Digestive system model answers

Question 1

What is the essential function of the digestive system?

Answer 1

Digestive system’s purpose is to break down food molecules into smaller chemical units that are soluble and can move through membranes into the blood

Question 2

Major types of nutrients in body

Answer 2

carbohydrates, lipids, proteins, (Macro vitamins and minerals (micro)

Question 3

difference between macro and micronutrients

Answer 3

• macronutrients need to be digested, - water is something that is a macronutrient which doesn’t need to be digested but absorbed to regulate osmolarity and concentration,
• vitamins and minerals have a variety of functions (needed calcium in muscle contraction, iron in haemoglobin structure)

Question 4

What is the difference between mechanical digestion and chemical digestion and how do they complement each other?

Answer 4

Physical digestion involves breaking food into smaller and smaller fragments, without any chemical change in the food. Chewing, grinding in the stomach, and emulsification are all physical processes. It results in a much greater surface area of food exposed for chemical digestion.
Chemical digestion involves the breaking of chemical bonds to release micromolecules from the macromolecules. Only micromolecules can be absorbed by cells.

Question 5

carbohydrates

Answer 5

• primary source of energy
• all chem reactions need ATP which this provides
• one polysaccharide (cellulose) is indigestible and forms fiber but is required in diet, it can’t be broken down since there is no enzyme for it but it helps to keep digestion moving, lowers rates of colon cancer and helps to keep fat molecules separated to make them easier to digest

Question 6

what is carbohydrate broken down into

Answer 6

carbohydrate is turned into maltose by salivary amylase (produced by salivary glands). then it goes to glucose by maltase

goes from polysaccharide to disaccharide (2 units of sugar) to monosaccharides (single units of sugar)

this is digested in the mouth and small intestine using enzymes produced in the pancreas (pancreatic amylase), mouth (ptyalin =salivary amylase) and small intestine (maltase, sucrase, lactase). it is reduced to monosaccharides

Question 7

lipids

Answer 7

• source of energy but there are other functions
• forms parts of membranes, building blocks for hormones, parts of cell membranes, help conduct nerve impulses
• don’t form polymers like carbohydrates
• not a repeating unit but a larger molecule (fats and oils are main group of lipids that we find in diet and use for energy)
• glycerol and fatty acids are in it

Question 8

how are lipids digested

Answer 8

lipids plus bile slats turn fat into fat droplets. this then gets emulsified by bile salts. Then the droplets are turned to glycerol and fatty acids through lipase.

digested in small intestine, using enzymes from pancreas (pancreatic lipase) and is reduced to fatty acids and glycerol

Question 9

proteins

Answer 9

• have 20 different amino acid building blocks but there are at least 21 acids in a chain
• you need lots of different enzymes to break these down
• easy to digest carbohydrates since they are repeating molecules
• bonds are the same on protiens but molecules on either side could be different
• structural: keratin, defense: antibodies, gas transport: haemoglobin, catalytic reactions: enzymes

Question 10

how are proteins digested

Answer 10

proteins go to peptides by pepsin. then it goes from peptides to amino acids by peptidases.

turn to long peptides

peptides vary in length but always consist of a number of linked amino acids. peptides from the stomach are usually too large to be absorbed by the intestinal lining but later they are broken down.

into short peptides
into dipeptides (2 amino acids linked together)
single amino acids are absorbed into blood

digested in stomach and small intestine using enzymes made in stomach (pepsin), pancreas (trypsin, chymotrypsin, aminopeptidase, carboxypeptidase) and small intestine (dipeptidase) and is reduced to aminoacids

Question 11

what happens at the mouth

Answer 11

• Mechanical and chemical digestion
  Salivary glands secrete saliva with ptyalin (salivary amylase) to chemically begin the digestion of starch
  mastication (mechanical digestion)

Question 12

what happens at esophagus

Answer 12

food passes through
Takes bolus from mouth to stomach
Peristalsis is triggered that helps propel the bolus downward

Question 13

what happens at stomach

Answer 13

Mechanical and Chemical
Stomach wall muscles pound the food to break it into smaller chunks
Pepsin begins the chemical digestion of proteins

Question 14

what happens at small intestine

Answer 14

Chemical
chemical digestion of proteins, carbs, and lipids. Absorption of micronutrients into the bloodstream (nutrients will be delivered to body tissues)

Question 15

what happens at large intestine

Answer 15

food passes through
Where undigested materials including fiber, water and dead cells are taken before being expelled
absorption of water

Question 16

what happens at anus

Answer 16

food just passes through

The waste product is then excreted through the colon thus ending the process of digestion

Question 17

What is an enzyme? And a digestive enzyme?

