contents respiration waste products aerobic respiration anaerobic respiration what is respiration?...
TRANSCRIPT
Contents
Respiration
Waste products
Aerobic respiration
Anaerobic respiration
What is respiration?
An energy-making process
Summary quiz
We know that we breathe constantly throughout life.
Also, we know that if we stopped breathing we would eventually die.
So, breathing in oxygen (O2) must be linked to somethingsomething that we need constantly and without it our bodies would die.
The answer is ENERGY making.
An energy-making process
Ingredients to make energy
The energy-making process depends on the breathing system and the digestive system.
This will produce energy in the form of heat but only if it is supplied with 2 main ingredients.
FUEL OXYGEN
Imagine a fire...
The bodies energy-making reaction needs similar things to the energy-making process of fire.
Like the fire, the body needs oxygen and a fuel.
+and the fuelfuel (in the form of digested food) comes courtesy of the digestive system.
2
the oxygenoxygen is supplied by the
breathing system
Our fuel
If we now think back over the journey of oxygen and digested food through the human body, we will realise that they both end up in the same place.
these substances eventually arrive at the body cells
food oxygen
breathing system
digestive system
BLOODBLOOD
Our pipelines to the cells
Every living cell needs to respire
Therefore, the raw materials for the energy-making process eventually arrive at the body cells.
This energy-making process is known as...
R E S P I R A T I O NR E S P I R A T I O N
Each living cell is supplied with food and oxygen in order to generate energy.
oxygen
blood
food++
capillary
muscle cell
Contents
Respiration
Waste products
Aerobic respiration
Anaerobic respiration
What is respiration?
An energy-making process
Summary quiz
Waste products
No chemical reaction is 100% efficient.
Therefore, as well as producing the useful energy, respiration also produces waste products.
These waste products must be removed from the
body.
This is exactly what happens!
If the process of breathing in is used to obtain the O2 for respiration, it would make sense for the body to use the process of breathing out to remove these waste products of this reaction.
If we study the composition of the air that is breathed out, we will identify the waste products of respiration.
Two tests help us identify these waste products.
Before you start exhaling, the lime water is a clear liquid
After a short while, the lime water becomes cloudy.
Test One
Blow gently through a straw into a test tube filled with lime water.
lime water
straw
What’s the waste?
Identification of the first waste product
If a gas is bubbles through lime water and the liquid becomes cloudy, the gas is identified as….
This is the first of our waste products of respiration.
carbon dioxide (CO2)
Test Two
On a freezing cold day, watch what happens when you breathe out.
The air you breathe out is visible because the mystery waste product condenses back into a liquid.
Seeing your breath
This waste product is water vapour and so our final waste product of the process of respiration is...
water
Using this information, we can now write out the full equation for respiration.
WATERCARBON DIOXIDE
++ ++ ENERGYFOOD (GLUCOSE)
OXYGEN++
from digestive system
from breathing system
USEFUL!waste product exhaled
waste product exhaled
The equation for respiration
Contents
Respiration
Waste products
Aerobic respiration
Anaerobic respiration
What is respiration?
An energy-making process
Summary quiz
However, to call this reaction just ‘respiration’ is not quite correct.
Let us try to understand why….. Think about what you do in an average day.
sometimes you are restingresting
low energy requirements
When is energy needed?
A busy day!
sometimes you are activeactive
high energy requirements
Food and fuel flexibility
Your body requires different amounts of energy at different times.
Therefore…the process of respiration must be able to ‘speed up’ and ‘slow down’
this will mean that we need different amounts of food to feed the reaction
it will also mean that we need different amounts of oxygen to feed the reaction
the blood will have to flow at different speeds according to demand
our rate of breathing will change
this is exactly what happens
Throughout the day…
Let’s take two extreme examples human activity and see how the process of respiration change...
It seems that the process of respiration changes during the course of the day.
This is not the daily activities of an average human, but this scenario will help us understand the process of respiration in more depth.
1. sleeping
2. running a marathon
SLEEPING
When we sleep, our body is at rest.
