Chapter 3: Digestion, Absorption and Metabolism Flashcards
1
Q
define: metabolism
A
- sum of all chemical reactions in the body
- Metabolism of nutrients: cellular respiration; captures all the energy in sugars, triglycerides and amino acids into ATP
2
Q
digestion
- describe 2 types
A
- Process that separates nutrients in food and breaks larger molecules into smaller ones
- Mechanical digestion: teeth chewing, stomach churning
- Chemical digestion: uses enzymes to alter the chemical structure of nutrients and reduces them to their building blocks
3
Q
enzymes
A
Speed up reactions and provides location for chemical reactions to occur
4
Q
hydrolysis
A
The input of water breaks down the molecule
5
Q
condensation
A
Combines molecules by liberating a water molecule
6
Q
hormones
A
Chemical messengers required for many physiological processes
7
Q
sphincters
A
Circular muscles that contract to close openings and relaxes to open them
8
Q
What are some things that impact digestive transit times. What is the average digestive time?
A
- Age, activity levels, diet, gender, medication, infection, emotional state
- ~2 days for food to pass through the entire tract
9
Q
List all the layers of the digestive tract wall (5)
A
- lumen
- mucosa
- submucosa
- muscularis
- serosa
10
Q
describe the following layer of the digestive tract wall: lumen and mucosa
A
- lumen: inner cavity of the small intestine tube
- mucosa: layer that secretes mucus, keeps digestive tract moist, and protects it from infection, plays a role in absorption
11
Q
describe the following layer of the digestive tract wall: submucosa
A
- Submucosa: connects mucosa to the more superficial muscularis layer, blood vessels, lymphatic vessels, and nerves are found here
12
Q
describe the following layer of the digestive tract wall: muscularis
A
- Muscularis: composed of smooth muscles that are autonomic; pushes food forward and helps it mix with digestive secretions
13
Q
describe the following layer of the digestive tract wall: serosa
A
- Serosa: outermost layer that consists of a layer of connective tissue; helps to reduce friction with organs or helps anchor tract in place
14
Q
explain the enteric nervous system
A
- Various nerves and nerve plexuses that create a system
- 500 million neurons arranged in groupings called a nerve plexeus
- all in the lining of the gastrointestinal system
15
Q
mouth
- chemical digestion
- manual digestion
- define bolus
A
- chem. digestion: saliva - from 3 main glands (parotid, submandibular, sublingual)
- 2 enzymes: salivary amylase becomes amylose (starch); lingual lipase (lipids)
- manual digestion: tongue and teeth
- bolus: uniform cohesive structure created through chewing and saliva
16
Q
pharynx
- role
- define: epiglottis
A
- Passageway for both food and air
- Epiglottis; flap of tissue that covers trachea opening when we swallow so food goes down the esophagus
17
Q
esophagus
- role
A
- Passageway for food from pharynx to stomach; Food enters stomach with the lower esophageal sphincter opens
18
Q
how does food move through the digestive tract?
A
- Peristalsis: smooth muscle contractions to move bolus further through the digestion tract
- Gravity helps too
- NOT segmentation
19
Q
stomach
- how long does food remain in the stomach
- what is chemically digested here
- mechanical digestion
- types of muscle (3)
- define chyme
- pyloric sphincter
- crypts
A
- 4-5 hours before it empties
- chemical digestion of protein begins; Partial absorption of water and amino acids occur here
- mechanical digestion: diagonal smooth muscle allows for churning to facilitate chemical digestion
- types of muscle: longitudinal, circular, diagonal
- chyme: bolus turns into semiliquid substance
- pyloric sphincter: opens to let chyme enter the small intestine
- crypts: invaginations in the stomach that increase surface area, allowing more stomach cells to be involved in digestion
20
Q
gastric juices (4)
A
- Mucus: lubrication and a medium for chemical reactions to occur in; lines the stomach’s inner wall protecting it from stomach acid and juices
