U3 LEC: CARBOHYDRATES (PT. 1) Flashcards
This is the primary source of energy for brain, erythrocytes, and retinal cells in humans.
Carbohydrates
Carbohydrates are a primary source of?
energy
These organs cannot store carbs. and only relies on steady supply of glucose to tissues.
- brain
- erythrocytes (RBCs)
- retinal cells
This is plasma found in extracellular fluid/blood, has a narrow range, and can cross the blood brain barrier.
Plasma glucose
Aside from energy supply, carbohydrates are also a?
major food source
Carbs are primarily stored as?
glycogen
Glycogen is stored in the?
liver and muscles
T/F: Liver is the primary storage of carbohydrates.
True
Carbs are involved in two disease states which are?
- hyperglycemia
- hypoglycemia
Increase in plasma glucose
hyperglycemia
Decrease in plasma glucose
hypoglycemia
Carbs are used for the diagnosis of?
Diabetes mellitus
What are the substances found in carbohydrates?
Carbon, Hydrogen, Oxygen
Each carbon has usually?
1 molecule of Hydrogen
All carbohydrates contain what functional groups?
- carbonyl (C=O)
- hydroxyl (-OH)
C=O
carbonyl group
-OH
hydroxyl group
Substances contained in protein
- CHO
- Nitrogen
Derivatives of the basic formula
Cx(H2O)y
Carbohydrates are classified based on?
- size or number of base carbon chain
- location of the CO functional group
- number of sugar units
- stereochemistry
Based on size or number of base carbon chains
- Triose
- Tetrose
- Pentose
- Hexose
Based on size or number of base carbon chains
3 carbon chain compound
Trioses
Based on size or number of base carbon chains
4 carbon chain compound
Tetroses
Based on size or number of base carbon chains
5 carbon chain compound
Pentoses
Based on size or number of base carbon chains
Examples of Pentoses
Ribose, deoxyribose
Based on size or number of base carbon chains
6 carbon chain compound
Hexoses
Based on size or number of base carbon chains
Example of Hexoses
Glucose, galactose, fructose
This triose is the smallest carbohydrate.
Glyceraldehyde
Based on location of CO functional group
- Aldose
- Ketose
Based on size or number of base carbon chains
Terminal carbonyl group
Aldose (aldehyde group)
Based on size or number of base carbon chains
O=CH-
Aldose (aldehyde group)
Based on size or number of base carbon chains
Carbonyl group in the middle linked to carbon atoms
Ketose (ketone group)
Based on size or number of base carbon chains
C=O
Ketose (ketone group)
Carbohydrate models
- Fisher Projection
- Haworth Projection
Carbohydrate models
Has a straight form
Fisher
Fisher Projection
Aldehyde/ketone group is found at the?
top
Fisher Projection
Carbons are numbered starting at the?
head (Aldehyde/ketone)
Haworth Projection
Represent compound in what form?
cyclic form
T/F: Fisher projection is more of a representative of the actual structure.
False
Haworth
Haworth Projection
This is formed when functional group reacts with what group, on the same sugar to form a ring?
alcohol group
Based on number of sugar units
- Monosaccharides
- Disaccharides
- Oligosaccharides
- Polysaccharides
Based on number of sugar units
This is the simplest sugar, and cannot be hydrolyzed
Monosaccharides
Based on number of sugar units
Examples of Monosaccharides
- Glucose
- Fructose
- Sucrose
Based on number of sugar units
2 monosaccharides joined by glycosidic bonds
Disaccharides
Based on number of sugar units
Disaccharides are joined by?
glycosidic bonds / link / linkage
Based on number of sugar units
Examples of Disaccharides
- Lactose (1 glucose, 1 galactose)
- Maltose (2 D-glucose)
- Sucrose (1 glucose, 1 fructose)
Based on number of sugar units
Chains of 3 to 10 sugar units, means few
Oligosaccharides
Based on number of sugar units
Formed by linkage of many units (more than 10)
Polysaccharides
Based on number of sugar units
Examples of Polysaccharides
- Glycogen
- Starch
This refers to having the same order and type of bonds, but different arrangement and properties.