There is a low demand for energy.
low energy demand
blood flow does not have to be rapid
low demand for food and oxygen
the breathing rate remains normal
In other words, the body has plenty of time to inhale the oxygen that it needs. It also has time to completely digest food to release the important chemicals (e.g glucose). The blood can efficiently transport these substances to the cells without increasing its rate of flow.
Sleeping
Contents
Respiration
Waste products
Aerobic respiration
Anaerobic respiration
What is respiration?
An energy-making process
Summary quiz
Aerobic respiration
When the body is performing respiration in such a way, it is given a special name.
When the body…
We say it is performing AEROBIC respiration.
OO22
has plenty of oxygenis able to completely digest foodcan supply the cells with the oxygen and food that they need
So our original equation for the process of respiration is actually the equation for aerobic respiration.
This is an efficient process... enough energy is made to supply the whole body.
Our bodies perform aerobic respiration for much of the day. In fact, as long as the supply of oxygen remains high enough, we will continue to perform aerobic respiration.
Of course, the amount of energy we produce will drop if the level of oxygen drops.
Glucose + Oxygen Carbon Dioxide + Water + Energy
Equation for aerobic respiration
Exercise: before - during - after
So, now we know that there is a form of respiration which is performed when there is a supply of oxygen to the body.
But, what happens in situation 2?
Are they performing aerobic respiration?
Well, in order to answer that question, we have to think about what their bodies are doing during the race.
duringduringbeforebefore afterafter
Remember the runners?
Energy demands
Oxygen available
Form of respiration
What’s happening?
beforelow high aerobic
during
high low / none aerobic
(but slowing)
afterdropping none / low
??
Physical activity dictates energy demands
??How can the body perform aerobic respiration in this situation?
Aerobic respiration requires oxygen but when you have been running a race or doing strenuous exercise, you cannot inhale enough oxygen for this reaction.
Glucose + Oxygen Carbon Dioxide + Water + Energy
This process fails!
But, if this process fails when the oxygen levels drop, the body would be left with absolutely no energy.
Running out of the good stuff
No energy would lead the body to stop working!
The body would stop working whenever it became short of oxygen.
The problem is that we often do exercise and our bodies continue working.
What must be happening when our oxygen levels drop to zero?
The body must be able to keep working through short periods of low/no oxygen.
But how?
Oxygen levels at zero
With aerobic respiration, the cells supply of oxygen and food is relatively constant.
oxygen
food
cellblood
When this supply is cut off, the cell is left with excess food and lacks energy.
It solves this problem by making energy from just the food alone!
Oxygen shortage at the cellular level
Contents
Respiration
Waste products
Aerobic respiration
Anaerobic respiration
What is respiration?
An energy-making process
Summary quiz
Now because it is releasing energy from food, it is still performing respiration.
But it is not aerobic respiration because there is nono oxygen present. (aero- means of air)
Therefore we call it ANAEROBICANAEROBIC respiration.
The energy being made by breaking down the food without oxygen.
This seems a better process!
To be able to make energy without needing oxygen would be very beneficial.
However, there is a problem.
Anaerobic respiration
Remember the last time you ran a race, carried a heavy weight or swam under water for too long and ran short of breath.
It probably felt uncomfortable.
Well, if anaerobic respiration was as efficient as it sounds, this lack of comfort would not happen.
Hitting the wall
When the cell breaks down the food to release the energy, it also makes a potentially harmful waste product.
The breakdown of the food is also incomplete.
It is not an efficient process.
So, what is the problem with anaerobic respiration?
What’s wrong with anaerobic respiration?
Glucose Lactic Acid + (some) Energy
This waste product is known as LACTIC ACID.
Therefore the equation for anaerobic respiration is…
from the digestive system
waste product
not as much energy as with aerobic
respiration
You will notice that this reaction is only an option for short periods of time.
This is because the waste product is harmful and not enough energy is made to satisfy the body.
The anaerobic equation
Well, this chemical can stop muscles within the body, from contracting and relaxing.
The lactic acid soaks the muscle cells and prevents the muscle cell from doing its job.
relaxation
contraction
If the muscles in your body stop contracting and relaxing they are said to be fatigued.