- Hydrochloric acid (HCl): unravels proteins, exposing sites where enzymes can further break them down; plays a role in activating pepsin
- Pepsinogen: proenzyme; HCl converts pepsinogen into pepsin; Pepsin: breaks down amino acid chains into smaller chains
- Gastric lipase: breaks down lipids
21
Q
small intestine
- describe the structure
- villi
- microvilli
- enterocytes
- capillary beds
- lacteal
- peristalsis and segmentation
A
structure
- 6m in length
- duodenum, jejunum, ileum
- large folds that face the lumen (increase SA and slow the passage of food along its path)
- villi
- microvilli: tiny projections in the enterocytes; make up the brush border; where digestive enzymes are stored (lactase, sucrase, maltase)
- enterocytes: small intestine cells that line the peaks and valleys of the villus surface
- Capillary beds exist within the submucosa of the villi; all nutrients are absorbed here except for large lipids and fat soluble vitamins
- Lacteal: lymphatic vessels that absorb large lipids and fat soluble vitamins; enter the blood by draining through the thoracic duct
- segmentation: movement that breaks material into smaller components while mixing it with digestive juices
22
Q
absorption in the small intestine
- osmosis
- simple diffusion
- facilitated diffusion
- active transportation
A
- Osmosis: movement of water in response to concentration differences
- Simple diffusion: fatty acids and fat soluble vitamins; absorbed along the spaces between phospholipids in the enterocyte cell membrane; do not require a transporter
- Facilitated diffusion: a protein transporter acts as tunnels to allow material to pass from an area of high concentration to low concentration; Certain sugars require this (fructose)
- Active transportation: glucose and amino acids move from an area of low concentration to high concentration; requires energy and a protein transporter to move against the concentration grain
23
Q
List the accessory organs
A
- pancreas
- gallbladder
- liver
24
Q
pancreas
- 2 functions
- list the enzymes (4)
A
- Regulates blood glucose using hormones (endocrine function)
- Insulin: when glucose rises tells body to store sugar
- Glucagon: tells liver to release stored sugar when glucose drops
- Releases pancreatic juices (exocrine function) that contain digestive enzymes into the small intestine
- Protease: protein digestion
- Lipase: lipid digestion
- Amylase: carbohydrate digestion
- Bicarbonate: buffer that reduces acidity of chyme, increasing the effectiveness of digestion in small intestine
25
Liver and gallbladder
- emulsification
- micelle
- The liver produces bile which promotes lipid digestion
- Gallbladder stores bile; secretes it when needed
- Emulsification: suspension of lipids to be easily transported within the small intestine’s lumen
- Micelle: grouped lipids within a ring of bile salts
26
summarize the chemical digestion that occurs in the small intestine for
- carbs
- proteins
- lipids
- see google doc
27
large intestine
- list the parts
- mechanical digestion
- rectum
- 1.5m in length but with a larger diameter than the small i
- ileum from small intestine
- -> cecum: first part of the large intetine
- appendix: hangs from the cecum; plays a role in microbiome composition
- cecum --> ascending, transverse, descending, and sigmoid colons (collectively known as the colon)
- mechanical digestion: peristalsis and segmentation
- rectum: where feces is held until it is ready to be excreted
28
microbiome
- define
- microbiota
- explain role
- genetic material of the non human organisms found in our body
- microbiota: all the non-human organisms found in our body
- Play a role in vitamin synthesis, energy harvesting, health/disease, appetite
- Fermentation of unused carbohydrates and production of short-chain fatty acids (energy harvesting)
- Promote healthy population of intesntinal cells
- Prevent allergies
- Prevent IBD
- Suppress growth of harmful bacteria
29
probiotics
- define
- found in?
