RAT 17 Flashcards
what is the final product that exits the papillary ducts?
urine
what is obligatory water reabsorption?
water is “obliged” by osmosis to follow solutes that have been reabsorbed
what percentage of water reabsorption is due to obligatory water reabsorption?
85%
what is facultative water reabsorption?
adjusted by hormones to meet the body’s needs and maintain fluid homeostasis
what percentage of water reabsorption is due to facultative water reabsorption?
15%
how does an adjustment in water reabsorption impact urine concentration?
the kidneys adjust facultative water reabsorption to produce either dilute or concentrated urine
what is the osmolarity of plasma ?
300 mOsm
what is the osmolarity of filtrate in the renal capsule?
the filtrate that exists the blood and enter the renal tubule initially is iso-osmotic to the plasma at 300 mOsm
what happens to the osmolarity of the filtrate in the descending limb of the nephron loop? why?
becomes much more concentrated (~900 mOsm) because the descending limb is permeable to water but not solutes
what happens to the osmolarity of the filtrate in the ascending limb of the nephron loop? why?
concentration decreases ~100 mOsm because the ascending limb is impermeable to water, water cannot follow the movement of the solutes
where does facultative water reabsorption take place?
the last distal tubule and collecting sytsem
what type of urine is produced if there is little facultative water absorption?
dilute urine (< 300 mOsm)
what type of urine is produced if there is a lot of facultative water reabsorption?
concentrated urine (> 300 mOsm)
where in the nephron loop is the filtrate most concentrated?
at the turn of the nephron loop
where in the nephron loop is the filtrate most dilute?
ascending limb
when would you be likely to produce dilute urine? describe the appearance and volume of the urine.
- when ADH secretion is low
- volume increases, color = clear to light yellow
when would you be likely to produced concentrated urine? describe the appearance and volume of the urine.
- from “turning on” facultative water reabsorption in the principal cells of the later distal tubule and collecting system by the release of ADH
- less volume, color = dark yellow
what type of water reabsorption determines if urine is dilute or concentrated?
facultative water reabsorption
if water moves by osmosis, what is needed in order to produce a concentrated urine?
osmotic gradient
what is the medullary osmotic gradient?
- osmotic gradient within the renal medulla
- interstitial fluid = 300-400 mOsm
- cortex/medulla boarder = ~1200 mOsm
what creates and maintains the medullary osmotic gradient?
countercurrent mechanism (mechanism that involves fluids flowing in opposite directions that exchange material or heat)
what are the three components of the countercurrent mechanism?
- countercurrent multiplier system in the nephron loops of juxtamedullary nephrons
- recycling of urea in the medullary collecting ducts
- countercurrent exchanger in the vasa recta
which types of nephrons are the focus for this section? why?
juxtamedullary nephrons because within is found the countercurrent multiplier, which helps to establish the medullary osmotic gradient
what is the purpose of the countercurrent multiplier?
to help the kidneys conserve water and produce concentrated urine
what does the countercurrent multiplier do?
it pumps large amounts of NaCl into the interstitial fluid of the renal medulla to establish a concentration gradient
how does the countercurrent multiplier do this?
in the descending limb, water leaves so that NaCl is left behind in the filtrate, which can then be pumped out
does each step of the countercurrent multiplier occur in sequence?
no, its more like a pendulum continually swinging in a circle
what is the vasa recta? describe the path that it takes in the kidneys
- a special system of blood flow around the nephron loops of juxtamedullary nephrons to maintain the medullary osmotic gradient
- descend into the renal medulla, follow the hairpin turn, ascend toward the renal cortex
why does chemical digestion vary for each type of nutrient?
because digestive enzymes are specific for a single type of bond in a single type of nutrient
what type of reaction is catalyzed by most digestive enzymes?
hydrolysis reactions
where does carbohydrate digestion begin?
mouth
what is the enzyme that begins carbohydrate digestion and where is it produced?
- salivary amylase
- salivary glands
what reaction does salivary amylase catalyze?
breakdown of long polysaccharides into shorter oligosaccharides
what enzyme continues the process of carbohydrate digestion in the small intestine? where is it produced?
