Biological molecules

1. Starter – Brainstorm
What are the main elements that
make up the human body?
65%
18%
10%
3%
4%

2. Structure of
Biological Molecules
Sunday, 18 February 2024

3. Lesson Objectives:
1. Identify the chemical elements
present in carbohydrates,
proteins and lipids (fats and oils)
2. Describe the structure of
carbohydrates, proteins and
lipids as large molecules made up
from smaller basic units
Sunday, 18 February 2024

4. Triple Prep
• Briefly describe the problems associated
with:
– A lack of protein in your diet
– Too much fats and oils
– Too much sugar
– A lack of dietary fibre (cellulose)

5. Carbohydrates
• Long chains of simple sugars
• Glucose is a simple sugar
(monosaccharide)
• When 2 glucose join together maltose is
formed (disaccharide)
• When lots of glucose join together
starch, glycogen or cellulose is formed
(polysaccharide)
Glycosidic bonds

6. Lipids
• Most lipids in the body are made up of
triglycerides
• Their basic unit is 1x glycerol and 3x
fatty acids
• The fatty acids vary in size and
structure
Ester bonds
3 x fatty acids
1 x Glycerol

7. Proteins
• Long chains of amino acids
• There are over 20 different amino acids
• The amino acids can be arranged in any
order, resulting in hundreds of
thousands different proteins
• When amino acids join together
proteins are formed
Peptide bonds

8. Triple Task:
1. Draw a model of a carbohydrate, fat
and protein in your books
2. Name the biological molecule
3. Label the monomer subunits within
the molecule
4. Brief description of the molecules
function
5. State the names of the elements
from within the biological molecules
6. State the location and name of
chemical bonds.

9. DoubleTask:
1. Make a model of a carbohydrate, fat and
protein using the shapes provided.
Glue models into exercise book.
2. Name the biological molecule
3. Label the monomer subunits within the
molecule
4. Brief description of the molecules
function
5. State the names of the elements from
within the biological molecules
6. State the location and name of chemical
bonds.

10. Plenary
Use your marking grid to peer
assess someone else’s work and leave
it with them.
Criteria Details Achieved
Diagram See white board.
Function Main fuel for supplying cells with energy via respiration
Name of monomers Simple sugars. Eg glucose
Name of polymer Polysaccharides. Eg Starch and Glycogen and Cellulose
Location of chemical bond Between each sugar unit.
Name of chemical bond Glycosidic bond
Elements present Carbon. Hydrogen. Oxygen

11. Starter
• Get your whiteboards ready to answer
the following questions:
• Keep a tally in the bottom corner of how
many questions you answer correctly
(it’s out of 3)

12. The name’s Bond….
…but which Bond???
Name the bond formed when amino acids
join together
PEPTIDE BOND

13. The name’s Bond….
…but which Bond???
Name the bond formed when glucose
molecules join together
GLYCOSIDIC BOND

14. The name’s Bond….
…but which Bond???
Name the bond formed between a glycerol
molecule and the fatty acids
ESTER BOND

15. FOOD TESTING
Glucose and starch tests

16. Lesson Objectives:
1. Name the food tests used for
glucose and starch
2. Describe tests for glucose and
starch
3. Carry out practical to test for
glucose and starch
Sunday, 18 February 2024

17. Testing for starch
• Iodine is used to test for starch in food
samples
• A positive test = yellow to blue/black
• A negative test = stays yellow

18. Testing for Glucose
• Benedict’s solution is used to test for
glucose
• A positive test =
green/yellow/orange/brick red
• A negative test = stays blue

19. Safety
• Wear aprons and goggles throughout
• Care of glassware
• Care of hot water
• Don’t eat the food…
• Be aware of any allergies

20. Recording your results
Food sample Starch present (x or ) Glucose present (x or )
Bread
Cake
Shredded Wheat
Dried milk
Cottage cheese
Yoghurt
Extension:
Can you identify any
patterns in your
results?
Write a simple conclusion
on which foods contained
starch and/or glucose

21. Starter – True or False
Carbon, Hydrogen and Oxygen are found in Lipids and
Carbohydrates
Glycosidic bonds are found in Lipids
Ester bonds are found in Proteins
Protein is a polymer
Fat is an immediate energy source
An Amino Acid is a polymer
Meat, Fish and Eggs contain carbohydrates
Starch is Insoluble
Glucose is Soluble
Starch and glycogen are a monomers

22. Enzymes
Sunday, 18 February 2024

23. Lesson Objectives:
1. Define the term catalyst and
enzyme.
2. Describe the role of enzymes in
catalysing reactions in living cells
3. State two factors that affect the
rate of an enzyme controlled
reaction.
4. Describe the effect of two factors
on the rate of an enzyme controlled
reactions.
Sunday, 18 February 2024

24. Discuss:
i. Meaning of the word catalyst.
ii. Link between enzymes and catalysts
iii. Function of enzymes
iv. 55 000 different enzymes in the
body….think up as many metabolic
reactions as possible.

