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An Sc 311 Midterm 1 > Lecture 2 - Digestion and Absorption of Nutrients > Flashcards

Lecture 2 - Digestion and Absorption of Nutrients Flashcards

1
Q

Definition of digestion

A

Process by which foodstuffs are broken down in the GI tract into absorbable units

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2
Q

Are food and nutrients inside the body during digestion?

A

No, considered to be outside the body, GI tract is hollow tube outside body

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3
Q

What are the four types of digestive processes

A

Mechanical
Chemical
Enzymatic
Microbial

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4
Q

Mechanical digestion includes…

A

Mastication (chewing)
Grinding action of the gizzard (birds)
Movement of the GI tract (segmentation and peristalsis)

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5
Q

What is peristalsis

A

series of wave-like muscle contractions that move food through the digestive tract

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6
Q

Chemical digestion involves

A

Gastric acid (HCl; pH 1.5-3.5)

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7
Q

Enzymatic digestion occurs where? Involves what?

A

In the lumen and the mucosa
Digestive enzymes are secreted into the GI tract

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8
Q

Definition of absorption

A

Process of moving digested products through the gut mucosal wall

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9
Q

Two types of absorption

A

Transcellular (across cell)
Paracellular (across tight jxn)

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10
Q

Three types of transport

A

Passive
Active
Osmosis

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11
Q

Describe passive transport

A

Relies on concentration/electrochemical gradients
Transcellular or paracellular
No energy required

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12
Q

What is osmosis

A

Water moves from low solute concentration to high solute concentration (water follows solute)

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13
Q

The electrochemical gradient is the combination of what

A

Chemical driving force (e.g. Na, K from low to high conc)
Electrical driving force (charge force; neg charge inside)

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14
Q

Describe active transport

A

Moves against concentration/electrochemical gradient
Needs energy (ATP)
Primary or secondary

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15
Q

What is secondary active transport

A

Movement of a solute against its gradient by pairing it with facilitated diffusion of a different solute with its concentration gradient

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16
Q

What molecules use secondary active transport

A

Glucose, aa, B-vitamins, bile salts

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17
Q

How much water do humans absorb/reabsorb per day? Where does this happen?

A

2L/day from food and drink + 7L per day from gut secretion = 9L a day

95% of it is absorbed in the small intestine

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18
Q

What kind of transport does water absorption use

A

Passive transport (osmotic gradient; transcellular and paracellular)

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19
Q

Amount of water secreted depends on? Location of absorption depends on?

A

Whether the animal is a carnivore or herbivore

Depends on species

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20
Q

Distribution of absorption in small intestine vs colon or dog vs horse

A

Dog = majority absorbed by SI (88%), 12% by colon

Horse = more even (58% SI, 42% colon)

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21
Q

Types of carbohydrates

A

Monosaccharide
Disaccharide
Polysaccharide

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22
Q

Examples of mono, di, and polysaccharides

A

Mono = glucose, fructose, galactose

Di = sucrose, maltose, lactose

Poly = starch, cellulose

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23
Q

Sucrose, maltose and lactose composition

A

Sucrose = glucose + fructose

Maltose = glucose + glucose

Lactose = glucose + galactose

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24
Q

What kinds of bonds are in starch? Cellulose?

