Mod 3 Flashcards
(60 cards)
1
Q
what is digestion
A
digestion separates the nutrients in food and breaks larger molecules into smaller ones so they can be absorbed
2
Q
what does polysaccharides break down into
A
sugars
3
Q
what does triglycerides break down into
A
fatty acids
4
Q
what does proteins break down into
A
amino acids
5
Q
two types digestion
A
- mechanical/physical
- chemical
6
Q
mechanical/physical digestion
A
uses physical process such as chewing to break food apart
7
Q
chemical digestion
A
uses enzymes to alter the chemical structure of nutrients
8
Q
enzymes
A
speed up the rate of reaction
- provide a location for chemical reactions to occur
- enzymes can participate in hydrolysis and condensation reactions
9
Q
hydrolysis
A
the input of water helps to break down the molcule
10
Q
condensation reactions
A
- the process of condensation binds molecules, such as amino acids, into larger chains of molecules. Water is liberated in the process.
- the binding of amino acids into a specific chain begins the process of protein synthesis
11
Q
Hormones
A
- hormones are chemical messengers that are required for many physiological processes, including digestion
- they are released from one area of the body and travel through the blood to different parts of the body
12
Q
The digestive Tract
A
- long, tube like structure
- sphincters often separate different parts of the tube
- takes ~2+ days for material to pass through the entire tract
- food spends most time in the large intestine
13
Q
digestive tract (in order)
A
- mouth
- pharynx
- esophagus
- stomach
- liver
- gallbladder
- pancreas
- small intestine
- large intestine
14
Q
The layers of the digestive tract wall
A
(inner to outer)
- lumen
- mucosa
- nerve plexus
- submucosa
- nerve plexus
- muscularis
- serosa
15
Q
The mouth
A
- teeth rip food apart
- tongue pushes food towards teeth and mixes it with saliva
- salivary glands secrete saliva into mouth, which contain:
–> salivary amylase digests amylose (starch)
–> lingual lipase digests lipids
–> mucus lubricates food
–> lysozyme = antibacterial substance that disinfects food - when food leaves the mouth it is a bolus
When we swallow food, the pharynx moves upward, putting the epiglottis in the path of food. The bolus of food pushes the epiglottis to close over the trachea, directing food towards the esophagus
16
Q
Pharynx
A
- aka throat
- common passageway for food and inspired air
- no active digestion or absorption
- the epiglottis directs food from the pharynx into the esophagus instead of down the wrong tube into the trachea (windpipe)
17
Q
the esophagus
A
- no active digestion or absorption
- peristalsis is a type of movement that occurs here and in other parts of the tract
- during peristalsis, circular smooth muscle contracts behind the food in a wave-like fashion, pushing it forward through the digestive tract. The relaxation of muscle in front of the bolus, opens a path for the food to be pushed down
18
Q
Stomach
A
- temporary reservoir for food
- food remains here 4-5 hours
- 3 layers of muscles allow stomach to churn
- lower esophageal sphincter and pyloric sphincter close as stomach churns food and mixes it with gastric juice
- when food leaves the stomach it is in a semi-liquid form = chyme
19
Q
3 layers of muscle in stomach
A
Outer to innermost
1. longitudinal muscle
2. circular muscle
3. diagonal muscle
20
Q
Gastric juice
A
Cells in the stomach crypts secrete contents of gastric juice:
1. mucus
- lubrication, medium for chemical reactions
2. gastric lipase
- breaks down lipids
3. hydrochloric acid
- unravels proteins, activates pepsinogen
4. pepsinogen
- becomes pepsin, which digests proteins
- pepsinogen (enzyme precursor) –> HCL –> pepsin (active enzyme)
21
Q
The small intestine
A
- primary site of digestion and absorption
- 3 sections: duodenum, jejunum, ileum
- long length (~6m), large circular folds, villi, microvilli contribute to its large surface area
22
Q
Villi of the small intestine
A
- the villus (plural = villi) is the main functional unit of the small intestine
- villi are invaginations of the small intestine wall
- the cells on their surface have extensions called microvilli (aka brush border) which secrete enzymes
- nutrient subunits are absorbed into the centre of the villus where they then enter the blood or the lymph
23
Q
Osmosis
A
transportation of water
24
Q
passive diffusion
A
consists of lipids, fat soluble vitamins
25
facilitated diffusion
- protein transporter required
- fructose
26
active transport
- protein transporter required
- glucose, amino acids
27
accessory structures of the digestive tract
- the liver, gallbladder, and pancreas secrete material into the duodenum of the small intestine
28
the pancreas
- secretes pancreatic juice into the small intestine (exocrine function)
Pancreatic juice contains:
- digestive enzymes
--> amylase, lipase, proteases
- bicarbonate
--> neutralizes chyme`
29
Liver and Gallbladder - Bile
- liver makes bile
- gallbladder stores bile
- bile is a lipid emulsifier, it breaks larger lipid globules into smaller ones and allows them to be suspended in a watery environment
30
How does bile function?
