1. Unit 4 - Bioenergetics Revision

2. Photosynthesis – the equation…
Green plants make food for all living things – that’s why we call them producers
During photosynthesis light energy is used to convert carbon dioxide (from the air) and water (from the soil) into the sugar glucose
The reactants/raw materials of photosynthesis = water and carbon dioxide
Energy for all living organisms comes from the Sun. Green plants use the suns energy to make glucose.
Carbon Dioxide
Water
Oxygen Glucose +
Chlorophyll
Starch
Water enters the plant through roots. It travels up the plant through xylem vessels
Glucose is the useful product of photosynthesis. It is a type of sugar this is a carbohydrate.
Carbon dioxide enters the plant through stomata (holes in the leaves)
Oxygen is released as a by-product/waste product.
Green plants are able to make their own food during the process of photosynthesis. Photosynthesis is a chemical reaction that happens in chloroplasts. Chloroplasts are in plant cells – leaf cells have lots of chloroplasts.
During photosynthesis light energy is absorbed by a green substance called chlorophyll.
Chlorophyll is found in chloroplasts in some plant cells and algae.
Glucose can be used for many things – some is stored as insoluble starch. Insoluble means it won’t
dissolve. Iodine is used to test for starch. It turns from yellow/brown to blue/black

3. Photosynthesis – limiting factors
Uses of glucose
The glucose produced in photosynthesis may
be:
• used for respiration
• converted into insoluble starch for storage
• used to produce fat or oil for storage
• used to produce cellulose, which strengthens
the cell wall
• used to produce amino acids for protein
synthesis.
To produce proteins, plants also use nitrate ions
that are absorbed from the soil.
What is a limiting factor??
Any factor that slows down the rate of photosynthesis if there is not enough of it. The 3 limiting factors are:
Temperature
Amount of carbon dioxide
Light
It is called a limiting factor because it “limits” the reaction from taking place. A limiting factor can slow down the rate of photosynthesis even if the other factors are in plentiful supply.
Producing food – for farmers to make a profit they need to adjust the conditions in
greenhouses to gain the maximum rate of
photosynthesis while still minimising costs.
Light provides energy for photosynthesis. More light = more photosynthesis. Eventually if you increase the light intensity there will be no further increase of photosynthesis. This is because CO2 conc. or temperature are limiting the rate
All chemical reactions happen faster in warmer conditions. The warmer it is the more photosynthesis occurs. Eventually if you increase the light intensity there will be no further increase of photosynthesis. This is because CO2 conc. or temperature are limiting the rate
Carbon dioxide is a raw materialfor photosynthesis. More CO2 = more photosynthesis. Eventually if you increase the CO2 conc. there will be no further increase of photosynthesis. This is because light intensity or temperature are limiting the rate
Rate of photosynthesis
CO2 conc

4. Photosynthesis Limiting Factors Photosynthesis
Name the limiting factors and explain why the factor is limiting.
What is the equation for photosynthesis?
What is used to test for starch?
What is the by-product of photosynthesis?
How Plants use Glucose
It is converted into ___________ _________________ for storage.
Used for respiration.
Converted into _______ and oils for storage.
Used to produce ____________ which strengthens cell walls
used to produce amino acids for _________ synthesis.
To produce proteins, plants also use _________ ions that are absorbed from the soil. .
What factors must be controlled in a greenhouse to improve plant growth?
In what part of the cell does photosynthesis happen?
What provides the energy for photosynthesis?
What process will use the waste product of photosynthesis?
These 3 graphs show the limiting factors for photosynthesis. Explain what each graph shows. 4

