Respiration and Biological Molecules

Respiration is described as an exothermic reaction. State what exothermic means.

Figure 1 shows three types of respiration. Name the substances shown at A, B and C.

Write the word equation for aerobic respiration.

Give three uses of the energy that organisms transfer by respiration.

Compare aerobic respiration and anaerobic respiration in muscles.

Explain why anaerobic respiration transfers much less energy than aerobic respiration.

Yeast is added to bread dough. Explain why the dough rises.

Compare anaerobic respiration in animal cells with anaerobic respiration in yeast cells.

Respiration is described as a universal chemical process. Explain what this means and what it supplies.

What type of reaction is respiration?

1. AEndothermic
2. BNeutral
3. CExothermic
4. DReversible

Which of these is the word equation for aerobic respiration?

1. AGlucose → lactic acid
2. BGlucose + oxygen → carbon dioxide + water
3. CCarbon dioxide + water → glucose + oxygen
4. DGlucose → ethanol + carbon dioxide

What is made when muscles respire anaerobically?

1. AEthanol
2. BCarbon dioxide and water
3. COxygen
4. DLactic acid

What is made when yeast respires anaerobically?

1. AEthanol and carbon dioxide
2. BLactic acid
3. CCarbon dioxide and water
4. DGlucose and oxygen

Why does anaerobic respiration transfer less energy than aerobic respiration?

1. AIt happens in the nucleus
2. BGlucose is only partly oxidised
3. CIt uses more oxygen
4. DIt makes more water

Where do most of the reactions of aerobic respiration take place?

1. AIn the nucleus
2. BIn the ribosomes
3. CIn the mitochondria
4. DIn the cell wall

Which of these is NOT a use of the energy transferred by respiration?

1. AProducing light
2. BMovement
3. CBuilding larger molecules
4. DKeeping warm

Which statement about respiration is correct?

1. AIt only happens in animals
2. BIt only happens in the day
3. CIt only happens during exercise
4. DIt happens in all living cells all the time

What does respiration supply in all living cells?

1. AOxygen
2. BATP
3. CChlorophyll
4. DStarch

Roughly how much ATP does aerobic respiration make per glucose compared with anaerobic respiration?

1. AThe same amount
2. BA little less
3. CHalf as much
4. DMany times more

State what is meant by the terms monomer and polymer.

Figure 1 shows how large molecules are made from small ones. Name the molecules shown at A, B and C.

Figure 2 shows how a lipid molecule is made. Name the parts shown at A, B and C.

Describe how proteins are made in a cell and how they are broken down.

Explain why the starch in a slice of bread is broken down before the body can use it.

Describe how you would test a food sample for starch, sugars, protein and lipids.

Explain the importance of sugars, amino acids, fatty acids and glycerol in the body.

What are the monomers that make a protein?

1. ASugars
2. BFatty acids
3. CAmino acids
4. DGlycerol

Which of these is a carbohydrate polymer used by plants to strengthen cell walls?

1. AGlycogen
2. BCellulose
3. CLipase
4. DGlycerol

What is a lipid made from?

1. AThree glycerol and one fatty acid
2. BAmino acids
3. CSugars
4. DOne glycerol and three fatty acids

Which enzyme breaks down proteins?

1. AProtease
2. BLipase
3. CAmylase
4. DCarbohydrase

What do animals use to store glucose?

1. AStarch
2. BCellulose
3. CGlycogen
4. DLipid

What is the colour change in the biuret test when protein is present?

1. ABlue to brick-red
2. BBlue to purple
3. COrange-brown to blue-black
4. DClear to cloudy

What does the synthesis of polymers need?

1. ALight only
2. BOxygen only
3. CStarch only
4. DEnzymes and energy from respiration

Which pair of molecules is made when a lipid is broken down?

1. AFatty acids and glycerol
2. BAmino acids and sugars
3. CSugars and glycerol
4. DStarch and fatty acids

Name the reagent used to test for starch.

State the colour change that shows that starch is present in a food sample.

Figure 1 shows four tests on a sample of food. Tube A contains iodine solution, tube B contains Benedict's reagent after heating, tube C contains Biuret reagent, and in tube D the food was shaken with ethanol and poured into water. Use Figure 1 to say whether the sample contains starch, sugar, protein and lipid.

Describe how you would test a food sample for sugar.

A student heats a test tube containing Benedict's reagent in a hot water bath, and not in a Bunsen burner flame. Suggest two reasons for this.

Describe how you would test a food for lipids, and what you would see if the result is positive.

A student also tests some distilled water with iodine solution. Explain why.

Food X gave these results: the iodine solution turned blue-black, Benedict's reagent stayed blue after heating, Biuret reagent stayed blue, and the emulsion test stayed clear. Say what food X contains and does not contain.

Describe two safety precautions that should be taken when doing the food tests.

A student has three foods, P, Q and R. Describe how the student could use Benedict's reagent to find out which food contains the most sugar.

Which reagent turns purple when protein is present?

1. AIodine solution
2. BBenedict's reagent
3. CBiuret reagent
4. DEthanol

A food is tested with iodine solution and the solution turns blue-black. What does the food contain?

1. AStarch
2. BSugar
3. CProtein
4. DLipid

What must be done after adding Benedict's reagent to a sample?

1. AAdd iodine
2. BLeave it in the freezer
3. CAdd ethanol
4. DHeat it in a water bath

In Benedict's test, a sample turns brick red. What does this show?

1. AThere is no sugar
2. BThere is a large amount of sugar
3. CThere is protein
4. DThere is starch

What is the positive result for the emulsion test for lipids?

1. AA blue-black colour
2. BA purple colour
3. CA cloudy white emulsion
4. DA brick-red colour

Why is the lipid test done with ethanol?

1. ALipids dissolve in ethanol
2. BEthanol turns purple
3. CEthanol is a protein
4. DEthanol is a sugar

Why should a student use a water bath instead of a flame to heat Benedict's reagent?

1. AA flame makes the sugar disappear
2. BBenedict's reagent only works in water
3. CA flame turns it blue
4. DThe liquid is less likely to boil over

A food gives no colour change with any of the four tests. What can you conclude?

1. AIt contains all four
2. BIt contains none of the four groups tested for
3. CIt contains only protein
4. DIt contains only water

Why is it useful to test a food that you know contains starch with iodine solution?

1. AIt shows what a positive result looks like
2. BIt makes the iodine work
3. CIt removes the starch
4. DIt cools the iodine

These tests are qualitative. What does this mean?

1. AThey give an exact amount
2. BThey only work at 75 °C
3. CThey show whether a substance is present, not exactly how much
4. DThey need a colorimeter