Answer 17

An enzyme is a protein that accelerates a chemical reaction. (Note that there are many enzymes that have nothing to do with the digestion of food. Every process in your body is run by enzymes.). A digestive enzyme is an enzyme that accelerates the breaking of bonds in a macromolecule, and releases smaller molecules.

Question 18

Why does your body use many different types of enzymes to accomplish the digestion of a single type of molecule (i.e. why are there many enzymes that are involved in different steps of digestion of proteins?)

Answer 18

The body uses many different types of enzymes for a few reasons. The first is that all enzymes will have specific substrates that they will break down and they will require specific conditions (temperature and pH) to operate the highest rate. In addition to this (and probably more importantly), several enzymes will create division of labour, which will provide a more complete breakdown of a nutrient in a shorter amount of time. This increases the efficiency of the digestive system.

Question 19

Explain how the pH affects the efficiency of chemical digestion in the stomach and in the intestine. How is the pH controlled in those organs?

Answer 19

Every enzyme has an optimal pH (the pH in which the enzyme has the best performance). In the stomach, the conditions are acidified by adding large amounts of HCl. This activates the enzyme pepsin and starts protein digestion. It also has secondary functions of killing off foreign microorganisms that may enter with the food, and unravelling big complex molecules in the food.
In the duodenum, the acid is neutralized by sodium bicarbonate which has a basic pH from the pancreas, and bile salts from the liver. This deactivates pepsin, preventing digestion of the intestines and their enzymes. It also provides the slightly basic conditions under which pancreatic enzymes work.

Question 20

Explain why HCl and pepsinogen are produced by different stomach cells?

Answer 20

Pepsinogen turns into its active form (pepsin) when in contact with HCl. If pepsinogen and HCl were secreted by the same stomach cells, this enzyme would be active and it would digest the stomach cell proteins and the mucosa (which is a protective layer of the stomach lining against the low pH of the stomach lumen). That could lead to to ulcer formation.

Question 21

Why is the inside surface of the jejunum and ileum so highly folded?

Answer 21

The many layers of folding (ridges, villi, microvilli) provide a huge surface area for the absorption of digested nutrients, allowing food nutrients to move into the circulatory system more rapidly.

Question 22

What are the functions of bile?

Answer 22

The main function of bile is to emulsify (suspend) fats in the intestinal fluid. The hydrophobic ends of the bile salts dissolve in tiny droplets of fat, and the hydrophilic ends then hold the droplets in suspension. This allows a large surface area for lipase to work on. A secondary function of bile salts is to neutralize some of the HCl from the stomach. Bile also acts a s disposal system for wastes generated by the breakdown of hemoglobin - bile pigments.

Question 23

digestion steps

Answer 23

• ingestion (placing food into mouth)
• mechanical digestion: crushing, grinding food to expose more surface area for enzymes during the chemical digestion (mouth and stomach)
• chemical digestion: addition of chemicals to break down complex molecules into simple structures, involves the use of digestive enzymes to break down food molecules into smaller molecules (mouth, stomach and small intestine)
• absorption: movement of nutrients from the digestive system to the blood (small intestine)
• storage of wastes: large intestine
• egestion: removal of undigested materials from the body (large intestine)

Question 24

bolus

Answer 24

food that is being chewed on and swallowed is called a bolus.
this then initiates a wave of contractions called peristalsis which will help to push food down the throat and down the esophagus

Question 25

bolus to stomach

Answer 25

then it goes to stomach. the rug are folds inside stomach wall. stomach has several layers of muscle which helps with the churning motion.

food enters the cardiac sphincter

extis via the pyloric sphincter

stomach wall is folded because of production and protection from digesting itself. the pits are called gastric pits.

Question 26

different cells in gastric pits

Answer 26

inside the gastric pits there are: parietal cells secrete HCL (stimulated by hormone GASTRIN) when protein is present in stomach and chief cells produce precursor hormone pepsinogen
you also find:
goblet cells: produce mucus protects lining of stomach from chemical digestion (pepsin enzyme)

Question 27

pepsin and HCL

Answer 27

• pepsin is produced when pepsinogen and HCL come in contact with each other.
• Pepsinogen and HCL are stimulated to release their contents into the pits which is when they come in contact with each other.
• stomach churning will force the contents of the pits into the lumen of the stomach which draws the mucus down to the pits which prevents the pepsinogen and HCL from coming in contact with each other before they are squirted out of the gastric pits