5. Aerobic Respiration– the equation…
Aerobic respiration is respiration using oxygen. Oxygen is delivered by the blood to all cells.
Respiration also needs glucose. This is also carried by the blood to all cells.
Aerobic respiration takes place continuously in both plants and animals.
The reactants/raw materials of respiration = oxygen and glucose.
Respiration is controlled by enzymes that are present in cells
Carbon dioxide and water are released as by-products/waste product.
Glucose enters the body in food. Carbohydrates are broken down into glucose. The glucose is absorbed through the small intestine wall into the blood.
Oxygen enters the blood through the lungs.
Energy is the useful product of respiration.
Carbon
Dioxide
Water
Oxygen Glucose + +
Energy
Most of the reactions in aerobic respiration take place inside mitochondria. Mitochondria are found in the cells cytoplasm.
If a cell needs lots of energy it will have lot of mitochondria. Examples….sperm cells have lots of mitochondria in their tails. Muscle cells need lots of mitochondria to produce energy for muscle contraction.
Test for CO2 is limewater goes from clear to cloudy
Energy has many uses. It is used for muscle contraction, making proteins, active transport
Oxygen enters the cell from the blood by diffusion. Carbon dioxide moves from the cell back into the blood also by diffusion.

6. Aerobic respiration questions
What is the word equation for respiration
7. What are the two reactants for respiration?
What are the two waste products for respiration?
What is the useful product of respiration?
Where in the cell does respiration occur?
Name two cells that have lots of mitochondria. Explain why in each case.
Cell 1
Cell 2
5. Respiration is controlled by ______________ in the cell.
How does glucose get into the blood?
How does oxygen get into the blood
There are 3 main organ systems involved in respiration!
Which organ system gets glucose from food?
Which organ system gets oxygen from air and removes CO2?
Which organ system takes O2 and glucose to cells?
6. How do you test for carbon dioxide?
What are the four uses of energy? 1 2 3 4

7. Anaerobic respiration
This reaction is only an option for short periods of time.
This is because the waste product (lactic acid) is harmful and not enough energy is made to satisfy the body.
Anaerobic respiration is the incomplete breakdown of glucose and produces lactic acid.
If muscles are subjected to long periods of vigorous activity your body may not be able to respond quick enough and supply oxygen fast enough.
e.g. high intensity, strenuous exercise like sprinting, rowing.
The muscles respond by respiring without oxygen – this is called anaerobic respiration.
The equation for anaerobic respiration is:
The reactions for anaerobic respiration occur in the cytoplasm of the cell.
Anaerobic respiration can supply energy quickly (useful in short sprints).
As the breakdown of glucose is incomplete, much less energy is released than during aerobic respiration.
If muscles are subjected to long periods of vigorous activity they become fatigued. Fatigued means muscles stop contracting efficiently. The cause of muscle fatigue is the build-up of lactic acid in the muscles. After anaerobic exercise blood flowing through the muscles removes the lactic acid
Anaerobic respiration in plant and yeast cells is represented by the equation:
glucose → ethanol + carbon dioxide + energy
C6H12O6 2C2H5OH CO2
Anaerobic respiration in yeast cells is called fermentation and has economic importance in the manufacture of bread and alcoholic drinks.
Higher Tier ONLY
Blood flowing through the muscles transports the lactic acid to the liver where it is converted back into glucose.
The oxygen debt is the amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the cells.
Why do you keep breathing faster and more deeply when your muscles have stopped exercising?
You cannot breathe lactic acid out like extra carbon dioxide.
It builds up in your muscles and causes fatigue. You have to break it down using extra oxygen breathed in after exercise. The equation for anaerobic respiration is;
Lactic acid + oxygen → Carbon dioxide + water
The term “oxygen debt” refers to the oxygen needed to get rid of the lactic acid after anaerobic exercise has occurred.
Blood flowing through the muscles transports the lactic acid to the liver where it is converted back into glucose.

