Nutrition and Digestion Flashcards
What does our body need to best function?
See Pyramid
What are essential nutrients?
How do we obtain them?
Essential Nutrients are those that we cannot synthesize or make ourselves. They must be obtained through our diet
What are Desaturases?
enzyme that removes two H atoms from a fatty acid, creating double bond
What are the three types of fatty acids?
Saturated
Monounsaturated
Polyunsaturated
How do we obtain polyunsaturated fatty acids?
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
What are the 4 steps involved in Digestion?
What takes place in each step?
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.
What are some examples of nutrients? How do we obtain them?
carbs, proteins and fats
we eat food that contain them
What are the classes of Essential Nutrients?
- Essential Amino Acids (9) - Amino acids that we cannot produce on our own
- Essential Fatty Acids - Humans can synthesize all but two essential fatty acids
- Vitamins - Organic or carbon-containing compounds vital for health (taken in smaller amounts)
- 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)
What are the two essential fatty acids?
linoleic acid and
alpha-linolenic acid
How do humans make cholesterol?
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.
Why do we need Cholesterol?
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
Why do we need vitamin D?
How do we obtain it? (4)
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.
- When light strikes a molecule of 7-dehydrocholesterol, it changes its shape and becomes a vitamin D called D3
- Enzymes can then complete the process of making it an active vitamin
- 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) - In Canada we are not always exposed to sunlight year-round so we have added Vitamin D to our milk (Fortified milk)
There are two types of Digestive Tracts. What are they? How do they work?
- 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.
- Complete Digestive Tract: Have two openings. The mouth and the anus
In what order does food go through the digestive tract?
What is the function of each part?
- Mouth - Food goes in, grinded by teeth, bolus by tongue, saliva from salivary glands
- Esophagus - transports food from mouth to stomach
- Stomach - Site of mechanical and chemical processing (digests proteins)
- Small Intestine - Site of chemical processing and absorption (digests carbs, proteins, fats. absorbs W + N)
- Large Intestine - Absorbs Water and forms feces (contains bacteria)
- Anus - Eliminates Feces
What are the Four accessory organs?
What are their functions?
- Salivary Glands - secrete enzymes that digest carbs; secrete saliva to lubricate food
- Liver - Secretes, molecules that aid in fat digestion; bile
- Gallbladder - stores secretions from liver (bile). empties its contents into SI
- Pancreas - secretes enzymes and other materials into the SI
What enzymes are involved with the breakdown of Carbohydrates? Where are they made? Where are they active? (2)
- Salivary Amylase, Salivary Glands, Mouth
- Pancreatic Amylase, Pancreas, Small Intestine
What enzymes are involved with the breakdown of Proteins? Where are they made? Where are they active?
(5)
- Pepsin, Stomach, Stomach
- Trypsin, Chymotrypsin, Elastase, Carboxypeptidase
made in Pancreas, active in Small Intestine
What enzymes are involved with the breakdown of Lipids? Where are they made? Where are they active?
(3)
- Lingual Lipase, Salivary Glands, Mouth
- Pancreatic Lipase, Pancreas, Small Intestine
- Bile Salts, Pancreas, Small Intestine
What do we need to eat with pasta in order to activate salivary amylase?
Salt (NaCl) because Chloride is needed to activate salivary amylase.
Why aren’t Fatty Acids absorbed directly into the bloodstream?
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
How does food get from the mouth to the stomach?
What process is used in the esophagus?
Peristalsis - See Photo
What is the pH of the stomach?
What regulates what goes in and out?
The Stomach is very acidic: pH of 2
10 mM HCl
Sphincters seal off the stomach from the esophagus and from the small intestine
What Cells Line The Stomach?
What are their functions?
(3)
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)
Why does the enzyme pepsin start off in its inactive form called Pepsiongen?
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
Which of the following molecules are absorbed from the lumen of the small intestine into epithelial cells through simple diffusion?
Correct Answer
Lipids
Carbs and Proteins are absorbed through facilitated diffusion and cotransport.
Starch digestion begins where?
In the mouth by salivary amylase
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?
Bile is an amphiphilic molecule, having both hydrophobic and hydrophilic regions
Glucose is transported from the intestinal lumen into epithelial cells through [ Select ] and from the intestinal epithelium into circulation by [ Select ].
cotransport with sodium
facilitated diffusion
The ______________ performs mechanical and chemical processing of food (digests proteins) and the _________ ________________ processes and absorbs proteins, fats, carbs and absorbs nutrients and water
Stomach
Small Intestine
Humans can only synthesize 12/20 amino acids, but eating meat provides a complete diet with all necessary amino acids
True or False?
False
Humans can synthesis 11/20 and need to obtain 9 through diet
Mucous cells in the stomach secrete HCl for breaking down food and killing ingested bacteria
True or False
False
Mucous cells secrete mucous
Parietal cells secrete HCl
Why does digestion occur in specialized compartments?
To avoid self-digestion
Name 3 adaptations for nutrient absorption in the mammalian small intestine
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
How do Bile Salts aid in the digestion of fats?
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.
Which of the following molecules are absorbed from the lumen of the small intestine into epithelial cells through simple diffusion?
lipids
Starch digestion begins where?
in the mouth
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?
Bile is an amphiphilic molecule, having both hydrophobic and hydrophilic regions.
Glucose is transported from the intestinal lumen into epithelial cells through___________and from the intestinal epithelium into circulation by___________
cotransport with sodium
facilitated diffusion
