iheartbio.weebly.comiheartbio.weebly.com/uploads/1/3/4/2/13422000/new_-_c... · Web viewc) Biological Molecules Identify the chemical elements present in carbohydrates, proteins and

2.11 Internal Assessment9/22/10 5:50 PM

Objectives:

c) Biological Molecules

2.5 Identify the chemical elements present in carbohydrates, proteins and lipids (fats and oils).

2.6 Describe the structure of carbohydrates, proteins and lipids as large molecules made up from smaller basic units: starch and glycogen from simple sugars; proteins from amino acids; lipids from fatty acids and glycerol.

2.7 Describe the tests for glucose and starch

2.8 Understand the role of enzymes as biological catalysts in metabolic reactions.

2.9 Understand how the functioning of enzymes can be affected by changes in temperature, including changes due to change in active site

2.10 Understand how the functioning of enzymes can be affected by changes in active site caused by changes in pH

2.11 Describe how to carry out simple controlled experiments to illustrate how enzyme activity can be affected by changes in temperature.

c. Biological Molecules9/22/10 5:50 PM

2.5 Recall the chemical elements present in carbohydrates, proteins and lipids (fats and oils).

Ref:

Green numbers – Cambridge Textbook

Orange numbers – Edexcel Textbook

Carbohydrates

Pg. 174.4 Starch and Sugars are Carbohydrates

Pg. 37

Proteins

Pg. 194.9 Proteins are chains of amino acids

Pg. 39

Lipids

Pg. 204.11 Fats are made of glycerol and fatty acids

Pg. 38

Complete the table:

Compound

Elements Present

Carbohydrate

Protein

Lipid

2.5 Elements in Biological Molecules9/22/10 5:50 PM

2.6 Describe the structure of carbohydrates, proteins and lipids as large molecules made up from smaller basic units: starch and glycogen from simple sugars; proteins from amino acids; lipids from fatty acids and glycerol.

Ref:



Carbohydrates

Pg. 174.5 Glucose is a simple sugar

Sucrose is a complex sugar

Starch is a polysaccharide

Pg 38

Proteins

Pg. 194.9Proteins are chains of amino acids

Pg 39

Lipids

Pg. 204.11Fats are made of glycerol and fatty acids

Pg 38

Complete the table:

Compound

Monomers

Polymers

Carbohydrate

Protein

Lipid

Carbohydrates

Notes:

This symbol usually represents a single glucose molecule.

When two glucose molecules join together they form a disaccharde.

Carbohydrates are polymers – they are formed from lots of single glucose molecules joined together. Both starch and glycogen are formed from long chains of glucose molecules.

Proteins

Proteins are complex molecules that are main from 20 basic monomers called amino acids.

The order in which the amino acids are arrange determines the function of the protein.

Each of these symbols represents a different amino acid ( I have only used 6 instead of the 20 that are available):

The number of amino acids and the sequence in which they are arranged varies between different proteins.

Lipids

Lipids are composed of two different monomers called fatty acids and glycerol.

2.6 Structure of Biological Molecules9/22/10 5:50 PM

2.7 Describe the tests for glucose and starch

Ref:



Glucose

Pg. 18Practical 4.1:Testing food for carbohydrates

Pg. 43

Starch

Pg. 18Practical 4.1:Testing food for carbohydrates

Pg. 43

Lipids

Pg. 20Practical 4.3:Testing food for fats

Protein

Pg. 19Practical 4.2:Testing food for Protein

Glucose - Benedict’s Test (learn this test)

Test – Benedict’s Test

Observation = Positive Result

Add 2cm3 of a solution to test.

Add an equal volume of Benedict’s solution. Shake and bring gently to the boil.

The initial blue colouration of the mixture turns green, then yellowish and may finally turn a brick-red.

Starch – Iodine Test (learn this test)

Test – Iodine Test


Add a few drops of iodine to the solution (or food) to test.