Stereoisomers
Stereoisomers
two forms
D or L type
Stereoisomers
Seen in the right, most sugars are in this form
D-isomer
Stereoisomers
Seen in the left
L-isomer
Stereoisomers account for?
spatial arrangement
What is being checked in stereoisomer?
position of hydroxyl group adjacent to central carbon
This refers to the asymmetric central carbons.
Chiral carbons
Chiral carbons are attached to?
Hydrogen and hydroxyl group
This refers to the separation of polysaccharides into monosaccharides.
Hydrolysis
What is consumed to separate the glycosidic link?
water
T/F: Digestion starts as soon as food enters the mouth.
True
This enzyme is released when chewing food.
Amylase (Salivary amylase)
These two components are derived once starch is broken down.
- Disaccharide
- Dextrin
Most ingested CHO are?
polymers / polysaccharides
Most ingested CHO
- Starch
- Glycogen
Important organs involved for carbohydrate digestion
- Mouth
- Intestines
- Liver
This is released in the small intestine to dissolve food.
Pancreatic amylase
Pancreatic amylase turns carbohydrates into?
monosaccharides
This is released in the intestinal mucosa to further hydrolyze / break down polymers or starch.
Maltase
Maltase is released in the?
intestinal mucosa
Other gut-derived enzymes
- Sucrase (for sucrose)
- Lactase (for lactose)
This is the only CHO that can be directly used for energy or storage.
Glucose
T/F: Only when polysaccharides are converted to monosaccharides are they absorbed by the gut and get delivered to tissues.
True
This condition refers to gastric juices, stops the action of amylase and is not useful for breaking down carbs.
acidic condition
How much starch is broken down once it reaches the stomach?
around 30%
Pathways of Glucose Metabolism
- Embden Meyerhof Pathway
- Hexose Monophosphate Shunt
- Glycogenesis
Ultimate goal for glucose is to convert it to?
carbon dioxide and water
What is obtained during pathways of glucose metabolism?
Adenosine Triphosphate (ATP)
EMP
Other term
Embden-Meyerhof-Parnas Pathway (EMPP)
EMP
Product
Pyruvate / Pyruvic acid (2)
EMP
Consumed and Gained ATP
2, 4
EMP
Net ATP
2
EMP
ATP is consumed through?
Phosphorylation
EMP
Phosphorylated products (consumes ATP)
- Glucose 6-phosphate
- Fructose 1,6-diphosphate
EMP
Products which alongside gains ATP
- 3-Phosphoglycerate
- Pyruvate
EMP
Product used for Krebs Cycle
Acetyl-coA
EMP
Aerobic pathway, in Mitochondria
Tricarboxylic Acid Cycle (Krebs Cycle / Aerobic Glycolysis)
EMP
Anaerobic pathway, in Cytosol
Glycolysis
EMP
This enzyme converts Pyruvate to Acetyl-coA
Lactate dehydrogenase
In absence of glucose, other substrates can be used such as:
- Glycerol
- Fatty acids
- Ketones
- Amino acids
Other substrates
For lipids
Glycerol
Other substrates
For proteins
Amino acids
This allows new formation of glucose using other substrates.
Gluconeogenesis
This refers to the detour of glucose-6-phosphate from glycolytic pathway.
Hexose Monophosphate Shunt
Hexose Monophosphate Shunt
Products
6-phosphogluconic acid / 6-phosphogluconate
T/F: There is no ATP produced in Hexose Monophosphate Shunt.
True
only byproducts
Hexose Monophosphate Shunt
This enzyme causes the glucose-6-phosphate to be dehydrogenated to 6-phosphogluconate.
Glucose-6-phosphate dehydrogenase (G6PD)
Hexose Monophosphate Shunt
This is the precursor to products used for biosynthetic reactions.
6-phosphogluconate
Hexose Monophosphate Shunt
Byproducts
- Ribose
- NADPH
- Glutathione disulfide (2G-SH)
Hexose Monophosphate Shunt
This has a reducing power, in which absence of this will result to a destroyed lipid membrane and will result to cell death.
Nicotinamide adenine dinucleotide phosphate (NADPH)
Hexose Monophosphate Shunt
This is used for nucleic acid production.