8. Respiration and exercise
The role of respiration during exercise
Muscles contract to move the bones in our bodies.
Respiration releases energy, which is used to contract the muscles:
When we exercise, our muscles contract more quickly and with more force.
This requires more energy.
This requires more glucose and oxygen.
Also, more carbon dioxide is created which needs to be removed.
The human body needs to react to the increased demand for energy during exercise.
Changes during exercise
During exercise a number of changes take place:
The rate and depth of breathing increases.
This increases the rate of gaseous exchange.
More oxygen is taken into the blood.
More carbon dioxide is removed from the blood.
The heart rate increases.
This increases rate of blood flow to the muscles
All of these changes increase the blood flow to the muscles and so increase the supply of sugar and oxygen and increase the rate of removal of carbon dioxide.
Glycogen
Glucose is stored as glycogen is in the muscles.
During exercise, glycogen is broken down into glucose in the muscles.
This increases the amount of glucose that can be respired.
Respiration and exercise
There are 3 main organ systems involved in respiration! The digestive system gets glucose from food and absorbs the glucose into the blood.
The respiratory system gets oxygen from air and into the blood and removes CO2 from the blood to the lungs to be breathed out.
The circulatory system takes O2 and glucose to cells and removes carbon dioxide from cells back to the lungs.
USES OF ENERGY
What is the energy released in respiration used for?
The energy released by respiration is used to:
Make large molecules from smaller ones (growth). In plants, for example, sugars, nitrates and other nutrients are converted into amino acids. Amino acids can then join together to make proteins.
Allow muscles to contract in animals
Maintain a constant body temperature in birds and mammal
In plants, to build up sugars, nitrates and other nutrients into amino acids which are then built up into proteins.

9. Higher tier only…SYMBOL EQUATIONS
Respiration can be summarised by the equation…. glucose + oxygen →  carbon dioxide + water (+ energy)
C6H12O6 + 6O CO H2O
Photosynthesis can be summarised by the equation….
carbon dioxide + water → glucose + oxygen
6CO H2O C6H12O6 + 6O2
Anaerobic respiration in plant and yeast cells is represented by the equation:
Glucose → ethanol + carbon dioxide + energy
C6H12O6 2C2H5OH CO2

10. Energy from Respiration questions
Aerobic Respiration
Write down the equation for aerobic respiration:
Where do most of the reactions for aerobic respiration take place?
The energy released may be used by the organism to:
Build larger _________________ from smaller ones.
Enable ________________contraction in animals.
Maintain a constant body temperature in colder surroundings in mammals and birds.
Anaerobic Respiration
Write down the equation for anaerobic respiration:
Where and when does anaerobic respiration take place?
What acid is produced?
Why do muscles become fatigued if you exercise hard?
Why is anaerobic respiration much more inefficient than aerobic?
What is oxygen debt?
Respiration is controlled by e ________________
It takes place all the time in a___________ and p________________.
Is called aerobic respiration because it uses o______________
Respiration takes place in the m________________.
Effect of exercise on the body
Why do muscles need more energy when you exercise?
What needs to be transported to the muscles?
To do this what changes take place?
What do muscles store glucose as?
If you need more energy when you exercise what other two things will you also need more of?
What also will you need to remove more of?
Aerobic or anaerobic??
Occurs in the cytoplasm
produces lactic acid
Produces less energy
produces more energy
Glucose is fully broken down
used more by sprinters
results in an oxygen debt
Glucose is partially broken down
Occurs in the mitochondria
Produces carbon dioxide
used more by marathon runners
No oxygen is involved
glucose reacts with oxygen
Energy is produced.
results in muscle fatigue
converts glucose into energy
A fit person has a ______________resting heart rate, before they begin to exercise
A fit persons heart rate rises more ______________
The maximum heart rate reached by the fit person is a lot __________________than the unfit person
A fit persons heart rate drops ____________when they finish exercise
The heart rate of a fit person returns to their resting heart rate in a _________________time. 10

11. Metabolism
Metabolism is the sum of all the reactions in a cell or the body.
The energy released by respiration in cells is used by living organisms for the enzyme controlled processes of metabolism that make new molecules.
Metabolism includes:
Using glucose to build larger molecules of starch, glycogen and cellulose
The formation of fat (lipid) molecules from a molecule of glycerol and three molecules of fatty acids
The use of glucose and nitrate ions to make amino acids. Amino acids are then used to synthesise(make) proteins
Respiration
The breakdown of excess proteins to form urea for excretion.