What are the differences between monosaccharides, disaccharides and polysaccharides, and provide examples
Monosaccharides: The simplest form of carbohydrates (single sugar units). Examples include glucose, fructose, and galactose.
Disaccharides: Two monosaccharides through a glycosidic bond. Examples include maltose, sucrose, and lactose.
Polysaccharides: Long chains of monosaccharides linked together. Examples include starch, glycogen, and cellulose.
Describe digestive enzymes involved in carbohydrate metabolism
Salivary Amylase: Breaks down starch into maltose and glucose in the mouth.
Pancreatic Amylase: Further digests carbohydrates in the small intestine.
Brush Border Enzymes: These include lactase, which breaks down lactose into glucose and galactose in the small intestine.
What is Enzymatic hydrolysis in carbohydrate metabolism? Provide an example including the enzyme involved.
It is a chemical process where complex carbohydrates are broken down into simpler sugars by the addition of a water molecules, catalysed by enzymes.
Examples: sucrose is broken down to glucose and fructose, by the catalytic action of sucrase enzyme
Describe the digestion and absorption of carbohydrates in the digestive tract, beginning in the mouth. Include of types of enzymes involved at each organ, and the end molecules produced. meow
- Mouth – chemical digestion from salivary amylase
- Stomach – Hydrochloric acid inhibits amylase, halting biochemical digestion.
- Pancreas: Secretes pancreatic amylase into the small intestine.
- Small intestine – the primary site of carbohydrate digestion. Pancreatic amylase continues breaking down starch into disaccharides. Brush border enzymes in the small intestine (e.g., lactase) further break down disaccharides into monosaccharides.
- Liver: Processes absorbed monosaccharides and helps regulate blood glucose levels.
- End molecules = disaccharides and monosaccharides
Formula for carbohydrates
- The general formula for carbohydrates is (CH2O)n, where “n” represents the number of carbon atoms.
What role does the stomach do in carbohydrate digestion and metabolism?
Hydrochloric acid inhibits amylase, halting biochemical digestion.
The stomach has 3 muscle layers, inner oblique, middle circular, and outer longitudinal layers which mix and churn food.
The end product of this is chyme
Describe the process of monosaccharide absorption of glucose, galactose, fructose, and how they enter the capillary.
- Absorption: Monosaccharides are absorbed by the enterocytes in the small intestine.
Glucose and galactose are absorbed via sodium-glucose cotransporter (SGLT) using active transport.
Fructose is absorbed through facilitated diffusion via GLUT-5. - The monosaccharides then exit the enterocytes and enter the capillaries via GLUT-2 by simple passive diffusion.
Role of liver
- The liver plays a central role in regulating blood glucose levels by storing glucose as glycogen and when there is bodily demand for glucose, the liver converts glycogen back into glucose.
- Produces 1L of bile a day
- Haematological regulation
- Metabolic regulation
How does carbohydrate metabolism differ from carbohydrate digestion?
- Metabolism = set of metabolic pathways which break down molecules into smaller units and release energy
- Digestion = process by which the body breaks down food so it can be absorbed by the blood stream
Composition and role of saliva
99.5% water, electrolytes and proteins
what are the accessory organs
- salivary glands
- Pancreas
- Liver
- Gall bladder
Lipids function
- Secondary energy source
- Lipids form phospholipid membranes and myelin sheaths, and adipose tissues to provide a protective layer for organs, insulation, and as a store of energy
- Lipids do not form polymers (repeating units of the same molecules or atoms)
structure of lipids
- The “OH” from the glycerol molecule binds to the “H” from the fatty acid
- A water molecule gets released, and the glycerol and fatty acid molecules link up.
Identify the 5 classes of lipids and describe their biochemical functions
- Free Fatty Acids: Used primarily as fuel and components of membrane lipids.
- Triacylglycerols: The storage form of fatty acids.
- Phospholipids: Key components of cell membranes, consisting of a polar head and nonpolar tails.
- Glycolipids: lipids that are bound to carbohydrates.
- Steroids: secreted by the endocrine system and function as hormones (e.g., estrogen, testosterone), and cholesterol.
Explain role of the liver, gallbladder, pancreas in lipid metabolism
- Liver: Produces bile (about 1L/day) that helps emulsify fats, making them more accessible for digestion.
- Gallbladder: Stores and concentrates bile, releasing it into the duodenum to aid in lipid digestion.
- Pancreas: Secretes pancreatic lipases into the small intestine, which break down triglycerides into fatty acids and monoglycerides.
Function of emulsification
- Mechanical processing in stomach creates large drops of lipids.
- Bile salts break droplets apart in a process called emulsification.
- Emulsifiers break large fat globules into smaller droplets.
- Emulsification makes lipids more accessible to digestive enzymes.
Explain lipid metabolism in a fed and fasted state
Fat metabolism in fed state
* Both unused fats from the diet and excess glucose will be stored as triglycerides in adipose tissue through a process called lipogenesis.
* This occurs when daily energy intake exceeds total energy demands
Fat metabolism in fasted state
* Follows period of time without food (such as between meals, during exercise, or during sleep)
* Lipolysis
This process releases fatty acids from stored triglycerides in adipose tissue.
What are monomers of lipids?
fatty acids and glycerol
The differences between monoglyceride, diglyceride, and triglyceride?
Monoglyceride – A lipid molecule that has 1 fatty acid attached to a glycerol molecule.
Diglyceride – a lipid molecule that has 2 fatty acids attached to a glycerol molecule.
Triglyceride - a lipid molecule that has 3 fatty acids attached to a glycerol molecule. Most common form of fat storage.
The meaning of Saturated fatty acids and Unsaturated fatty acids.
Saturated fatty acids
Saturated = as many hydrogens as possible
Only has single bonds making it linear
Solid at RT and high melting points
Bad because they block blood vessels which can prevent blood flow
Examples are pork, beef, cheese, milk, butter
Unsaturated fatty acids
Unsaturated = not saturated with hydrogen
Have one or more double bonds between carbons
Liquid at RT
They come in 2 forms: monounsaturated (one double bond) or polyunsaturated (multiple double bonds).
Enzymes involved in lipid digestion
- Lingual Lipase: Secreted in the mouth and initiates the breakdown of triglycerides.
- Gastric Lipase: Produced in the stomach and continues triglyceride digestion.
- Pancreatic Lipase: Secreted by the pancreas and plays a major role in breaking down triglycerides into fatty acids and monoglycerides in the small intestine.
The role of gallbladder
- Small pear-shaped, muscular sac
- Stores and concentrates bile produced by the liver.
- Releases bile into the small intestine duodenum.
- Aids in lipid digestion by emulsifying fats which makes them more accessible to digestive enzymes.
The meaning of micelles and chylomicrons.
- Micelles: Structures formed by bile salts surrounding the products of fat digestion (fatty acids and monoglycerides). Micelles help transport these products to the intestinal cells for absorption.
- Chylomicrons: one type of lipoprotein— Transports dietary lipids from intestinal cells to elsewhere in the body
Lipid digestion in infants
- Infants rely on lingual and gastric lipases for fat digestion. Breast milk contains lipase enzymes that are activated in the baby’s small intestine. The mother makes lipases and sends them in breast milk to help her baby digest the milk fats. Since there is increased activity of lingual and gastric lipases as well as the lipases contained in breast milk, young infants can efficiently digest fat for growth and brain development.
