Food and digestion - Detalles

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Iron is needed to produce haemoglobin - for the transportation of oxygen. Sources: red meat, nuts and liver. Iron deficiency, anaemia, causes people to become tired/ weak because blood doesn't transport enough oxygen.

Why do we need the mineral iron ?

Calcium is needed to maintain healthy bones and teeth. It is needed for normal muscle contraction and blood clotting. Sources: cheese, eggs and milk and green veg. Calcium deficiency leads to weak bones, muscle spasms and poor clotting.

Why do we need the mineral calcium ?

Vitamin A is needed for good vision in the dark. Sources: dairy products - milk. Vitamin A deficiency leads to night blindness.

Why do we need Vitamin A?

VD is needed to maintain healthy bones/teeth. Sources : exposure to sunlight, oily fish,eggs and margarine. Vitamin D deficiency leads to rickets.

Why do we need Vitamin D?

Is needed to make fibres of a material called connective tissue. It is also needed to help heal wounds. Sources : citrus fruits. VC deficiency leads to scurvy - wounds don't heal bleeding/ swelling of gums.

Why do we need Vitamin C ?

Lack of VB1 result in weakening of the muscles and paralysis - beri-beri. This compound is needed for cell respiration.

Why do we need Vitamin B1?

Sources include, whole grains and veg. Dietary fibre prevents bowel cancer/constipation. Dietary fibre provides bulk(roughage) for the gut to push food against in the small intestine.

What are the sources and functions of dietary fibre?

Not all the heat energy will heat up the water - some will heat up the air around. There could be incomplete burning of the food sample. Heat energy could be lost whilst getting food to light and moving to hold under the boiling tube does not go towards heating up the water.

How can the 'energy content of food' experiment be improved - list the problems.

Measure 20cm of water and pour into the boiling tube. Record the start temp and record the mass of the food sample. Set food sample alight and put under the tube to heat up the water. Record final temp and use the equation ( mass of water(20g) x 4.2 x temp increase ALL divided by the mass of food sample) to calculate energy content.

What is the method to measure the energy content of food ?

The distance of the flame from the tube must be the same. The starting temp of the water must be the same. The same volume of water and mass of food.

What are the control variables when measuring the energy content of food ?

Protein: Carbon, hydrogen, oxygen, sulfur and nitrogen. Lipids: Carbon, hydrogen and oxygen. Carbs: Carbon, hydrogen and oxygen.

What are the chemical elements present in Proteins, lipids and carbs.

Carbs: source of energy-cereal,wheat rice, pasta, potatoes,bread. Protein: growth and repair of tissues. Found in meat, fish, eggs, pulses and nuts. Lipids: store of energy/insulation- butter, oil and nuts.

What are the sources and functions of carbohydrates, proteins and lipids?

Add Benedict's solution to the sample solution in a test tube. Heat at 60-70 degrees in a water bath. If it contains a reducing sugar, it will turn from blue to brick red.

Method for testing for reducing sugars?

Add drops of iodine solution to food sample. If starch is contained, the colour will change from yellow-brown to blue-black.

Method for testing for starch?

Add drops of Biuret solution to the food solution. The colour should hange from blue to purple if the solution contains protein.

Method for testing for protein?

Food sample is mixed with 2cm of ethanol and is shaken. The ethanol is added to an equal volume of water. a cloudy emulsion will form if the food sample contains lipids.

Method to test for a lipid ?

Enzymes are proteins -biological catalysts that are specific to one substrate. They can be affected by temp/ph.

What are enzymes?

Starch solution is heated and iodine is added to wells of a spotting tile. Amylase is added to the starch solution and mixed well. Every minute droplets of solution are added to new well. continued until iodine stops turning blue-black. Record the time it stops and repeat the experiment at different temps to see how enzyme activity may decrease/ increase due to temperature.

Describe the effect of temperature practical.

If the ph is too high or low, the bonds that hold the amino acid chains together can be broken. This will change the active site and so the enzyme will become denatured ?

Effect of ph on enzyme activity?

Enzymes will have added kinetic energy and so the molecules will move faster and there will be more successful collisions between the active site and substrate - this is at the optimum temp/ ph where enzyme activity is the quickest. buffer solution keeps the ph the same.

How does the enzyme function at its optimum ph?

Age - energy needs for adults decrease as they age. Activity levels - the more active, the more energy required. Pregnancy - energy is needed to support the growth of the fetus and to support the mass of the baby that will be carried around.

What factors affect the amount of energy a person needs ?

The pancreas secretes carbohydrase, protease and lipase. It also secretes pancreatic juices to create alkaline conditions for the enzymes.

What is the role of the pancreas during digestion?

Bile is made in the liver and stored in the gall bladder. It neutralises hydrochloric acid released from the stomach an creates alkaline conditions for lipase enzymes. It also emulsifies the lipids.

What is Bile ?

The churning action of the stomach converts the food into fluid and so increases the surfaces area for digestion. The stomach also releases hydrochloric acid to kill bacteria

2 important actions the stomach carries out ?

The duodenum is where the food from the stomach finishes being digested by enzymes - secreted from the walls and pancreas.The ileum is the second section where absorption takes place.

Describe and explain the two sections of the small intestine

Peristalsis is the wave-like contractions of the gut which push food through by a series of contractions and relaxations in the small intestine and oesophagus.

What is peristalsis ?

Food is mechanically digested by emulsification, chewing and churning in order to increase the surface area for enzymes to work in.

Why is food partially digested mechanically?

Digestion is the chemical and mechanical breakdown of food. It converts large insoluble molecules into small soluble molecules which can be absorbed into the blood.

What is digestion?

Salivary amylase digests starch into a disaccharide - maltose. This is then further digested by the enzyme maltase into glucose.

Explain how carbohydrase digests starch.

Pepsin is produced in the stomach and trypsin is produced in the pancreas - they digest proteins into amino acids.

Describe the function of porteases.

They digest lipids into fatty acids and glycerol.

What do lipase enzymes do?

Absorption is the movement of food molecules from the digestive system into the blood (glucose and amino acids) and lymph.

What is absorption ?

The ileum is adapted as it is very long and has a highly folded surface with millions of villi. These adaptations massively increase the surface area.

How is the ileum adapted to its function ?

Villi have a large surface area due to folding and microvilli. they have thin walls to provide a short distance for diffusion and active transport and they have a network of capillaries so that glucose and amino acids can easily be transported away from the small intestine into the blood. They also contain a lacteal to transport fatty acids/ glycerol away from the SI in the lymph.

Adaptation of villi.

Animals and fungi store carbs as glycogen and plants store as starch.

How are carbs stored in animals, plants and fungi?

Enzymes work more slowly at lower temps. They have less kinetic energy and so there will be less collisions.

Why would the enzyme not function well at 20 degrees Celsius?

It doesn't function in alkali conditions and becomes denatured.

Why would the enzyme not break down protease in an alkali ph?

To kill bacteria - stop food poisoning!

Why is hydrochloric acid secreted by the stomach?

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