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BPK 110 > 3: Digestion, Absorption, Metabolism > Flashcards

3: Digestion, Absorption, Metabolism Flashcards

1
Q

What is Digestion

A

separates nutrients in food and breaks larger molecules into smaller ones so they can be absorbed

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2
Q

Individually, what do polysaccharides, triglycerides, and proteins break into? Why can’t they be absorbed?

A
  • Polysaccharides → sugars
  • Triglycerides → fatty acids
  • Proteins → amino acids

cannot be absorbed as they are found in food, broken down to pass membranes of intestinal cells

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3
Q

What are the two types of digestion

A

Mechanical (physical), chemical digestion

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4
Q

Example of Mechanical/physical digestion

A

physical process like our teeth chewing and stomach churning to break food apart

  • does not alter the chemical composition of the nutrients
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5
Q

Define Chemical digestion and give examples

A

uses enzymes to alter chemical structure of nutrients and reduces them to their building blocks
Ex: starch —> maltose —> glucose
Proteins —> dipeptides —> single amino acids

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6
Q

Define Enzymes and its reaction

A

speed up the rate of reaction
- Provide a location for chemical reactions to occur
- participate in hydrolysis and condensation reactions

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7
Q

Hydrolysis reaction

A

Input of water helps to break down larger molecule into a smaller one

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8
Q

Condensation reactions

A

Combine molecules by liberating a water molecule
Ex: binding amino acids into specific chain begins process of protein synthesis

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9
Q

What does the prefix of enzymes tell us

A

which substrate it acts on
- sucrase breaks down sucrose
- proteases break down protein
- lipases break down lipids

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10
Q

Define Hormones

A

chemical messengers that are required for many physiological processes, including digestion

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11
Q

How do hormones work

A

released from one area of the body and travel through the blood to different parts of body
- communicate info about specific parts of digestive tract to brain and other digestive structures

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12
Q

Give an example of hormone communication

A

fat and protein enter small intestine, local cells release hormone Cholecystokinin (CCK) signals brain theres food in small intestine, leading to decrease hunger

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13
Q

Digestive tract structure

A

long tube-like structure that begins in the mouth and ends in the anus
- length/various folds provide large SA for digestion and absorption

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14
Q

Sphincters

A

Circular muscle found between certain organs and regulate passage from one organ to the next
- 2+ days for material to pass through entire digestive tract
- food spends most time in large intestine

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15
Q

Factors that affect transit time in the digestive system

A

Age, activity levels, diet, gender, medication use, infection

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16
Q

What organs are accessory structures of the digestive tract

A

liver, gallbladder and pancreas are not part of digestive tract but are part of the digestive system and critical to its function
- all secrete into the digestive tract

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17
Q

List the digestive tract

A

Mouth - pharynx - esophagus - stomach - (liver) - (gallbladder) - (pancreas) - small intestine - large intestine

(Accessory organ)

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18
Q

Digestive tract is made of what four main layers

A

Lumen, submucosa, muscularis, serosa

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19
Q

Define Lumen and what is found

A

inner cavity of the small intestine tube; it is where you will find food and digestive secretions

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20
Q

Function of Mucosa

A

secretes mucus, keeps digestive tract moist and protects it from infection.
- plays a critical role in absorption, especially in the small intestine

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21
Q

Define Submucosa and what is found in it

A

connects the mucosa to the more superficial muscularis layer.
- Blood vessels, lymphatic vessels and nerves are found here

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22
Q

Nerve Plexus

A

500 million neurons arranged in a grouping
- various nerves and plexus makeup up the enteric nervous system

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23
Q

Enteric nervous system

A

communicates with the brain but can also function independently
- helps regulate muscular contractions, messaging and digestive tract secretions

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24
Q

Muscularis layer (smooth muscle)

A
  • cant voluntarily control movement (autonomic, involuntary, control)
  • two layers of muscles, inner layer is circular pattern along tubes circumference, outer layer longitudinal along long axis of tube
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25
Q

Function of the muscularis layer (smooth muscle)

A

responds to the movement needs of the digestive tract, pushing food forward and helping it mix with digestive secretions

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26
Q

Define Serosa and its function

A

Tracts outermost layer
- consists of a layer of connective tissue
- helps reduce friction with organs adjacent to tract/anchors into place

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27
Q

Mechanical process of Mouth

A

Mechanical: Teeth rip food apart, tongue pushes food towards teeth and mixes it with saliva

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28
Q

Function of Saliva

A

Secreted into the mouth to facilitate digestion

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29
Q

What are the three salivary glands

A

The parotid, submandibular and sublingual
- collectively release this water-based substance into the mouth to begin the digestion of food

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30
Q

Saliva contains what two enzymes

A
  • Salivary amylase: digests amylose, type of starch
  • Lingual lipase: digests lipids
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31
Q

T/F: There are no protein digesting enzymes in saliva

A

True, chemical digestion of protein begins in the stomach

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32
Q

Lysozyme

A
  • antibacterial component in saliva
  • disinfects material arriving in our food to help reduce the chances that an active infectious agent can enter
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33
Q