They eventually seize and you experience cramp.
Why is lactic acid so harmful?
If you want to consider the full impact of damage caused by the presence of lactic acid, just remember that the heart is made of muscle cells!
This leaves us with a problem...
if we want to do exercise
We want the energy that anaerobic
respiration produces
YES NO
So the answer is for anaerobic respiration to be a ‘gap-fill’ during periods of very low / no oxygen availability.
But we don’t want the lactic acid waste
product
Striking the right balance
time
oxygen levels
rest
exercise
exercise stops
aerobic
anaerobic
Anaerobic respiration keeps our bodies going until we can breathe in more oxygen again.
Whilst we are performing anaerobic respiration, our bodies are building up a ‘debt’ of oxygen.
Oxygen debt
This is rather like owing the bank some money.
Once you get some money, you have to pay off that debt.
We can think of that debt as being the presence of lactic acid in the body.
Paying it off
When our bodies convert from aerobic to anaerobic respiration, we start making lactic acid.
As soon as this begins, the body starts building an oxygen debt.
This is equivalent to the amount of oxygen it would have used if aerobic respiration had continued.
Doing the sums
Dealing with the lactic acid build-up
This oxygen debt will have to be repaid when the exercise stops.
Oxygen will be used to break down the lactic acid that is present in the body.
The oxygen ‘oxidises’ the lactic acid.
In fact, the lactic acid is oxidised into carbon dioxide and water.
In this way, the process of aerobic respiration can be converted into
The process of anaerobic respiration which can then turn back into...
The body has the ability to produce energy, despite changes in the supply of oxygen.
Here are the two forms of respiration.
glucose + oxygen carbon dioxide + water + energy
Aerobic respiration (complete breakdown of food)
Anaerobic respiration (incomplete breakdown of food)
Aerobic respiration is performed when oxygen is present.
Anaerobic respiration is performed when oxygen is absent.
glucose + oxygen carbon dioxide + water + lactic acid + little energy
Respiration summary
Work through the following tasks, filling the missing words or crossing out the wrong words where necessary.
The body can perform two types of respiration.
These are:
1. ____________ respiration (performed in plenty of O2)
2. ____________ respiration (performed in little or no O2)
A
Aerobic Respiration
_______ + ______ _______ _______ + ______ + ______
B
Respiration…do I really need oxygen?
Aerobic respiration is performed when the supply of oxygen to the cells is HIGH / LOW.
It is the COMPLETE / INCOMPLETE breakdown of food and so is very INEFFICIENT / EFFICIENT.
It is a method of respiration that produces LOTS / LITTLE energy for the body.
If the body does not get enough oxygen to the cells it CAN / CAN’T perform aerobic respiration.
Instead it has to perform __________ respiration for a LONG / SHORT period of time.
C
Respiration…do I really need oxygen?
Two common reasons for the body being short of energy would be if a human was performing…
1. HEAVY / LIGHT exercise for LONG / SHORT periods of time.
2. HEAVY / LIGHT exercise for LONG / SHORT periods of time.
D
Anaerobic Respiration
_______ + ______ _______ _______ + ______
waste product useful
E
Why would the body be short of oxygen?
Anaerobic respiration is performed when the supply of oxygen of the cells is HIGH / LOW.
It is the COMPLETE / INCOMPLETE break down of food and so is very INEFFICENT / EFFICIENT.
It is a method of respiration that produces LOTS / LITTLE energy for the body.
F
Why would the body be short of oxygen?
The acid test
fatigued
oxygen
muscle
contracting
anaerobicaerobic
broken
If we then relax and breathe again the body recovers. The supply of ___________ increases and the lactic acid is ___________ down. The body can now stop performing ___________ respiration and go back to performing __________ respiration.
This is poisonous. It can build up in _________ cells and stop them ___________ and relaxing. We say the cell is tired or __________.
Contents
Respiration
Waste products
Aerobic respiration
Anaerobic respiration
What is respiration?
An energy-making process
Summary quiz
Multiple-choice quiz