Energy In Cells - Diet and Digestion

Question 1

Which 3 biological molecules does our body require as nutrients?

Answer 1

• carbohydrates
• proteins
• lipids (fats)

Question 2

What food sources can you get carbohydrates from?

Answer 2

Bread, potatoes, rice, cereals and fruit.

Question 3

What is the function of carbohydrates?

Answer 3

Fuel for respiration.

Question 4

Which food sources can you get proteins for?

Answer 4

Meat, eggs, fish, quinoa, quorn

Question 5

What is the function of proteins?

Answer 5

• growth and repair of cells and tissues
• fuel for respiration

Question 6

Which food sources can you get lipids (fats) from?

Answer 6

Butter, cooking oil, cream, avocados

Question 7

What is the function of lipids?

Answer 7

• store of energy
• thermal and electrical insulation
• fuel for respiration

Question 8

What is the most common substrate?

Answer 8

The carbohydrate glucose.

Question 9

Where can glucose be found in plants and animals?

Answer 9

• starch in plants
• glycogen in animals

Question 10

How is the energy used in our bodies?

Answer 10

Around 70% of the energy we use every day is used just to keep our body running. We use energy to keep our heart beating, transport molecules (active transport) and repair our cells . The remaining 30% can be used for extra work and activities e.g. walking, running, talking

Question 11

Order the people who would need the most to least energy:
- pregnant woman
- builder
- school boy (15 yr old)
- breast feeding woman
- new born baby
- male office worker
- school girl (15 yr old)

Answer 11

1. Builder
2. Breastfeeding woman
3. Pregnant woman
4. School boy
5. School girl
6. Male office worker
7. New born baby

Question 12

What is energy measured in?

Answer 12

Kilojoules (kJ)

Question 13

How can you find the amount of energy in food?

Answer 13

By burning it and seeing how much heat energy is released.

Question 14

Describe the method of how to measure the amount of energy in food.

Answer 14

To investigate the energy content of food, you can burn a known mass of the food and use the thermal energy released to heat the water. Begin by measuring 25cm^3 of water, pouring it into the boiling tube and recording the starting temperature. The food sample is lit over a Bunsen, and then held under a boiling tube of water to heat it. If the food stops burning, it needs to be relit until it will no longer burn. Measure the finishing temperature of the water and calculate the temperature change. Use this formula to calculate the energy content.
Temperature change * volume of water * 4.2 / Mass of food * 1000

Question 15

What is the formula to calculate energy content?

Answer 15

Energy content (kj/g^-1)
Temperature change * volume of water * 4.2 / Mass of food * 1000

Question 16

Which vitamins and minerals does our body require?

Answer 16

• iron
• calcium
• vitamin A
• vitamin C
• vitamin D

Question 17

What is the function of iron, which food sources can you get iron from and what is the name of the deficiency disease of iron?

Answer 17

• function : forms the part of haemoglobin which binds to oxygen
• food sources : red meat, liver and spinach
• deficiency disease: anaemia

Question 18

What is the function of calcium, which food sources can you get calcium from and what is the name of the deficiency disease of calcium?

Answer 18

• function: needed to form bones and teeth
• food sources: milk and dairy products, fish, fresh vegetables
• deficiency disease: rickets

Question 19

What is the use in the body of vitamin A, which food sources can you get vitamin A from and what is the name of the effect of vitamin A deficiency?

Answer 19

• use in body: making a chemical in the retina and protects the surface of the eye
• food sources: fish liver oil, liver, butter, carrots
• effect of deficiency: night blindness and damaged cornea

Question 20

What is the use in the body of vitamin C, which food sources can you get vitamin C from and what is the name of the effect of vitamin C deficiency?

Answer 20

• use in the body: needed for cells and tissues to stick together
• food sources: fresh fruit and vegetables
• effect of deficiency: scurvy

Question 21

What is the use in the body of vitamin D, which food sources can you get vitamin D from and what is the name of the effect of vitamin D deficiency?