1. large lipid globules cannot suspend within the watery environment of small intestine, they're also too large for the enzyme lipase to act on
2. the liver and gallbladder secrete bile into the small intestine when lipids are present
3. Bile's hydrophobic tails arrange themselves to face the lipid, the heads arrange themselves to face the watery lumen
4. Large lipid globules are broken into smaller lipid droplets surrounded by bile. This structure is called a micelle
5. Micelles allow lipids to be suspended within and freely move around the small intestine lumen. They also allow lipase to act on lipids
31
large intestine
- approx 1.5m in length
- the colon is the main part of the large intestine
- this is where any unabsorbed material is either: packaged for removal, or acted upon by bacteria (microbiota)
32
Microbiome
The genetic material of the non-human organism found in our body
- the largest population of non-human cells is found in the large intestine
33
microbiota
All the non-human organisms found in our body (mostly bacteria & about 300-500 different species)
Microbiota have roles in:
- vitamin synthesis (K, B12, B2)
- energy harvesting
- health/disease
- appetite
34
Digestive secretions of the mouth
- salvia
- salivary amylase
- salivary lipase
- lysozyme
- mucus
35
digestive secretions of the pharynx and esophagus
mucus
36
digestive secretions of the stomach
Gastric juice:
- mucus
- HCL
- pepsinogen
- gastric lipase
37
digestive secretions of the small intestine
- mucus
- brush border enzymes: lactase, sucrase, and maltase
38
digestive secretions of the large intestine
mucus
39
digestive secretions of the pancreas
pancreatic juice:
- pancreatic amylase
- pancreatic lipase
- pancreatic proteases
- bicarbonate
40
probiotics
cultures of living organisms (ex: bacteria)
- found in yogurt and kombucha
- cannot treat or cure any disease, but may help in the management of certain conditions
41
prebiotics
carbohydrates that act as food for the microbiota
- found in asparagus, garlic, bananas
- support the health of the microbiome
42
ulcers
Weakened, damaged parts of the lining of the digestive tract
Examples:
1. Canker sores
- occur in mouth and resolve on its own
2. Peptic ulcers
- occur in esophagus, stomach, small intestine
- typically related to infection with H. pylori bacteria
43
gastroesophageal reflux disease
gastroesophageal reflux = where lower oesophageal sphincter weakens; acidic stomach contents spill into esophagus
- aka heart burn
- can lead to GERD which then leads to ulcers, Barretts esophagus
44
irritable bowel syndrome (IBS)
- cause unknown
- symptoms of IBS include abdominal pain, bloating, cramping, diarrhoea, constipation, faltulence
- treatment focuses on alleviating symptoms: avoiding trigger foods, managing stress, drinking plenty of fluids
45
Diverticulitis
- Diverticula = weakened walls of the large intestine form outpouchings
- diverticula can become inflamed = diverticulitis
- diverticula can blead = diverticulosis
- age, obesity, smoking, physical inactivity increase risk
- diets low in fibre and high in animal fat increase risk
46
gallstones
- hardened bile deposits that form stones in the gallbladder
- can be painful, especially when fat is consumed and gallbladder contacts to release bile
- diets high in simple sugars, saturated fat and energy increase risk
- gallbladder may need to be removed
47
digestive tract cancers
cancer = uncontrolled multiplication of our cells
- can occur anywhere in digestive tract; most common in colon
- colorectal cancer has both genetic and lifestyle risk factors
- physical inactivity, obesity increase risk
- diets high in red and processed meats increase risk, those high in vegetables, fruits, and fibre decrease risk
48
constipation
Bowel movements that are difficult to pass or less frequent
- stools tend to be dry, hard and can be painful to excrete
- increases risk for haemorrhoids
