Section 2e Nutrition Flashcards
Describe: Ingestion, digestion, absorbtion, assimilation and egestion.
Ingestion - Taking food into body through the mouth.
Digestion - Breaking down of large molecules into smaller molecules so they can be absorbed into blood vessels.
Absorbtion - Diffusion across the wall of small intestine into blood vessels.
Assimilation - The digested molecules are used to make new molecules.
Egestion - When food cannot be digested, they are removed from the body as faeces.
Describe functions of the mouth, oesophagus, stomach, small intestine, large intestine and pancreas.
Mouth - Food is taken in and broken down by chewing. It is also broken down by amylase enzymes secreted by the salivary glands.
Oesophagus - The bolus passes down this tube through peristalsis, wave-like muscle contraction. When the longitudinal muscles in the oesophagus contract, the circular muscles relax. When the circular muscles contract, the longitudinal muscles relax. These wave-like contractions help push the bolus through the oesophagus. This is done so that the movement of food in the gut DOESNT depend on gravity.
Stomach - Walls of the stomach secrete hydrochloric acid, which kills any pathogens in the food. Digestive enzymes are further secreted to help continue the breakdown of food. These enzymes have a pH that allows them to work in their acidic environment.
Small intestine - Food is broken down here by enzymes. Most food is absorbed into the blood vessels in the small intestine. The walls are lined with villi.
Large intestine - Water is reabsorbed into the blood vessels here.
Pancreas - Releases enzymes into the small intestine. Releases lipase, trypsin and amylase.
Describe the function of the liver and bile. Also, where is bile stored?
Liver - Produces bile. Bile is stored in the gallbladder.
Bile has two jobs:
-Neutralises stomach acids (changing pH) in the small intestine so enzymes present there can breakdown the food.
-Emulsifies large lipid molecules into smaller lipid molecules; therefore increasing surface area to ratio allowing enzymes to breakdown the lipids quickly.
Describe the structure of villi and describe how this helps the absorption of food into the blood vessels.
The Villi has a number of adaptations that help increase diffusion rate.
- Thin walls - Walls are one cell thick, allowing faster diffusion.
- Good blood supply - The blood is carried away quickly, maintaining a concentration gradient.
- Surface area - Villi have a large surface area increasing rate of diffusion. Microvilli further help increase diffusion by creating a larger surface area.
Describe the role of digestive enzymes in the digestion system.
Carbs -> Amylase, Maltase -> Glucose
Proteins -> Peptidases, Trypsin, Pepsin -> Amino Acids
Lipids -> Lipase -> Fatty acids & Glycerol
