Nutrition and Digestion

Question 1

What does our body need to best function?

Answer 1

See Pyramid

Question 2

What are essential nutrients?
How do we obtain them?

Answer 2

Essential Nutrients are those that we cannot synthesize or make ourselves. They must be obtained through our diet

Question 3

What are Desaturases?

Answer 3

enzyme that removes two H atoms from a fatty acid, creating double bond

Question 4

What are the three types of fatty acids?

Answer 4

Saturated
Monounsaturated
Polyunsaturated

Question 5

How do we obtain polyunsaturated fatty acids?

Answer 5

Polyunsaturated fatty acids cannot be made by us, obtained through food
-Omega 6 (linoleic acid) and omega 3 (alpha-linolenic acid) desaturase missing in human
specificity from end t0 tail to other essential fatty acids synthesized from a-linoleic acid

Question 6

What are the 4 steps involved in Digestion?
What takes place in each step?

Answer 6

Ingestion - bringing food into the digestive tract (GI)

Digestion - Mechanical or Chemical breakdown of food into smaller particles. Facilitated by enzymes

Absorption - Uptake of nutrients (certain ions and molecules) across epithelium cells that line the GI Tract

Elimination - Disposal of wastes.

Question 7

What are some examples of nutrients? How do we obtain them?

Answer 7

carbs, proteins and fats
we eat food that contain them

Question 8

What are the classes of Essential Nutrients?

Answer 8

1. Essential Amino Acids (9) - Amino acids that we cannot produce on our own
2. Essential Fatty Acids - Humans can synthesize all but two essential fatty acids
3. Vitamins - Organic or carbon-containing compounds vital for health (taken in smaller amounts)
4. Minerals - INorganic substances used as structural components of enzyme cofactor components
   (Na+, K+, and Cl- are the major ions)
   (Calcium and Phosphorus are needed in larger amounts)
   (Iron and copper needed in smaller amounts)

Question 9

What are the two essential fatty acids?

Answer 9

linoleic acid and
alpha-linolenic acid

Question 10

How do humans make cholesterol?

Answer 10

We can make ISOPRENES, which can join together to form the Carbon-30 Molecule SQUALENE.
By closing some binds in squalene, we end up with cholesterol.

Question 11

Why do we need Cholesterol?

Answer 11

It is the precursor for many steroid hormones.
It is also a precursor for Vitamin D, which is involved in the reabsorption of Calcium, which is essential for our bones

Question 12

Why do we need vitamin D?
How do we obtain it? (4)

Answer 12

Vitamin D is needed in our bodies to absorb calcium in our SI. People with Vitamin D efficiency, do not have enough calcium for proper bone growth and maintenance. Can lead to rickets or osteomalacia.

1. When light strikes a molecule of 7-dehydrocholesterol, it changes its shape and becomes a vitamin D called D3
2. Enzymes can then complete the process of making it an active vitamin
3. People exposed to enough sunlight can perform all the necessary steps to make their own vitamin D, otherwise it must be obtained through diet.
   (fish like Tuna, Salmon and Cod)
4. In Canada we are not always exposed to sunlight year-round so we have added Vitamin D to our milk (Fortified milk)

Question 13

There are two types of Digestive Tracts. What are they? How do they work?

Answer 13

1. Incomplete Digestive Tract: have a single opening, the mouth, where the organism both ingests food and eliminates waste. Mouth opens to the gastrovascular cavity where food is digested.
2. Complete Digestive Tract: Have two openings. The mouth and the anus

Question 14

In what order does food go through the digestive tract?
What is the function of each part?

Answer 14

1. Mouth - Food goes in, grinded by teeth, bolus by tongue, saliva from salivary glands
2. Esophagus - transports food from mouth to stomach
3. Stomach - Site of mechanical and chemical processing (digests proteins)
4. Small Intestine - Site of chemical processing and absorption (digests carbs, proteins, fats. absorbs W + N)
5. Large Intestine - Absorbs Water and forms feces (contains bacteria)
6. Anus - Eliminates Feces

Question 15

What are the Four accessory organs?
What are their functions?

Answer 15

1. Salivary Glands - secrete enzymes that digest carbs; secrete saliva to lubricate food
2. Liver - Secretes, molecules that aid in fat digestion; bile
3. Gallbladder - stores secretions from liver (bile). empties its contents into SI
4. Pancreas - secretes enzymes and other materials into the SI

Question 16

What enzymes are involved with the breakdown of Carbohydrates? Where are they made? Where are they active? (2)

Answer 16

1. Salivary Amylase, Salivary Glands, Mouth
2. Pancreatic Amylase, Pancreas, Small Intestine

Question 17

What enzymes are involved with the breakdown of Proteins? Where are they made? Where are they active?
(5)

Answer 17

1. Pepsin, Stomach, Stomach
2. Trypsin, Chymotrypsin, Elastase, Carboxypeptidase
   made in Pancreas, active in Small Intestine

Question 18

What enzymes are involved with the breakdown of Lipids? Where are they made? Where are they active?
(3)

Answer 18

1. Lingual Lipase, Salivary Glands, Mouth
2. Pancreatic Lipase, Pancreas, Small Intestine
3. Bile Salts, Pancreas, Small Intestine

Question 19

What do we need to eat with pasta in order to activate salivary amylase?