Bolus

A

food chewed and mixed with saliva, forms a uniform cohesive structure

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34
Q

What is the chemical digestion in the mouth

A

Salivary breakdown of lipids and starch
(Salivary amylase and lingual lipase)

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35
Q

Pharynx (throat)

A
  • passageway for food and air
  • when not eating, pharynx opens trachea, allowing air to float in and out of our lungs
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36
Q

Epiglottis

A

directs food from the pharynx into the esophagus instead of down the wrong tube into the trachea (windpipe)

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37
Q

Esophagus

A
  • not directly add to the digestion process but a conduit for food from pharynx to stomach
  • No active digestion or absorption
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38
Q

Peristalsis

A

waves of circular smooth muscle contraction to move a bolus of food forward

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39
Q

Lower esophageal sphincter

A
  • found at end of the esophagus
  • When open, food can enter stomach
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40
Q

Define Stomach and its time transit

A

temporary reservoir for food before entering the small intestine
- Food remains here 4-5 hours
- chemical digestion of protein begins

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41
Q

Chyme

A

When food leaves the stomach it is in a semi-liquid form

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42
Q

How does chyme enter the small intestine?

A

The pyloric sphincter must open

43
Q

T/F: A small amount of absorption occurs in the stomach

A

True, limited to the partial absorption of water and amino acids

44
Q

How does a stomach churn food?

A

3 layers of muscles allow stomach to churn
- Lower esophageal sphincter and pyloric sphincter close as stomach churns food and mixes it with gastric juice

45
Q

What are the three muscle layers in the stomach?

A

Longitudinal - outer layer
Circular - middle layer
Diagonal - inner layer

46
Q

What is the mechanical digestion when the stomach churns?

A

Stomach churning, promotes mechanical digestion

47
Q

What is the chemical digestion when the stomach churns?

A

mixing foodstuffs with enzymes

48
Q

Crypts

A

increase SA to allow more stomach cells to be involved in digestion
- different cells (secrete mucus, pepsinogen)

49
Q

Gastric juice

A

Cells in stomach crypts secrete contents of gastric juice for digestion
(Mucus, gastric lipase, hydrochloric acid, pepsinogen)

50
Q

Mucus

A

Lubrication, medium for chemical reactions
- also lines the stomach’s inner walls, creating a protective layer that stops stomach acid and juices from damaging the stomach wall

51
Q

Hydrochloric acid (HCl)

A
  • highly corrosive acid (pH = 2)
  • unravel proteins, exposing sites where enzymes can further break them down
  • activates pepsinogen
52
Q

Pepsinogen

A

proenzyme secreted by certain stomach cells
- becomes an active enzyme when acted upon by HCl, converting pepsinogen into active form, pepsin, which digests protein

53
Q

Pepsinogen

A

proenzyme secreted by certain stomach cells
- becomes an active enzyme when acted upon by HCl, converting pepsinogen into active form, pepsin, which digests protein

54
Q

Gastric lipase

A
  • continues the breakdown of lipids that lingual lipase began in the mouth
  • accounts for approximately 30% of lipid digestion
55
Q

T/F: Enzyme salivary amylase found in mouth is inactivated in stomach, since there are no carb-digesting enzymes secreted by stomach

A

True, negligible carbohydrate digestion occurs in the stomach

56
Q

Small intestine

A

Primary site of digestion and absorption
- Long length (~6m), large circular folds, villi, microvilli contribute to its large surface area

57
Q

What are the three parts of the small intestine?

A

Duodenum, jejunum, ileum

58
Q

Duodenum

A
  • first part of the small intestine
  • hooked tube, about 25 cm in length
  • small opening that receives secretions from liver, gallbladder and pancreas
59
Q

Jejunum

A
  • Middle part of small intestine
  • 2m in length
60
Q

Ileum

A
  • terminal part
  • 3 m in length
61
Q

Villus (plural = villi)

A

increase the SA and slow passage of food along its path
- invaginations of small intestine wall
- Main functional unit of small intestine

62
Q

Microvilli (brush border)

A
  • tiny finger-like projections
  • extensions which secrete enzymes on the surface of villus
  • part of the enterocyte and are oriented towards the lumen
63
Q

How do nutrient sub units enter the blood or lymph?

A

Nutrient subunits are absorbed into the center of the villus where they then enter the blood or the lymph

64
Q

Villi in small intestine:
Lacteal

A

lymphatic vessels are one-way tubes filled with watery, non-blood liquid that removes material from tissues
- absorbs larger lipids and fat-soluble vitamins

65
Q

Thoracic duct

A

Material that ends up in the lacteal will eventually drain into the bloodstream through thoracic duct

66
Q

Villi in small intestine:
Capillary bed

A

all nutrient subunits are absorbed here, except for larger lipids and fat-soluble vitamins

67
Q

Methods of no transporter required

A

Osmosis (water), passive diffusion (lipids, fat, soluble vitamins)

68
Q

Methods of protein transporter required

A

Facilitated diffusion (fructose),
Active transport (glucose, amino acids)

