Lecture Quiz 3 Flashcards
<p>Define nutrient</p>
<p>a substance that promotes normal growth, maintenance, and repair</p>
<p>What are the major nutrients?</p>
<p>carbohydrates, lipids, proteins</p>
<p>What are other nutrients?</p>
<p>vitamins and minerals
| water</p>
<p>Define metabolism</p>
<p>all chemical reactions necessary to maintain life</p>
<p>What is an anabolic reaction?</p>
<p>synthesis of larger molecules from smaller ones</p>
<p>What is a catabolic reaction?</p>
<p>hydrolysis of complex structures into simpler ones</p>
<p>What happens during cellular respiration? (vague)</p>
<p>food fuels are broken down within cells and some of the energy is captured to produce ATP</p>
<p>What do enzymes do during cellular respiration?</p>
<p>shift the high energy phosphate groups of ATP to other molecules
these phosphorylated molecules are activated to perform cellular functions</p>
<p>What are the three major stages of metabolism?</p>
<p>digestion
anabolism
oxidative breakdown
occurs in the mitochondria</p>
<p>What happens during digestion?</p>
<p>breakdown of food
| nutrients are transported to tissues</p>
<p>What happens during anabolism of metabolism?</p>
<p>nutrients are built into lipids, proteins, and glycogen
| nutrients are broken down by catabolic pathways to pyruvic acid and acetyl CoA</p>
<p>What happens during oxidative breakdown of metabolism?</p>
<p>nutrients are catabolized to carbon dioxide, water, and ATP
complete breakdown of foods</p>
<p>What catalyzes redox reactions?</p>
<p>enzymes
| dehydrogenases</p>
<p>When does oxidation occur?</p>
<p>gain of oxygen
| loss of hydrogen</p>
<p>What is a rule of thumb for redox reactions?</p>
<p>whenever one substance is oxidized, another substance is reduced</p>
<p>What are the energy shifts in redox reactions?</p>
<p>oxidized substances lose energy
| reduced substances gain energy</p>
<p>What do coenzymes do in redox reactions?</p>
<p>act as hydrogen/electron acceptors</p>
<p>What are the two important coenzymes and what are they derived from?</p>
<p>nicotine adenine dinucleotide (NAD+) - derived from B3 niacin
Flavin adenine dinucleotide (FAD) - derived from B2</p>
<p>Where does substrate level phosphorylation occur?</p>
<p>cytoplasm and mitochondria</p>
<p>What happens during substrate level phosphorylation?</p>
<p>high-energy phosphate groups are transferred directly from phosphorylated sunstrates to ADP
ATP is synthesized in glycolysis and Krebs cycle</p>
What is oxidative phosphorylation?
only occurs in the mitochondria
uses chemiosmotic process whereby the movement of substances across a membrane is coupled to chemical reactions
Where does oxidative phosphorylation occur?
carried out by electron transport proteins in the cristae of the mitochondria
Give a brief overview of oxidative phosphorylation
nutrient energy is used to pump H+ into intermembrane space
steep diffusion gradient results
H+ ions flow back across membrane through ATP synthase
energy is captured and added to ADP
Where do the bile duct and main pancreatic duct join the duodenum?
hepatopancreatic ampulla
What are the bile duct and main pancreatic duct controlled by?
sphincter of Oddi
What is the purpose of the structural modifications of the small intestine?
increases surface area
ideal for absorption
What are the plicae circulares?
deep circular folds of the mucosa and submucosa
What are the villi?
fingerlike extensions of the mucosa
What are the microvilli?
tiny projections of absorptive mucosal cells plasma membranes
What is the epithelium of the mucosa of the small intestine made up of?
absorptive cells and goblet cells
enteroendocrine cells
interspersed T cells called intraempithelial lymphocytes (IELs)
What do IELs do?
release cytokines upon encountering Ag
What do the cells of intestinal crypts do?
secrete intestinal juice
What are found in the submucosa?
Peyer’s patches
What are Brunner’s glands?
found in the duodenum
release alkaline mucus
What are Paneth’s cells?
fortifying small intestine defenses by releasing antimicrobial agents defensins and lysozymes
What is intestinal juice?
slightly alkaline and isotonic with blood plasma
largely water
enzyme poor
contains mucus
provides little of what is needed for digestion
What secretes intestinal juice?
intestinal glands
in response to distension or irritation of the mucosa
What is the status of nutrients when chyme enters the duodenum?
carbohydrates and proteins are only partially digested and no fat digestion has taken place
Describe how digestion continues in the small intestine
chyme is released slowly into the duodenum
mixing is required for proper digestion due to low pH
required substances needed are supplied by the liver and pancreas
virtually all nutrient absorption takes place here
What is the most common motion of the small intestine?
segmentation
contents moved steadily toward the ileocecal valve
What cells initiate segmentation in the small intestine?
