SACE Biology · Stage 2
SACE Biology Stage 2: Cells as the Basis of Life — Flashcards & Quiz
SACE Biology Stage 2 Cells as the Basis of Life topic explores the fundamental unit of life and the processes that sustain cellular function. These free flashcards and true/false questions cover cell theory and its historical development, prokaryotic versus eukaryotic cell structure, organelle function and ultrastructure, the fluid mosaic model of cell membranes, passive and active transport mechanisms, cell division including mitosis and the cell cycle, cellular respiration and ATP production, and photosynthesis. Every card is aligned to the SACE Board subject outline so you study exactly what your Stage 2 external examination requires.
Key Terms
- Cell membrane
- The phospholipid bilayer surrounding all cells, selectively controlling the passage of substances via passive and active transport mechanisms. SACE Board Stage 2 external examinations assess the fluid mosaic model and the roles of integral and peripheral proteins in membrane function.
- Mitosis
- The division of a eukaryotic cell nucleus into two genetically identical daughter nuclei through the stages prophase, metaphase, anaphase, and telophase. SACE Stage 2 skills and applications tasks require students to describe chromosome behaviour at each stage and explain the importance of accurate DNA segregation.
- Cellular respiration
- The metabolic pathway that converts glucose and oxygen into carbon dioxide, water, and ATP through glycolysis, the Krebs cycle, and oxidative phosphorylation. SACE Board Stage 2 investigation tasks assess the inputs, outputs, and cellular locations of each stage in both aerobic and anaerobic conditions.
- Photosynthesis
- The process by which autotrophs convert light energy into chemical energy (glucose), with light-dependent reactions in the thylakoids producing ATP and NADPH, and light-independent reactions (Calvin cycle) in the stroma fixing carbon dioxide. SACE Stage 2 external assessments test the complementary relationship between photosynthesis and respiration.
- Active transport
- The movement of substances across a cell membrane against their concentration gradient, requiring energy input from ATP hydrolysis. SACE Stage 2 Biology distinguishes active transport from passive processes (diffusion, osmosis, facilitated diffusion) in examination questions about nutrient uptake and ion regulation.
- Organelle
- A membrane-bound or non-membrane-bound structure within a cell that performs a specialised function, such as mitochondria (respiration), chloroplasts (photosynthesis), or ribosomes (protein synthesis). SACE Board Stage 2 skills and applications tasks assess the relationship between organelle structure and function in eukaryotic cells.
Sample Flashcards
Q1: Define an ecosystem and distinguish between biotic and abiotic factors.
An ecosystem is a community of living organisms (biotic) interacting with their non-living environment (abiotic) in a defined area. Biotic factors include organisms, food sources, predators, competitors and decomposers. Abiotic factors include temperature, rainfall, sunlight, soil type, pH, wind and salinity.
Q2: Explain the difference between a food chain and a food web.
A food chain is a single linear pathway showing energy transfer from one organism to the next (producer -> primary consumer -> secondary consumer -> tertiary consumer). A food web is a complex network of interconnected food chains showing all feeding relationships in an ecosystem. Food webs are more realistic because most organisms feed on multiple species.
Q3: Describe the trophic levels in an ecosystem.
Trophic levels represent feeding positions: Level 1 — Producers (autotrophs) synthesise organic matter from inorganic substances (e.g. plants, algae). Level 2 — Primary consumers (herbivores) eat producers. Level 3 — Secondary consumers (carnivores) eat primary consumers. Level 4 — Tertiary consumers (top predators) eat secondary consumers. Decomposers break down dead organisms at all levels, returning nutrients to the soil.
Q4: Explain why energy transfer between trophic levels is inefficient.
Only approximately 10% of energy at one trophic level is transferred to the next (the 10% rule). Energy is lost at each level through: cellular respiration (heat), excretion (urine, faeces), and indigestible material. This limits the number of trophic levels and explains why there are fewer top predators than producers in an ecosystem.
Q5: What is the role of decomposers in an ecosystem?
