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ib biology > digestion test!!!!! > Flashcards

digestion test!!!!! Flashcards

1
Q

essential nutrients

A

Cannot be replaced or synthesized, must be ingested/disgested. Example: water, minrals, some vitamins, some unsaturated fatty acids, some amino acids. Dietary fiber is also necessary but it is not absorbed so it is not a nutrient. Fiber helps prevent constipation /cancer/heart attacks, as well as reduces hunger, and aids movement of food through digestive tract (alimentary canal).

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2
Q

non-essential nutrients

A

Can be synthesized by the body or have a replacement nutrient that serves same dietary purpose, so are not necessary in the diet. Carbohydrates/sugars/ starches (energy could come from proteins/fats). Other minerals and some vitamins, saturated fatty acids, some amino acids.

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3
Q

causes of PKU

A

Genetically inherited disease (autosomal recessive). Caused by a person’s chemical inability to metabolize the amino acid phenylalanine (into tyrosine). This disease builds up in tissues and the bloodstream due to a lack of the enzyme phenylalanine hydroxylase. This breaks down phenylalanine into tyrosine from inheriting a mutated form of gene. Excess phenylalanine can result in mental deficiency, behavioral problems, seizures, etc.

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4
Q

why food needs to be digested

A

Digestion is important for breaking down food into nutrients, which the body uses for energy, growth, and cell repair. Foods and drinks must be broken down into smaller molecules of nutrients before the blood absorbs them and carries them to cells throughout the body. The digestive system breaks down food into nutrients such as carbohydrates, fats, and proteins. They can then be absorbed into the bloodstream so the body can use them for energy, growth, and repair.

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5
Q

roles of HCL

A

HCL lowers pH ~ 2. This denatures proteins. HCL in the stomach helps denature proteins and kill pathogenic bacteria and fungi in ingested foods. Pariteal cells within the stomach lining secete hydrochloric acid. Low pH acitivates pepsn. Acetylcholine, gastrin, and histamine stimulate the proton pump in parietal cells to release hydrogen ions and decrease pH.

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6
Q

roles of PPIs

A

Acidic conditions of the stomach (low pH) are maintained by proton (H+) pumps (membrane proteins) in parietal cells in the gastric pits (H+/K+ ATPase). Parietal cells normally actively pump protons into the stomach (where they combine with chlorine ions to form hydrochloric acid. Certain medications, diseases, etc. can increase the secretion of hydrogen from parietal cells which lower the pH of the stomach. PPIs bind to proton pumps and prevent hydrogen secretion by raising the pH of the stomach. (can cause susceptibility to gastric infection).

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7
Q

step 1 of hormonal and nervous mechanisms

A

Site/ smell of food triggers a reflex response – brain (medulla) sends impulses (via the vagus nerve) to gastric glands in the stomach to secrete gastric juice (ensures gastric juice (pepsinogen) and HCl and mucous) presence in the stomach by time food consumed/ when the food arrives)

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8
Q

step 2 of hormonal and nervous mechanisms

A

Food enters stomach causing distention – detected by stretch receptors in stomach lining

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8
Q

step 3 of hormonal and nervous mechanisms

A

Impulses from stretch receptors sent to brain (to medulla oblongata) which sends signal to stomach through vagus nerve that triggers gastrin (hormone) secretion into bloodstream (from endocrine cells in stomach wall), and causes stomach to begin producing and secreting HCl (parietal cells) and pepsinogen (chief cells)

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9
Q

step 4 of hormonal and nervous mechanisms

A

Gastrin causes sustained release of gastric juices (particularly acid component - HCl)

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10
Q

step 5 of hormonal and nervous mechanisms

A

If pH becomes too low (< 1.5-2.0), gastrin inhibited by hormones (secretin from the small intestine/ somatostatin from the hypothalamus)

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11
Q

step 6 of hormonal and nervous mechanisms

A

Once digested food (chyme) passes into small intestine, duodenum releases hormones secretin and CCK (cholecystokinin) to stimulate pancreas to release pancreatic juices (bicarbonate ions to neutralize stomach acids and pancreatic digestive enzymes) and liver to release bile (emulsify fats)

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12
Q

hormones are chemicals that are produced by ____ and secreted into the ____

A

endocrine glands
into the bloodstream (to exert their effects on cells in “other” locations in the body)s

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13
Q

role of pancreas as endocrine gland

A

The pancreas secretes enzymes into the lumen of the small intestine

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14
Q

what enzymes does the pancreas secrete

A

amylase, lipase, protease, and nuclease

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15
Q

amylase, lipase, protease, and nuclease macromolecules

A

starch, glycogen, lipids and nucleic acids

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16
Q

amylase

A

site of action is lumen of SI, substrate is starch and produces maltose.

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17
Q

lipase

A

site of action is lumen of SI, substrate is trigylcerides, and produces fatty acids/glycerol

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18
Q

protease/endopeptidase

A

site of action is lumen of SI, substrate is proteins/peptides, and produces amino acids.

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19
Q

nuclease

A

site of action is the lumen of SI, the substrate is nucleic acids, and the products are nucleosides.

