Respiration (OCR GCSE Combined Science A (Gateway): Biology): Flashcards
Exam code: J250
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Define cellular respiration.
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Define cellular respiration.
The chemical process that transfers energy from the breakdown of glucose, supplying ATP for the cell to use.
Why is respiration described as a universal chemical process?
It happens continuously in every living cell, in all organisms.
What molecule stores the energy transferred by respiration?
ATP, which the cell can then use in processes that need energy.
Give three processes that use the energy supplied by respiration.
Building larger molecules from smaller ones.
Muscle contraction for movement.
Keeping warm, to maintain a constant body temperature.
Which organelle is the site of most aerobic respiration?
The mitochondria.
Write the word equation for aerobic respiration.
glucose + oxygen → carbon dioxide + water
Write the balanced symbol equation for aerobic respiration.
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O
Respiration is controlled by ＿＿＿＿＿＿＿＿, so its rate is affected by temperature and pH.
Respiration is controlled by enzymes, so its rate is affected by temperature and pH.
Define exothermic reaction.
A reaction that transfers energy to the surroundings, usually as heat.
Why is cellular respiration described as exothermic?
It transfers heat energy to the surroundings.
This is why the body warms up during exercise.
Respiration is an ＿＿＿＿＿＿＿＿ reaction because it transfers energy to the environment as heat.
Respiration is an exothermic reaction because it transfers energy to the environment as heat.
Other than glucose, name a molecule that can be broken down in respiration.
Proteins or lipids can also be used as respiratory substrates.
True or False?
Respiration and breathing are the same process.
False.
Respiration is a chemical reaction inside cells that transfers energy from glucose. Breathing moves air in and out of the lungs.
True or False?
Energy released by respiration can be used directly by the cell.
False.
It is first stored in ATP, which the cell then uses where energy is needed.
Define aerobic respiration.
The chemical reaction in cells that uses oxygen to break down nutrient molecules and release energy.
Define anaerobic respiration.
The chemical reaction in cells that breaks down nutrient molecules to release energy without using oxygen.
What is the substrate for both aerobic and anaerobic respiration?
Glucose.
What are the products of aerobic respiration?
Carbon dioxide and water.
What is the product of anaerobic respiration in animals?
Lactic acid.
What are the products of anaerobic respiration in plants and fungi?
Ethanol and carbon dioxide.
Write the word equation for anaerobic respiration in animals.
glucose → lactic acid
Write the word equation for anaerobic respiration in plants and fungi.
glucose → ethanol + carbon dioxide
How many molecules of ATP does aerobic respiration yield per glucose?
About 32 molecules of ATP.
How many molecules of ATP does anaerobic respiration yield per glucose?
Only 2 molecules of ATP.
Why does anaerobic respiration release far less energy than aerobic?
Glucose is only partly broken down, so energy is left stored in the bonds of the products.
Anaerobic respiration in animals mainly takes place in ＿＿＿＿＿＿＿＿ cells during vigorous exercise.
Anaerobic respiration in animals mainly takes place in muscle cells during vigorous exercise.
Anaerobic respiration in yeast is also known as ＿＿＿＿＿＿＿＿.
Anaerobic respiration in yeast is also known as fermentation.
Under what condition do plant root cells respire anaerobically?
In waterlogged soil, where there is little or no oxygen available.
Why do muscle cells respire anaerobically during vigorous exercise?
The muscles demand energy faster than the body can deliver oxygen, so oxygen becomes a limiting factor.
True or False?
Anaerobic respiration releases more energy per glucose molecule.
False.
Aerobic respiration releases far more — about 32 ATP compared with only 2 ATP.
True or False?
Anaerobic respiration in animals and in fungi gives the same products.
False.
Animals produce lactic acid; plants and fungi produce ethanol and carbon dioxide.
Define monomer.
A small basic unit that joins with others to build a larger molecule.
Define polymer.
A large molecule made of many monomers joined together in a long chain.
Which three elements do all carbohydrates contain?
Carbon, hydrogen and oxygen.
What is the monomer used to build complex carbohydrates?
A simple sugar (monosaccharide), such as glucose.
Name three polysaccharides made by joining glucose molecules.
Starch, glycogen and cellulose.
Which two monosaccharides join together to form maltose?
Two glucose molecules.
A ＿＿＿＿＿＿＿＿ is formed when two monosaccharides join together.
A disaccharide is formed when two monosaccharides join together.
What are the monomers of proteins?
Amino acids.
How are proteins built up and broken down?
They are synthesised by joining amino acids into a long chain.
They are broken down back into their amino acids, which can then be used to build new proteins.
Why can amino acids make so many different proteins?
They can be joined in any order, so different sequences give hundreds of thousands of different proteins.
What determines the function of a protein?
Its shape, which comes from the sequence of amino acids in its chain.
Name two examples of proteins in the body.
Enzymes and haemoglobin. Keratin is another example.
What are lipids built from?
One glycerol molecule bonded to three fatty acid chains.
A lipid made of one glycerol molecule and three fatty acids is called a ＿＿＿＿＿＿＿＿.
A lipid made of one glycerol molecule and three fatty acids is called a triglyceride.
What is the difference between a fat and an oil?
Fats are solid at room temperature.
Oils are liquid at room temperature.
True or False?
Lipids are polymers.
False.
Unlike carbohydrates and proteins, lipids are not made from a long chain of repeating subunits.
True or False?
Starch and cellulose are both made from glucose.
True.
Both are polysaccharides built from many glucose monomers, joined in different ways.
Which reagent is used to test for reducing sugars?
Benedict's solution, which is blue.
Describe how to carry out the Benedict's test.
Add Benedict's solution to the sample.
Heat in a water bath at about 75 °C for 5 minutes.
What colour change shows a positive Benedict's test?
Blue to orange or brick red.
A negative result stays blue.
How does a Benedict's test show how much sugar is present?
The colour changes further with more sugar, through green → yellow → orange → red.
Which reagent is used to test for starch?
Iodine solution, which is orange-brown.
In a positive test for starch, iodine solution turns from orange-brown to ＿＿＿＿＿＿＿＿.
In a positive test for starch, iodine solution turns from orange-brown to blue-black.
Which reagent is used to test for protein?
Biuret solution, a mixture of sodium hydroxide and copper sulfate.
What colour change shows a positive biuret test?
Blue to purple or violet.
A negative result stays blue.
Describe how to carry out the emulsion test for lipids.
Shake the sample with ethanol and let it dissolve, then strain it into a clean tube.
Add the solution to an equal volume of cold distilled water.
What is a positive result in the emulsion test for lipids?
A cloudy white emulsion forms.
The more lipid present, the milkier it looks.
The emulsion test uses ＿＿＿＿＿＿＿＿ to dissolve the lipid before cold water is added.
The emulsion test uses ethanol to dissolve the lipid before cold water is added.
Why must eye protection be worn during these food tests?
Biuret solution contains copper sulfate and corrosive sodium hydroxide, and iodine is an irritant.
Why must ethanol be kept away from a Bunsen burner?
Ethanol is highly flammable.
True or False?
The Benedict's test needs to be heated in a water bath.
True.
The sample is heated at about 75 °C for 5 minutes; without heating the colour change does not develop.
True or False?
Iodine solution turns purple when starch is present.
False.
It turns blue-black. Purple is a positive result for protein in the biuret test.
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