The initial yellow/brown colour of the iodine turns blue/ black is starch is present.

Lipids – Emulsion Test (you do not need to learn this test)

Test – Emulsion Test


Add 2cm3 of ethanol to a test-tube containing 2cm3 of oil.

Dissolve the lipid by shaking vigorously. Add an equal volume of cold water.

A cloudy white suspension.

Proteins – Biuret’s Test (you do not need to learn this test)

Test – Biuret’s Test


Add 2cm3 protein solution to a test-tube. Add an equal volume of potassium hydroxide solution and mix.

Add two drops of copper sulphate solution slowly down the side of the test tube.

Then mix.

No heating is required.

A blue ring appears on adding the copper sulphate.

A purple colour develops slowly on mixing.

Practical

You are going to carry out a practical on simple food tests.

Instructions:

You are provided with 4 beakers labelled A, B, C and D.

The beakers contain either glucose, starch, protein or lipid.

Your aim is to carry out simple food tests to determine which beaker is which.

Design

Design a table to record your results.

You may have to carry out more that one test on each beaker.

Questions

1. An investigation was carried out using starch solution and amylase solutions which were kept separately in a water-bath at 20 °C for five minutes. After this time the investigation was started by mixing the solutions as shown in the diagram.

At ten minute intervals one drop of the contents of each test tube was removed and added to one drop of iodine to test for starch.

At ten minute intervals one drop of the contents of each test tube was removed and added to one drop of iodine to test for starch.The results are shown in the table.

a. Why should the starch solution and the amylase solutions be kept separately in the water-bath for five minutes before the investigation begins? (1)

b. What do the results at the start of the investigation show? (1)

c. Explain the results in test-tube A after 20 minutes. (2)

d. Name the substance produced when starch is broken down. (1)

e. Explain the results for test tube B. (2)

f. Explain the results for test tube C. (2)

2. A pupil set up an investigation into the activity of amylase extracted from barley seeds. Starch discs were placed in amylase solution in a test tube and every five minutes one of the discs was removed and tested for the presence of starch, using iodine solution as shown in the diagram.

a. What is produced by the action of amylase on starch. (1)

b. How long does it take for amylase to digest all the starch disc?(1)

c. Explain why the temperature of the amylase in the test tubes was kept at 25°C during the investigation and suggest how this was done. (2)

d. The investigation was extended by repeating the experiment with solutions of amylase extracted from other plants. The results are shown in the table.

Time for amylase to digest starch/min

Potato

Maize

Oats

Pea

25

35

30

20

Suggest two conditions which must be kept constant to ensure a fair comparison. (2)

3. Amylase is a starch digesting enzyme.

The diagram shows an experiment to find the conditions which affect enzyme activity.

a. Give two conditions which affected the rate of enzyme activity. (2)

b. Explain the result obtained for tube C. (2)

c. What change, if any, would there have been in the results obtained for tubes A and D, if they had been left for 30 minutes? (2)

d. In which part of the digestive system is there no amylase activity? (1)

4. The diagram shows a test for the identification of sugars.

a. Name the reagent and identify the final colour. (2)

Reagent ............................................... Final colour ...............................................

b. Carbohydrates are broken down to simple sugars. Name the reagent used to test for simple sugars. (1)

c. The drawing shows apparatus used to carry out food tests.

Describe how the apparatus could be used to test for sugar in a pear.(3)

What colour change would show that sugar is present? (2)

Before ...............................................

After ................................................

2.7 Food Tests9/22/10 5:50 PM

2.8 Understand the role of enzymes as biological catalysts in metabolic reactions.

Ref:



Pg. 123.1 “Enzymes are Biological Catalysts”

3.2“Enzymes change substrates to products”

3.3“Enzymes have active sites”

Pg. 46

Pg. 133.4“All Enzymes have certain properties”

Pg. 4-6

Read each section of the book listed above.