69
Q

Villi in small intestine:
Enterocytes

A

in contact with the small intestine lumen
- helps increase total SA, needed to perform a wide range of digestive and absorptive functions

70
Q

Function of Enterocytes

A

in contact with the small intestine lumen
- helps increase total SA, needed to perform a wide range of digestive and absorptive functions

71
Q

Osmosis

A
  • Water can move across walls of the enterocytes without a transporter
  • moves in response to differences in dissolved particles. If there are more dissolved particles within the villus, water moves into this area to decrease their relative concentration
72
Q

Passive (Simple) diffusion

A

move from an area of high concentration to one of low concentration
Ex: lipids, fat soluble vitamins

73
Q

T/F: Fatty acids and fat-soluble vitamins do not require a transporter

A

True, they can be absorbed along the spaces between phospholipids in the enterocyte cell membrane

74
Q

Facilitated diffusion

A

tunnels that allow material to pass from an area of high concentration to low concentration

75
Q

What nutrient used the absorption process, facilitate diffusion?

A

Certain sugars such as fructose require a protein transporter

76
Q

Active transport

A

move from an area of lower concentration to one of higher concentration
- movement against a concentration gradient also requires energy
- contributes to our daily total energy expenditure

77
Q

What nutrients use the absorption process, active transport

A

glucose and amino acids move from an area of lower concentration to one of higher concentration

78
Q

What digestive enzymes are stored at the brush border (microvilli)

A

lactase, sucrase and maltase

79
Q

Where do the secretions of accessory organs drain into?

A

Secretions from the pancreas, liver and gallbladder collect into a common tube that drains into the duodenum

80
Q

Pancreas

A

Glands with two types of functions (endocrine and exocrine)

81
Q

What is the endocrine function of the pancreas?

A

blood glucose-regulating function, due to the production and secretion of the hormones insulin and glucagon

82
Q

What is the exocrine function of the pancreas?

A

pancreas secretes pancreatic juice into the small intestine
- secretions are called pancreatic juice

83
Q

Pancreatic juice contains what

A

Digestive enzymes: protein-digesting protease, lipase and carbohydrate-digesting amylase
Bicarbonate: important buffer that neutralizes the highly acidic chyme

84
Q

Liver

A

Metabolism, detoxification, digestion
- production of bile, which promotes lipid digestion

85
Q

Gallbladder

A

Bile is made in liver BUT stored in the gallbladder for quick secretion when needed

86
Q

Bile

A

lipid emulsifier – it breaks larger lipid globules into smaller ones and allows them to be suspended in a watery environment

87
Q

What do the salts within bile contain?

A

a hydrophilic (water-loving; lipid-hating) head and a hydro- phobic (water-hating; lipid-loving) tail

88
Q

Micelle

A

Allow lipids to be suspended and freely move around the small intestine lumen
- also allow lipase to act on lipids
- arrange itself so lipids groups together in smaller mixtures within a ring of bile salts

89
Q

Emulsification

A

Breakdown of large lipid globules through bile salts that create the micelle structure for enzyme lipase to digest lipids

90
Q

Large intestine

A
  • Approx 1.5 m in length
  • colon is main part of large intestine
  • any unabsorbed material is either:
    Packaged for removal or Acted upon by bacteria Microbiota
91
Q

What are the four sections of the large intestine?

A

ascending, transverse, descending and sigmoid colons

92
Q

What is the first part of the large intestine?

A

Cecum, material moves from the ileum of the small intestine into the cecum

93
Q

Segmentation of the large intestine

A

break material into smaller components while mixing it with digestive juices

94
Q

Segmentation of the large intestine

A

break material into smaller components while mixing it with digestive juices

95
Q

What movements occur in the large intestine

A
  • Slow waves of peristalsis due to contractions of its muscularis layer
  • segmentation
96
Q

How is waste created?

A

large intestine draws water out and packages waste into solid feces, which is easier to excrete

97
Q

Rectum

A

stores feces until it is ready to be excreted

98
Q

Distal anus

A
  • muscular sphincter that regulates passage of material out from the rectum
  • sphincter is regulated by both involuntary and voluntary muscle
99
Q

Microbiota

A
  • total composite of non-human microorganisms found in our bodies
  • 300-500 different species
    Ex: viruses, fungi and other microorganisms, but mainly bacteria
100
Q

Microbiome

A

genetic material of the non-human organisms found in our body
- 150 times more genes than human DNA – greatly expanding our own DNA potential

101
Q

The Microbiome

A

largest population of non-human cells is found in the large intestine
- contribute to both health and disease

102
Q

What roles does the microbiota have?

A
  • Vitamin synthesis (vitamin K, B2, B12)
  • Energy harvesting
  • Health/disease
103
Q

T/F: Diet does not alter the composition of the Microbiome

A

False, processed foods high in refined carbs can negatively affect diversity of the microbiome, altering its metabolic capacity and potentially leading to higher energy harvesting

104
Q

What digestive tract structure secrete mucus?

A

Pharynx, esophagus, stomach, small intestine, large intestine

BPK 110 (7 decks)

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