Class Notes (838,055)
Canada (510,630)
Biology (1,303)
BIOL 103 (255)
Lecture 2


16 Pages
Unlock Document

BIOL 103
Virginia K Walker

BIOL103 WEEK 2 HOMEWORK ABSORPTION SMALL INTESTINE -nearly all digestion and absorption of food + water occurs in the first quarter -hydrolytic enzymes break down molecules of organic nutrients into monomers -enzymes are on the lumen surface of the intestinal lining cells or secreted by pancreas -monomers absorbed across epithelial cells and enter blood -vitamins and minerals not digested, absorbed in s. intestine -water absorbed by osmosis from s. intestine in response to movement of nutrients gradient -large SA due to infoldings and specializations along length (villi and microvilli --> brush border) -large SA ^ chance of food particle meeting a digestive enzyme andn being absorbed -lacteal blood vesselin the centre of villi -->most too bulky to enter capillaries; fats absorbed through larger, wider lacteals of lymphatic system -->materials absorbed by lacteals enters circulatory system -->other nutrients absorbed directly into capillaries-->veins -duodenum, jejunum, ileum -herbivores have longer small intestine than carnivores (added time for plant material to be digested/absorbed) -less nutritious foods=longer s. intestine LARGE INTESTINE -cecum forms a small pouch, extends into the appendix -colon (ascending, transverse, and descending) -sigmoid colon (terminal portion of descending) empties into rectum, ending at the anus -chyme enters the cecum through a sphincter, which relaxes and opens after a meal -larger diameter, but smaller SA than s. intestine -l. intestine temporarily stores undigested material; concentrates it be absorbing salts and water -defecation: when contractions of rectum and relaxation of sphincter muscles expels feces through anus -absorbtion of products formed by bacteria living here (eg. small amounts of vitamins) -->other bacterial products: gas CARBS -starch digestion begins in the mouth, by salivary amylase -acid in stomach destroys amylase, preventing further digestion from saliva -starch digestion resumes in s. intestine by pancreatic amylase; mostly completed in s. intestine -->products via amylase are maltose -maltose, sucrose, and lactose broken down into fructose, glucose, and galactose by enzymes on brush border of s. intestine -monosacch. moved across epithelial membrane into blood -->fructose enters epith. cells via facilitated diffusion -->glucose and galactose enter epith. cells via secondary active transport coupled to sodium -monosacch. leave epith. cells and enter blood via facilitated diffusion transporters -->transepithelial transport: transport of substances from the lumen to blood, across epith. cell layer PROTEINS -broken down into peptides in the stomach by pepsin and in the small intestine by trypsin and chymotrypsin (latter 2 secreted by pancreas as zymogens: inactive precursors of enzymes, prevents enzyme from digesting pancreas itself) -once zymogen enters the s. intestine, it is enzymatically cleaved into the active molecules -trypsin activates zymogen form of chymotrypsin -peptide fragments further digested into amino acids by proteases on luminal membranes of epith. cells -amino acids enter epith. cells by secondary active transport coupled to sodium -leaves epith. cells and enters blood via facilitated diffusion carrier -mostly completed in upper portion of the small intestine FATS -most ingested fats in the form of triglycerides -digestion occurs entirely in s. intestine by pancreatic lipase: catalyses splitting of bonds linking fatty acids to glycerol--> 2 fatty acids + monoglyceride -poor water solubility; digestion of fats can only take place at the surface layer of a lipid glob -to ^ rate of digestion, fat is emulsified: disrupts large lipid droplets into smaller droplets (^ SA and exposure to lipase) -emulsification requires mechanical disruption -->caused by muscular contractions of stomach and s. intestine -->bile serves as an emulsifying agent (amphipathic) -absorption of poorly soluble products of lipase rxn facilitated by formation of micelles: bile salts, phospholipids, fatty acids, monoglycerides, core of fat-soluble vitamins and cholesterol -micelle continually breaks down/reforms near epith. membrane; individual molecules released into sol'n and diffuse across epith. membrane -fatty acids and monoglycerides enter epith. cells, triglycerides released on other side of epith. cell into interstitial fluid -->in epith. cell, resynthesized into triglycerides -->occurs in S.E.R. -->resynthesized triglycerides aggregate into chylomicrons -->released by exocytosis from epith. cell and passes into lacteal of intestinal villi, emptying into veins VITAMINS + MINERALS + WATER -not digested, absorbed in their complete form -water-soluble vitamins absorbed by diffusion or active transport -fat-soluble vitamins absorbed as fats would be -malabsorption: any interference w/ secretion of bile that decreases the absorption of fat-soluble vitamins --> leads to vitamin and mineral deficiency -small amounts of