Lecture 6 - Metabolism Flashcards
What are the foods and their percentages used by the body?
Carbohydrates (50% of American dietary calories)
Proteins (11-14%)
Lipids
Cholosterol
What is the only food that can move through the intestinal mucosa in its native state?
Cholesterol
What are the four main functions of the Digestive System?
- Motility
- Secretion
- Digestion
- Absorption
What is Motility?
Movement through the Digestive Tract
What is Secretion?
Release of enzymes, hormones and other substances that help the body digest food.
What is Digestion?
Breaking down the food into smaller components so it is able to cross the plasma membrane
What is Absorption?
Transfering the nutrient to the blood or lymph system
What is a Herbivore?
An animal that only eats plants (Deer)
What is a Carnivore?
An animal that only eats meat (Lion)
What is an Omnivore?
An animal that eats both plants and meat
What are the two types of herbivores?
- Ruminants
- Simple Stomach Herbivores
What is different about Ruminants compared to Simple Stomach Herbivores?
Ruminants are able to absorb FA and microbiota as they have a large intestine while SS herbivores cat use fermentation as they do not have a large intestine
What Is a Ruminants stomach like?
As ruminants, cows have a four-chamber stomach designed to break down parts of plants that humans, with our single-chamber stomachs, can’t. Each chamber in the ruminant stomach has a distinct function: The rumen is a 55-gallon chamber where a cow’s gut bacteria begin the process of digestion.
What are the two types of Digestion in animals?
1.) Enzymatic Digestion
2.) Microbial Digestion: Fermentation
What is the Digestion in Carnivores mostly?
Enzymatic
What is the Digestion in Herbivores and Omnivores?
Enzymatic and Microbial
What is the consequence of enzymatic and mcirobiotal digestion in SS herbivores and ruminants?
Reversed
What are polysaccharides?
Starch: complex carbohydrate
What are Disaccharides?
Maltose, Sucrose, Lactose
What are Monosacchardies?
Glucose, Galactose, Fructose
What are most carbs ingested as?
Starches
What is the most commonly digested sugar?
Sucrose (table sugar) and lactose (milk)
What does amylase do?
Takes starch (polysaccharide) and convert it into disaccharide
What are some brush border enzymes?
Dextrinase, Glucoamylasse, Lactase, Maltase, Sucrase
What do the BB enzymes do?
They convert the disaccharide into a monosaccharide
What does a-dextrinase do?
Targets small polymers of glucose into multiple molecules of glucose
What happens when we chew food?
It mixes our food with our salivary secretions that contains ptylalin (a-amylase)
What does ptyalin do?
Hydrolyze starch into maltose and other glucose polymers (30-40%) in the mouth and stomach
What happens to the salivary amylase?
Because people do not chew their food for very long periods of time. the salivary amylase turns inactive by the stomach pH and the rest of the complex carb gets digested by the pancreatic amylase
What do pancreatic secretions contain?
Large amounts of amylase
What is pancreatic amylase?
Is more potent then salivary amylase
Where do carbohydrates get hydrolyzed?
In the small Intestine (duodenum)
What happens within 30 minutes of carbohydrate digestion?
All carbohydrates will be hydrolyzed into maltose (and other glucose polymers) in the duodenum and jejunum
What is an overview of the Digestion of Carbohydrates?
Salivary amylase starts in the mouth, gets inactivated in stomach, pancreatic amylase begins to start in the stomach, Brush border enzymes in the small intestine turn the starch into monosaccharides
What happens to disaccharides?
Sucrose, lactose and maltose get broken down by brush border enzymes: lactase, sucrase and maltase
What happens to the monosaccharides that are formed?
Internalized by the absorptive cell and and diffuse out into the intestinal villi (go into small small intestine, diffuse into microvilli)
What is the solubility of a monosaccharides?
Water-soluble, therefore absorb right into the blood stream
What is the typical breakdown product?
80% glucose
10% fructose
10% galactose
What happens to the blood leaving the villi of the small intestine?
It drains into blood vessels leading to the hepatic portal system (liver)
What is the blood leaving the villi like?
Rich in nutrients
Where can this blood go?
Tthe general circulation system
What happens to blood viscosity?
It can be increased which can have an effect on blood pressure
What is the first pass effect?
As the blood passes through the vessels of the liver, much of the nutrient loaf is removed
What are the stages of the Hepatic Portal System?
1.) SI absorbs the products of digestion
2.) Nutrient molecules travel to hepatic portal vein to liver
3.) Liver monitors blood content
3.) Blood enters general circulation by hepatic vein
What is Glucose?
An essential nutrient for energy production
What happens with excess glucose?
Glucose can be converted into glycogen and stored in the liver
What happens to glucose in the blood stream?
Insulin is released by the pancreas (islet of langerham), insulin binds to cell surface receptors, trigger glucose uptake by facilitated diffusion
What does a “high” Glycemic index mean?
They can make your blood sugars rise
What is a low GI?
Less than 55
What is a medium glycemic index?
Between 55 - 69
What is high GI?
Greater then 70
What happens during low GI foods?
Your blood sugar rises, but your insulin keeps up
What happens during high GI foods?
Your blood sugar rapidly rises, and then your blood sugar crashes and the insulin tries to keep uo
What was the findings of the mice with a high GI?