Answer 21

• use in body: needed to absorb calcium and phosphate ions from food
• food sources: dairy products, oily fish
• effect of deficiency: rickets, caused by weak bones

Question 22

What else does the body need?

Answer 22

Water and fibre

Question 23

Why do you need sufficient water and dietary fibre?

Answer 23

• sufficient water: water is an essential solvent (allows things to be dissolved into it), it is used to transport the components of blood and is crucial for temperature regulation. e.g. sweating
• dietary fibre: fibre is a plant material that you cannot digest, it is mainly a chemical called cellulose (found in the cell wall of plants). Fibre helps the movement of food through the intestine, preventing constipation and bowel cancer.

Question 24

What are good sources of fibre?

Answer 24

• fruit
• vegetables
• grains (wheat, oats, etc)
  because all contain cellulose

Question 25

What is the alimentary canal?

Answer 25

The alimentary canal forms a tube through the centre of the body- like a bagel. Food is ingested, digested, absorbed and egressed from this canal for the purpose that the food can be assimilated.

Question 26

Label the digestive system.

Question 27

What are the stages of digestion?

Answer 27

- ingestion: taking food in through the mouth and swallowing - digestion: breaking down large insoluble molecules in food into smaller pieces (physical digestion) and smaller, soluble molecules (chemical digestion) - absorption: movement of small soluble molecules out of the gut and into the blood by diffusion and active transport - egestion: passing out undigested food through the anus - assimilation: building larger biological molecules from small soluble molecules in all cells

Question 28

What is the first structure in the alimentary canal and what happens there?

Answer 28

- the first structure is the mouth - where ingestion takes place - digestion, the breakdown of large insoluble molecules into small soluble molecules, also begins here - two types of digestion takes place here : chemical and mechanical - mechanical digestion: food is broken up into smaller pieces in the mouth by chewing. This increases the SA for enzymes and also prevents discomfort when swallowing - chemical digestion: saliva is released into the mouth by the salivary glands, which makes food easier to swallow and contains the enzyme amylase. Amylase breaks down the starch to maltose. - amylase works best at neutral pH, so denatures when reaches the stomach and stops working.

Question 29

Describe what happens whilst swallowing.

Answer 29

Before swallowing the food is shaped into a ball by the tongue and moved towards the back of the mouth. The ball is called a bolus. There is a flap called the epiglottis which blocks the food from entering the trachea.

Question 30

Describe what happens in the oesophagus.

Answer 30

The oesophagus is a long tube which connects the mouth to the stomach and bolus is pushed down it by peristalsis (contraction and relaxation of muscle). Food is also moved along by peristalsis in the small and large intestines.

Question 31

What happens in the stomach?

Answer 31

The gastric glands in the stomach secrete the enzyme pepsin, which begins the process of digesting proteins into peptides(shorter chains of amino acids). The contraction of the stomach wall causes mixing of the contents of the stomach, maximising contact between enzymes and food, Pepsins’ optimum conditions are an acidic pH, due to the release of hydrochloric acid by the gastric glands. It has a v.low pH and would burn through the stomach if it was not covered by a mucus lining. The hydrochloric acid also kills many bacteria and fungi which may be present in the food we eat.

Question 32

What happens in the small intestine?

Answer 32

- digestion and absorption - digestion happens in the first section - duodenum

Question 33

What happens in the duodenum?

Answer 33

- final site of chemical digestion - pancreas makes several enzymes and secretes them into the duodenum: trypsin, amylase and lipase - trypsin : protein to peptide - amylase: starch to maltose - lipase: lipid(fat) to glycerol and fatty acids - duodenum wall contains glands which make enzymes and secrete them into the duodenum: Maltase and peptidase - maltase: maltose to glucose - peptidase: peptide to amino acids - duodenum contains bile

Question 34

What is the function of bile?

Answer 34

- produced by the liver - stored in gall bladder - released into the duodenum through the bile duct - functions: - neutralises the stomach acid because enzymes in the duodenum work best at pH 7-8 - emulsifies lipids- break large droplets into smaller droplets, increasing the SA for lipase to digest the fats

Question 35

What happens in the ileum?

