B3 organisation and the digestive system

Students should be able to use the ‘lock and key theory’ as a simplified model to explain enzyme action. Students should be able to recall the sites of production and the action of amylase, proteases and lipases. Students should be able to understand simple word equations but no chemical symbol equations are required. Students should be able to relate knowledge of enzymes to Metabolism. Students should be able to describe the nature of enzyme molecules and relate their activity to temperature and pH changes.

the human digestive system

The digestive system is an example of an organ system in which several organs work together to digest and absorb food.

when food is eaten it is insoluble. Digestion is the breakdown of food into smaller pieces that can diffuse into the blood.

during digestion, glucose is extracted from the food and diffuses into the blood to be transported to the cells

role of digestive system (2)

Absorption - process of absorbing these small food molecules into the body

Digestion - process of breaking down large food molecules into smaller molecules 

Enzymes

Enzymes catalyse specific reactions in living organisms due to the shape of their active site.

Students should be able to understand simple word equations but no chemical symbol equations are required. Digestive enzymes convert food into small soluble molecules that can be absorbed into the bloodstream.

explain the following enzymes ;carbohydrase , lipase and protease

Carbohydrases break down carbohydrates into simple sugars. Amylase is a carbohydrase which breaks down starch.

Proteases break down proteins into amino acids.

Lipases break down lipids (fats) into 1 molecule of glycerol and 3 molecules of fatty acids.

The products of digestion are used to build new carbohydrates, lipids and proteins. Some glucose is used in respiration.

bile

where?

Bile is made in the liver and stored in the gall bladder.

what?

bile is an emulsifier

It is alkaline to neutralise hydrochloric acid from the stomach. It also emulsifies fat to form small droplets which increases the surface area. It’s not an enzyme

why?

The alkaline conditions and large surface area increase the rate of fat breakdown by lipase into small droplets. It also neutralises the HCL in the stomach so the enzymes in the stomach work at an optimum rate

levels of organisation

cells: smallest unit of an organism aka the building clocks

tissues: a group of cells specialised to form a particular function

organs:a group of simalar tissues working together to perform a particular function

organ systems:a group of organs working together to perform a particular fuction

organisms:a group of organ systems working together to keep the organism alive and healthy

salivary glands /mouth

mouth: mechanical digestion which breaks down food into smaller pieces

saliva is a lubricant that makes it easier to swallow food.

saliva has an enzyme called amalyse that breaks down starch into simple sugars. once food enters the mouth chemical breakdown begins and increase SA:V

oesophagus

what? thin tube connected to the mouth. it helps move food quickly and easily to your stomach. it contracts which pushes the food down the stomach

stomach

• located between the oesophagus and the small intestine

• releases proteases which break down protein

• stomach acid(hydrochloric acid) has a PH of 2-3

• the acid destroys athogens and provides the ideal coniditions for proteases to digest proteins

• also mechanically churns the food in the stomach

smooth muscle tissue in the stomach

contract to churn the contents of the stomach

glandular tissue in the stomach

a group of cells that secrete chemicals like enzymes and horemone

epithelial tissue in the stomach

covers the outside of the stomach so it doesnt get corroded by the hydrochloric acid

liver

• makes bile which emulsifies fats and helps break them down

• once made its stored in the gall bladder and then releases the bile in the small intestine

• example of mechanical digestion

• useless amino acids get broken down and turned into urea

gall bladder

stores bile to be released in the duodenum

pancrease

• produces all 3 types of enzyme

• releases the enzymes in an alkaline solution in the duodenum which raises the PH

• food does not pass through the pancreas it just releases enzymes into the small intestine

small intestine

• called smol but is the longest its just narrow which is why its called smol

• absorbs the products of digestion into the blood where it is transprted to the area it is needed

