Unit 5 Review Flashcards
Function of the pancreas in maintaining blood glucose levels
if blood glucose is too high beta cells in the pancreas secrete insulin into the blood which triggers all cells in the body to take up glucose, cellular respiration is increased, glucose in liver cells, adipose cells, and muscle cells is converted into glycogen, these activities decrease glucose in the blood and cause less insulin to be secreted
if blood glucose is too low alpha cells in the pancreases secrete glucagon into the blood which causes liver cells to break down glycogen into glucose and release it into the blood stream, cellular respiration rates are decreased, these activities raise glucose in the blood which causes less glucagon to be secreted
How the structures of the different parts of the nephron are adapted to their functions
Afferent larger than efferent arterioles which creates high pressure Bowman’s capsule
Glomerulus is highly branched to increase surface area
Podocytes lining Bowman’s capsule are only one cell thick to decrease filtration distance
Epithelial cells in the PCT have microvilli to increase surface area and are only one layer thick to decrease diffusion distance
Peritubular capillaries surround the PCT reabsorption
Descending limb of Loop of Henle only permeable to water
Ascending limb of Loop of Henle only permeable to salt ions to create more dilute filtrate
The role of the kidney in osmoregulation
Descending limb of Loop of Henle permeable to water (water passes out of filtrate by osmosis into high salt concentration – hypertonic environment – in medulla of kidney)
Ascending limb of Loop of Henle permeable to salt ions (salt ions actively pumped out of filtrate into medulla); creates more dilute filtrate
LENGTH of loop of Henle is positively correlated with need for water conservation (longer in desert animals -kangaroo rats, shorter in amphibians- frogs and toads)
Collecting duct reabsorbs water into blood through osmosis (under control of ADH)
-Osmoreceptors in hypothalamus monitor water content of blood
-If water content too low, pituitary releases ADH (anti-diuretic hormone = released when you Are Dehydrated) into blood
-ADH acts to increase permeability of collecting duct to water (more aquaporins); more water reabsorbed back into blood; urine more hypertonic (concentrated)
-As water content of blood increases, no more ADH secreted, collecting duct remains impermeable to water, more water in urine so becomes more hypotonic/ less concentrated (negative feedback – opposite effect)
How proteins, lipids, and starch are digested and absorbed in the human body.
Proteins
First digested in the stomach by pepsin that turns it to peptides
Then endopeptidase and protease digest the peptides and proteins into amino acids
Absorbed in the small intestine via facilitated diffusion and active transport
Lipids Lipase is secreted by the pancreas into the lumen of the small intestine to turn triglycerides into monoglycerides, fatty acids, and glycerol Pass through epithelial cells through simple diffusion Are then absorbed into lacteals Starch Salivary amylase from the salivary glands begins breaking down starch in the mouth and esophagus Amylase is secreted into the lumen of the small intestine from the pancreas that turns starch to maltose Immobilized enzymes (maltase) hydrolyze maltose to glucose Glucose is absorbed via facilitated diffusion and active transport
Causes, consequences, and treatment options for type I and type II diabetes
Type I Diabetes
- early-onset diabetes, beta cells are damaged or destroyed by body’s own immune system
- triggered by various factors like illness but it is usually not genetic
- controlled through insulin injections to regulate blood glucose levels
Type II Diabetes
- adult-onset diabetes, insulin receptors on cells become desensitized to insulin
- related to obesity, poor diet, age, ethnicity, genetic history, and lack of exercise
- controlled by managing diet, more fiber, less saturated fat, smaller meals, foods with lower glycemic index, more complex carbs
Both have the symptoms of high blood sugar, glucose in urine, increased thirst and urination, hunger, fatigue, and weight loss
Role of melatonin
pineal gland is the sleep/wake clock in the brain and produces melatonin in the dark
Dark/ longer nights = more melatonin produced
Bright light (daylight and screens) = more blue wavelengths = suppress/ inhibit melatonin production
Amount and timing of melatonin secretion become entrained in the body over time
Part of the 24-hour biological clock (CIRCADIAN RHYTHM)
Role of Thyroxin
Thyroid gland produces thyroxin in response to signals from the hypothalamus
Thyroxin regulates body’s basal metabolic rate
When released, thyroxin acts on ALL cells, causing increase in energy use/more oxidation of glucose and fatty acids, increase in metabolic rate, increase in oxygen consumption/ ATP hydrolysis (which produces more heat too and increases body temperature)
Role of Leptin
Cells in adipose tissue produce and secrete leptin
Leptin targets cells in the hypothalamus to suppress apatite
More adipose tissue and more eating causes more leptin in the body which then suppresses hunger to communicate that enough food has been consumed which causes less eating
The methods of transport used to absorb different nutrients in the small intestine
Diffusion: Fatty acids and other small, non-polar substances easily pass through the hydrophobic cell membranes of epithelial cells through simple diffusion
Osmosis: Water diffuses across epithelial cell membranes in response to movement of ions and other hydrophilic monomers
Facilitated Diffusion: protein channels within the epithelial cell membranes allow the passage of hydrophilic food molecules (fructose, vitamins, glucose, amino acids, and minerals)
Active Transport: Glucose and amino acids are pumped (membrane proteins) against their concentration gradients, or they are transported with Na+ ions (co-transport) as Na+ ions are actively pumped across the membrane
Endocytosis: Invagination of the cell membrane to form a vesicle around bulk fluids/ large molecules that must remain intact in the intestinal lumen and bring them into the cell
How insects excrete nitrogenous wastes
Insects have MALPIGHIAN TUBULES (connect to digestive system) to carry out removal of nitrogenous wastes and osmoregulation:
Tubules branch off intestine
Filter water, salts, and ammonia out of hemolymph that surrounds them (hemolymph = fluid like blood) into digestive tract
Water, salts, and solutes reabsorbed into hemolymph and ammonia forms a solid paste and combines with undigested food and is eliminated with feces
How the structure of the villus is adapted to its function
Microvilli: increase surface area for absorption and contain immobilized enzymes (maltase etc.) for hydrolysis of disaccharides (maltose hydrolyzed to glucose)
Rich capillary network: minimize diffusion distance and maintain large concentration gradient for rapid absorption
Single epithelial layer: Minimal diffusion distance (cells connected
by TIGHT JUNCTIONS - impermeable barrier/ ensure one-way
flow of nutrients and ensuring separation of body and
digestive fluids
Lacteals: Absorb lipids into lymphatic system
Intestinal crypts (between villi): release juices that act as carrier fluids for nutrients
Membrane proteins/ mitochondria: Active transport
Differences between osmoregulators and osmoconformers.
Osmoregulators: organisms whose internal tissues maintain DIFFERENT solute concentrations than environment
Osmoconformers: organisms whose internal tissues maintain the SAME solute concentrations as environment
