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Flashcards in Food and Digestion Deck (18):

Identify the chemical elements present in carbohydrates, proteins and lipids

Carbohydrates: Carbon, hydrogen oxygen

Protein: Carbon, hydrogen, oxygen, nitrogen, (sulfur)

Lipids: Carbon, hydrogen, oxygen


Describe the structure of carbohydrates, proteins and lipids

Carbohydrates: Smaller units (e.g. glucose) join together to make complex carbohydrates (e.g. starch)
Monomer unit: glucose
Disaccharides: sucrose, maltose
Polysaccharides: starch, cellulose, glycogen

Protein: Made up of long chains of amino acids

Lipids: Built from fatty acids and glycerol


Describe the tests for glucose and starch

Glucose: small spatula measure of glucose is placed in a test tube and a little water added. Test tube is shaken to dissolve the glucose. Several drops of Benedicts solution are added to the tube, enough to colours the mixture blue. Water bath is prepared by half-filling a beaker with water and heating it on a tripod and gauze. Test tube is placed in the. beaker and the water allowed to boil. After a few seconds the clear blue colour gradually changes form a brick red precipitate of copper oxide.

Starch: Starch powder is placed on a spotting tile. A drop of dilute iodine solution is added to the starch. The iodine reacts with the starch, forming a very dark blue colour.


What are the role of enzymes?

Enzymes are biological catalysts: increases the rate of reaction without being used up.

Each enzyme has an active site that’s a specific shape; can catalyse only one reaction


How does temperature affect the functioning of enzymes?

Heat affects enzyme activity: the more heat, the more energy the enzymes have. Makes them more likely to collide successfully and bind.

However, too much heat will start to denature the enzyme; active site changes shape and is no longer complementary to the substrate.


How is the functioning of enzymes affected by changes in pH?

Change in PH can denature enzymes by breaking the bonds that hold the structure in place. So the active site no longer fits with the the substrate it is meant to be breaking down. The PH at which this happens is different for different enzymes, but generally an extreme PH will denature any enzyme.


Describe experiments to investigate how enzyme activity can be affected by changes in temperature.

1. Set up a test tube in a water bath, connected to a delivery tube which is placed underneath a measuring cylinder (which is in water)
2. Put the enzyme catalase into a test tube with hydrogen peroxide solution
3. This will catalyse the breakdown of hydrogen peroxide into water and oxygen
4. Change the temperature in the water bath
5. Measure how much oxygen is being given off in one minute (use a stop watch)


Why do plants require mineral ions?

Contains nitrogen to make amino acids and proteins
Needed for cell growth
Not enough; stunted growth, yellow older leaves

Contains phosphorus to make DNA and cell membranes
Needed for respiration and growth
Not enough; poor root growth, purple older leaves

To help enzymes needed for photosynthesis and respiration
Not enough; poor flower/fruit growth, discoloured leaves

Makes chlorophyll
Needed for photosynthesis
Not enough; yellow leaves


Describe a balanced diet

A balanced diet should include appropriate proportions of carbohydrate, protein, lipid, vitamins, minerals, water and dietary fibre


Identify sources and describe functions of components in a balanced diet

Carbohydrates– Provides energy
Found in: pasta, rice, sugar

Lipids (fats and oil)- Provides energy, acts as an energy store, provides insulation
Found in: butter, oily fish

Proteins– Needed for growth and repair of tissue, provides energy in emergencies
Found in: meat, fish, egg

Vitamins– Stops deficiency diseases:

Vitamin A– Helps maintain good vision and keeps skin/hair healthy (liver)
Vitamin C– Needed to prevent scurvy and for healthy gums (oranges)
Vitamin D– Needed for calcium absorption (eggs)
Mineral ions:

Calcium– Needed to maintain healthy bones and teeth (milk/cheese)
Iron– Needed to make haemoglobin for healthy blood (red meat)
Water– Need a constant supply to replace water loss through urinating, breathing and sweating
Found in: food and drink

Dietary Fibre– Aids movement of food through the gut
Found in: wholemeal bread


How do energy requirements vary with activity levels, age and pregnancy?

More active people need extra energy due to the increased muscle activity.
Teenagers need more energy than adults as they need energy to grow and they are generally more active.
Pregnant need more energy than other women as they have to provide energy for their babies to develop.


Describe the structures of the human alimentary canal and describe the functions of the mouth, oesophagus, stomach, small intestine, large intestine and pancreas

Mouth– Contains salivary glands to produce amylase in saliva
Teeth break down food mechanically

Oesophagus– Muscular tube connecting mouth and stomach

Stomach– Muscular walls pummel food, produces pepsin , produces hydrochloric acid; to kill bacteria, give the right pH (pH2) for protease to work and protects us from food poisoning..

Pancreas– Produces protease, amylase, lipase which is released into the small intestine

Liver– Where bile is produced

Gall bladder– Where bile is stored

Duodenum – use protease, amylase, lipase secreted from the pancreas to break down food.
ileum - digested food is absorbed

Large intestine– Where excess water is absorbed from food and faeces is stored

Anus– Where faeces come out


Describe the processes of ingestion, digestion, absorption, assimilation and egestion

Ingestion– putting food/drink into your mouth.
Digestion– Break down of large insoluble molecules, into small soluble ones. There’s mechanical (teeth and stomach muscles) and chemical digestion(enzymes and bile).
Absorption– Moves molecules through walls of the intestines, into the blood.
Assimilation– After absorption, digested molecules move into body cells. Digested molecules become part of the cells.
Egestion– Undigested stuff form faeces; gets rid of them by the anus.


Explain how and why food is moved through the gut by peristalsis

Waves of muscular contraction push food along the gut, when the circular muscles contract and the longitudinal muscles relax the gut is made narrower. When the opposite happens its made wider.


What are the roles of digestive enzymes?

Big molecules (starch, proteins, fats) are too big to pass through the walls of the digestive system; they’re insoluble.
Smaller molecules (sugars, amino acids, glycerol and fatty acids) pass easily; they’re soluble.

Digestive enzymes break down big molecules into smaller ones:

Amylase; breaks down starch –> maltose
Maltase; breaks down maltose –> glucose
Protease; breaks down protein –> amino acids
Lipase; breaks down lipid –> glycerol and fatty acids


What is bile?

Bile is produced in the liver, and stored in the gall bladder, then released into the small intestine.

Bile is alkaline; neutralises acid, making conditions alkali
These are the conditions that the enzymes work best in the small intestine (the hydrochloric acid in the stomach makes pH too acidic for enzymes in the small intestine to work properly)
Bile emulsifies fats; breaks fat into tiny droplets, so there’s a bigger SA of fat for lipase to work on (making digestion faster).


Describe the structure of a villus and explain how this helps absorption of the products of digestion in the small intestine

Millions of villi give an enormous surface area in contact with digested roofs. Each villus has hundreds of microvilli which increase the surface area for absorption even more.
Lacteral transports fatty acids and glycerol away form the small intestine. It also forms part of the body lymphatic system, which transports lymph, this drains into the blood system.


Describe an experiment to investigate the energy content in a food sample.

Mass of sample is found by weighing it on a balance. 20cm3 of water is placed in a boiling tube and the tube supported in a clamp on a stand. Temperature of water is measured. Food is speared on the end of a needle and held in a Bunsen burner until it catches fire. When the food is alight, the needle is used to hold the burning food underneath the boiling tube of water so that the flame heats up the water. This is continued until the food can no longer burn.

Ft - ST x 20 x 4.2 / mass