Decomposers (bacteria and fungi) break down dead organic matter (detritus) and waste products through extracellular digestion, releasing inorganic nutrients (nitrogen, phosphorus, carbon) back into the soil, water and atmosphere. This nutrient recycling is essential for producers to continue growing and for the ecosystem to sustain itself.
Q6: Outline the carbon cycle.
Carbon enters the biotic environment through photosynthesis (CO2 fixed into glucose by producers). It moves through food chains as organisms consume each other. Carbon returns to the atmosphere as CO2 through cellular respiration, decomposition and combustion of fossil fuels. Carbon is stored long-term in fossil fuels (coal, oil, gas), limestone and ocean sediments. The ocean also absorbs dissolved CO2.
Q7: Describe the nitrogen cycle and the role of bacteria.
Nitrogen gas (N2) makes up 78% of the atmosphere but is unusable by most organisms. Key steps: 1) Nitrogen fixation — nitrogen-fixing bacteria (Rhizobium in legume root nodules, free-living Azotobacter) convert N2 to ammonia (NH3). 2) Nitrification — nitrifying bacteria convert ammonia to nitrites to nitrates (NO3-), which plants absorb. 3) Assimilation — plants incorporate nitrates into amino acids and proteins. 4) Ammonification — decomposers break down organic nitrogen to ammonia. 5) Denitrification — denitrifying bacteria convert nitrates to N2, returning nitrogen to the atmosphere.
Q8: Define population and describe the factors that affect population growth.
A population is a group of organisms of the same species living in the same area at the same time. Population growth is affected by: birth rate (natality), death rate (mortality), immigration and emigration. When births + immigration exceed deaths + emigration, the population grows. Growth can be exponential (unlimited resources) or logistic (limited resources, reaching carrying capacity).
Sample Quiz Questions
Q1: An ecosystem includes only the living organisms in a defined area.
Answer: FALSE
An ecosystem includes both biotic (living organisms) AND abiotic (non-living physical and chemical) factors interacting in a defined area.
Q2: In a food chain, arrows point in the direction of energy flow — from the organism being eaten to the consumer.
Answer: TRUE
Arrows represent the transfer of energy from prey to predator (from the eaten organism to the consumer). This is a critical convention in ecology diagrams.
Q3: Decomposers only operate at the highest trophic level in an ecosystem.
Answer: FALSE
Decomposers break down dead organisms and waste from ALL trophic levels, not just the highest. They recycle nutrients from producers, consumers and top predators alike.
Q4: Approximately 10% of energy at one trophic level is transferred to the next level.
Answer: TRUE
The 10% rule states that roughly 10% of energy at one trophic level is passed to the next — the rest is lost as heat through respiration, excretion and indigestible matter.
Q5: A pyramid of energy can be inverted, with more energy at higher trophic levels.
Answer: FALSE
A pyramid of energy is ALWAYS upright because energy is lost at each trophic level through respiration. Unlike pyramids of numbers or biomass, energy pyramids cannot be inverted.
Why It Matters
Organisms and their environment explores the interactions between living things and their ecosystems, from the fundamental unit of all living organisms to the complex metabolic processes that sustain life. This topic requires you to understand cell structure at both the light and electron microscope level, explain how membranes regulate the movement of substances, and describe the metabolic pathways of cellular respiration and photosynthesis. Exam questions often present microscopy images, experimental data on transport processes, and diagrams of metabolic pathways. Mastering cell biology gives you the essential framework for understanding all other Stage 2 Biology topics, from DNA and proteins to homeostasis and evolution. Membrane transport concepts reappear in the homeostasis module when explaining how cells regulate their internal environment. Exam questions on cells commonly present experimental data on osmosis or enzyme activity and require you to interpret graphs and draw conclusions, so practise explaining trends in unfamiliar data sets.
Key Concepts
Cell Theory and Cell Structure
Understand the three tenets of cell theory and the technological advances that led to its development. Compare prokaryotic and eukaryotic cells, identifying key structural differences. Use electron micrographs to identify organelles including the nucleus, mitochondria, chloroplasts, endoplasmic reticulum, Golgi apparatus, lysosomes and ribosomes.
