B9: Respiration

What do organisms need energy for?

1. Movement

2. Keeping warm

3. Chemical reactions to build larger molecules

How is the energy we need supplied?

Cellular respiration

What type of reaction is respiration and why?

Exothermic

• Releases energy

When does respiration take place?

Continually in all living cells

Cellular respiration

An exothermic reaction which is continuously occurring in living cells

What does the energy transferred from respiration supply energy for?

Living processes

What does respiration do?

Transfer energy

2 types of respiration

1. Aerobic

2. Anaerobic

Word equation for aerobic respiration

Glucose + oxygen → carbon dioxide + water

How much energy does aerobic respiration release and why?

Lots

• Glucose molecule fully oxidised

Symbol equation for aerobic respiration

C6H12O6 + 6O2 → 6CO2 + 6H2O

When do cells carry out aerobic respiration

When there is O2

When does anaerobic respiration occur?

When there isn’t enough O2

Where does anaerobic respiration occur?

• In muscles

• In plant + yeast cells

What do muscle cells need lots of energy for?

Contraction

Word equation for anaerobic respiration in muscles

Glucose → lactic acid

How much energy does anaerobic respiration release and why?

Much less than aerobic

• Oxidation of glucose in incomplete

Word equation for anaerobic respiration in plant + yeast cells

glucose → ethanol + carbon dioxide

Fermentation

Anaerobic respiration in yeast cells

What is anaerobic respiration of yeast (fermentation) economically important for?

The manufacture of:

• Bread

• Alcoholic drinks

Type in alcohol produced from the fermentation of yeast

Ethanol

What product of fermentation is used to make bread and how?

CO2 creates bubbles in dough → causes bread to rise

Does anaerobic or aerobic respiration transfer more energy?

Aerobic

When we are relaxing do we need lots of energy- why or why not?

No, need little- we aren’t moving

Does our body need lots or little energy during exercise?

Lots- for muscle contraction

When the body needs lots of energy eg for exercise / muscle contraction, what increases?

Aerobic respiration

When aerobic respiration increases, what do body cells need?

More O2

During exercise what does the human body react to?

The increased demand for energy

To provide extra O2 for contraction, what happens?

• Breathing rate increases

• Breathing volume increases

• Heart rate increases

Why does breathing rate + breathing volume increase during exercise?

To supply muscles with more oxygenated blood

• More oxygen enters BS

Why does heart rate increase during exercise?

To pump oxygenated blood around th ebody

When exercising hard, what happens if insufficient oxygen is supplied to muscles?

Anaerobic respiration takes place in muscles

What does the incomplete oxidation of glucose in anaerobic respiration lead to?

• Build up of lactic acid

• Creates O2 debt

What does lactic acid cause during long periods of vigorous activity?

Muscles become fatigued

What does muscle fatigue cause?

Muscles stop contracting efficiently

How does the body recover from muscle fatigue?

By removing lactic acid from muscles

Oxygen debt

The amount of extra O2 the body needs after exercise to react with the accumulated lactic acid + remove it from cells

How does the body deal with the accumulated lactic acid?

• Blood flowing thru the muscles transports the lactic acid to the liver

• In liver, it’s converted back into glucose in a series of chemical reactions

What does reacting with accumulated lactic acid + removing it from cells need?

O2

Why do people continue breathing rapidly for sometime after finishing exercise

To supply the extra oxygen needed to pay off the oxygen debt

During exercise, your cells need more energy for respiration.

True or false?

False

• During exercise, your cells need more energy FROM respiration

Causes of muscle fatigue

Anaerobic respiration

• Build up of lactic acid → oxygen debt

What creates the oxygen debt?

Removing lactic acid from muscles requires oxygen → oxygen debt

Oxygen debt repayment equation

Lactic acid + oxygen → Carbon dioxide + water

How is the energy released by respiration in cells used in an organism?

Continual enzyme-controlled processes of metabolism that synthesise new molecules

Metabolism

Sum of all the reactions in a cell or the body

How is glucose used in plants?

1. Converted to cellulose → strengthens plant cell wall

2. Converted to starch → storage form of glucose

3. Reacted with nitrate ions → makes AA → used to synthesise proteins

How is glucose used in humans?

Converted to glycogen → storage form of glucose

How is a lipid made and where is it found?

1 glycerol molecule + 3 fatty acid molecules → lipid

• Cell membrane

Where are lipids found in cells?

Cell membranes

What happens to excess proteins?

Broken down into urea

What is urea excreted by?

Kidneys

5 metabolic reactions

1. Conversion of glucose to starch, glycogen + cellulose

2. Formation of lipid molecules from 1 molecule of glycerol + 3 molecules of fatty acids

3. Glucose + nitrate ions to make amino acids to synthesise proteins

4. Respiration

5. Breakdown of excess proteins to form urea for excretion

Role of liver

1. Detoxify poisonous substances

2. Pass down breakdown products into blood so they can be excreted in urine via kidneys

3. Breaking down old, worn out blood cells + storing the iron unit it is needed to synthesise more blood cells

4. Dealing with lactic acid

What does blood flowing thru muscles do?

Transport lactic acid to liver

What is lactic acid converted to in the liver?

Glucose