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NUTR 301 > Lecture 2 - Digestion/Absorption Physiology, Intro to Energy > Flashcards

Lecture 2 - Digestion/Absorption Physiology, Intro to Energy Flashcards

1
Q

What is food? Why do we need it?

A

Energy
There are different formats of food, some are essential
To maintain health and avoid certain diseases

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2
Q

Can humans exist without energy?

A

No

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3
Q

What is the body’s energy currency?

A

ATP; easier to use than macronutrients. Transferable

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4
Q

Which nutrients have energy?

A

CHO, PRO, Lipids, alcohol, vitamins and minerals (can elicit energy)

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5
Q

What are the physiological processes requiring energy?

A

Everything
Kreb’s cycle, glycolysis, bowel movements
Exercise, movement, getting from A to B, rest, etc.

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6
Q

How is most ATP created?

A

Most ATP is created by oxidation of food fuels to CO2 and H2O
- done through substrate level oxidation and oxidative phosphorylation

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7
Q

Why do we need nutrients?

A

We need them for energy
Energy = the capacity to do work
Carbohydrates, lipids, proteins, alcohol = Potential energy
Nutrients must be converted to ATP (“captured”) - the major energy currency of the cell

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8
Q

What are the three things energy is required for? **

A
  1. Basal Metabolism - normal processes of growth and maintenance; most of heat production
  2. Thermic effect of food (TEF) - assimilation or use of dietary fuels
  3. Physical activity (EEPA)
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9
Q

Energy released from energy-yielding nutrients is ‘captured’ by…

A

ATP and other carriers (i.e. NADPH)

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10
Q

Can ATP be stored?

A

ATP cannot be stored, but balance between ATP and ADP/AMP is highly regulated like casino chips!

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11
Q

The process of energy production also produces…?

A

Heat (only a small fraction of total energy released from food is captured and actually usable by us)

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12
Q

What are the 3 sources of heat production?

A
  1. Obligatory processes
  2. Regulatory processes
  3. Some heat produced via thermogenesis from TEF and EEPA
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13
Q

Explain Obligatory (essential) heat production

A
  • Released from anabolic and catabolic reactions (using and synthesizing ATP)
  • Produced by fundamental molecular transport processes (e.e. reactions involved in absorption, digestion, storage of nutrients (Na/K pump, H+ pump for ETC)
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14
Q

Explain Regulatory heat production

A
  • Reactions involved in homeostasis of body temperature and overall body maintenance
  • Also essential but regulated. Dependent on the environment (e.g. -25 vs 21)
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15
Q

What are the major function(s) of the GI tract?

A

Digest complex molecules
Absorb nutrients
Barrier to entry of bacteria

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16
Q

What does saliva have in it?

A

Antibacterial properties: thiocyanate, lactoferrin, lysozyme
Amylase (breaks down starch into sugar)

17
Q

What are the movements in the stomach?

A

Propulsion, grinding, retropulsion

18
Q

Does the stomach participate in digestion?

A

Yes it is part of digestion through mechanical means but is not really an absorptive organ and not much chemical digestion occurs

19
Q

What do glans in stomach secrete?

A

They secrete gastric juices containing water, electrolytes, and enzymes
Examples:
- Parietal (oxyntic) cells —> HCl, IF (B12 absorption)
- Neck (mucous) cells —> HCO3-, mucous
- Chief cells —> pepsinogens
- Enteroendocrine cells —> hormones

20
Q

Why is the stomach so acidic?

A

Activates zymogens, denatures proteins, kills bacteria

21
Q

How long is the small intestine?

A

10ft or 3m

22
Q

What occurs in the small intestine?

A

Bulk of absorption; movement of solute; water and nutrients

23
Q

What is the surface area of the small intestine? Why is this important?

A

200m2.
Surface area and type facilitates absorption and transport

24
Q

What is the major site of absorption?

A

Jejunum

25
Q

What is the lifespan of the enterocyte? Why is this important?

A

Lifespan is 72 hours so it is very metabolically active, and it costs a lot of energy because they only last 3 days

26
Q

How are water-soluble nutrients transported? What are these water-soluble nutrients?

A

Water-soluble nutrients enter directly into capillaries, feeding the portal vein (directly to liver)
- includes amino acids, monosaccharides, glycerol, short chain fatty acids (SCFAs), electrolytes, water-soluble vitamins
- Quite quick. About 15 minutes after digesting glucose

27
Q

How are lipid-soluble nutrients transported?

A

Lipid-soluble nutrients are transported via chylomicrons into lymphatics
- CMs too large to enter blood capillaries therefore enter lymphatic capillaries via fenestrations of lacteals; eventually enter blood circulation via lymphatic vessels (thoracic duct)
- Fat takes 4 hours (peak) or longer to absorb
- can accumulate

28
Q

Where is Somatostatin located and what do they do?

A

Located in pancreatic (D)-cells and intestinal cells
- Inhibits gastric secretions and motility and pancreatic exocrine and gall bladder secretions

29
Q

What does gastrin do and how does it act?

A

Gastrin is released by G-cells in antrum of the stomach and proximal small intestine
- acts in stomach to increase secretion of gastric acid, motility, pepsinogen release

30
Q

What is secretin released by and what does it do?

A

Secretin secreted by S-cells in duodenum in response to acidic chyme. It stimulates release of pancreatic juice (HCO3-) and enzymes

31
Q

What is cholecystokinin (CK) secreted by and what does it do?

A

Secreted by I-cells in proximal small intestine and by enteric nerves in the ileum and colon
- stimulates release of pancreatic juice and enzymes and gall bladder contraction

32
Q

What does ghrelin, motilin, PYY, GIP, GLP do?

A
33
Q

What are the 5 sites of nutrient absorption?

A
  1. Stomach: water, alcohol, some minerals
  2. Small intestine: most vitamins and minerals to varying degrees in duodenum, jejunum, and ileum
  3. Jejunum: lipids, monosaccharides, amino acids, small peptides.
  4. Ileum: bile salts and acids
  5. Large intestine: water, electrolytes, as well as vitamin K, biotin, SCFAs from bacteria

NUTR 301 (2 decks)

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