25. Enzymes
Add as many ideas as you can about enzymes:
Enzymes
What are they?
Where are they
found?
Examples
What do they
do?
What type of
molecule are
they?
What processes are
they involved in?

26. Definition:
A catalyst is a chemical that speeds up
the rate of a chemical reaction without
being used up. Enzymes are biological
catalysts. Enzymes speed up the rate of
chemical reactions inside the body /
metabolic reactions.

27. Enzyme structure
Enzyme
Substrate
Active Site
Location on
enzyme where
reaction occurs
Substrate
Molecule to be
broken down
Substrate
Molecule has the
exact shape for this
particular enzyme
Active Site
Site shape
matches that of
the substrate
Enzyme-substrate complex
A substrate fits exactly
into the active site of the
enzyme
Products
Substrate broken
down into smaller
pieces
Active Site
Releases the products
which no longer fit into
the active site. Now free
to bind with another
substrate molecule

28. Breaker Enzymes

29. Builder Enzymes

30. How enzymes work:
Task:
Watch this animation.
Create your own
storyboard on how
enzymes work
Key words:
Enzyme, substrate,
active site, lock and key,
enzyme-substrate
complex, product
Animation

31. Catalase Plenary
Hydrogen peroxide is an unstable colourless
liquid H2O2. It ‘decomposes’ to form water and
oxygen:
2H2O2 → 2H2O + O2
This reaction can be sped up with a catalyst or
an enzyme – e.g. catalase, which is found in living
tissue

32. • Which tissue do you think contained the most
catalase?
• Can you explain the result for boiled liver?
Catalase Plenary
Living tissue Maximum froth height (mm)
Liver 130
Muscle 10
Apple 1
Potato 8
Boiled liver 2
Tube with H2O2 only 0

33. Starter
In pairs discuss where in the body would
you find enzymes involved in digestion

34. The Effect of temperature on
enzyme action
LOs
• Carry out practical work to reveal the
effect of temperature on enzyme action
• Be able to describe the experiment

35. Enzymes build/break molecules and
speed up reactions in living things
• Amylase breaks
long starch
molecules down
into small glucose
molecules.
• Only the small
molecules can be
absorbed in
digestion
Amylase is found in saliva

36. At low temperatures enzyme controlled reactions go
slowly because the molecules have low kinetic energy.
The rate of an enzyme controlled reaction is
affected by temperature

37. • When temperature increases the reaction also
increases as the molecules have more kinetic energy
The rate of an enzyme controlled reaction is
affected by temperature
But this only occurs up to
the optimum temperature
(usually about 40oC)
The temperature at
which the rate of
reaction is fastest is
known as the optimum
temperature

38. Rate
Of
Reaction
Temperature/oC
0 10 20 30 40 50 60 70
Optimum temperature
Enzyme
is denaturing
Rate of reaction of an enzyme reaction changes
at different temperatures
Molecules gain
kinetic energy

39. After the optimum temperature the heat causes the
enzyme to denature
The enzyme changes shape and the active site no longer
matches the shape of the substrate molecule
The rate of an enzyme controlled reaction is
affected by temperature

40. The rate of an enzyme controlled reaction is
affected by temperature
Equipment:
8 x test tubes
Iodine
4xpipettes
2x spotting tiles
Marker pen
Stop clock
Amylase solution
20ᵒC 30ᵒC 40ᵒC 50ᵒC
1
2
3
4
5
6

41. Method
Hypothesis: temperature affects the rate
at which an enzyme works
• 4 test tubes – 5cm3 starch
• 4 test tubes – 1cm3 amylase
• Label and put one of each
into each water bath (20°C,
30°C, 40°C, 50°C)
• Two spotting tiles next to
each other with two drops
of iodine in each.
20 30 40 50

42. Method
• Add the amylase to the starch – shake
to mix – start stopclock
6
5
4
3
2
1
• Immediately take a pipette of
the starch/ amylase from a
water bath back to your bench
• Add a drop to the first well
for that temperature
• Each minute add a drop to the
next well for that temperature
• Record time taken for starch
solution to stop turning the
iodine black (all digested)
20 30 40 50

43. Results
• Copy this table and record your results
as you go
Temperature
(ᵒC)
20 30 40 50
Time taken for
starch to be
digested
(mins)
1/Time

44. Prep
• Draw a graph to represent your results
• Use 1/Time as your dependent variable
(y-axis)
• Temperature as your independent
variable (x-axis)

45. • Enzymes prefer to work at an optimum pH. Outside of its
pH range the enzyme is denatured.
Rate
Of
Reaction
pH
1 2 3 4 5 6 7 8 9 10 11 12
pepsin amylase
The activity and shape of enzymes is also
affected by pH
Optimum pH