Exam 3 slides 6 Flashcards
What three macronutrients predominate the human diet? List two micronutrients.
o Carbohydrates, Lipids, Proteins
What is the primary and preferred fuel source for the human body?
carbs and fats
Define glycogen. Name some potential dietary sources of carbohydrate.
o Excess glucose is converted to glycogen or fat and stored in the liver
o Primarily from plants
o Starches: complex carbohydrates – grains, vegetables
o Sugars: mono and disaccharides in fruit, sugarcane, honey, milk
o Small amounts from the glycogen in meat
Make a list of the different types of lipid in the human diet that were mentioned in class. Next to each one, write a functional use for that type of lipid.
o Adipose tissue for protection, insulation, fuel storage
o Phospholipids for myelin sheaths, cell membranes
o Cholesterol to stabilize membranes; a precursor of bile salts and steroid hormones
o Prostaglandins for smooth muscle contraction, BP control, inflammation
o Absorption of fat-soluble vitamins
o Fuel for hepatocytes and skeletal muscle
List the structural and functional uses for protein. What’s the difference between a complete protein source and an incomplete protein source?
o Structural materials – keratin, collagen, elastin, muscle protein
o Functional molecules – enzymes and hormones
o Complete Proteins: contain all essential AAs
o Animal products – eggs, milk, fish, meats
o Soybeans
o Incomplete Proteins: lacking some essential AAs
o Beans, nuts, cereals
After digestion, the chemical subunits of the nutrients we eat are absorbed through what type of epithelial cell?
Enterocytes lining the GI tract are polarized and connected by tight junctions
Material must move through the enterocytes – enters via apical membrane, exits through basolateral membrane to interstitial fluid
Know the absorption pathway for each type of digested nutrient.
Certainly! Here’s an overview of the absorption pathways for each type of digested nutrient:
-
Carbohydrates:
- Absorption primarily occurs in the small intestine.
- Monosaccharides (such as glucose, fructose, and galactose) are absorbed across the epithelial cells lining the small intestine via specific transporters.
- Glucose and galactose are transported into enterocytes via sodium-dependent glucose transporters (SGLT1) and then exit the enterocytes into the bloodstream via glucose transporters (GLUT2).
- Fructose is transported into enterocytes via facilitated diffusion and exits into the bloodstream via GLUT5 transporters.
-
Proteins:
- Absorption primarily occurs in the small intestine.
- Proteins are broken down into amino acids, dipeptides, and tripeptides by proteolytic enzymes in the lumen of the small intestine.
- Amino acids, dipeptides, and tripeptides are absorbed across the epithelial cells lining the small intestine via specific transporters.
- Amino acids are transported into enterocytes via various amino acid transporters and then exit into the bloodstream.
- Dipeptides and tripeptides are transported into enterocytes via specific peptide transporters (PEPT1) and are then broken down into amino acids within the enterocytes before being released into the bloodstream.
-
Lipids:
- Absorption primarily occurs in the small intestine.
- Lipids are broken down into fatty acids, monoglycerides, and other lipid digestion products by pancreatic lipase and other enzymes.
- Lipid digestion products are absorbed across the epithelial cells lining the small intestine.
- Fatty acids and monoglycerides are reassembled into triglycerides within enterocytes and packaged into chylomicrons.
- Chylomicrons are transported via the lymphatic system into the bloodstream, where they deliver dietary lipids to various tissues.
Each nutrient has its specific transport mechanisms and absorption pathways to ensure efficient uptake by the body for energy production, tissue repair, and other physiological processes.
What are the smallest chemical subunits of carbohydrate? Of protein? Of lipid? Of nucleic acid?
o Carbs – glucose, fructose, galactose
o Protein – amino acids
o Lipid – free fatty acids and glycerol
Be able to state what enzyme is primarily driving digestion of each type of nutrient.
o Carbs – amylase
o Protein – protease
o Lipid - lipase
Appreciate the extra steps required to satisfactorily digest lipids (i.e. micelles, chylomicrons).
Certainly! The digestion and absorption of lipids involve several steps:
- Emulsification: Large fat globules are broken down into smaller droplets by bile salts secreted by the liver and stored in the gallbladder. This process increases the surface area of the fat, facilitating the action of lipases.
- Hydrolysis: Pancreatic lipase, along with co-lipase and other digestive enzymes, hydrolyzes triglycerides into fatty acids and monoglycerides in the small intestine.
- Micelle Formation: Fatty acids, monoglycerides, and other lipid digestion products combine with bile salts to form micelles. Micelles are small, water-soluble particles that transport lipid digestion products to the surface of the intestinal absorptive cells (enterocytes).
- Absorption: Lipid digestion products are absorbed by enterocytes in the small intestine. Once inside the enterocytes, fatty acids and monoglycerides are reassembled into triglycerides.
- Chylomicron Formation: Triglycerides, along with cholesterol and fat-soluble vitamins, are packaged into chylomicrons within the enterocytes. Chylomicrons are large lipoprotein particles that transport dietary lipids through the lymphatic system and eventually into the bloodstream.
- Transport: Chylomicrons travel through lymphatic vessels and enter the bloodstream via the thoracic duct. They deliver dietary lipids to various tissues throughout the body.
These steps are essential for the efficient digestion, absorption, and transport of dietary lipids, ensuring that the body can utilize them for energy production, cell membrane synthesis, hormone production, and other physiological functions.
What solute is primary responsible for creating and maintaining the concentration gradient needed to drive the reabsorption of water by the LI?
Na+
Define malabsorption and celiac disease.
o Malabsorption: can result from anything that interferes with delivery of bile or pancreatic juice or from anything that damages intestinal mucosa (ex: bacterial infections or antibiotics)
o Celiac Disease/Gluten-Sensitive Enteropathy: a common malabsorption disease
o Chronic, genetic condition that causes an immune reaction to gluten
o Gluten is a protein found in many grains
o Intestinal villi and brush borders are damaged
o Affects 1:100 people
o Symptoms: bloating, diarrhea, pain, malnutrition
o Treatment: gluten-free diets
Recall the equation of cellular respiration and generally know the three stages of metabolism. Where does stage II occur? Which stage occurs in mitochondria?
o Cellular Respiration: a group of catabolic reactions – glycolysis + citric acid cycle + oxidative phosphorylation – that produces ATP
o Stage I: Digestion, Absorption, Transport to Tissues
o Stage II: Cellular Processing in the Cytoplasm
o Synthesis of lipids, proteins, glycogen
o Catabolism into pyruvic acid and acetyl CoA (glycolysis)
o Stage III: Catabolism in the Mitochondria
o Oxidative breakdown into CO2, H2O, and ATP
What are the rooting and sucking reflexes?
o Rooting Reflex: head turns towards the stroked cheek
o Sucking Reflex: sucking upon stimulus to the roof of the mouth
Review the congenital defects associated with the digestive tract. How does cystic fibrosis play a role in impaired digestion?
Cystic Fibrosis: impairs the pancreas through production of abnormally thick mucus – blocks the digestive organs’ ducts
