) for energy production.
Acetyl-CoA → Ketone Bodies:
In the liver, excess acetyl-CoA can lead to ketogenesis.
Ketone bodies (such as β-hydroxybutyrate and acetoacetate) are produced.
These ketones serve as an alternative fuel source during prolonged fasting or starvation
Proteins → Amino Acids:
Proteins are broken down into amino acids.
mention the hormones that affect glucose levels in the human body
- Epinephrine (stress hormone) inhibits insulin secretion, increasing glycogenolysis, and promoting lipolysis.
- Cortisol, decreases intestinal cell uptake and increases gluconeogenesis, glycogenolysis, and lipolysis so as to increase blood glucose levels
- Growth hormone: decreases the entry of glucose into the cells and increases glycolysis
- ACTH: stimulates cortisol release from the adrenal cortex
- Thyroxine that stimulates glycogenolysis, gluconeogenesis, and intestinal absorption of glucose
- Somatostatin produced by the δ-cells of the islets of Langerhans of the pancreas
~inhibits insulin, glucagon, growth hormone, and other endocrine hormones.
How do tubes containing sodium fluoride and potassium oxalate affect glycolysis?
These tubes inhibit glycolysis, preventing the breakdown of glucose, and can preserve blood samples for up to 3 days at room temperature.
What are the three measurement methods for glucose testing?
- Hexokinase Method: This enzymatic method measures glucose by using hexokinase to convert glucose to glucose-6-phosphate.
- Glucose Oxidase Method: Glucose oxidase reacts with glucose to produce gluconic acid and hydrogen peroxide, which is then detected.
- Glucose Dehydrogenase Method: Glucose dehydrogenase converts glucose to gluconolactone, and the resulting NADH is measured.
expain the working principle of a glucometer
Glucose meters employ enzymes such as glucose oxidase, hexokinase, or glucose dehydrogenase. These devices predominantly utilize pyrroloquinoline quinone (PQQ) or a combination of glucose oxidase and NAD for accurate glucose measurement. The final reading can be obtained through reflectance photometry or electrochemical methods
What is the purpose of the glucose tolerance test?
The glucose tolerance test assesses how effectively cells can utilize glucose
Which types of diabetes can be diagnosed using glucose clearance test?
gestational diabetes, type 1 diabetes, and type 2 diabetes
What are the three versions of glucose clearance test
1-hour, 2-hour, and 3-hour tests.
How much glucose is administered during each version glucose clearance test
50g, 75g, and 100g
What is the dosage of glucose given to children during glucose clearance test?
1.75 g/kg of glucose, up to a maximum dose of 75 g
Explain patient preparation for glucose clearance test
- patient should be ambulatory and on a normal to high carbohydrate intake for 3 days before the test.
- Patient dhould fast for 8 to atleast 10 hours
why should patient clearance be done in the morning
because of hormonal diurnal effect