Membrane Structure and Transport
The fluid mosaic model describes membranes as dynamic structures with phospholipids, proteins and cholesterol. Understand passive transport (diffusion, osmosis, facilitated diffusion) and active transport (pumps, endocytosis, exocytosis). Relate membrane structure to selective permeability and explain how cells regulate their internal environment.
Cell Division and the Cell Cycle
The cell cycle includes interphase (G1, S, G2) and mitotic division. Understand the stages of mitosis and their significance for growth, repair and asexual reproduction. Explain how checkpoints regulate the cell cycle and how disruption of these controls can lead to uncontrolled cell division.
Cellular Respiration and Photosynthesis
Cellular respiration converts glucose to ATP through glycolysis, the Krebs cycle and the electron transport chain. Photosynthesis captures light energy to produce glucose through the light reactions and the Calvin cycle. Understand the complementary relationship between these processes and their significance for energy flow in living systems.
Common Mistakes to Avoid
- Stating that prokaryotic cells contain membrane-bound organelles such as mitochondria or a nucleus — SACE Board Stage 2 marking rubrics require students to clearly distinguish prokaryotic cells (no membrane-bound organelles, circular DNA in nucleoid region) from eukaryotic cells.
- Describing osmosis as the movement of water from high concentration to low concentration without specifying that it refers to water moving from a region of lower solute concentration to higher solute concentration across a selectively permeable membrane — SACE Stage 2 external examination answers require precise directional language.
- Confusing the stages of cellular respiration by placing the Krebs cycle in the cytoplasm instead of the mitochondrial matrix — SACE Stage 2 investigation assessments require correct identification of cellular locations: glycolysis in the cytoplasm, Krebs cycle in the matrix, and electron transport chain on the inner mitochondrial membrane.
- Claiming that animal cells do not have vacuoles — SACE Board Stage 2 assessment expects students to note that animal cells may contain small vacuoles, while plant cells characteristically have a large central vacuole for turgor maintenance.
- Omitting cytokinesis when describing cell division, leading to an incomplete account that ends at telophase — SACE Stage 2 external examinations allocate marks for describing how the cytoplasm divides (cleavage furrow in animal cells, cell plate in plant cells) following nuclear division.
Study Tips
- Create flashcards for each organelle with its structure and function, then review with spaced repetition to build rapid identification skills for microscopy questions.
- Practise comparing prokaryotic and eukaryotic cells by drawing labelled diagrams from memory, noting the key differences in size, structure and genetic organisation.
- For membrane transport questions, create a comparison table of passive versus active transport methods, noting the energy requirements and examples of each.
- For extended responses about human impacts, draw and annotate the stages of mitosis from memory, linking each stage to its key events and the significance of accurate chromosome segregation.
- Summarise cellular respiration and photosynthesis as complementary processes by mapping inputs, outputs and cellular locations for each stage of both pathways.
- Before your exam, work through the practice questions in this set at least twice using spaced repetition. Testing yourself repeatedly is the most effective revision strategy for long-term retention.
Related Topics
Frequently Asked Questions
What does SACE Biology Stage 2 Cells as the Basis of Life cover?
This topic covers cell theory and its historical development, prokaryotic versus eukaryotic cells, organelle structure and function, the fluid mosaic model, passive and active membrane transport, cell division (mitosis and the cell cycle), cellular respiration, photosynthesis and the relationship between cell structure and function.
How many flashcards are in this set?
This free set contains 20 flashcards and 20 true/false quiz questions covering all key concepts in SACE Biology Stage 2 Cells as the Basis of Life, aligned to the SACE Board subject outline. Build a strong foundation in cell biology for your exam preparation.
Are these flashcards aligned to the SACE Board syllabus?
Yes — every flashcard and quiz question is mapped to the SACE Board Stage 2 Biology subject outline for the Cells as the Basis of Life topic, ensuring relevance to your external examination.
Last updated: March 2026 · 20 flashcards · 20 quiz questions · Content aligned to the SACE Board