Lecture 17- 18 Flashcards
How does the carbohydrate metabolism work?
-starts in the mouth
-amylase breaks down carbohydrates
-enzymes are transported from the small intestine to the bloodstream
How does Carbohydrate absorption and transport occur?
Maltose is broken down into two glucose molecules
-malt sugar, ex: beer, bread, sweet potatoes
Sucrose is broken down into fructose and glucose, seen in fruits
Lactose is broken down into galactose and glucose
-dairy products
Starch is broken down into three glucose molecules
-seen in corn, potatoes starch-like molecules
-active and facilitated transport completed into circulation
-glucose is transported into the bloodstream through capillaries and travels to the liver
What are some bad health conditions that occur from carbohydrate transport?
-celiac disease
A deficiency in lactase causes lactose intolerance
-don’t secrete enough of the lactase in your body by the brush border
-symptoms could occur in the gi tract or could be diarrhea
-when the villa becomes normal surface area increases and is no longer lactose intolerant
-glucose and galactose are absorbed by active transport move to the bloodstream
-fructose is absorbed by facilitated transport
How does peptide and amino acid transport?
examples of protein: beans, legumes and chicken
1. Proteins broken down intosmaller peptides- start as long strings of amino acids
-cotransport with sodium
-cared directly across the cell by transcytosis
-di- and tripeptides cotransport with hydrogen
2. Epithelial cells secrete peptidases to break down larger peptides into individual amino acids
3. Transported throughout the body via the bloodstream in order to produce energy (in
liver) or protein synthesis
What occurs when emulsifying fat makes fat soluble in bile?
-fats are found in almost every food consumed
Ex: peanut butter, oil
lipid digestion starts in the stomach with the secretion of gastric lipase
-fat globule (non-polar)- equal sharing of electrons
-water (polar)- unequal sharing of electrons
-increase pancreatic lipase, which hydrolyzes fatty acids
-goes from mouth to stomach to small intestine
- small intestine- chyme triggers the release of bile from the gall bladder
-bile salts break down large lipids
-into fat droplets (nonpolar), phospholipids and triglycerides in water (polar
-Bile salts are Amphipathic:
Hydrophilic (interface water) AND lipophilic/hydrophobic (interface lipids), like a
soap or detergent
How does the breakdown of fat lipase occur?
-a closer look at the small intestine
Lipase (from the pancreas) attaches to monoglyceride due to a hydrolysis reaction
Monoglyceride absorbs the fatty acid and turns into micelles, which help in the absorption of lipid vitamins
The absorptive cell is included in the brush border
Microvilli transport fats into cells
How does lipid absorption and transport occur?
Absorbed as fatty acids and monoglycerides
-from brush border
Reassembled into triglycerides and packaged
as chylomicrons (a type of lipoprotein)
Chylomicrons (transport glycerol) are too large to cross the capillary wall…
first absorbed into the lymphatic system
-Will re-enter circulation via thoracic duct near the heart
What is included in the large intestinal phase of digestion and absorption?
-chyme gets into the transverse colon
Ileal chyme (a chemical and particle-rich liquid) comes from the ileum (ileocecal valve)
-Any unabsorbed nutrients
Hormones and chemical messengers
-Soluble fibre (prebiotic)
-Insoluble fibre (bulking agent)
-Microbes (probiotics and others)
-Cellular debris
-Excretion products from the liver
What happens in the large intestine (cecum plus colon)?
-The absorption of water takes place in the colon, as opposed to the small intestine, which absorbs sodium (key takeaway)
- The colonic epithelium absorbs water and simple ions like sodium potassium magnesium and calcium
- The resident microbes digest and absorb the chemicals that they can (prebiotics) in a process called fermentation. They produce short-chain fatty acids and end products of fermination; bacterial species are byproducts.
- The resident microbes produce some vitamins (vitamin K and some vitamin B’s) as a by-product of their metabolism. Some of their end products can have hormone-like activity-breakdown of unabsorbed nutrients
- The residence microbes produce gases during their digestion and consumption of the illegal chime (carbon dioxide methane hydrogen sulfide)
- Newly arriving live microbes (probiotic or other) seek to get a foothold in the microbial ecosystem and multiply.
What motivates you to eat?
What is hedonic hunger, or eating?
“the drive to eat to obtain pleasure in the
absence of an energy deficit.”
-full from a meal but still eat anyway; excess calorie intake
A certain level is unhealthy and can lead to eating disorders (not listing your body)
-to a certain level is a good thing
What is homeostatic hunger, or eating?
“Increased motivation to eat following depletion of energy stores”
-truly require calories for energy
What is normal eating?
stomach, mouth, or heart hunger?
review the last slide of this lecture
testable, like asking questions—is this an example of normal eating?
What is the Energy Distribution System?
Energy is defined as the capacity to do work
ATP: the medium of energy exchange
Adenosine Triphosphate,
Energy Currency of the Cell- use ATP
-Triphosphate: high energy phosphate bonds
What are some quick facts about Substrate Oxidation and ATP-producing pathways?
-Glucose and fatty acid metabolism generate most of the ATP … relatively little
from amino acids (protein) (but still some)- carbohydrate-site of glycolysis
-Some ATP is generated by glycolysis and Kreb’s cycle
-Glycolysis, beta oxidation and Kreb’s cycle produce reducing equivalents….
NADH and FADH2- fat
-produces acetyl CoA
-NADH and FADH2 supply protons (H+) and
electrons (e-) to the electron transport chain. *THIS is where most of the ATP is made.
-oxygen is the final electron acceptor
What is Anaerobic ATP production?
-ATP can also be generated WITHOUT O2 by:
* Phosphocreatine (PCr) degradation
* about 9-10 seconds worth !
ATP → ADP + Pi
PCr + ADP + H+ → ATP + Cr
*ATP is rebuilt by adding a phosphate to ADP
Glycolysis will also continue to produce ATP (end product is *lactate in anaerobic conditions)
- E.g sprints!
What are macronutrients and how do they store energy?
- Fat: most energy is stored as triglycerides (a form of fat)
in our adipocytes - Carbohydrate is stored as:
- Glycogen in liver (~150 g); most concentrated as liver is only ~2 kg!
-liver is 4 pounds so glycogen is highly concentrated. - Glycogen in muscle (~350 g); ~40% body mass is muscle
-more muscles in body, with men having more than women typically - *Only ~ 30 g of glucose is found in the blood—not much!
- Protein also represents a large potential energy source
(~40% body mass is muscle.)
The body will not break down proteins at the first site - This is obviously protected, but will be used in starvation or caloric restriction- when we are really hungry and lose muscle mass
Example: someone who is very sick and does eat is bedridden.
Protein must be broken down.