- pancreatic amylase
- pancreas
what reaction does pancreatic amylase catalyze?
reactions that breakdown the remaining polysaccharides into oligosaccharides
where are brush boarder enzymes located?
small intestine
name three brush boarder enzymes
- lactase
- maltase
- sucrase
what reactions do lactase enzymes catalyze?
digestion of the sugar lactose into glucose and galactose
what reaction do maltase and sucrase catalyze?
breakdown of oligosaccharides to disaccharides and monosaccharides
what are the three products of those reactions?
- glucose
- fructose
- galactose
once carbohydrates in the small intestine lumen are broken down into monosaccharides, how are they transported into the enterocyte?
- glucose and galactose are transported across the enterocyte’s apical membrane
- they must move against their concentration gradient
how are they transported out of the enterocyte on the basal side?
by the same facilitated diffusion mechanism
what happens next to the monosaccharides?
diffuse through the ECF and into the capillaries in the villus
what is the enzyme that begins protein digestion and where is it produced?
- pepsin
- chief cells of gastric glands
what reaction does pepsin catalyze?
reaction that digest proteins into smaller polypeptide, oligopeptides, and some free amino acids
where does the remainder of protein digestion occur?
small intestin
what enzymes aid the remainder of protein digestion?
pancreatic and brush boarder enzymes
why are the pancreatic enzymes released in an inactive form?
protect the pancreas from autodigestion
name a pancreatic enzyme that aids in protein digestion. what is the inactive form of the enzyme called?
- trypsin
- inactive: trypsinogen
where are the last enzymes in the protein digestion process located? what do they catalyze?
- enterocytes
- digestion of oligopeptides into free amino acids
how are amino acids transported into the enterocyte on the apical side?
secondary active transport membrane proteins that use a sodium ion gradient
how are amino acids transported out of the enterocyte on the basal side?
facilitated diffusion
what happens next to the amino acids?
enters the capillaries in the villus
most of the lipids ingested in the diet are in what form?
triglycerides
what happens to lipids in a water-based solution? why does this limit the amount of digestion that occurs?
- form large globules by sticking together
- enzymes would have very little surface area to work to catalyze reactions
what are two ways that lipid globules can be broken apart?
- mechanical digestion
- use of bile salts
what is emulsification?
physical break up of the lipid globules into smaller pieces
what is an emulsion?
mixture of multiple tiny lipid droplets each coated within bile salts
which enzymes catalyze reactions that digest nucleic acids?
nucleases
about how much water is processed by the digestive tract each day?
9 liters
about how much water is absorbed by the small intestine?
8 liters
about how much water is absorbed by the large intestine?
1 liter
how do osmotic laxative work?
- these drugs consist of solutes that are either not absorbed or are given in amounts of excess of what can be absorbed
- result: water is retained in the feces, softening them and making them easier to eliminate
what drives the reabsorption of anions such as chloride and bicarbonate?
sodium ion absorption
what is intrinsic factor? where is it produced?
a chemical produced by the parietal cells of the stomach to be absorbed by the ileum
what is the function of the intrinsic factor?
aids in the absorption or B12
what is a calorie?
the amount of heat required to raise the temperature of one gram of water by one degree Celsius
in terms of the human diet, what is a Calorie?
- kilocalorie
- the amount of heat required to raise the temperature of one kilogram of water by one degree Celsius
what is metabolism?
the sum of the body’s chemical reactions
what are the four basic processes of metabolism?
- harnessing the energy in the chemical bonds of nutrient obtained from the diet that may be used to make ATP
- converting one type of chemical into another for the cell’s synthesis reaction
- carrying out synthesis reactions and assembling macromolecules
- breaking down macromolecules into their monomers or other small compounds
what is catabolism?
substance broken down into smaller parts
what is anabolism?
smaller compounds are combined to make a larger compound
what is an exergonic reaction?
reaction that releases energy
what is an endergonic reaction?
reaction that requires the input of energy to proceed
explain how these reactions are coupled together.
cell “pays for” an endergonic reaction with the energy released by an exergonic reaction
what are the products of glycolysis?
- 2 pyruvate
- 2 ATP
- 2 NADH
when one molecule of glucose is completely oxidized, how many ATP molecules are produced?
