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Biochemistry- 1 > Midterm 2: Digestion > Flashcards

Midterm 2: Digestion Flashcards

(89 cards)

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1
Q

Digestion is a form of ___________

A

catabolism

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2
Q

A hydrolytic process

A

breaks down large food molecules (carbohydrates, proteins, lipids) into smaller ones (monosaccharides, amino acids, fatty acids)

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3
Q

Path of the digestive tract:

A

mouth–> esophagus–> stomach–> small intestine–> large intestine (colon)–> rectum

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4
Q

What other organs are involved in digestion?

A

pancreas, gallbladder, liver

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5
Q

True/False: Most of our supply of carbohydrates (i.e., glucose) is obtained through our diet.

A

True

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6
Q

Can our body synthesize glucose? If so, how?

A

gluconeogenesis; amino acids, pyruvate, and lactate can be used to synthesize glucose

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7
Q

What are the building blocks of carbohydrates?

A

Monosaccharides (simple carbs)

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8
Q

What type of bonds join monosaccharides together?

A

glycosidic bonds (covalent bonds) form disaccharides and polysaccharides (complex carbs)

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9
Q

Monosaccharides include:

A

glucose, galactose, and fructose

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10
Q

Disaccharides include:

A

lactose, maltose, sucrose

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11
Q

Polysaccharides include:

A

glycogen, starch, cellulose, and GAGs

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12
Q

Where does carbohydrate digestion begin?

A

mouth

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13
Q

What enzyme is contained in saliva? What does it break down? How?

A

salivary amylase (Enzyme) that hydrolyzes 5% of starch in the mouth

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14
Q

Amylase breaks down starch into what two components?

A

maltose and a polysaccharide

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15
Q

Salivary amylase is inactivated by what?

A

the acidity of the stomach

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16
Q

(Minimal/maximum) carbohydrate digestion occurs in the stomach?

A

Minimal

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17
Q

After digestion occurs in the stomach, carbohydrate digestion continues where?

A

in the lumen of the small intestine

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18
Q

What two components are secreted from the pancreas into the small intestine for carb digestion?

A

Bicarbonate (HCO3-) and amylase

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19
Q

What is bicarbonate?

A

It is a buffer that neutralizes acidic stomach contents in the small intestine (secreted by the pancreas)

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20
Q

Pancreatic amylase has what function?

A

It hydrolyzes disaccharides and complex carbs into monosaccharides in the small intestine (secreted by the pancreas)

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21
Q

What enzymes are secreted by the small intestine, aiding in carb digestion?

A

Disaccharidases (lactase, sucrase, maltase) are secreted from the small intestines

Hydrolyze disaccharides into monosaccharides

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22
Q

At the end of carbohydrate digestion in the small intestine, what have the carbs become?

A

~80% of monosaccharides are glucose

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23
Q

After carb digestion occurs in the small intestine, the monosaccharides go where?

A

they are absorbed into enterocytes (small intestine cells) of the intestinal mucosa to reach blood capillaries

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24
Q

How do the monosaccharides enter enterocytes?

A

Substances cannot pass between epithelial cells because these cells are bound by tight junctions, so they enter enterocytes by co-transport and facilitated diffusion