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20
Q

general function and structure of villi

A

Villi (HIGHLY FOLDED finger-like projections) in the ileum (last section of small intestine) increase surface area and have a rich blood supply. Villi increase the surface area of epithelium over which absorption is carried out.

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21
Q

the villi absorbs

A

monomers formed by digestion as well as mineral ions and vitamins.

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22
Q

what is the villus surrounded with?

A

a single layer of epithelial cells (decreases distance nutrients must diffuse to be absorbed into bloodstream). Each epithelial cell contains an outer layer of folded projections called microvilli

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23
Q

what do the microvilli do

A

Microvilli increase the surface area for absorption (>100x), they contain immobilized enzymes in their membranes to aid in digestion (peptidase, disaccharide) and they contain membrane/ channel proteins to assist in nutrient uptake/ absorption (into blood)

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24
Q

what do capillaries do (villi)

A

Capillaries in the villus minimize the diffusion distance of nutrients. They also maintain a large concentration gradients for the rapid absorption of nurtrients

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25
Q

lacteal in the villi

A

Lacteals absorb lipids into the lymphatic system where fats are transported and tissues of excess fluids are drained.

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26
Q

different forms of transport

A

diffusion, facilitated diffusion, active transport, endocytosis

27
Q

diffusion

A

where fatty acids and other small non-polar substances easily pass through the hydrophobic cell membranes of epithelial cells through simple diffusion.

28
Q

facilitated diffusion

A

where protein channels within epithelial cell membranes (of villi and microvilli) allow passage of hydrophilic food molecules (water-soluble/ polar molecules like fructose, vitamins, glucose, amino acids, and minerals)

29
Q

osmosis

A

where water diffuses across epithelial cell membranes in response to movement of ions and other hydrophilic monomers (occurs in small intestine and large intestine)

30
Q

active transport

A

where 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)

31
Q

endocytosis

A

where the 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 (pinocytosis: “cell drinking”.

32
Q

large intestine main function

A

The main function of the large intestine is the absorption of water, minerals, vitamins, and ions.

33
Q

large intestine structure

A

The LI is highly folded which maximizes the surface area for absorption of water into the blood.

34
Q

role of large intestine

A

secretes mucus which lubricates passing feces and helps with the movement of undigested/undigestable food products. Materials that are not absorbed are egested

35
Q

belch abbreviation

A

bile pigment, epithelial cells, lignin, cellulose, and human microflora

36
Q

why are cellulose and lignin not digested

A

Cellulose and lignin are not digested because humans do NOT possess enzymes (cellulase) or gut bacteria to break them down. Glucose exists in two forms: alpha and beta (difference in OH group). Humans have enzymes/ gut bacteria able to break down alpha form (in glycogen/ starch) but not beta form (cellulose –plant cell walls)

37
Q

role of fiber in the diet

A

Fiber is important in the diet because it helps “clean out” old/ damaged intestinal cells and unabsorbed materials, it provides bulk to keep materials moving, it absorbs water to keep faeces soft and easy to pass, “works out” the body’s normal microflora, reduces frequency of constipation, lowers risk of colon and rectal cancers, lowers blood cholesterol, regulates blood sugar levels (slows absorption rate of glucose), and decreases hunger (aids in weight management/ prevention of obesity).

38
Q

how does the toxin cholera cause dehydration

A

V. cholerae releases a toxin that binds to a receptor on the epithelial cells in the intestine. This activates ion channels in these cells so that ions (including chloride ions/ Cl-) are pumped out of these cells and into the intestine. Water from the cells follows the ion concentration gradient (by osmosis). Excess water dilutes feces = diarrhea and will cause dehydration (if left untreated) as water is continuously removed from body tissues.

39
Q

cause of ulcers

A

This is because H. pylori survives the acidic conditions of stomach by penetrating mucus lining (mucosa). Then it secretes urease to increase pH and neautralize gastric acids for survival.

40
Q

treatment of ulcers

A

antibiotics and PPIs

41
Q

what are stomach ulcers

A

Ulcers are inflamed/ damaged areas of/ open sores in the stomach wall (caused by exposure of stomach cells to stomach acids)

42
Q

dual supply of liver

A

The liver is the largest gland in the body and it performs over 500 different vital functions, it has a unique input of blood from two separate sources.

43
Q

dual supply for liver (1)

A

first, there is the hepatic artery which branches off the aorta and delivers oxygen-rich blood from the heart to the liver

44
Q

dual supply for liver (2)

A

the hepatic portal vein that delivers nutrient-rich blood from the gut (from the capillaries of the villi in the intestines) to the liver (blood from pancreas/ spleen/ stomach/ colon too)

45
Q

circulation of blood through sinusoids of the liver

A

They filter, detoxify and balance levels of nutrients in the blood which removes excess nutrients to be stored in the liver. This removes toxins and adds nutrients. Sinusoids also engulf and break down “old”/ damaged erythrocytes (red blood cells)

46
Q

structure and function of sinusoids

A

Sinusoids are small blood vessels (similar to capillaries) that facilitate material exchange (between the blood and the hepatocytes). Blood drains into each sinusoid through hepatic arterioles (oxygen-rich blood from heart) and hepatic portal venules (nutrient-rich blood from intestine)

47
Q

what is each sinusoid lined with and what do they contain

A

a single layer of hepatocytes (one cell layer thick) and contains specialized macrophages (phagocytic cells = Kupffer cells),

48
Q

sinusoids drain…

A

“filtered” blood into a central hepatic vein (which will take clean, deoxygenated blood, under lower pressure, back to the heart).

