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bio > Chapter 4 - Digestive System > Flashcards

Chapter 4 - Digestive System Flashcards

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Biology 101 flashcards
1
Q

Functions of the digestive system

A

IDEA
Ingest (take in) food
Digest (break down) foo into small pieces -> chemical and physical
Eliminate waste
Absorb and provide nutrients to the body cells

A comes before E but its just for the acronym Loll

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2
Q

carbohydrates

A

elements: carbon, hydrogen, oxygen
- monosaccharides 1
- disaccharides 2
- oligosaccharides 2<x<10
- polysaccharides 10 or more

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3
Q

monosaccharides

A
  • small enough to be directly absorbed into blood
  • common monosaccharides:
    -> glucose (source of ATP)
    -> fructose (found in fruits, soft drinks)
    -> galactose (found in milk)
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4
Q

disaccharides

A
  • made up of 2 monosaccharide subunits
  • digested by enzymes into monosac. before absorption into the blood
  • common disaccharides:
    -> sucrose (table sugar) = glucose + fructose
    -> maltose = glucose + glucose
    -> lactose (milk sugar) = glucose + galactose
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5
Q

polysaccharides

A
  • many monosac. (e.g. glucose) joined together by glycosidic bonds
  • digested into monosac. before absorption
  • major polysaccharides:
    -> starch from plants: main source in out diet, digested into glucose
    -> glycogen from animals: not an important source in our diet
    -> cellulose from plants: indigestible, provides fiber in our diet
    -> chitin cell wall of fungi
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6
Q

protein

A

elements: C,H,N,O,S
- long chains of amino acids joined by peptide bonds
- 20 common amino acids -> essential (must be supplied by diet) /non essential (our body can make them)

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7
Q

function of proteins

A
  • enzymes (speed up reactions; e.g. amylase, pepsin, proteases, lipases)
  • muscle contraction, e.g. actin and myosin
  • hormones, e.g. insulin, parathyroid hormone, growth hormone
  • hemoglobin (for oxygen transport)
  • antibodies (for immune defense)
  • ion channels, carriers and pumps
  • membrane receptors
  • energy source (after glucose/glycogen and fats are exhausted
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8
Q

what are enzymes

A

biological protein catalyst that speed up reactions.
- they recognise specific molecules
e.g the amylase in our saliva recognises and breaks down only starch

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9
Q

lipids/fat

A
  • triglycerides -> glycerol and 3 fatty acids; digested by lipase
  • fatty acids -> saturated (no double bond), unsaturated (have at least 1 bond)
  • cholesterol
  • phospholipids -> glycerol + 2 fatty acids + 1 phosphate group (e.g. lecithin found in egg yolk and soya bean)
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10
Q

function of lipids

A
  • triglycerides: source of energy (ATP)
  • adipose tissue: cushion and protect internal organs, insulate body, store energy
  • phospholipids -> forms bilayer of cell membrane
  • cholesterol -> component of cell membrane, precursor for synthesis of steroid hormones e.g. sex hormones, component of bile salts which emulsify fats to id in their digestion and absorption
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11
Q

vitamins

A

organic chemicals needed in small quantities
A: vision
B complex: coenzymes for enzymes
C: antioxidant, collagen synthesis
D: absorption of calcium in intestines
E: antioxidant
K: blood clotting

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12
Q

minerals

A
  • calcium (Ca): strong bone and teeth, muscle and nerve functions, blood clotting
  • sodium (Na): osmoregulation, nerve and muscle functions
  • potassium (K): nerve and muscle functions
  • iron (Fe): component of hemoglobin, components of enzymes
  • phosphorus (P): component of ATP, nucleic acids, phospholipids, cell membranes
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13
Q

water

A
  • medium for all biochemical reactions
  • transport of solutes
  • maintain body heat
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14
Q

digestive tract

A

mouth, throat/pharynx, esophagus, stomach, small intestine, large intestine/colon, anus

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15
Q

accessory organs

A

teeth, salivary glands, pancreas, liver, gall bladder

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16
Q

mouth/oral cavity

A
  • saliva secreted by salivary glands
    -> moistens food
    -> lubricates mouth
    -> saliva contains lysozyme (antibacterial) and salivary amylase which digests starch
  • teeth cut, tear, crush and grind food which physically break down food into smaller pieces
17
Q

throat/pharynx

A
  • common gateway to the entrance of the trachea and esophagus
    -> when we swallow food and drinks, epiglottis closes the opening of the trachea so food and drinks can enter the esophagus instead of trachea
18
Q

esophagus

A
  • muscular tube carrying food from throat to stomach
  • behind the trachea
  • once swallowed, food is propelled down esophagus into stomach within seconds by strong smooth muscular contractions called peristalsis
19
Q

stomach

A
  • muscular bag that can expand to 20x its original size
  • holds up to 2L of food and gastric juice
  • muscular stomach wall mixes and church food with acidic gastric juice
  • stomach lining contains gastric glands which secret gastric juice
  • protein digestion begins here
  • pyloric sphincter acts like a valve to release small amounts of stomach content into small intestine
20
Q

gastric juice components

A
  • mucous (by mucous neck cells): coats and protects stomach lining from digestion by pepsin
  • hcl (by parietal cells): converts pepsinogen to pepsin, inhibits salivary amylase, inhibits bacteria
  • pepsinogen (by chief cells): precursor of protein, pepsin digests proteins
  • hormones (e.g. gastrin; by endocrine cells): gastrin controls gastric juice secretion

excessive gastric juice secretion causes stomach ulcers because the corrosive action of hcl (pH 1-2) eats into the stomach wall.

21
Q

small intestine

A
  • major site for digestion and absorption
  • abt 6m long
  • 3 sections: duodenum 25cm, jejunum 2.5m, ileum 3.5m
22
Q

how is the small intestine adapted for its function

A
  • increase surface area for absorption
    -> wall forms circular folds
    -> villi, finger-like projections from the circular folds
    -> S.I. epithelial cells possess microvilli
  • blood capillaries and lacteals run through the villi
    -> capillaries transport amino acids and glucose to the liver
    -> lacteal transports lipids to the lymphatic circulation
23
Q

what is segmentation

A
  • mixes food back and forth
  • distribute food throughout the S.I. to ensure good absorption
  • both directions
  • only in small intestine

as compared to peristalsis which
- one direction
- esophagus to anus

24
Q

large intestine

A
  • 1.5m long
  • caecum -> appendix attached to caecum, colon, rectum, anus (opening)
  • absorbs remaining water, minerals and vitamins
  • eliminates indigestible food as faeces
  • many resident bacteria -> e. coli in colon provides host with vitamin K in return for nutrients and shelter, resident bacteria prevent harmful ones from colonizing
25
Q

pancreas (ao)

A
  • behind stomach
  • secretes alkaline pancreatic juice into S.I. juice containing: amylase (starch), proteases (protein), lipases (lipid), bicarbonate (HCO3-) ion to neutralize HCL
  • secrete hormone insulin and glucagon which regulate blood glucose levels

insulin: lower b.g.
glucagon: raises b.g

26
Q

liver (ao)

A
  • located on right side of the body under the diaphragm
  • connected to the gall bladder
  • absorbed monosac. and amino acids are transported from the small intestine to liver before delivery to rest of body

functions:
- produce bile which emulsifies fat
- detoxify drugs and toxins
- stores excess glucose as glycogen

27
Q

gall bladder

A
  • stores bile produced by liver
  • bile is secreted into duodenum via bile duct
  • bile aids in mechanical digestion of fats (emulsification)

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