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25
What uses movement of 1 molecule through the cell membrane from higher to lower concentration to power the movement of another from lower to higher concentration?
Co-transport
26
What uses the movement of substances from an area of higher to an area of lower concentration using a carrier protein in the cell membrane?
facilitated diffusion
27
After entering blood capillaries, monosaccharides are transported to where? Pathway?
the liver via the hepatic portal vein
28
What 3 things occur here (in the liver with carb digestion)?
Galactose is primarily converted to glucose Fructose is primarily converted to glucose and lactate Glucose is stored as glycogen or transported to peripheral tissues
29
How is glucose stored in the liver?
glucose is stored as glycogen or transported to peripheral tissues
30
Glycogen is used to maintain blood glucose levels at _________________ mg/dL.
70-100 mg/dL
31
In the peripheral tissues of the liver, glucose is used for
energy production or stored as glycogen
32
When liver cells and peripheral tissue are saturated with glycogen, what happens?
excess glucose is converted into fatty acids
33
Where are undigested carbohydrates (fiber) eliminated?
by the colon
34
What cannot be digested by humans?
Dietary fiber is from plant cell walls (i.e., cellulose) and is resistant to human digestive enzymes; Unable to be digested and absorbed
35
How are undigested carbs classified?
insoluble or soluble
36
Insoluble fiber passes through the digestive tract relatively untouched, why?
Speeds up digestion; Adds bulk to stool so it can pass easier
37
Soluble fiber forms a gel when mixed with water in the digestive tract, what does this do?
Slows down digestion and absorption of glucose, thereby preventing blood glucose spikes Fermented by colon bacteria into short-chain fatty acids and gases
38
Why do some amino acids have to be obtained from our diet?
Because our body cannot synthesize them
39
Essential amino acids include the following:
histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine PLT HI LMTV (lets move to Venice)
40
What are the building blocks of proteins?
Amino acids
41
• Amino acids are joined together by what type of bond? Forming?
in a peptide bond to form peptides and polypeptides (proteins)
42
Peptides and polypeptides take on a 3-D shape through various bonds:
``` Hydrogen bonds Ionic bonds van der Waals interactions Hydrophobic interactions Disulfide bridges ```
43
Where does digestion begin for proteins?
Digestion begins in the stomach
44
What denatures proteins in the stomach?
Stomach acid
45
What hydrolyzes peptide bonds?
Pepsin
46
After leaving the stomach, where does protein digestion continue?
in the lumen of the small intestine
47
Bicarbonate (HCO3-), trypsin, chymotrypsin, and carboxypeptidase are secreted from where? To help digest what?
the pancreas into the small intestine; protein
48
What is the role of bicarbonate in protein digestion?
it is a buffer that neutralizes acidic stomach contents
49
What is the role of Trypsin, chymotrypsin, carboxypeptidase in protein digestion?
hydrolyze peptide bond
50
What are secreted from the small intestine in protein digestion? What is their role?
Peptidases; Hydrolyze peptides into amino acids
51
Amino acids are then absorbed into enterocytes of the intestinal mucosa to reach blood capillaries, Is this the same thing that occurs with carb digestion?
YES!
52
Substances cannot pass between epithelial cells because of??
tight junctions
53
How do amino acids enter enterocytes?
by co-transport
54
Once in the blood capillaries, monosaccharides are transported to the liver via the _____________ Used for protein synthesis, converted into _________, converted into __________, or transported to peripheral tissues for protein synthesis
hepatic portal vein; glucose; fatty acids
55
Small amount of protein is eliminated by _______.
the colon
56
Are lipids synthesized or obtained through our diet?
BOTH: they can either be synthesized or obtained through our diet
57
How are lipids classified?
due to their hydrophobicity
58
What does hydrophobicity mean?
Do not dissolve in water; Cluster together away from water (form fat globules)
59
Lipids are which three?
triacylglycerol (triglyceride, TAG), cholesterol, phospholipids
60
TAG is composed of __________.
3 fatty acids + glycerol (a sugar) and comprises 90% of dietary lipids
61
Phospholipids are composed of ___________.
2 fatty acids + Glycerol + Phosphate + 1 of 4 polar groups
62
Cholesterol is composed of ___________.
a steroid core of 4 fused rings + side chains
63
Does any digestion for lipids occur in the mouth or stomach?
Limited digestion occurs in the mouth and stomach Lingual lipases and gastric lipases hydrolyze fatty acids with ≤12 carbons
64
Fat globules leave the stomach and enter the ___________.
small intestine
65
__________ are secreted from the gallbladder (synthesized in the liver from cholesterol) into the small intestine. (lipid digestion)
Bile salts
66
Amphipathic molecules that emulsify fat globules (surround pieces of fat globules and break them into smaller droplets)
Bile Salts
67
What is the function of bile salts?
Increases the surface area of lipids and makes them more accessible to digestive enzymes
68
_____________ are secreted from the pancreas into the small intestine (lipid digestion)
Bicarbonate (HCO3-) and lipases
69
___________ is a buffer that neutralizes acidic stomach contents
Bicarbonate
70
Pancreatic lipase hydrolyzes triglycerides into ___________.
monoglyceride and (2) free fatty acids
71
Bile salts continue to surround fat droplets forming ____________ ?
micelles
72
What are micelles?
They are a core of lipids (hydrophobic regions inside and hydrophilic regions outside) surrounded by bile salts
73
Transport lipids through the intestinal lumen to the epithelial lining
Bile salts that surround fat droplets forming micelles
74
Once micelles reach the epithelial lining of the small intestine, where are they are then absorbed?
into enterocytes
75
How do Micelles enter enterocytes?
by simple diffusion
76
movement of substances from an area of higher concentration to an area of lower concentration,
Simple diffusion
77
Where are Bile salts are absorbed?
in the more distal small intestine and transported back to the liver through the portal vein
78
Once inside the enterocyte, _______ is reformed and packaged into ____________, along with other lipids
TAG; chylomicrons
79
__________ are a core of lipids (hydrophobic regions inside and hydrophilic regions outside) surrounded by lipoproteins
Chylomicrons
80
Transport lipids through the bloodstream from the __________ to the ____________.
intestine to the liver
81
Chylomicrons enter____________, bypassing blood capillaries. Why?
lymph capillaries; Chylomicrons are too LARGE to enter blood capillaries directly
82
Lipid process through blood?
Lymph → Veins → Arteries → Blood capillaries
83
Within blood capillaries, _________ are digested. __________ hydrolyzes triglycerides into fatty acids and glycerol. Glycerol returns to the __________ to be reused. Fatty acids enter cells to be used as an energy source or stored as __________ (if entering adipose tissue). Chylomicron remnants are transported to the liver.
chylomicrons Lipoprotein lipase liver TAG
84
In the liver, chylomicron remnants are recycled and TAG is reformed TAG, along with other lipids (mainly ___________), is packaged into _______ for transport through the bloodstream to tissues The structure of ________is similar to chylomicrons and allows transport of lipids between tissues in an ________ environment
cholesterol VLDL VLDL aqueous
85
Within blood capillaries, what is digested? (lipid)
VLDL is digested
86
Loss of triglycerides and some apoproteins | converts _________ to __________
VLDL into LDL (low density lipoprotein)
87
LDL is an important carrier of __________ to tissues
cholesterol
88
Cholesterol can be deposited in the cell membrane, used to make what?
Vitamin D, bile acid or steroid hormones
89
_______________ carries excess cholesterol away from tissues to the liver
HDL (high density lipoprotein)

Biochemistry- 1 (6 decks)

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