Review #5 presentation Flashcards
Why is the digestion of food molecules essential
most food molecules are not readily usable
- must be broken down for absorption and for reassembly into new products
- contains certain substances not suitable for human tissue so they have to be removed or seperated
Explain the need for enzymes in digestion
enzymes: break large, insoluble molecules into smaller, soluble molecules (monomers) that are easily absorbed into the bloodstream
biological catalysts; allow breakdown of specific substrates in organism (specific temps, ph, etc) and substrates are broken down independently of others
- they are globular proteins that lower the activation energy needed to start and speed up the rate of chemical reactions
- increase the rate of digestion
- digestive enzymes released into gut from pancreas (endocrine glands)
- exocrine glands have ducts and secrete substances to an epithelial surface
Salivary amylase
Site of production (SP), site of action (SA), pH, Substrates (S), and Products (P)
SP: Salivary glands SA: Mouth/Esophagus pH: Neutral 7 S: Starch (amylose) P: Maltose
Pepsin/protease
Site of production (SP), site of action (SA), pH, Substrates (S), and Products (P)
SP: stomach SA: stomach pH: acidic (1-2) S: proteins P: peptides
Amylase
Site of production (SP), site of action (SA), pH, Substrates (S), and Products (P)
SP: pancreas SA: lumen of small intestine pH: 7-8 (neutral to slightly alkaline) S: starch P: maltose
Lipase
Site of production (SP), site of action (SA), pH, Substrates (S), and Products (P)
SP: pancreas SA: lumen of small intestine pH: 7-8 (neutral to slightly alkaline) S: triglycerides P: monoglycerides, fatty acids, glycerol
Endopeptidase/Protease
Site of production (SP), site of action (SA), pH, Substrates (S), and Products (P)
SP: pancreas SA: lumen of small intestine pH: 7-8 (neutral to slightly alkaline) S: Proteins/peptides P: amino acids
Nuclease
Site of production (SP), site of action (SA), pH, Substrates (S), and Products (P)
SP: pancreas SA: lumen of small intestine pH: 7-8 (neutral to slightly alkaline) S: nucleic acids P: nucleosides
what are the main parts of the alimentary canal
stomach
small intestine
large intestine
What organs are included in the human digestive system
Salivary glands oesophagus stomach liver gall bladder pancreas small intestine large intestine rectum/anus
function of salivary glands
moistens food into a bolus
begins polysaccharide digestion
function of oesophagus
transports food to stomach
stomach function (general)
stores and churns food
begins protein digestion
liver function
detoxifies certain molecules
stores vitamins, iron, and glycogen
synthesizes bile
gall bladder function
stores/concentrates bile
pancreas function
releases digestive enzymes releases hormones (ie insulin)
small intestine function (general)
absorbs nutrients
large intestine function (general)
absorbs water and ions
rectum/anus function
stores and expels faeces
stomach functions (in depth)
1 begins protein digestion
- acidic pH denatures and proteases break down
2 begins mechanical digestion
- breaking food into smaller parts without breaking bonds
3 mixes food to promote digestion
4 produces chyme
small intestine functions (in depth)
1 completes digestion of food molecules
2 absorption of nutrients/water
3 receives secretions from pancreas/gall bladder to aid in digestion
4 mixing of digested food products
5 secretion of intestinal juices
6 contains villi - increase surface area for absorption
large intestine function (in depth)
1 absorption of water, minerals, and ions
2 eliminates feces solid waster
why are cellulose and lignin not broken down
humans lack enzymes to break down beta-glucose (linkages found in cellulose and lignin)
they are important in diet - fiber
clean out old cells and “work out” natural microflora
Microvilli function in villus
increase surface area for absorption and contain immobilized enzymes (maltase etc) for hydrolysis of disaccharides (maltose hydrolyzed to glucose)
rich capillary network function in villus
minimize diffusion distance
maintain large concentration gradient for rapid absorption
single epithelial layer function in microvillus
minimal diffusion distance (cells connected by tight junctions) - impermeable barrier and ensure one-way flow of nutrients and ensuring separation of body and digestive fluids
lacteal function in villus
absorb lipids into lymphatic system
intestinal crypts function in microvillus
release juices that act as carrier fluids for nutrients
membrane proteins/mitochondria function in microvillus
active transport
what happens after macromolecules are hydrolyzed into small polymers or monomers
they can be absorbed into the bloodstream through the cells of the small intestine
outside to inside order of the transverse sections of the small intestine
serosa longitudinal muscles circular muscles submucosa mucosa
serosa function in the transverse sections of the small intestine
protective outer covering
longitudinal muscles in the transverse sections of the small intestine
peristalsis (move food along gut/mix with enzymes)
circular muscles function in the transverse sections of the small intestine
segmentation
prevent backward movement of food/mix with enzymes
submucosa function in transverse sections of the small intestine
seperates innermost mucosa from muscles
mucosa function in transverse sections of the small intestine
highly follded inner epithelial layer
increase the surface area for absorption of monomers from the intestinal lumen
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
(occurs in small intestine and large intestine)
facilitated diffusion