Discuss each section.

Write brief bullet point summary notes on each section.

Enzymes are Biological Catalysts

Catalyst =

Metabolic reactions =

Enzymes =

Examples of Enzymes

………………………… digests starch to ……………………. in the digestive system.

………………………… digests protein to ……………………. in the digestive system.

……………………….. breaks down hydrogen peroxide to …………………….. and …………………….. in liver and potato cells.

Enzymes change substrates to products

Substrate =

Product =

Substrate Product

Substrate

Product

Enzyme

Starch

Water and Oxygen

Lipase

Protein

Enzymes have active sites

Use the information on pg. 12, the words and diagram provided below to explain how enzymes act on food breaking it down into smaller particles. On the diagram label:

Product

Enzyme

Substrate

Enzyme-substrate complex

(1) (2) (3)

All enzymes have certain properties

Below is a list of the properties shared by all enzymes, write down a few bullet points of explanation for each.

Proteins

Catalysts

Denatured in high temperatures

Specific Optimum pH

Specific

Questions

1. Use the words below to correctly fill in the sentence that follows.

LargeSolubleBlood streamBreak-downAbsorbed

Digestion is the ___________________of _________________ , insoluble food pieces into smaller, _____________________ food particles. Large particles cannot enter our ______________________ and so they are broken down into smaller pieces, which can be ______________________ across the intestine wall into the blood.

2. Below are a list of food groups, a list of enzymes and a list of the products of digestion. Draw a line to match up the correct sequence from the food to the enzyme, which acts on it to the products of digestion.

Food GroupEnzymeProducts of Digestion

Carbohydrates¤¤ Protease¤¤ Fatty acids and glycerol

Proteins¤¤ Lipase¤¤ Simple sugars e.g. glucose

Lipids ¤¤ Amylase¤¤ Amino acids

3. In the diagram below, name the product in the first reaction and the food type in the second reaction.

(Product = Food type = )

4. Which type of enzyme is illustrated in the diagram below, explain how you know.

(Enzyme = Explanation = )

5. Bread contains starch, protein and fat. Complete each sentence by choosing the correct words from the box.

amino acidsprotein

fatstarch

fatty acidssugar

Amylase speeds up the digestion of .................................... . The product of this digestion is ............................. . Protease speeds up the digestion of ............................. . The product of this digestion is .............................................. .

6. In an experiment to investigate the effect of pH on enzyme activity, protease was mixed with solutions of different pHs. The mixture was placed in a hole cut in the centre of a dish of protein jelly. When the protease digests the protein jelly a clear zone forms. The appearance of the plates after 24 hours is shown.

a. Measure and record the diameters of the clear zones in a suitable table. (4)

b. At what pH does the protease work best? (1)

c. Suggest a suitable control for this experiment (1)

d. State two factors which must be kept constant throughout this experiment. (2)

7. The graph shows the effect of pH on the reaction rate of three different enzymes.

a. What is the optimum pH for salivary amylase? (1)

b. Suggest how a pH of 9 affects the activity of salivary amylase.(1)

c. Salivary amylase breaks down starch into maltose. Explain why this enzyme will not digest fat. (2)

8. The graph shows the effect of chewing on the amount of starch remaining in the bolus.

a. Give the amount of starch present after 2 minutes. (1)

b. Describe the effect of chewing on the amount of starch remaining in the bolus. (1)

c. Name the enzyme, present in saliva, which brings about this change. (1)

2.8 Enzymes9/22/10 5:50 PM

2.9 Understand how the functioning of enzymes can be affected by changes in temperature

Ref:



Pg. 13-143.5 “Temperature affects enzyme-catalysed reactions”

Pg 4-6

Notes

Use the page references above to jot down some notes on how temperature affects the rate of enzyme controlled reactions.