Answer 19

Salt (NaCl) because Chloride is needed to activate salivary amylase.

Question 20

Why aren’t Fatty Acids absorbed directly into the bloodstream?

Answer 20

Fatty acids are hydrophobic molecules, so they are not soluble in water
If we would release them into the bloodstream
we would need to bind them to some proteins to efficiently transport them

so instead
within the epithelial cells, triglycerides are re-synthesized and packaged with other proteins to
a lipoprotein called chylomicrons
these are expelled from the epithelial cells into the bloodstream via a process of exocytosis

Question 21

How does food get from the mouth to the stomach?
What process is used in the esophagus?

Answer 21

Peristalsis - See Photo

Question 22

What is the pH of the stomach?
What regulates what goes in and out?

Answer 22

The Stomach is very acidic: pH of 2
10 mM HCl

Sphincters seal off the stomach from the esophagus and from the small intestine

Question 23

What Cells Line The Stomach?
What are their functions?
(3)

Answer 23

Mucous Cells - Secret Mucous which protects the stomach lining from the acid (HCl)

Chief Cells - Secrete Pepsinogen which is a precursor of pepsin

Parietal Cells - Secrete hydrochloric acid (HCl)

Question 24

Why does the enzyme pepsin start off in its inactive form called Pepsiongen?

Answer 24

Pepsin is a protease which digests proteins
If cells which make pepsin accumulate large amounts of it, the enzyme would begin to break the cell’s own proteins and the cells would die

So the cells which make pepsin secrete the pre-inactive precursor pepsinogen

Question 25

Which of the following molecules are absorbed from the lumen of the small intestine into epithelial cells through simple diffusion?
Correct Answer

Answer 25

Lipids

Carbs and Proteins are absorbed through facilitated diffusion and cotransport.

Question 26

Starch digestion begins where?

Answer 26

In the mouth by salivary amylase

Question 27

Bile, which is synthesized in the liver and stored in the gallbladder, is important in lipid digestion. What feature/function of bile makes it an effective emulsifying agent?

Answer 27

Bile is an amphiphilic molecule, having both hydrophobic and hydrophilic regions

Question 28

Glucose is transported from the intestinal lumen into epithelial cells through [ Select ] and from the intestinal epithelium into circulation by [ Select ].

Answer 28

cotransport with sodium

facilitated diffusion

Question 29

The ______________ performs mechanical and chemical processing of food (digests proteins) and the _________ ________________ processes and absorbs proteins, fats, carbs and absorbs nutrients and water

Answer 29

Stomach

Small Intestine

Question 30

Humans can only synthesize 12/20 amino acids, but eating meat provides a complete diet with all necessary amino acids
True or False?

Answer 30

False

Humans can synthesis 11/20 and need to obtain 9 through diet

Question 31

Mucous cells in the stomach secrete HCl for breaking down food and killing ingested bacteria
True or False

Answer 31

False

Mucous cells secrete mucous
Parietal cells secrete HCl

Question 32

Why does digestion occur in specialized compartments?

Answer 32

To avoid self-digestion

Question 33

Name 3 adaptations for nutrient absorption in the mammalian small intestine

Answer 33

Highly folded villi (made of epithelial cells) with high surface area for minimum absorption (including microvilli)

High concentration of membrane-bound proteins for facilitated diffusion and active transport

Extensive blood supply and lymph vessels for moving nutrients into the circulatory system

Question 34

How do Bile Salts aid in the digestion of fats?

Answer 34

Bile salts act as emulsifying agents.
They break down fat molecules into smaller pieces so they are easier to digest by Lipases.
They are amphiphilic.

Question 35

Which of the following molecules are absorbed from the lumen of the small intestine into epithelial cells through simple diffusion?

Answer 35

lipids

Question 36

Starch digestion begins where?

Answer 36

in the mouth

Question 37

Bile, which is synthesized in the liver and stored in the gallbladder, is important in lipid digestion. What feature/function of bile makes it an effective emulsifying agent?

Answer 37

Bile is an amphiphilic molecule, having both hydrophobic and hydrophilic regions.

Question 38

Glucose is transported from the intestinal lumen into epithelial cells through___________and from the intestinal epithelium into circulation by___________

Answer 38

cotransport with sodium

facilitated diffusion