Question 28

what protects stomach

Answer 28

• has mucus lining
• pepsinogen and HCL are in separate cells so they are not always active
• stomach is ideal for pepsin pH
• Gastrin controls the release of chemicals from the gastric pits which will switch off when the stomach empties (detects more acid then food) which reduces the churning and production of HCL and pepsinogen
• there are stem cells that replace the lining of the gastric pits. every few days. this prevents damage from the acidic environment

Question 29

from stomach to small intestine

Answer 29

• leaves from the pyloric sphyincter
• small intestine is 6m in length
• duodenum is the mixing pot of the small intestine
• allows juices from the pancreas (which releases sodium bicarbonate) to neutralize the cyme
• this will release in response to hormone secretin (response to acidity in duodenum)
• also causes another hormone called CCK (gall bladder release bile and contract)
• cyme is now the name of the food from stomach with acid in it
• CCK causes pancreas to release a series of enzymes: pancreatic lipase, pancreatic amylase, tripsin etc.
• jejunum and ileum have overlapping functions: both absorb and chemically break down because they have enzymes that digest remaining breakdown of macromolecules.
• starch is too large to diffuse across small intestine membrane but glucose can
• since this is diffusion: you need to speed it up by having high SA: bends in the intestine, also the wall itself is lined with vili which are finger like things. The vili in small intestine secrete peptidases and maltase which complete the digestion of protein to amino acids and starch to glucose

Question 30

absorption of food in small intestine

Answer 30

• takes places in jujenum and ileum
• the glucose and amino acids diffuse directly into the blood stream
• the nutrient poor blood that arrives at the small intestine via the anterior mesenteric artery which then leaves through the hepatic portal vein towards the liver
• liver metabolizes nutrients, stores glucose, converts animo acids and has losts of enzymes that remove chemicals that may be in your food
• fats take a different route (not soluble in blood)
• engulfed by cells, deposited along with proteins into an lactiel which is a part of the lymphatic duct which will be carried into the lymphatic system until it reaches regular circulation via subclavian veins

Question 31

accessory glands

Answer 31

• not part of digestive tract but play a role in digestion
• liver produces bile, gall bladder stores bile and secretes it in the duodenum
• pancreatic duct also connects to it to deposite enzyme and sodium bicarbonate which neutralizes the chime which creates bad environment for pepsin but good for other enzymes
• bile digests fats by emulsifying the facts by having a region of the molecule that is attracted to the fat and water too, helps keep globule apart to make digestion faster

Question 32

small intestine to large intestine

Answer 32

• cetum meets the small intestine
• colon is main body
• rectum is where feces is stores
• anal sphincter egestst the material

Question 33

features of large intestine

Answer 33

• honeycomb pattern increases surface area
• colon is mainly for water absorption (large SA)
• any indigestible food passes through
• water and soluble vitamins will be taken back into body by colon
• feces contains some fibre, cells, musus, bacteria
• stored in rectum until removed
• unique feature: bacteria helps you gain access to certain nutrients that you can’t get from diet all by yourself ex. vitamin K, B12, thiamine and riboflavin
• also bacteria can digest small amounts of cellulose

Question 34

breakdown of cell thing

Answer 34

goes from organ to tissue to cell

Question 35

Three different kinds of mechanical digestion

Answer 35

chewing (mastication), grinding (stomach–> done by rugae) and emulsification of fats (done by bile salts in small intestine)

Question 36

a molecule of fat goes from

Answer 36

small intestine to a capillary to a lymph node to the liver from the heart (which carries nutrient poor blood)

Question 37

nucleic acid digestion

Answer 37

pancreas produces nuclease which turns nucleic acid into nucleotides then the intestinal wall produces nucleosidase which breaks down nucleotides into sugar and phosphate

Question 38

salivary glands produce

Answer 38

salivary amylase which breaks down starch into maltose

Question 39

stomach wall

Answer 39

produces pepsin which breaks protein into long peptides

Question 40

pancreas

Answer 40

produces

• pancreatic amylase: breaks down starch to maltose
• pancreatic lipase: fats to glycerol and fatty acids
• trypsin: long peptides to short peptides
• chymotrypsin: long peptides to short peptides
• amino peptidase: short peptides to dipeptides
• carboxypeptidase: short peptides to dipeptides
• nuclease: nucleic acid to nucleotides

Question 41

intestinal wall

Answer 41

• maltase: maltose to glucose
• sucrase: sucrose to fracture + glucose
• lactase: lactose to galactose + glucose
• dipeptidase: dipeptides to amino acids
• nucleaosidase: nucleic acid to nucleotides??