Questions

1. This student is investigating enzymes.

a. What is the temperature of the water in the beaker? (1)

b. What does an enzyme do? (2)

2. An enzyme is used in a chemical reaction. The graph shows the speed of the reaction at different temperatures.

a. Complete the following sentence in your own words. (1)

At 37 °C the reaction ……………………..

b. Why would this enzyme could work well in the human body? (1)

c. At temperatures much higher than its optimum temperature an enzyme is .................. (1)

3. Enzymes affect certain chemical reactions in living things.

a. What effect do enzymes have on these reactions? (1)

b. Complete the sentence.(1)

When an enzyme affects a chemical reaction it is acting as a biological ..................

4. The graph shows how the rate of an enzyme-catalysed reaction changes with temperature.

Explain why, in terms of particles, the rate of most reactions increases as the temperature is increased. (3)

5. Egg white is a protein. Protease enzymes will digest cubes of boiled egg white.

A student investigated the effect of temperature on the digestion of egg white by protease enzyme solution.

The graph shows the student’s results.

a. Estimate the time it would take to digest the egg white cubes at 8°C. (1)

b. At what temperature does this enzyme work best?(1)

c. Why is the time taken to digest egg white cubes greater at 60°C than at 30°C? (1)

2.9 Effect of temperature on Enzymes9/22/10 5:50 PM

2.10 Understand how the functioning of enzymes can be affected by changed in pH

Ref:

Pg. 143.6 “pH affects enzymes”

Pg. 5

Notes

Use the page references above to jot down some notes on how pH affects the rate of enzyme controlled reactions.

2.10 Effect of pH on Enzyme Activity9/22/10 5:50 PM

2.11 Describe how to carry out simple controlled experiments to illustrate how enzyme activity can be affected by changes in temperature.

There are three sections to writing an Internal Assessment.

The format is the same for each assessment.

Design (D) = 6 marks

Data Collection and Processing (DCP) = 6 marks

Conclusion and Evaluation (CE) = 6 marks

You are going to complete an Internal Assessment which will count along with Test scores towards your grade for reports.

You will be provided with guidelines on how to complete the Design, Data Collection and Processing and Conclusion and Evaluation.

Research topic:

Investigate the effect of temperature on enzyme activity.

A B C

Amylase+ starch

Boiledcooledamylase+ starch

Water+ starch

Key Starch present

Starch absent

Result of starch test

Time/min Test tube A Test tube B Test tube C

0 (start)

10

20

5 mins 10 mins 15 mins 20 mins



Blue/black Purple Yellow

Dimple in spotting tile Starch disc

Iodine solution

Time when disc is taken from dish

Tube A

Tube B

Tube C

Tube D

Left for5 minutesat 20 ºC




Amylase + starch solution Iodine solution

Iodine solution

Iodine solution

Iodine solution

Amylase + starch solution

Boiled amylase + starch solution

Amylase + starch solution+ dilute acid

Colour change to black

No colour change



HeatReagent Final colour

Simple sugar

pH2 Holecontainingmixture

Clearzone

Proteinjelly

pH6 pH8

pH4

Dish

mm

Rate ofreaction(arbitraryunits)

1 2 3 4 5 6 7 8 9

Pepsin Sucrase Salivaryamylase

pH

2.0

1.5

1.0

0.5

0.00 1 2 3 4

Time chewed/minutes

Am

ount

of s

tarc

h/a r

bitr a

ry u

nits

Speedof

reaction

Fast

Slow37 °C Temperature

4.0

3.0

2.0

1.0

0.00 10 20 30 40 50 60

Temperature in °C

Rate ofreaction in

mg ofproducts per

unit time

35

30

25

20

15

10

5

0

Time taken todigest egg whitecubes in minutes

0 10 20 30 40 50 60Temperature in ºC

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iheartbio.weebly.comiheartbio.weebly.com/uploads/1/3/4/2/13422000/new_-_c... · Web viewc) Biological Molecules Identify the chemical elements present in carbohydrates, proteins and