Cajal cells in the circular smooth muscle
What happens after nutrients have been absorbed in SI?
peristalsis begins with each wave starting distal to the previous
meal remnants, bacteria, mucosal cells, and debris are moved into the large intestine
What coordinate intestinal motility?
local enteric neurons of the GI tract
What do cholinergic neurons cause in SI?
contraction and shortening of the circular muscle layer
shortening of longitudinal muscle
distension of the intestine
What do non cholinergic impulses do to the SI?
relax the circular muscle
What do gastroileal reflex and gastrin do to SI?
relax the ileocecal sphincter
allow chyme to pass into the large intestine
ensures contents of stomach are completely removed
How do fatty acids and monoglycerides enter interstitial cells?
diffusion
What happens to fatty acids after they have entered interstitial cells?
combined with proteins within the cells
resulting chylomicrons are extruded
they enter lacteals and are transported to the circulation via lymph
How does fat digestion happen?
lipase breaks fat down to fatty acids/monoglycerides
polar end of bile salt binds to fatty acid forming micelles
micelles ferry fatty acids to intestinal wall
fatty acids detach and diffuse into epithelial cells
recombined with proteins and form chylomicrons
enter lacteals and are carried away by lymph
How are nucleic acids absorbed?
active transport via membrane carriers
absorbed in villi and transported to the liver via hepatic portal vein
What enzymes are used in nucleic acid absorption?
pancreatic ribonucleases
deoxyribose in small intestines
How are electrolytes absorbed?
actively along the small intestine
requires energy
How is Na+ absorbed?
coupled with absorption of glucose and amino acids
How is ionic iron absorbed?
transported into mucosal cells
binds to ferritin
How are anions absorbed?
passively follow the electrical potential established by Na+
How is potassium absorbed?
across the intestinal mucosa in response to osmotic gradients
How is calcium regulated?
regulated to blood levels of ionic calcium
regulated by vitamin D and parathyroid hormone (increases Ca2+)
Describe water absorption
95 % happens in SI by osmosis
moves in both directions across mucosa
coupled with solute uptake
as water moves into mucosal cells, substances follow along their concentration gradient
When does net osmosis occur?
whenever a concentration gradient is established by active transport of solutes into the mucosal cells
What causes malabsorption of nutrients?
anything that interferes with delivery of bile or pancreatic juice
What is gluten enteropathy?
celiacs
gluten damages the intestinal villi and reduces the length of microvilli
What is the teniae coli?
three bands of longitudinal smooth muscle in the muscularis of LI
What are the haustra?
pocketlike sacs caused by the tone of the teniae coli in LI
What are the epiploic appendages?
fat-filled pouches of visceral peritoneum
significance unknown
Describe the cecum
lies below the ileocecal valve in the right iliac fossa
contains a wormlike vermiform appendix
How are the transverse and sigmoid portions anchored?
mesenteries known as mesocolons
intraperitoneal
Where are the ascending and descending portions of the colon located?
retroperitoneal
Where is the anal canal found?
external to the peritoneal cavity
last segment of large intestine
What stops feces from being passed with gas?
three valves of the rectum
Describe the internal sphincter of the anus
composed of smooth muscle
involuntary
remains closed aside from time of defecation
Describe the external sphincter of the anus
skeletal muscle
voluntary
remains closed aside from time of defecation
What cells line the colon mucosa?
simple columnar epithelium no villie no secretory cells no enzymes numerous deep crypts lined with goblet cells
What cells line the anal mucosa?
stratified squamous epithelium
What do the anal sinuses do?
exude mucus and compress feces
Describe the vasculature of the anus
superficial venous plexuses
inflammation results in itchy varicosities called hemorrhoids
What are anal columns?
longitudinal folds superior to the pectinate line
aids in emptying anal canal
What does the bacterial flora of the large intestine consist of?
bacteria surviving the small intestine that enter the cecum
those entering via the anus
What does the bacterial flora do?
colonize the colon
ferment indigestible carbohydrates
release irritating acids and gases
synthesize B complex vitamins and vitamin K
What are the functions of the large intestine?
main function is propulsion of fecal matter toward anus
not essential for life
no digestion
Describe haustral contractions
slow segmenting movements that move the contents of the colon
sequentially contract as they are stimulated by the distension
What does presence of food in the stomach do to LI?
activates gastrocolic reflex
initiates peristalsis that forces contents towards the rectum
Describe what happens during defecation
rectal wall distended by feces
stimulates contraction of the rectal walls
relaxes the internal anal sphincter
voluntary signals stimulate relaxation of the external anal sphincter
What is Valsalva’s maneuver?
contraction of diaphragm, abdominal muscles, levator ani muscle
increases abdominal pressure
aids in defecation
