food and energy test

Question 1

Obesity

Answer 1

this is being severely overweight and is caused by having a higher energy intake that the energy used in exercise etcetera

Question 2

heart disease and stroke

Answer 2

cholesterol and other fatty substances build up in the walls of the arteries. This stops blood reaching cells in heart or the brain, cells do not get glucose and oxygen so the cells cant respire and the cells die

Question 3

diabetes

Answer 3

type 2 diabetes occurs when the body suffers sugar overload and insulin stops being effective in controlling sugar levels

Question 4

Biological molecules

Answer 4

food we eat is made up of biological molecules of which there are 3 important groups; carbohydrates, proteins and fats

all contain hydrogen, carbon and oxygen all proteins also contain the element nitrogen

Question 5

carbohydrates

Answer 5

sugars such as lactose and glucose
complex carbs such as cellulose, starch and glycogen
these sugars taste sweet and are soluble in water. more complex carbs of long chains of sugar are joined together

Question 6

starch

Answer 6

broken down to glucose during digestion. we store carbohydrate as glycogen and this can be broken down to glucose when our sugar reserves are low

Question 7

cellulose

Answer 7

found in plant cell walls and cannot be digested by humans but still plays an important role in the diet as fiber, adding bulk to diet and helping muscles of intestines push food along

Question 8

sugar and starch

Answer 8

fast acting energy source
starch is a slow release source

Question 9

Protein

Answer 9

building blocks for growth and repair of cells but can be used for energy when carbohydrate and fat reserves are low
protein are complex molecules consisting of long chains of amino acids
there are 20 different amino acids which can join in different sequences and produce many thousands of different proteins

when proteins we eat are digested, amino acids are absorbed into blood and in our body cells, are reassembled into different proteins the body needs

Question 10

fat

Answer 10

known as lipids. fat is an excellent energy store, providing double the energy per gram of carbohydrate and protein. fat insulates body and protects internal organs

when fat is digested each molecule is broken down into one molecule of glycerol and three molecules of fatty acids

Question 11

testing for starch

Answer 11

half fill a test tube with starch solution
add 2 drops of iodine
the solution will go form yellow- brown to blue black

Question 12

testing for sugar

Answer 12

half fill a test tube with glucose
add a few drop of benedicts solution
carefully heat the test tube in a water bath
the solution will go form blue to brick red precipitate

Question 13

testing for protein

Answer 13

half fill a test tube with protein solution
add s few drops of biuret (sodium hydroxide then copper sulfate)
the color will go from pale blue to purple

Question 14

testing for fats

Answer 14

fats will not dissolve in water but they will dissolve in alcohol. If a solution of fat in alcohol is added to water, the fat forms tiny globules which float in the water.
called an emulsion
the globules of fat make the water look milky

Question 15

the energy released by a food sample is measured in joules(J) and can be calculated using the following equation

Answer 15

energy released in joules = mass of water multiplied by rise in temperature multiplied by 4.2

Question 16

necessary to calculate energy released by each gram of food burned. done by dividing energy released by the mass of the food burned

Answer 16

energy released ( J/g) = energy released by food sample divided by mass of food sample

this can be converted to kilojoules by dividing by 1000

Question 17

Method

Answer 17

using a measuring cylinder add exactly 20 cm of water to a boiling tube, clamped in a retort stand as shown in the diagram
using a thermometer, take initial temperature of water and record in your table of results.
weigh approximately half a potato crisp and record mass
secure crisp on a mounted needle
light food in a Bunsen burner flame and quickly hold it under the boiling tube of water
keep burning crisp under boiling tube until it is completely burned. If necessary, relight and replace under the boiling tube
record maximum temp of water after crisps has burned.
repeat 1 to 7 with two more samples of the same type of crisp
record the results in a table

Question 18

3 variables you should keep the same each time you test a food using apparatus used above, to give valid results

Answer 18

same distance between burning food and test tube
same amount of water
same flame when lighting crisp