The Digestive System 1.2 Flashcards
What are the monomers called in carbohydrates?
Monosaccharides
They contain carbon, oxygen and hydrogen.
What is digestion?
The breaking down of larger molecules into smaller molecules.
What are the monomers called in proteins?
Amino acids
They contain hydrogen, carbon, oxygen and nitrogen.
Explain how the oesophagus takes food into the stomach.
It uses waves of muscle contractions called peristalsis. Mucus is also secreted from tissues in the walls, to Lubricate the foods passage.
Describe and explain the stomachs role in digestion.
The stomach has lots of folds so that it can expand. The entrance and exit to the stomach are controlled by the sphincter muscles.gastric juice is produced from the cell walls to break down the food. Pepsin hydrolyses proteins into shorter polypeptide chains. Peristalsis of the stomach turns the food into acidic fluid called chyme.
What does gastric juice consist of?
Hydrochloric acid, pepsin and mucus.
Describe and explain the role of the small intestine in digestion.
It has two main parts the duodenum and the ileum. Chyme is moved along the small intestine by peristalsis. In the duodenum bile and pancreatic juice neutralise the acidity of the chyme and beak down the smaller molecules. In the ileum, the smaller, soluble molecules are absorbed through villi.
Describe and explain the role of the large intestine in digestion.
The large intestine absorbs water, salts and minerals. It has folded walls which provides a large surface area for absorption.
Describe and explain the role of the rectum in digestion.
Faeces are stored in the rectum and then pass through the sphincter muscles at the anus, during defecation.
Which bond is formed when two amino acids join together?
Dipeptide
Name the similarities and differences between amino acids.
They have different variable groups.
They all have the same COOH and NH2 group.
What reaction forms a polypeptide bond?
Condensation reaction.
What does amylase hydrolyse?
Starch into maltose
Where is amylase secreted?
The salivary glands and the pancreas.
What does pepsin hydrolyse?
Protein to peptides.
What does the pancreas secrete?
Amylase, trypsin, chymotrypsin, carboxypeptidase, lipase
What does maltase hydrolyse?
Maltose to glucose.
What does sucrase hydrolyse?
Sucrose into glucose and fructose.
What does lactase hydrolyse?
Lactose into glucose and galactose.
What does peptidase hydrolyse?
Peptides to amino acids.
What bond is formed when two monosaccharides join together?
Glycosidic bond
Outline the buiret test for proteins.
- Solution must be alkaline so add sodium hydroxide.
- Add copper(II) sulphate
Turns purple in the presence of proteins.
How does lactose intolerance cause diarrhoea?
Undigested lactose is fermented by bacteria, or lactose travels to the small intestine where it lowers the water potential in the lumen, water travels into the small intestine by osmosis and causes diarrhoea.
Outline the non reducing sugars test.
- First you have to break them down into monosaccharides by boiling with HCL.
- Then neutralise it with sodium hydrogen carbonate.
- Then carry out the Benedict’s test.
- Then carry the Benedict’s test again to rule out it being a reducing sugar.
When Benedict’s reagent is added to a reducing sugar what would you expect to see?
The solution would turn brick red with a red precipitate.
Which two polysaccharides make up starch?
Amylose and amylopectin
What test do you carry out to test for starch?
Add iodine dissolved in potassium iodide solution to the sample. If starch is present the sample changes from brown to blue/black.