38 ATP
what are the components of triglycerides?
3 fatty acid chains and glycerol backbone
what is lipolysis?
the breakdown of fats and other lipids by hydrolysis to release fatty acids
when one molecule of palmitic acid is completely oxidized, how many ATP molecules are produced?
129 ATP
what are the two main nutrient energy storage forms in the body?
glycogen and adipose (fat)
what is glycogenesis?
- glycogen synthesis
- series of enzyme-catalyzed reactions that add glucose units to the growing glycogen molecule
what is glycogenolysis?
breakdown of glycogen
what is gluconeogenesis?
synthesis of glucose from non-carbohydrate precursors
what is lipogenesis?
fatty acid and triglycerides synthesis
what nutrients are converted into fat?
glucose and amino acids
what is the fate of excess amino acids consumed in the diet?
converted to other compounds for storage
what part of the brain regulates feeding?
hypothalamus
which hormones stimulate the satiety center? where is the hormone produced?
- leptin
- adipocytes
which hormone stimulate hunger? where is this hormone produced?
- ghrelin
- stomach mucosa
what is the primary source of body heat?
metabolism
why is heat production a good way to measure energy expenditure?
because most of the body’s energy is eventually lost to the environment as heat
what is the basal metabolic rate (BMR)?
the minimal rate of metabolism for an awake individual, or the “energy cost of living”
what are the three categories of macronutrients?
- carbohydrate
- lipid
- protein
what are the two categories of micronutrients?
- vitamins
- minerals
what is the RDA?
recommended dietary allowance
what is an essential nutrient?
compounds the body is unable to produce
what are simple sugars?
monosaccharides and disaccharides
why are they considered “empty calories”?
nutrient poor and highly processed
what are complex carbohydrates?
polysaccharides, grains, vegetables
what are some risks of eliminating carbohydrates from the diet?
wasting of skeletal muscle tissue and other vital organs such as the heart and ketone bodies can accumulate in the blood, affecting blood pH
what is an essential fatty acid?
those that the body cannot make and must be supplied in the diet
what is a nonessential amino acid?
can be synthesized from carbon skeletons
what is an essential amino acid?
must be supplied by the diet
what is a complete proteins?
when it supplies all the essential amino acids
what is an incomplete protein?
lacks one or more of the essential amino acids
what is gluten?
a protein composite (2 proteins naturally occurring in wheat and some other grass-based grains)
is gluten harmful?
no only to those with allergies
what is a vitamin?
an organic compound required for the body’s functions
what are some roles of vitamins in the body?
act as hormones and influence the function of other cells, act as enzyme cofactor, antioxidants
what is a fat-soluble vitamin? which vitamins are fat-soluble?
- contain one or more hydrocarbon rings and long hydrocarbon chains, nonpolar, hydrophobic
- vitamin A, D, E, K
what is a water-soluble vitamin? which vitamins are water-soluble?
- contain predominantly polar bonds, hydrophilic, soluble in water
- vitamin B and C
what is a mineral?
any element other than carbon, hydrogen, oxygen, and nitrogen that is required by living organisms
should you take megadoses of vitamins and minerals?
no
what are some functions of cholesterol in the body?
- produce steroid hormones, vitamin D, bile salts
- forms part of plasma membranes
what is BMI? how can it be useful clinically?
- body mass index
- BMI: weight/height
- allows classification of an individual: underweight, normal, overweight, obese
what conditions create a positive energy balance? what effect will each have on body mass?
- total Calories takin in > total number of expended Calories
- increases BMI
what conditions create a negative energy balance? what effect will it have on body mass?
- total Calories takin in < total number of expended Calories
- decreases BMI
what are the causes of obesity?
- positive energy balance
- sedentary lifestyle
- widespread availability of food (high-caloric food)
- genetics
- hypothyroidism
- Cushing’s syndrome
what are the consequences of obesity?
- increase risk of type 2 diabetes, coronary artery disease, osteoarthritis, certain types of cancer, hypertension, obstructive sleep apnea
- concern with social in nature, stigmatization
- high costs (health insurance)
- employment discrimination