They had 2x more body fat then the mice on a low glycemic diet
What are the stages of insulin resistance?
High fat diet –> high blood glucose
—> constant high insulin levels –> insulin receptors become resistance –> glucose not being absorbed –> insatiable hunger and cravings
What does a low carb diet and insulin do?
Low Carb Diet –> decreasing insulin levels –> fat burn –> weight loss
What is ozempic?
It is a GLP1 (glucagon like peptide 1) receptor agonist
What does a GP1 receptor do in your brain?
Decreases appetite
What does it do in your pancreas?
Increase insulin
What does it do in your stomach?
Decrease gastric motility and emptying
What are some benefits of GLP1 receptors?
- Weight loss
- Decrease in CV disease
- Type 2 Diabetes
- Better insulin and glucose control
What are some negatives of GLP1 receptors?
- Hypoglycemia
- lifelong problems of the GI tract
- Thyroid tumours
What are examples of cholesterol?
- Yolks, butter, milk, creek, meat
How is cholesterol absorbed?
Without digestion
How much blood cholesterol comes from the liver?
85%
How much blood cholesterol comes from our diet?
15%
How is cholesterol transported in the blood?
Associated with lipoproteins
What is cholesterol a major component of
Cell membranes
What is cholesterol the base substrate for?
Steroid Hormone synthesis
What are the major types of fats?
- Triglycerides
- Phospholipids
- Sterols
Where does a small amount of fat digestion occur?
In the stomach
What are triglycerides digested by?
Lingual lipase swelled with saliva which accounts for about 10% of fat digestion
What is the problem with lipids not being water-soluble?
The enzymes can not get to them
What do enzymes in solution have?
Only limited access to the insoluble lipid
What do bile salts do?
Help lipid digestion by emulsifying them (breaking them into small droplets)
What do bile salts help with
The effect of greatly enhancing access of the lipase to lipid molecules
What are the enzymes that digest triglycerides and phospholipids?
Lipase - only present in pancreatic juices
Where can lipid digestion only occur?
In the small intestine (following emulsification of bile)
What do triglycerides get digested by?
Pancreatic lipase
What does pancreatic juice contain?
An enormous amount of pancreatic lipase
What does pancreatic lipase do?
Splits the triglyceride into free fatty acids and monoglyceride
Where do the products of triglycerides go?
Diffuse into the absorptive cells
What do these Absorptive Cells do?
Re-synthesize tryglcerides from monoglycerides and fatty acids and leave the cells by exocytosis and enter the lacteals of the villi
What are chyomicrons secreted into?
The lacteals of the villi, passing through the lymphatic system until they reach the bloodstream through the thoracic duct
What do the chylomicrons add in the blood?
ApoE protein
What does ApoE protein do?
Helps bind to the capillaries in the target muscles and adipose tissue
How are the chylomicrons digested?
In target tissues by lipoprotein lipase, releasing the fatty acids - used by skeletal muscles for energy
What happens after the triglyceride is broken up
The depleted chylomicron particle goes back through circulation into the liver
What are proteins?
Chains of amino acids
How does protein digestion occur?
Via proteases produce large polypeptides (shorter chains of AA)
How does digestion of large polypeptides occur?
Via peptidases which produces smaller amino acids
What do the BB enzymes peptidases do?
Covert small polypeptides into amino acids
What is the important proteinase in the stomach?
Pepsin (functions at a pH of 2 - 3, inhibited at pH greater then 5)
What is pepsin one of the only enzymes capable of?
Digesting collagen
What are the pancreatic proteolytic enzymes?
Trypsin
Chymotrypsin
Carboxypeptidase
Proelastate
What are Enterocytes?
Contain other peptidases that are specific for linkages between amino acids
What do endopeptidases do?
Cleave internal bonds
What do exopeptidase do?
Cleave off the ends
What are 99% of final protein products?
Single amino acids that pass into the blood stream
What are AA’s transported into absorptive cells by?
Transport Proteins (carrier-mediated transport)
What are peptides digested by?
Brush Border Peptidases - the AAs fired are transported by a transporter associated with the enzyme into the absorptive cell
What do transport proteins do?
Carry the AAs out of the absorptive cells to the capillaries of the villi
Can AAs be stored?
No - expect for components of cell protein
What is the amine unit of the AA?
Removed to make urea, remaining part of molecule is converted into a lipid
What is urea excreted as?
A component of urine
What are calcium ions for?
Active absorption in blood
What does your parathyroid hormone do?
Activates Vitamin D - enhances calcium absorption
What are iron ions important for?
Formation of Hb
What are K+., Mg2+, phosphates important for?
Direct absorption through the intestinal mucosa
Where does vitamin absorption occur?
Mainly by the passive process of diffusion in the jenumim and ileum
What are fat soluble vitamins absorbed with?
Dietary Lipids (Vitamins A, E, D, K)
What do water soluble vitamins (B1 thiamine, B2 riboflavin, B2 niacin) do?
Diffuse into blood (all expect B12)
What does B12 do?
Combine with intrinsic factor produced by the stomach
What do water soluble vitamins do?
Pass into urine when their concentration in palms exceeds the renal capacity for reabsorption