water absorbed from chyme in stomach -epith. cell membranes of s. intestine very permeable to water; water flows via osmotic gradient set by solutes EXCRETORY SYSTEM (Ch 47) -maintenance of body water levels is important (and ratio of water to salt in body) Elimination of Nitrogenous Waste -proteins in food and RNA broken down to smaller components- products are nitrogenous wastes: molecules w/ N from NH2 amino groups -toxic in high [ ] -eliminated in the form of ammonia and ammonium ions, urea, or uric acid (depending on species + environment) -only certain species (sharks, ray, skates) can survive with high [N waste] in blood and bodily fluids NH3 and NH4+ ions: most toxic; disrupts pH, ion electrochem. gradients, and redox rxns -animals that excrete this usually live in water -excreted across skin (invertebrates) or via gills and kidneys (fish) -b/c it's so toxic, aquatic animals excrete it as quickly as it's formed Urea: all mammals, most amphibians, some fish + reptiles +invertebrates -urea is less toxic than ammonia, doesn't require large V of water for excretion -animals can tolerate some accumulation of urea in blood, tissues, and bodily fluids -conserves water, removes need to constantly excrete, reduces chance of toxicity -converting ammonia--> urea uses moderate amount of ATP Uric acid: birds, insects, and most reptiles; also excrete purines (nitrogenous compounds) -less toxic than urea, but are more costly in terms of ATP to produce -poor solubility in water, not excreted in watery urine -mixed w/ other salts and waste into semisolid excretion -E usage requires is balanced w/ water conservation eg. Freshwater fish -b/c freshwater has very little [salt], salt gradient could move salts from fish's body into water -could move water into the fish -freshwater fish lose salt and gain water when ventilating gills; can cause dangerous decrease in [blood salt] -solution: kidneys adapted to produce lots of dilute urine to eliminate water; specialized gill cells actively transport Na+ and Cl- from lake water into fish's capillaries (important salt ions recaptured form the lake water) eg. Saltwater fish -tends to gain salts and lose water across gills (seawater has higher osmolarity than their bodies) -gain of salts and loss of water partly offset by kidneys-->produces very little urine with high [salt] to retain water -to prevent dehydration, saltwater fish drink water-->but, seawater is very salty -->the ingested salt is eliminated: gill cells pump salt of fish's blood and into surrounding water -drinks water to place water lost through gills by osmosis; uses E to move excess salt swallowed out of body EXCRETION 1. Filtration -organ acts like a filter, removing some water and small solutes from blood and interstitial fluid, while leaving behind blood cells and large solutes (eg. proteins) -eg. mammalian kidney: plasma of blood under pressure through capillaries into kidney tubules -filtrate: material that passes through filter and enters excretory system of organ 2. Reabsorption -some of the material in the filtrate is recaptured back into the blood -to filter blood and remove soluble wastes, salts, sugars, a.acids and needed molecules are also filtered in the process-->reclaimed at this stage -requires active transport pumps or other transport systems -urine: remaining part of filtrate 3. Secretion -sometimes solutes excreted from body in higher quantities than those found in the filtrate -some solutes actively transported from the interstitial fluid surrounding tubule cells into tubule lumen -supplements the amount of a solute that would normally be removed by filtration alone -often a way in which excretory organs eliminate really toxic compounds from the body; very effective -additional unwanted solutes actively removed from blood and interstitial fluids and directly enter the lumen of the excretory tubule 4. Excretion -urine is excreted -liver: metabolized + filters out toxins; converts toxic ammonia to urea -kidney: filters urea from blood from liver into urine MAMMALIAN KIDNEY -urine formed in each kidney collects in renal pelvis; flows through the ureters into bladder; eliminated via urethra -renal cortex: outer kidney -primary site of flood filtration -renal medulla: inner region -urine is concentrated by reabsorption of water back into blood NEPHRON consists of... 1.renal corpuscle: initial filtering component -contains a cluster of capillaries called glomerulus: has tiny holes in its walls that allow rapid flow of plasma out of capillary -supplied w/ pressurized blood from afferent arteriole -glomerulus protrudes into fluid-filled space called Bowman's capsule: filters plasma and blood 2. collecting duct: narrow tubule that extends out form the renal corpuscle -tubule made up of single layer of epithelial cells -proximal convoluted: Bowman's capsule drains into this first portion -particular solutes reabsorbed from filtrate (eg. Na+, K+, Cl-, glc, a.acids that passed through) -some ions diffuse
More Less

Related notes for BIOL 103

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.