A

Starch = alpha-1,4 glycosidic bond

Cellulose = beta-1,4 glycosidic bond

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25
How many carbons in glucose, fructose and galactose
Glucose/galactose = six Fructose = five
26
Steps in amylose digestion
Amylose broken down into dextrins by salivary alpha-amylase Dextrins broken down to maltose by pancreatic a-amylase Maltose broken down into glycose by maltase
27
Slide 17**
Polysaccharide digestion
28
What transports glucose across the brush border membrane? Fructose?
Sodium glucose transporter 1 GLUT5
29
How does glucose transport vary in low-sugar vs high-sugar meal
Low-sugar = sodium glucose transporter 1 is used (secondary active transport) High-sugar = GLUT2 allows glucose to be absorbed passively
30
What kinds of CHO are absorbed
Monosaccharides only
31
What happens to lactase activity over time? Enzyme activity varies with...
Constantly decreasing after birth Age, region of SI
32
Parts of an amino acid
Amino group, carboxylic acid group, R group
33
Proteins are
Large molecules consisting of amino acids linked by peptide bonds
34
Primary, secondary, tertiary and quaternary protein structure
Primary = sequence of a chain of aa Secondary = H bonds of the peptide backbone (B-sheet, a-helix) Tertiary = 3D folding pattern of a protein due to side chain interactions Quaternary = protein consisting of more than one amino acid chain
35
How are gastric enzymes activated
HCl in the stomach leads to denaturation of protein, this triggers the activation of pepsinogen into pepsin
36
Gastric protease enzyme is called (unactivated and activated)
Pepsinogen (proenzyme) -> pepsin
37
Pancreatic protease enzymes and how they're activated
Trypsinogen is activated by enterokinase and becomes trypsin Trypsin activates the rest: Chymotrypsinogen -> chymotrypsin Proelastase -> elastase Procarboxypeptidase A -> Carboxypeptidase A Procarboxypeptidase B -> carboxypeptidase B
38
What happens to large peptides at the brush border
Turned into di- and tri- peptides or free aa by brush border peptidases
39
What happens to di- and tri and free aa inside the brush border membrane
Small amounts of di- and tri- peptides will cross through, most turned into aa by cytoplasmic peptidases Amino acids carried through membrane
40
How does brush border membrane transport differ for aa
Neutral, basic and acidic aa have different transport systems, use different ion gradients
41
Slide 29**
Protein and CHO recap
42
Most ingested fats are in the form of
triglycerides
43
What is a triglyceride composed of
Glycerol + 3 fatty acids
44
Where are bile salts produced and stored
Produced in liver Stored in gallbladder
45
Two parts of bile salts...
One part is negatively charged (hydrophilic head), the other is hydrophobic tail (positive charge)
46
Slide 33***
Lipid digestion
47
Fat goes from...
Large fat drops -> + bile -> small, emulsified fat drops -> products of degradation absorbed by micelles -> free f.a. + monoglyceride diffuse into cell
48
What breaks down fats into monoglycerides and f.a.
Pancreatic lipase, colipase
49
What happens to the f.a. and monoglycerides that are produced by fat breakdown
Stored in micelles, move out of micelles and enter cell by diffusion
50
Absorbed fats + cholesterol + proteins inside the intestinal cell form what? Where does this go?
Form chylomicrons They are released into the lymphatic system
51
Nucleotide vs nucleoside
Nucleotide = Sugar + base + phosphate group Nucleoside = sugar + base
52
Purines? Pyrimidines?
Purines = adenine, guanine Pyrimidines = thymine, cytosine, uracil
53
RNA has what instead of what?
Uracil instead of thymine
54
Nucleosomes are formed when what happens? Eventually leading to the formation of...
When DNA wraps around a protein (histone) Eventually forming chromosomes
55
Steps in nucleic acid digestion/absorption
1. Denatured by gastric acid 2. Broken down to nucleotides by pancreatic nucleases 3. Phosphatase on brush border cleave P ion 4. Nucleosidase catalyzes breaking of covalent bond btw nitrogenous base and pentose sugar Slide 38**
56
Major enzymes in nucleic acid digestion/absorption
Pancreatic nucleases Phosphatase Nucleosidase
57
Products of nucleotide breakdown are absorbed in the... Transported to...
Duodenum and jejunum Liver and other tissues
58
what kind of transport are electrical and chemical driving forces
Passive transport
59
How does primary active transport work
Na+ binds transporter, stimulates phosphorylation by ATP = conformational change, K+ then binds causing release of P and back to original conformation
60
bile salts are required for __________ digestion
Lipid

An Sc 311 Midterm 1 (8 decks)

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