Answer 35

- digestion is over - absorption begins - ileum has many folds and is covered in finger-like projections called villi - it is through these that’s all soluble molecules are absorbed, some are absorbed by diffusion however some such as glucose are also absorbed via active transport which move particles against a concentration gradient using ATP

Question 36

How is the rate of diffusion increased in the ileum?

Answer 36

- large SA: folding of the ileum, villi and microvilli - short diffusion distance: villi walls one cell thick - high concentration gradient: provided by capillary network and lacteals removing absorbed molecules

Question 37

What happens in the large intestine?

Answer 37

- broken down into two sections: colon and rectum - colon: site for all reabsorption of water - faeces: stored in rectum and egested from anus - assimilation then takes place in all cells using the food molecules absorbed to build more complex molecules such as proteins

Question 38

What are the three enzyme groups? Name the biological molecule that they act upon and the end products.

Answer 38

- enzyme group: carbohydrases , acts upon carbohydrates, end products: smaller carb molecules, e.g glucose - enzyme group: proteases, acts upon proteins, end products : amino acids - enzyme group: lipases, acts upon lipids, end products: glycerol and 3 fatty acids

Question 39

Name all of the enzymes, the part of the AC they are in, the source of the enzyme and the digestive action.

Answer 39

- salivary amylase : mouth : salivary glands : starch to maltose - pepsin : stomach : gastric glands in stomach wall : proteins to peptides - amylase : duodenum : pancreas : starch to maltose - lipase: duodenum : pancreas : lipids to fatty acids + glycerol - trypsin: duodenum : pancreas : proteins to peptides - maltase: duodenum : lining of duodenum : maltose to glucose - peptidase: duodenum : lining of duodenum : peptides to amino acids

Question 40

How can you speed up the rate of enzyme controlled reactions?

Answer 40

Provide more enzymes / more substrates

Question 41

Why does temperature increase the rate of reaction?

Answer 41

As temperature increases the rate of reaction increases - this occurs until the optimum (best) temperature is reached. This is because the higher temperature gives the enzymes and substrates more kinetic energy. They move faster and collide more often, so you get more reactions per second. Above the optimum temperature the heat breaks the forces holding proteins in the correct shape. The shape of the enzyme (a protein) therefore changes - this means the active site changes shape so that it is no longer complementary to the substrate. The substrate cannot bind to the active site and the reaction cannot occur. We say the enzyme has been denatured.

Question 42

why does pH increase the rate of reaction?

Answer 42

The pH inside cells is neutral (pH 7) and most enzymes work best at this pH. Others work at different pH values in specialised parts of the body. If the pH of the environment changes it can affect the shape of the enzyme. The active site changes shape so it is no longer complementary to the substrate. The enzyme is denatured and the reaction can no longer occur.

Question 43

What is an experiment to find the effect of temperature on enzymes?

Answer 43

Amylase digests starch. Mix 10cm3 of 10% starch suspension and 5cm3 of 5% amylase in a boiling tube and heat in a water bath. Amylase digests starch. Mix 10cm3 of 10% starch suspension and 5cm3 of 5% amylase in a boiling tube and heat in a water bath. hen digestion is complete and no starch is present, iodine solution will stay orange (rather than turning blue black). Repeat this using water baths of different temperature.

Question 44

What is an experiment to find out the effect of pH on enzymes?

Answer 44

You can use any enzyme to investigate the effect of pH. Potato contains the enzyme catalase, which breaks down hydrogen perioxide, forming water and oxygen gas. Add 10 potato disks (1cm thick, cut with a cork borer) to 20cm3 catalase and measure the volume of gas produced in 5 minutes. The pH can be altered by adding different volumes of a weak alkali (e.g. sodium carbonate) or a weak acid (e.g. ethanoic acid) – use universal indicator paper to determine the pH of the solution each time.