• first sections is called duodenum

• in the duodenum the PH is alkaline 8-9

• ileum is the second section

• food molecules are absorbed

• lined with vili to increase the surface area to volume ratio

• so absorption happens faster

large intestine

• water gets absorbed and the rest in the colon becomes poopoo

• poopoo gets stored in the rectum before it gets pooped out

• full of indegestible fibre and water that enters from the small intestine

• absorbs salts

villi in the small intestine

projections that increase the surface area to volume ratio

this allow more digested food to be absorbed into your blood

villus has a prficient blood suplly from capillarie swhich moves food to the other parts of the body

peristalsis in small intestine and oesophagous

little rings of muscle yjay contract and squash lumps of food called boluses. they create a rhythemical contraction behind boluses to push food

anus

opening at the end of the digestive system

• removes solid waste

• aka defacation

Digestion: Basics

The digestive system is an example of an organ system in which several organs work together to digest and absorb food Digestion is a process in which relatively large, insoluble molecules in food (such as starch, and proteins) are broken down into smaller, soluble molecules that can be absorbed into the bloodstream and delivered to cells in the body These small soluble molecules (such as glucose and amino acids) are used either to provide cells with energy (via respiration), or with materials with which they can build other molecules to grow, repair and function

food tests

photo

Testing for starch: method

1. Using a pipette, add two drops of solution A into a well of a spotting tile

2. Add two drops of iodine solution to this and record the colour observed.

3. Repeat this for the other four solutions

4. If starch is present, a blue-black colour will be produced. Use your results to determine which tube contained starch.

Testing for glucose: method

1. Add 1 cm° of solution A to a boiling tube

2. Add 10 drops or 1 cm' of Benedict's reagent to this.

3. Place in a hot water bath (around 80°C) and leave for 5 minutes

4. Record the colour observed in your table.

5. Repeat this for the other four solutions.

6. If glucose is present, a brick-red precipitate will form. If it is not present, the solution will remain the blue of the Benedict's reagent. Use your results to determine which tube contained glucose.

Testing for protein: method

1. Add 2 cm° of solution A to a test tube.

2. Add 2cm° of biuret solution to this.

3. Record the colour change in your table.

4. Repeat this for the other four solutions.

5. If protein is present, the solution will turn a light lilac purple colour. If it is not present, the solution will be a cloudy blue. Use your results to determine which tube contained protein.

Testing for oil lipids: method

1. Half fill a test tube with water.

2. Add one drop of solution A to this.

3. Move the test tube from side to side to mix thoroughly.

4. Place your thumb over the top of the test tube and shake.

5. Repeat this for the other four solutions.

6. As oils do not dissolve in water, an emulsion will form. This will make the water go cloudy if lipids are present.

lock and key theory of enzymes

what?

The ‘lock and key theory’ is one simplified model that is used to explain enzyme action The enzyme is like a lock, with the substrate(s)the keys that can go into the active site of the enzyme with the two being a perfect fit

ezymes are specific to the substrates because of their specific shapes.

how?

the part that attaches to the substrate is called the active sight. they collide and become attached to the active site. then the enzyme breaks the bonds holding them together

why?

to break down food molecules into parts that are useable for respiration or making into other molecules

how the conditions an enzyme affect metabolism

• enzymes work at optimum temperatures and PH

• these conditions e.g ph 3 in the stomach are the conditions where they are the most effective

• enzyme reactivity is slower and less effective if these ideal conditions change

denaturing enzymes

anzyme work at an optimum and so once the conditions become extreme they start to denature and change shape. When they change shape the enzyme is no longer specific to the substrate

synthesis enzymes

create complex molecules from simpler enzymes

e.g protein synthesis of amino acids to make muscle

what happens in enzymes

Enzymes and substrates move aboutrandomly in solution 2. When an enzyme and its complementary substrate randomly collide – with the substrate fitting into the active site ofthe enzyme – an enzyme-substrate complex forms, and the reaction occurs 3. A product(or products)forms from the substrate(s) which are then released from the active site. The enzyme is unchanged and will go on to catalyse further reactions

induced fit model

Another modelthat explains enzyme activity is the ‘induced-fit theory’ In reality when a substrate(s) binds to the active site ofthe enzyme,the active site and substrate change shape slightly to fit more perfectly together This makes it easierfor bonds within the substrate to break and new bonds to form, producing product(s)

explain theadaptations of vili

There are many villi, which gives them a large total surface area over which to absorb nutrients

They have a single layer of cells on their surface, which means nutrients only have to diffuse a short distance.

They have a good blood supply which maintains a strong concentration gradient between the lumen and the blood 

The cells lining the villi have microvilli on their surface, which further increases the surface area

function of liver

The liver is a critical organ in the human body that is responsible for an array of functions that help support metabolism, immunity, digestion, detoxification, vitamin storage