Ribose
Hexose Monophosphate Shunt
Other term for glutathione disulfide
Oxidized glutathione
Hexose Monophosphate Shunt
This is an antioxidant
Glutathione disulfide (2G-SH)
T/F: Antioxidants prevent oxidative stress or damage, but does not prevent action of free radicals.
False
This pathway refers to storage of glycogen in the liver to reuse it in conditions of exhausted glucose in plasma or blood.
Glycogenesis
This pathway happens only when the body’s energy requirements are being met
Glycogenesis
This pathway converts glycogen back to glucose, only in the liver.
Glycogenolysis
The liver is the only organ where it synthesizes
Glucose-6-phosphatase
This enzyme converts glucose to glycogen.
Glycogen synthase
This enzyme converts to glucose-UDP.
Uridine triphosphate (UTP)
Used for brief fasting (decreased glucose, increased glycogen)
Glycogenolysis
Used for fasting for more than 24 hours (decreased glycogen in liver, use other substrates)
Gluconeogenesis
Metabolism of glucose molecule to pyruvate or lactate for energy production
Glycolysis
Formation of glucose-6-phosphate from noncarbohydrate sources
Gluconeogenesis
Breakdown of glycogen to glucose
Glycogenolysis
Conversion of glucose to glycogen for storage
Glycogenesis
Conversion of carbohydrates to fatty acids
Lipogenesis
Decomposition of fat
Lipolysis
Carbohydrate Metabolism Regulation
Organs involved
- Liver
- Pancreas
- Other endocrine glands
Carbohydrate Metabolism Regulation
Major hormones involved:
- Insulin
- Glucagon
Carbohydrate Metabolism Regulation
Other hormones involved
- Somatostatin
- Epinephrine
- Cortisol & ACTH
- Thyroxine
- Growth Hormone
This organ is elongated, tapered, and is located behind the stomach.
Pancreas
Pancreas
Widest part, found in the back of duodenum, acts as the first entry to small intestine
Head of pancreas
Pancreas
These are small, scattered clusters that are concentrated in the body of pancreas.
Islet of Langerhans
Pancreas
Most abundant in the islet of langerhans, arranged in central core
Beta cells
This hormone is released by the beta cells of the islets of langerhans in pancreas.
Insulin
Primary hormone responsible for entry of glucose into the cell
Insulin
This is the ONLY HORMONE THAT CAN DECREASE GLUCOSE LEVEL.
Insulin
Agent which decreases blood glucose
Hypoglycemic
This hormone is produced by alpha cells of islets of langerhans in the pancreas.
Glucagon
Glucagon is released during?
stress, fasting states
This hormone is produced by the delta cells of islets of langerhans in pancreas.
Somatostatin
Somatostatin is also known as?
Growth hormone inhibiting hormone
Somatostatin regulates?
insulin and glucagon
This hormone is produced in the adrenal medulla.
Epinephrine
Epinephrine is released in times of?
stress
MOA of Epinephrine
- inhibits insulin
- increases glycogenolysis
- promotes lipolysis
This is also known as stress hormone.
Cortisol
Cortisol is produced in the?
zona fasiculata (Adrenal cortex)
Cortisol is produced on stimulation of?
Adenocorticotropic hormone (ACTH)
ACTH is produced by the?
pituitary gland
MOA of Cortisol
- decreases intestinal entry into the cell
- increases gluconeogenesis, lipolysis, glycogenolysis
This hormone is produced in the thyroid gland.
Thyroxine
Thyroxine is stimulated by the production of?
Thyroid Stimulating Hormone (TSH)
MOA of Thyroxine
- increases glycogenolysis, gluconeogenesis, intestinal absorption of glucose
This hormone is produced in the anterior pituitary gland.
Growth Hormone
Growth Hormone is stimulated by?
decreased glucose levels
MOA of Growth Hormone
- decreasing entry of glucose into cells
- increases glycolysis
This disease is associated with too much cortisol.
Cushing’s syndrome
This disease is associated with lack of cortisol.
Addison’s Syndrome
Hyperglycemia is categorized too high if?
FBS is higher than 100mg/dL
Hyperglycemia
non fasting
140 mg/dL
Blood sugar is considered too low if it is?
lower than 50mg/dL
Hypoglycemia can be one of trigger factors for?
seizures
