basic functional and structural units in a living organism
Tissue
A group of cells of similar structure working together to form a particular function
Organs
made from a group of different tissues working together to form a particular function
organ system
made from a group of organs with related functions, working together to perform functions in the organism
Role of the stomach
To start protein digestion
Protein digestion in the stomach
1. Stomach produces proteases like pepsin
2. Proteases digest proteins into amino acids
Hydrochloric acid
Aids proteindigestion
Helps proteins unravel so enzymes can breakbonds holding amino acids together
Inhibits many microorganisms that may be present in food, reducing chance of infection
Acid produced by glandulartissue in the stomach
Digestive system
A number of organs that break down large insolublemolecules into smaller, soluble food molecules to provide the body with nutrients
Three types of tissue found in the stomach are muscular, epithelial and glandular. These tissues work together to allow the stomach to carry out its role
Digestive system
An example of an organ system in which several organs work together to digest and absorb food
Digestion
1. Large, insoluble molecules in food (such as starch, proteins) are broken down into smaller, soluble molecules
2. Smaller, soluble molecules (such as glucose and amino acids) are absorbed into the bloodstream and delivered to cells in the body
Small soluble molecules
Used either to provide cells with energy (via respiration), or with materials with which they can build other molecules to grow, repair and function
Alimentary canal
teeth are responsible for mechanical digestion
The oesophagus pushes the bolus towards the stomach by peristalsis
the stomach will break down food by churning and digest protein using protease
Hydrochloric acid will kill bacteria and create an acidic pH
Alimentary canal (2)
Digestion is completed in the duodenum
soluble food molecules are absorbed in the ileum due to the presence of villi
Water is absorbed in the colon and faeces is formed
Stored in rectum before leaving through anus
Accessory organs+functions
salivary glands- secreteamylase for starchdigestion
pancreas- produces variousdigestiveenzymes in an alkalinefluid
gallbladder- where bile is stored
Liver- where Bile is produced for the emulsification of lipids+ increase in pH
Mouth
Where mechanical digestion takes place
Mechanical digestion in the mouth
1. Teeth chew food to break it into smaller pieces
2. Increase surface area to volume ratio
3. Amylase enzymes in saliva start digesting starch into maltose
Bolus formation
1. Tongue shapes food into a ball
2. Saliva lubricates the bolus so it can be swallowed easily
Oesophagus
Tube that connects the mouth to the stomach
Wave-like contractions push the food bolus down without relying on gravity
Stomach
Food is mechanically digested by churning actions
Protease enzymes start to chemically digest proteins
Hydrochloric acid kills bacteria and provides optimum pH for protease enzymes
Small intestine
Duodenum is where food from the stomach finishes being digested by enzymes produced here and from the pancreas
pH is slightly alkaline (around 8-9)
Ileum is where absorption of digested food molecules takes place, it is long and lined with villi to increase surface area
Large intestine
Water is absorbed from remaining material in the colon to produce faeces
Faeces is stored in the rectum and removed through the anus
Pancreas
Produces amylase, protease and lipase enzymes
Secretes enzymes in an alkaline fluid into the duodenum to raise the pH of fluid coming out of the stomach
Liver
Produces bile to emulsify fats (mechanical digestion)
Breaks down amino acids not used to make proteins (deamination) which produces urea
Gall bladder
Stores bile to release into the duodenum as required
Digestive system
organs
A) salivary glands
B) stomach
C) bile duct
D) large intestine
E) rectum
F) anus
G) appendix
H) small intestine
I) pancreas
J) gall bladder
K) liver
L) oesophagus
M) mouth
Large intestine
Home to hundreds of species of bacteria
Microbial ecosystem (microbiota, gut flora)
Bacteria that play an essential role in human digestion of food
Role of gut microbiota in human digestion
1. Breaking down substances we can't digest (like cellulose)
2. Supplying essential nutrients
3. Synthesising vitamin K
4. Providing competition with any harmful bacteria to restrict their growth
Taking antibiotics
Can disrupt the gut microbiota
Disrupting the gut microbiota
Can cause short-term problems with digestion
enzyme- biological catalyst
Enzymes
Lock& Key model (bottom labels are unscientific)
A) Enzyme
B) Lock
C) Active site
D) Substrate
E) Key
Enzyme specificity
can only catalyse reactions with the correct shaped substrate
Metabolism
The sum of all the reactions happening in a cell or organism, in which molecules are synthesised (made) or broken down
Enzymes& metabolism
They speed up chemical reactions in cells, allowing reactions to occur at much faster speeds than they would without enzymes at relatively low temperatures (such as human body temperature)
They temporarily bind to the active site of an enzyme, which leads to a chemical reaction and the formation of a product(s) which are released
They remain unchanged at the end of a reaction, and they work very quickly
How temperature affects enzymes
As temperature increases so does kinetic energy, which means more substrate complexes are formed
the temperature with the highest rate of reaction is the optimum temperature
When the temperature is high enough to break the bonds in the amino acids- enzyme denatures and loses its shape
Optimum pH for most enzymes
pH 7
Some enzymes produced in acidic conditions have lower optimum pH (pH 2)
Some enzymes produced in alkaline conditions have higher optimum pH (pH 8 or 9)
If pH is too high or too low
Bonds that hold the amino acid chain together to make up the protein can be destroyed
Bonds that hold the amino acid chain together being destroyed