protin channels within epithelial cell membranes (of villi and microvilli) allow passage of hydrophilic food molecules (water-solble/polar molecules like fructose, vitamins, glucose, amino acids, and minerals)
active transport - requires ATP
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 (secondary active transport)
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
ie: absorption of antibodies (those in breastmilk passed onto infants)
what can limit homeostasis
blood glucose concentration body temperature appetite water balance negative feedback mechanisms
what is negative feedback
outcome of the mechanism is the opposite effect
ie temp too high -> negative feedback works to bring temp back down
Describe circadian rhythms (24 hr biological clock)
pineal gland = sleep and wake clock in brain
- produces melatonin (secreted in the dark)
- retina (eye) detects light (amount/duration)
- dark/longer nights = melatonin produced
- bright light/blue wavelengths = inhibit melatonin production
- amount of timing of melatonin secretion become entrained in body over time (cycle can cause jet lag in new time zones)
describe appetite
hypothalamus = appetite control center
- cells in adipose tissue produce and secrete leptin
- leptin targets cells in hypothalamus
- inhibits appetite (feel full)
- more adipose tissue/more eating = more leptin in blood -> so less eating
- obese people can develop a leptin resistance (decreased sensitivity)
- leptin injections are not a viable treatment for obesity
pancreas and blood glucose
pancreas produces and secretes two antagonistic hormones into the blood to maintain homeostasis of blood glucose
(both an endocrine AND exocrine gland)
what is diabetes (general)
the reduced ability of body to control blood glucose levels through insulin (hyperglycemia)
what happens if blood glucose is too high
1) beta cells in the pancreas produce the hormone insulin
2) insulin is secreted into the bloodstream
3) insulin acts on all cells in the body, triggering them to take up glucose
4) cellular respiration rates are increased causing an increase in breakdown of glucose
5) glucose in liver cells, adipose cells, and muscle cells is converted to and stored as glycogen, decreasing blood glucose
6) glucose uptake and storage by cells decreases blood glucose levels (insulin production/release decreases as well)
what happens if blood glucose is too low
1) alpha cells in the pancreas produce glucagon (hormone)
2) glucagon is secreted into the bloodstream
3) glucagon stimulates hepatocytes to break down glycogen into glucose
4) cellular respiration rates are decreased causing a decrease in the breakdown of glucose
5) glucose is released by hepatocytes into the bloodstream, increasing blood glucose levels
6) rising blood glucose levels stimulate less glucagon to be produced
type I diabetes
- early onset
- beta cells damaged by the body’s own immune system
- autoimmune disease: not enough insulin is produced
- triggered by various factors - not usually genetic
- controlled by insulin injections to regular blood glucose levels
type II diabetes
- adult onset
- insulin receptors on cells (liver, muscle, etc) are fewer and or become less sensitive to insulin
- decrease in body response to insulin
- related to obesity, poor diet, genetic history, lack of exercise, age, ethnicity
- controlled by managing diet (more fiber (beans and broccoli) and less saturated fat (processed meat - bacon) and smaller meals) and life style
what do type 1 and 2 diabetes have in common
symptoms: high blood sugar, glucose in urine, increased thirst/urination, hunger, fatigue, weight loss
too much glucose in the blood -retinal damage and blindness, kidney failure, nerve damage, cardiovascular disease, and poor wound healing
body temperature
hypothalamus is the biological thermostat
HYPOthermia
- body temp is too low (metabolic reactions can’t occur and death occurs below 32 degrees celsius)
- thermoreceptors in skin send signals to hypothalamus
- hypothalamus releases chemical signals that can trigger:
- vasoconstriction: arterioles get smaller, blood diverted to deep tissues, less heat loss
- shivering of skeletal muscle generates heat
- goosebumps - raises hair follicles on skin (traps heat/insulates against heat loss)
HYPERthermia
- body temp is too (tissues/enzymes damaged, above 40 degrees celsius is deadly)
- thermoreceptors in skin send signals to hypothalamus
- hypothalamus releases chemical signals that trigger:
- vasodilation: arterioles get bigger, fill with blood, transfer heat to skin and out of body
- increased sweat gland activity (evaporative cooling)
Thyroid gland
- produces and secretes thyroxin in response to signals from hypothalamus
- thyroxine regulates body’s basal metabolic rate (amount of energy used at rest)
- thyroxin acts on all cells, causing
an increase in energy use/oxidation of glucose and fatty acids
increase in metabolic rate
increase in oxygen consumption
this produces more heat and increases body temp
kidney function
filters blood remove toxins osmoregulation (water/solute balance) reabsorption of nutrients excretion - removal of nitrogenous waste products of metabolism (urea)
the type of nitrogenous waste produce is correlated with …
evolutionary history
ammonia
VERY TOXIC, requires A LOT of water to dilute, but not much energy to produce
- fish/aquatic organisms
urea
somewhat toxic can be stored short-term requires some water to dilute requires some energy to produce - mammals, amphibians, sharks
uric acid
requires A LOT of energy to produce
insoluble in aqueous solutions
does not need to be diluted
- so it can be stored long-term in developing eggs
- reptiles, birds, and insectsmalpighian tubules
insects have them and they connect to digestive system to carry out removal of nitrogenous wastes and osmoregulaition