49
Q

role of the liver in the regulation of nutrient levels

A

Receives, processes, and stores nutrients from the absorbed from the intestines to balance nutrient levels in the blood

50
Q

carbohydrate metabolism

A

Excess glucose in the blood is stored as glycogen in hepatocytes (controlled by insulin - pancreas). If blood glucose levels drop, the liver hydrolyzes glycogen into glucose and releases it back into the blood (controlled by glucagon - pancreas). IF hepatic glycogen stores are depleted, the liver CAN synthesize glucose from other sources (such as fats).

51
Q

protein metabolism

A

Using amino acids from digested proteins, hepatocytes make and secrete plasma proteins (produced by Rough ER and modified by the Golgi within these cells). Hepatocytes also break down the protein component of hemoglobin (globin) into amino acids. Amino acids from these sources can also be used by the liver to synthesize nonessential amino acids. Excess amino acids CANNOT be stored in the body, so the liver breaks them down. In doing so, it removes the amine (NH2) group (deamination) and converts it into urea (nitrogenous waste removed by the kidneys).

52
Q

lipid metabolism

A

Excess carbohydrates and proteins are converted into fatty acids and triglycerides in the liver. These are stored, or used to make cholesterol and phospholipids, which are either stored or transported to other parts of the body by lipoproteins. LDLs take cholesterol TO cells and HDLs bring cholesterol back to the liver. Excess cholesterol in the liver is converted to bile salts, which are used to make bile or egested via the large intestine

53
Q

Explain how erythrocytes (red blood cells) are broken down (by Kupffer cells) and the recycling of their components by the liver.

A

Kupfer cells (phagocytic cells in the liver sinusoids) engulf (phagocytosis) ruptured red blood cells and their “pieces”/ hemoglobin, and break down their hemoglobin molecules into heme (contains iron) and globin.

54
Q

Outline the roles/ functions of hepatocytes in the sinusoids of the liver

A

Each sinusoid is lined with a single layer of hepatocytes (one cell layer thick) and contains specialized macrophages (phagocytic cells = Kupffer cells). To facilitate the exchange of a wide variety of substances between the blood and hepatocytes, the hepatocytes are directly exposed to the blood passing through the organ, by being in close contact with the liver blood sinusoids.

55
Q

production of bile

A

Bile (made of bile salts, water, cholesterol, and bilirubin/ bile pigment) is made in the liver (hepatocytes)

56
Q

how is bile transported

A

via bile ductules (in the sinusoids) to the gallbladder for storage

56
Q

jaundice

A

a condition in which there is an excess of/ high levels of bilirubin (bile pigment) in the body (and bilirubin leaks out of liver into the blood) - bilirubin is produced by the breakdown of hemoglobin/ heme (from RBC’s) in the liver.

57
Q

causes of jaundice

A

Liver disease (hepatitis, liver cancer, cirrhosis), gall bladder obstruction/ blocked bile duct/ gall stones, increased RBC damage (anemia), infection (parasite), immature liver (in newborns)

58
Q

consequences of jaundice

A

yellowing skin, yellowing sclera (whites of eyes), itchiness, pale/ grey feces, darkened urine, brain damage (in infants)

59
Q

type I diabetes

A

Early onset, Beta cells damaged/ destroyed by body’s own immune system – autoimmune disease (not enough/ no insulin produced), Triggered by various factors (illness etc.) – not usually genetic, Controlled by insulin injections to regulate blood glucose levels

60
Q

type II diabetes

A

Adult onset, Insulin receptors on cells (liver, muscles etc) are fewer and/ or become less sensitive to insulin (decreased body response to insulin), Related to obesity, poor diet, genetic history, lack of exercise, age, ethnicity, Controlled by managing diet (more fiber/ complex carbs/ smaller meals/ reduce sugar intake = slower/ reduced glucose release into blood; less saturated fat = lose weight), and lifestyle.

61
Q

what do both types of diabetes have

A

high blood sugar, glucose in urine, increased thirst/ urination, hunger, fatigue, weight loss etc.

62
Q

leptin is secreted by cells

A

in adipose tissue

63
Q

leptin acts on cells in the

A

hypothalamus (to suppress/ inhibit appetite, as the hypothalamus is the appetite control center in the brain)

64
Q

more adipose =

A

more fat = more leptin = reduced appetite/ less eating (but obese people can develop leptin resistance/ insensitivity)

65
Q

6-8 mark pancreas question!!

A

go write it down!!!

ib biology (6 decks)

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