- risks factors include age, female sex, genetics, physical inactivity, the use of certain medications and IBS
- diet low in fruits, vegetables and water also increases risk
49
diarrhea
- occurs when matter passes too quickly through the large intestine
- stools are loose and have a liquid like consistency
- typically due to bacterial and viral infections
- can be caused by food poisoning
50
delivery of nutrients to the liver
- nutrients that enter the blood capillaries at the villi will then enter veins that lead to the liver (all nutrients except large lipids and fat-soluble vitamins)
- at the liver, material is stored, used, detoxified, or sent off to the rest of the system
- the material that enter the cardiovascular system can then be transported to where it is needed
51
Dietary toxins and detoxification
- recall that toxins are substances that can be found in food that can cause damage to the body
- ex: persistent organic pollutants (POPs)
- levels of toxins in a well-balanced diet are typically below the threshold for harm
- also the liver, kidneys, and lungs remove toxins from the body
- lack of evidence to support the use of commercial detox diets for detoxification/improved health
52
metabolism
sum of chemical reactions that occur in our body
53
anabolism
- smaller molecules come together to form larger ones
- requires an input of energy
54
catabolism
- larger molecules are broken down into smaller ones
- leads to a net release of energy
- the catabolism of the energy-yielding nutrients (carbs, fats, proteins) leads to the release of energy
- this energy is captured with ATP
55
cellular respiration
- the catabolism of the energy-yielding nutrients leading to the production of ATP
- primarily occurs in the mitochondria of the cell
- it occurs over several steps, known as a metabolic pathway
56
glucose metabolism
1. glycolysis = breakdown of glucose
- anaerobic; produces minimal ATP
- glucose breaks down into 2 pyruvate
2. breakdown of Pyruvate
- pyruvate catabolism depends on whether oxygen is present (aerobic conditions) or not (anaerobic)
- aerobic conditions = acetyl CoA is formed
- anaerobic condition = pyruvate is formed (and some ATP is formed, cannot be sustained, and reversible back to pyruvate when oxygen is available again)
3. Citric Acid Cycle
- this cycle is a complex set of reactions that begins when acetyl CoA combines with oxaloacetate
- produces CO2, water, and the capture of energy in GTP (~ATP)
- electron transporters (NADH + H+, FADH2) capture electrons and move to the mitochondrial membrane to begin the electron transport chain
4. The Electron Transport Chain
- electrons are exchanged between the electron transporters (NADH + H+, FADH2) and membrane-bound proteins
- this leads to a build up of protons (H+) on one side of the membrane
- these protons will move through a protein pump that is associated with an enzyme called ATP synthase
- this process leads to the production of more than 30 molecules of ATP
57
lipid metabolism
- triglycerides have 3 fatty acids attached to a glycerol backbone
- majority of energy is derived from fatty acids
- beta-oxidation splits the fatty acid two carbon atoms at a time
- each two-carbon molecule of a fatty acids can be used to form acetyl CoA
- proceeds through remaining stages of cellular respiration
58
ketogenesis
- can occur when diet is high in fat and very low in carbohydrates
- the citric acid cycle requires carbohydrates
- on a very low carb diet, fatty acids cannot enter citric acid cycle, instead form ketones
59
amino acid metabolism
- first, the nitrogen group of the amino acid must be removed (deaminated)
- there are 21 amino acids - each with a unique side chain (therefore there are 21 possibilities for what remains)
- deaminated amino acids will either be used to form: pyruvate, acetyl CoA, citric acid cycle intermediates
60
non-energy uses of sugars, lipids and amino acids
when we consume more energy than we need, most of the excess is stored as lipid in our fat tissue