- impact
- Cultures of living organisms, typically bacteria
- Found in: some supplements, yogurt, kombucha
- Need to be taken for a month+ for effects to be evident: Antibiotic associated diarrhea, traveller’s diarrhea, acute respiratory infections, infant colic, type of colitis; Ongoing research on effect of IBS, obesity, cardiovascular disease, cancer
30
prebiotics
- Act as food for the microbiome and support its function
- Medium length carbs that our gut microbes ferment
- Sources: asparagus, beet sugar, onion, wheat, honey, banana, barley, tomato, rye, soymilk, peas, beans, and seaweed
31
ulcers
- what
- how
- 2 types
- Open sores that can occur along the lining of a body structure
- Caused by a weakening of mucosal layer of the digestive tract wall
- Canker sores: ulcer in the mouth; caused by biting the cheek, eating a lot of acidic food, burning the inside of the mouth
- Peptic ulcers: occur in the esophagus, stomach, or small intestine; related to H. pylori bacteria infection
32
Gastroesophageal reflux disease aka acid reflux
- what
- treatments
- what can it lead to
- Weakening of the lower esophageal sphincter that allows stomach acid to spill upward into the esophagus
- Weight loss improves acid levels and symptoms of acid reflux
- Elevating the head of the bed reduces reflux
- Decreasing tobacco, alcohol, chocolate, large meals, spicy foods, high fat meals reduce symptoms
- Can lead to the narrowing of the esophagus and promote esophageal ulcers
33
Irritable bowel syndrome (IBS)
- Illness that impacts the large intestine, symptoms include abdominal pain, bloating, cramping, diarrhea, constipation, flatulence
- Cause: muscular and nervous system impairment, inflammation, infection, gender (being a woman), family history can all increase risk
- Changes in the microbiota may promote and aggravate symptoms
34
Diverticulitis
- define
- diverticula
- bleeding diverticula
- what can increase your risk to get diverticulitis
- diverticula: weakened walls of the large intestine form outpouching
- Inflamed diverticula= diverticulitis
- Bleeding diverticula= diverticulosis
- Age, obesity, smoking, physical inactivity, low fibre high animal fat diet can increase risk
35
gallstones
- define
- how can it occur
- risk factors
- Hardened bile deposits that accumulate in the gallbladder or bile duct; can cause pain when fat is consumed and the gallbladder contracts to release bile
- Occur due to an overabundance of cholesterol
- Risk factors: gender (women), estrogen-containing contraceptives, obesity, rapid weight loss, physical inactivity
36
Colorectal cancer
- Physical activity and obesity increase risk
- Diets high in red and processed meats increase risk
- Diets high in vegetables, fruits, and fibre decrease risk
37
constipation
- Difficult to pass or less frequent bowel movements
- Increases risk for hemorrhoids
- Stools are hard and dry, can be painful to excrete
- Risk factors: age, female sex, genetics, physical inactivity, IBS, use of certain medications
- Diets low in fruits, vegetables and water increase risk
38
diarrhea
- When matter passes too quickly through large intestine
- Stools are loose and have a liquid like consistency
- Typically due to bacterial and viral infections; body tries to pass bacteria or viruses out of body quickly
39
Food allergies
Immune system reacts to non harmful antigens called allergens
- First exposure: begins the process with the production of antibodies
- Second: allergens bind to antibodies and cause release of histamine
- Symptoms: redness, swelling, hives, tingling on tongue/lips, difficulty breathing, decreased blood pressure
- Extreme cases lead to anaphylaxis
40
celiac disease
- Inherited disease
- Gluten protein triggers an immune response which damages villi
- Symptoms and complications: abdominal pain, diarrhea, fatigue, malnutrition, weight loss, anemia, osteoporosis, intestinal cancer
- Treatment: avoid gluten all together
41
liver
- Nutrients absorbed in the small intestine enter hepatic portal vein that lead to the liver
- Acts as a gatekeeper for nutrients: use them, store them, send them to the rest of the body, detoxify them
- Can store glucose → glycogen
- Whatever isn’t used here is sent to the rest of the body through the bloodstream
42
lymphatic system
- what
- 3 functions
- Network of lymph vessels that contain infection fighting cells
3 functions
- Clears tissues of excess fluid
Immune response is launched when an antigen is detected in the lymph
- Large lipids and water insoluble materials are absorbed into the lymph
- Lymph then drains into CVS cvs via the thoracic duct
43
anabolism
- Smaller molecules coming together to make large ones
- Require added energy
- Example: protein synthesis
44
catabolism
- Large molecules being broken down into smaller ones
| - Process gives off energy
45
cellular respiration
- metabolic pathway
- location it occurs
- formula
- metabolic pathway
- catabolic process that leads to the capture of released energy within ATP
- occurs in the mitochondria
- see doc
- Metabolic pathway: steps that create ATP
46
glucose metabolism
- see google doc
47
lipid metabolism
- see google doc
48
ketogenesis
- Occurs when diet is high in fat and very low in carbohydrates
- Citric acid cycle requires carbohydrates
- On a low carb diet, fatty acids cannot enter citric acid cycle, instead form ketones
49
amino acid metabolism
- see google doc
50
Non energy uses of sugars lipids and amino acids
Most of the excess is stored as lipid in our fat tissue
51
Synthesizing new molecules
- Energy yielding nutrients that are not used for energy are used to form other molecules (requires ATP)
Glucose:
- Forms glycogen
- Small energy reserve in the muscle/liver
- Forms fatty acids, stored in fat tissue
Fatty acids:
- Stored in fat tissue
- May also be used to help form cell membranes, regulatory molecules
Amino acids:
- Used to synthesize body proteins
- May also be converted into fatty acids and stored in fat tissue
