mechanical and chemical digestion, absorption and assimilation

Question 1

what is mechanical digestion?

Answer 1

a physical process that aids the process of digestion

Question 2

in what parts of the body does mechanical digestion take place?

Answer 2

the mouth (buccal cavity), stomach

Question 3

in what parts of the body does chemical digestion take place?

Answer 3

salivary glands - produces saliva
gastric glands (stomach wall) produce gastric juice
liver makes bile
pancreas produces pancreatic juice (digestive enzyme)
intestinal glands (small intestine wall) produces intestinal juice (enzymatic digestion)

Question 4

What digestive processes take place in the buccal cavity?

Answer 4

mechanical digestion by food being chewed means that the digestive process that takes place is much easier, due to the larger surface area that is created for chemical digestion
the salivary glands release salivary amylase which breaks down starch into maltose

Question 5

what digestive processes take place in the oesophagus?

Answer 5

food travels down the oesophagus which is made up of thick muscular wall, and when these muscles contract and relax, it creates a wave like motion, which allows the food to move down.
This process is called peristalsis

Question 6

what digestive processes take place in the stomach?

Answer 6

a layer of thick muscles with the inner layer producing enzymes
the stomach can store and digest food including proteins
the enzyme pepsin digests these proteins
another gland in the stomach produces mucus which prevents the stomach being digested by it’s own enzymes
HCL released to destroy harmful bacteria and microorganisms. This provides an optimum working condition for pepsin (PH)

Question 7

what digestive processes take place in the small intestine?

Answer 7

gastric juice is passed into the small intestine to be further digested by enzymes
the inner wall in folded into villi, which provides a larger surface area for the absorption of products from digestion into the blood stream
digestion of fat by lipase
digestion of protein by trypsin
digestion of starch by amylase

Question 8

what digestive processes take place in the pancreas?

Answer 8

pancreatic juice contains the enzyme lipase, trypsin, and amylase

Question 9

what digestive processes take place in the liver?

Answer 9

liver stores excess glucose as glycogen and is also the site of deamination (amino groups removed from excess proteins) and produces bile

Question 10

what does bile do?

Answer 10

converts large molecules of fats into tiny droplets and this process is called emulsification which increases surface area, therefore aiding digestion

Question 11

what digestive processes take place in the large intestine?

Answer 11

water absorbed from chyme (fluid from stomach) which leaves faeces
most of the water that is reabsorbed comes from the secretions of many digestive glands
faeces stored in rectum, and removal via the anus is called egestion

Question 12

what does chemical digestion do?

Answer 12

breaks down large, insoluble molecules into smaller soluble ones
it uses enzymes that function by hydrolysis- called hydrolases
they are called carbohydrates- monosaccharides, lipases- glycerol/ fatty acids and proteases- amino acids

once hydrolysed, they are absorbed via different mechanisms into the blood stream to either be incorporated into the body tissues or help with different processes, this is called assimilation

Question 13

how are carbohydrates broken down and where? what is the product?

Answer 13

salivary amylase- salivary glands- maltose
pancreatic amylase- pancreas and small intestine-maltose
maltase-small intestine- maltose

Question 14

how are proteins broken down and where? what is the product?

Answer 14

pepsin-stomach mucosa-peptides
trypsin-pancreas-peptides
peptidases-intestinal mucosa-amino acids

Question 15

how are fats broken down and where? what is the product?

Answer 15

lipase-pancreas-fatty acids and monoglyerides

Question 16

what are enzymes?

Answer 16

little ‘machines’ that increase the speed of a chemical reaction without themselves undergoing chemical change

Question 17

how do enzymes work?

Answer 17

the substrate sucrose consists of glucose and fructose bonded together
the substrate binds to the enzyme, forming an enzyme-substrate complex
the binding of this place stress on the glucose fructose bond and the bond breaks
the products are released and the enzyme is free to bond to other substances

Question 18

what are the main enzyme producing structures of the human digestive system?

Answer 18

salivary glands
stomach
pancreas
liver
small intestine

Question 19

what is the first major region of the small intestine, where digestive action is carried out?

Answer 19

the duodenum
pancreas enzymes are secreted into the duodenum (pancreatic juice contains protease, amylase, lipase, sodium hydrogen carbonate) it travels through the pancreatic duct to mix with food in the duodenum
it connects the pyloric sphincter of the stomach
it is the shortest region (10 inches)
partially digested food or chyme from the stomach is mixed with bile from the liver and pancreatic juice to complete it’s digestion in the duodenum

Question 20

what is the second major region of the small intestine, where digestive action is carried out?

Answer 20

the jejunum
middle section that serves as the primary site of nutrient absorption
3 feet in length

Question 21

what is the third major region of the small intestine, where digestive action is carried out?

Answer 21

the ileum- empties into the large intestine
6 feet long
completes the absorption of nutrients that were missed in the jejunum
lined with villi which help to increase surface area
this helps to increase the rate of absorption and digestion
each villus is covered with a one cell thick layer called the epithelium
there is a network of blood capillaries that help to absorb glucose and amino acids
a blind-ended lacteal absorbed the products of digestion of fat
it contains muscles to move around, mixing food with enzymes

Question 22

what is sodium hydrogen carbonate?

Answer 22

an alkaline solution that neutralises the acidity from the stomach- in pancreatic juice which is passed into small intestine

Question 23

what does bile contain?

Answer 23

bile salts
bile pigments
sodium hydrogen carbonate

Question 24

what do bile salts do?

Answer 24

help to emulsify fats which means to change large droplets of fat into smaller ones
called emulsification

Question 25

what are the roles of the liver?

Answer 25

adjusts blood glucose level
some glucose is used by the liver cells in respiration
pancreas secretes insulin hormone
makes blood proteins

Question 26

what is absorption?

Answer 26

enzymes in the gut convert large molecules into smaller molecules
the digested food molecules are transported across the lining of the gut into the blood

Question 27

where does absorption occur?

Answer 27

ilium in the small intestine

Question 28

how is the villus adapted for its job?

Answer 28

microvilli increase the surface area by 20 times
epithelium = one cell thick, therefore short distance for absorption
contains a goblet cell which produces mucus that protects the gut lining against digestion by the body’s own enzymes
contains capillaries which transport glucose and amino acids
has a lacteal which transports fatty acids and glycerol (lymph vessel)
has a circular, muscular layer which is responsible for peristalsis

Question 29

what is assimilation?

Answer 29

food molecules move into cells where they are used
mainly occurs in the liver
liver sorts out digested food molecules and the food is absorbed into the capillaries

Question 30

what are the main functions of the liver?

Answer 30

produces bile which helps digest fats
stores glucose as glycogen
converts amino acids into products important for the body by transamination (chemical reaction that transfers amino groups to form new amino acids)
-excretes excess amino acids in a process called deamination