Digestive system - B3

• Tissue - group of cells with similar functions and structures 

• Organs - collections of tissue performing specific functions. 

• Organs turn into organ systems to work together to form organisims. 

Muscular tissues - contract to bring movement

Glandular tissues - secretory cells which release hormones and enzymes

Epithelial tissues - covers outside of body and organs 

• Digestive system - an organ system where several organs work together to digest and absorb food. 

• Pancreas and Salivary glands - produce enzymes in digestive juices.
• Stomach - digestion occours
• liver - produces bile 
• small intestine - digestion and absorption of soluoble food due to villi 
• large intestine - water is absorbed from undigested food - faeces
• Mouth - Breaks down food, produces saliva and amalayse
• Stomach - breaks down food, acid and muscle churn it up. Produces enzymes that work in hydrochlotic acid
• Liver - Nuetralises food, releases bile which emulsifies fats
• Small intestine - Absorbs foods nutrients, villi
• Large intestine - Absorbs water

• Carbohydrates - sugars 

• Simple sugars - carbohydrates that ontain 1 or 2 sugar units- Benedicts soloution red when heated. 

• Complex Carbohydrates - long chains of simple sugar units. Starch turns yellow to red iodine soloution blue - black. 

• Lipids - 3 molocules of fatty acids bonded to glycerol. To test it use ethanol and see if it goes a cloudy white. 
• protein - chains of amino acids. Biuret reagent turns from blue to purple. 

• Catalysts = speed up chemcical reactions 

• Enzymes = biological catalysts. They speed up reactions in living organisms. due to the lock and key theory... 

The substrate fits into the active site, once in place they bind together and the reaction takes place quickly. Products are released on the surface

• Enzymes are proteins. Amino acids - form the active site, matches the shape of a substrate molecule. 

• Substrate binds to active site and reaction is catalysed by enzyme 

• Metabolism - sum of all reactions in cell or body. 

• Affected by temperature and PH. 

• High temperature - denature enzyme at 40 degrees, active site changes shape. 

• PH - can affect shape of active site, the shape can be lost and the enzyme is no longer a catalyst! sobs :(

• Digestion - breakdown of large molecules into smaller substances. Can then be absorbed into blood accross wall of small intestine. 

• Digestive enzymes - specialised cells in glands and lining of digestive system. 

• Carbohydrates - amalayse, catalyse the breakdown of carbs to simple sugars 

• Proteases - catalyse proteins to amino acids 

• Lipases - catalyse lipids to fatty acids and glycerol. 

Digestive juices coat the food

Stomach acid: 

Between 20 and 100ml of hydrochloric acid - pH 1.5 to 3.5 

Kills most bacteria 

Provides ideal condition for protease, pepsin.

Stomach wall is covered in mucus to stop acid attacking it. If there wasnt mucus you would get a gastric olser.

INSERT PHOTO FROM BOOK

Bile: 

Produced in liver, greenish liquid

stored in gaul bladder until needed

Nuetralsies stomach acid as it is alkali, provides ideal conditions for small intestine enzymes to work. 

emulsifies lipids, increasing surface area allowing them to be digested easily by lipases. 

emulsifies = water and fats mix

Increasing the surface area: 

Allows as many nutrients as possible to be absorbed, to keep us and our cells healthy

Villi - 

Finger like projections in the small intestine

increase surface area of small intestine from 0.5m^2 to 200m^2