Digestion Flashcards
What is digestion?
The process which large (insoluble) molecules are hydrolysed by enzymes into small, soluble molecules which can be absorbed
Which organs are involved in digestion?
Mouth
Salivary glands
Oesphagus
Stomach
Liver
Gall bladder
Pancreas
Small intestine (ileum)
Large intestine
Rectum
Anus
What is the function of the mouth?
Food is ingested and teeth physically/mechanically digest the food
What is the function of the salivary glands?
Produces salivary amylase which begins the chemical digestion of starch
What is the function of the oesophagus?
Tube connecting the mouth to the stomach
What’s the function of the stomach?
A muscular bag that churns food (mechanical/physical break down) adds acid and pepsin to start the digestion process
What’s the function of the ileum?
A long tube with villi, site of final stages of digestion and absorption of monomers
What’s the function of the liver?
Produces bile (for emulsification of fats) that is stored in the gall bladder
What’s the function of the pancreas?
Produces many digestive enzymes which are released into the duodenum
What is the function of the large intestine?
Where water and ions are absorbed
What is the function of the rectum?
Storage of faeces before being expelled from the anus
What is ingestion?
When food is taken in through the mouth
What is absorption?
Where small soluble molecules are absorbed through the ileum into the blood
What is egestion?
Any food that can’t be digested is eliminated from the body (eg, cellulose, aka fibre -plant cell walls)
What are proteins broken down into?
Protestases hydrolyse the peptide bonds to form AMINO ACIDs
What are the different types of peptidases?
Endopeptidase
Exopeptidase
Dipeptidase
What is the purpose of ENDOpeptidases?
Work in the stomach along the chain to produce MULTIPLE SHORTER POLYPEPTIDES
What is the purpose of EXOpeptidases?
Removal terminal (ends of chain) amino acids to form DIPEPTIDES AND AMINO ACIDS
What is the purpose of DIpeptidases?
They are membrane bound in the duodenum and ileum and the hydrolyse the peptide bonds between dipeptides to produce amino acids which can be absorbed via contransport
How are carbohydrates broken down into monosaccharides?
Give an example
Starch is hydrolysed by amylase to form Maltose
Maltose is hydrolysed by Maltase to form alpha glucose - which can be absorbed
Which enzymes hydrolysed lactose?
LactASE
Which enzyme hydrolysed sucrose?
SucrASE
How are lipids digested?
Lipases hydrolyse the ester bond in triglycerides to form glycerol, fatty acid and monoglycerides
What is peristalsis?
Waves of muscular contractions which move food boluses into the stomach
Give an example of an endopeptidase?
Pepsin
Tripsin
What is the purpose of bile?
Emulsifies large lipid droplets into micelles to increase its surface area for lipases to work on
How is the ileum adapted to increase the efficiency of absorption?
- Lining of ileum folded into villi - increase the surface area
- Villi have thin walls for short diffusion pathway
- Epithelial cells have micro Lili
- Inside is a rich blood supply which can carry away absorbed molecules to maintain the concentration gradient
- Villi waft/move so we can ,is food to maintain the concentration gardient
How are monosaccharides and amino acids absorbed into the blood?
Co-transport
Describe the process of co-transport?
Na+/K+ pump is used on the basal membrane of epithelial cells
Na+ actively pumped out of epithelial cells into blood by active transport
Simultaneous K+ transported into epithelial cells
This creates a low Na+ ion concentration in epithelial cells
Low concentration of glucose in the lumen of the intestine compared to epithelial cell (much smaller)
Na+ diffuses down its concentration gradient by facilitated diffusion taking glucose with it
This provides energy and drives transport of glucose into the cell with it - against its concent gradient by co-transport
The glucose then moves out of epithelial cells into the blood by facilitated diffusion (using a carrier protein)
Lipids are digested by which two chemicals?
Lipase
Bile salts
Where are bile salts produced?
In the liver
What is the purpose of bile salts?
Emulsify lipids to form tiny droplets called micelles
What is the purpose of micelles?
Increase the surface area of lipids for lipase to act on
What is a micelle?
A vesicle that contain fatty acids, glycerol, monoglycerides and bile salts
How do micelles aid lipid absorption?
Make fatty acids more soluble in water (allows simple diffusion - lipid soluble molecules )
They carry the fatty acids to epithelial cells of the ileum
They help to maintain a higher concentration of fatty acids compared to the epithelial cells of the ileum
What happens to fatty acids (micelles) once they enter cells?
Fatty acids and monoglycerides are modified into triglycerides inside the endoplasmic reticulum and Golgi body
If a protein is added to the lipid it makes chylomicron
How do modified lipid leave the epithelial cells?
Vesicle containing the chylomicron are released and move towards the cell membrane
They are released by exocytosis
They are absorbed/enter the lacteal (lymphatic system)
