LS2 Science- Digestive System Flashcards
Food is needed to…
- Provide us with energy for our daily activities
- Produce heat to maintain our body temperature
- Grow new cells and tissues
- Maintain a healthy body
- Repair worn-out tissues
Carbohydrates
Found in the form of starch, sugar or cellulose
- Big or small molecule size
- Provides immediate source of energy
[Cellulose- found in plants]
Proteins
Made up of several small molecules called AMINO ACIDS
-Large molecule size FUNCTIONS: -To make new cells for body -To repair worn out tissues -To make complex proteins called enzymes
Fats
Made up of glycerol and fatty acids
-Large and insoluble in water
FUNCTIONS:
-Serves as body’s store of energy
-Prevents the body from losing too much heat
Water
-Very small molecule size
- Acts as a solvent, helping to transport soluble nutrients and excretory products around the body via the bloodstream
- Required for important chemical reactions in cells
- To maintain body temperature
Reason for digestion of food
Cell membranes of cells- [partially permeable]
Large molecules e.g. Fats, starch and proteins CANNOT PASS THROUGH a
The large molecules are broken down during digestion,
allowing it to pass through the cell membrane
Mouth
To cut and grind food into smaller pieces.
-Salivary glands secrete saliva which contains the enzyme, salivary amylase
(Tongue)
- Pushes food around the mouth while we chew
- Pushes the food to the back of the mouth and down into the esophagus
Esophagus (gullet)
A muscular tube measuring about 25cm long
-Does not digest food; [transport food]
Stomach
Glands on the stomach walls secrete gastric juice containing:
-Protease
-hydrochloric acid
Small intestine
Food is mixed with intestinal juice, pancreatic juice and bile to help digestion.
- The liver and pancreas are connected to the small intestine
- The final products are absorbed into the bloodstream
- Undigested food passes into the large intestine
Large intestine:
Colon;
Rectum
[Large intestine]
Colon:
- Absorbs water and mineral salts from undigested food
- Bacteria in the colon make vitamins for the body
Rectum:
- Temporarily stores the remaining undigested food (faeces)
- Faeces leave the body through the anus
Small intestine> Bile, intestinal juice, pancreatic juice
Bile: Liver No Enzyme ---------- Intestinal juice: small intestine Maltase, protease, lipase ---------- Pancreatic juice: Pancreas Amylase, Protease, Lipase
Bile
Yellowish-green fluid stored in the gall bladder
When we eat food, the gall bladder contracts and releases bile into the small intestine through the bile duct
- Bile breaks down fat into smaller fat droplets
- Process: emulsification
Absorption in the small intestine
After digestion is completed in the small intestine, the food molecules are absorbed by the body
- Only food molecules that are small enough can pass through the walls of the small intestine and blood vessels
- The small food molecules enter the bloodstream and are transported throughout the body
- Small Food molecules are absorbed by body cells to be used for respiration, cell repair and other processes
Parts of the digestive system working together
[Physical digestion]
-Teeth grind food into smaller pieces
-Stomach muscles contract and relax to digest food
[Chemical digestion]
-Salary amylase digest starch
-Protease digest proteins
-Starch and proteins are further digested and fat digestion begins
The process of digestion might be affected if an organ of the system is not working.
