Biology • Year 11 • Module 2 • Lesson 6

Autotrophs vs Heterotrophs

Lock in the core vocabulary, the photosynthesis and respiration equations, and the comparison of nutrient and gas requirements for autotrophs and heterotrophs.

Build · Anatomy & Vocab

1. Label the autotroph vs heterotroph comparison diagram

The diagram below summarises how autotrophs and heterotrophs differ in their energy and nutrient acquisition, and where the two groups overlap. Write the correct label into boxes A–H. Each label is drawn from the lesson's Key Terms or Cards 1–4. 8 marks

Autotroph (e.g. plant, alga, cyanobacterium) Energy source A: ______________________ Carbon / nutrient source B: ______________________ Gas in (daytime, net) C: ______________________ Key organelle for energy capture D: ______________________ Shared with heterotrophs Performs cellular respiration in mitochondria Heterotroph (e.g. animal, fungus, most bacteria) Energy source E: ______________________ Carbon / nutrient source F: ______________________ Gas in (always, net) G: ______________________ Photosynthesis capability H: ______________________ Shared with autotrophs Performs cellular respiration in mitochondria SHARED
BoxYour label
A
B
C
D
E
F
G
H
Stuck? Revisit lesson Cards 1 (definitions) and 4 (full comparison table).

2. Term–definition match

The eight definitions below are shuffled. In the right-hand column write the matching term from this list: autotroph, heterotroph, photosynthesis, cellular respiration, chloroplast, mitochondrion, gas exchange, glucose. 8 marks

#Definition (shuffled)Matching term
2.1The process by which all living cells break down glucose to release ATP, occurring in the mitochondria.
2.2An organism that obtains organic molecules by consuming other organisms or their products.
2.3The process by which photoautotrophs use light energy to convert CO2 and H2O into glucose and O2 in chloroplasts.
2.4A six-carbon sugar that is the primary energy currency and carbon source for cellular metabolism in all organisms.
2.5An organism that produces its own organic molecules from inorganic sources using light or chemical energy.
2.6The organelle in plant and algal cells where photosynthesis occurs, containing chlorophyll.
2.7The movement of oxygen and carbon dioxide between an organism and its environment across a respiratory surface.
2.8The organelle in eukaryotic cells where aerobic cellular respiration occurs, producing most of the cell's ATP.
Stuck? Revisit lesson § Key Terms panel.

3. Complete the equations

Fill in each blank to complete the word and symbol equations for photosynthesis and cellular respiration. 8 marks (1 per blank)

Photosynthesis (word equation)

__________ + __________ → glucose + __________

(light energy is required; occurs in the __________)

Photosynthesis (symbol equation)

6CO2 + __________ → C6H12O6 + __________

Aerobic cellular respiration (word equation)

glucose + __________ → __________ + water + __________

(occurs in the __________; in ALL living cells including autotrophs)

Aerobic cellular respiration (symbol equation)

C6H12O6 + __________ → 6CO2 + 6H2O + __________

Stuck? Revisit lesson § Cards 2 and 3.

4. True or false, with correction

For each statement, circle T or F. If the statement is false, write the corrected version on the line provided. 8 marks (1 for T/F, 1 for correction where needed)

4.1 Plants only photosynthesise, they do not perform cellular respiration.    T  /  F

4.2 Both autotrophs and heterotrophs produce ATP via cellular respiration.    T  /  F

4.3 The net gas exchange of a plant at night (in complete darkness) is CO2 in and O2 out.    T  /  F

4.4 Heterotrophs obtain organic molecules by consuming other organisms or their products.    T  /  F

Stuck? Revisit lesson § Cards 1 and 3 (especially the misconception callout).

5. Fates of glucose in an autotroph

Five fates of glucose produced by photosynthesis are listed in the table below. For each, write the name of the product or process involved and its purpose in the plant. 10 marks (1 per cell)

What happens to the glucoseProduct or process namePurpose in the plant
Oxidised in mitochondria to release energy
Polymerised for long-term energy storage (in chloroplasts, roots, seeds)
Polymerised to form structural cell wall material
Combined with fructose and loaded into phloem for transport
Carbon skeletons used (with inorganic nutrients) to build amino acids, lipids, nucleotides
Stuck? Revisit lesson § Card 5 and the “Copy into your books” section.
Answers, Do not peek before attempting

Q1, Labelled diagram

A: Light energy (sun / solar energy). B: Inorganic sources, CO2 from air (carbon) and H2O from soil; minerals absorbed via roots. C: CO2 (absorbed through stomata for photosynthesis; net uptake exceeds respiration output during daylight). D: Chloroplast (contains chlorophyll; site of photosynthesis). E: Chemical energy from food (glucose, fats, proteins obtained by consuming other organisms). F: Organic molecules obtained by consuming other organisms or their products. G: O2 (absorbed for cellular respiration; no photosynthesis to consume CO2). H: Cannot photosynthesise (no chloroplasts; no mechanism to fix inorganic carbon from CO2).

Q2, Term–definition matches

2.1 cellular respiration • 2.2 heterotroph • 2.3 photosynthesis • 2.4 glucose • 2.5 autotroph • 2.6 chloroplast • 2.7 gas exchange • 2.8 mitochondrion.

Q3, Equation completion

Photosynthesis word: carbon dioxide + water → glucose + oxygen (light energy; chloroplast).

Photosynthesis symbol: 6CO2 + 6H2O → C6H12O6 + 6O2.

Respiration word: glucose + oxygen → carbon dioxide + water + ATP (mitochondria).

Respiration symbol: C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP.

Q4, True / false with correction

4.1 False. Correction: Plants perform cellular respiration continuously (24 hours a day, in all living cells), including at night when photosynthesis stops. Photosynthesis and respiration are independent processes; the plant uses both.

4.2 True. Both autotrophs and heterotrophs break down glucose in mitochondria to produce ATP via cellular respiration.

4.3 False. Correction: At night, photosynthesis stops completely so there is no CO2 uptake. Only cellular respiration continues, the plant takes in O2 and releases CO2, exactly like an animal.

4.4 True.

Q5, Fates of glucose

What happensProduct or processPurpose
Oxidised in mitochondriaCellular respiration / ATPProvides immediate usable energy for all cell processes
Polymerised for energy storageStarchLong-term energy reserve used when photosynthesis rate is low (night, winter)
Polymerised for cell wall structureCelluloseStructural support and rigidity of cell walls
Combined with fructose, loaded into phloemSucrose / phloem transportTransporting energy to non-photosynthetic tissues (roots, growing tips, fruit)
Carbon skeletons for biosynthesisAmino acids, lipids, nucleotidesGrowth and repair, building proteins, membranes, and DNA

HSCScience • Biology • Year 11 • Module 2 • Lesson 6 • Worksheet 1 (Build)