ACT SSC Biology — Unit 2
Cell Structure — Flashcards & Quiz
Cell structure sits in Unit 2 Cells and Organisms of the BSSS Biology A/T course (from 2023). The course asks you to compare prokaryotic and eukaryotic cells, which share many features because of their common evolutionary past, and to explain how specialised organelles in eukaryotic cells carry out photosynthesis, cellular respiration, the synthesis of complex molecules and the removal of cellular products and wastes. Link each organelle's structure to its role, and connect it to how membranes and enzymes control biochemical processes in the cell.
Key Points
- Prokaryotes (bacteria and archaea) have no nucleus and no internal membrane-bound organelles, usually have a single circular chromosome, are much smaller than eukaryotes and exist as single cells.
- Eukaryotes (animals, plants, fungi and protists) keep linear chromosomes in a nucleus and contain membrane-bound organelles.
- All cells share a plasma membrane, cytosol, ribosomes and DNA, which reflects their common evolutionary past.
- Nucleus: houses DNA and controls gene expression; it is bounded by a double membrane (nuclear envelope) with nuclear pores.
- Mitochondria (aerobic respiration) and chloroplasts (photosynthesis) have double membranes and their own circular DNA, evidence of endosymbiotic origin.
- Rough ER (with ribosomes) makes proteins; smooth ER makes lipids; the Golgi apparatus modifies, sorts and packages proteins into vesicles.
- Lysosomes, vacuoles and vesicles break down, store and remove cellular products and wastes.
Common Mistakes to Avoid
- Claiming prokaryotes have a nucleus. They do not; their DNA lies in the cytosol (the nucleoid region).
- Mixing up rough ER (protein synthesis) and smooth ER (lipid synthesis).
- Forgetting that mitochondria and chloroplasts contain their own DNA and ribosomes.
- Confusing the cell wall (plants, fungi, bacteria) with the plasma membrane (all cells).
- Naming an organelle without linking its structure to its function, for example cristae increasing surface area for ATP production.
Exam Strategy
ACT SSC Biology is assessed through tasks set and marked by your college, such as tests, practical reports and research tasks, so question styles vary. Cell structure tasks commonly ask you to label a diagram, compare cell types or explain a structure–function relationship. Method: (1) identify the cell type and the evidence for it, (2) name the organelles involved and their structural features, (3) link structure to function (for example, folded inner mitochondrial membranes increase the surface area for ATP synthesis), (4) compare with the other cell type where relevant.
Sample Flashcards
Q1: How do prokaryotic and eukaryotic cells differ in structure?
Prokaryotic cells (bacteria and archaea) lack a nucleus and internal membrane-bound organelles, are much smaller, usually have a single circular chromosome in the cytosol and exist as single cells. Eukaryotic cells (plants, animals, fungi and protists) enclose linear chromosomes in a nucleus and contain membrane-bound organelles such as mitochondria, endoplasmic reticulum and the Golgi apparatus.
Q2: What features do all prokaryotic and eukaryotic cells share, and why?
Every cell has a plasma membrane that controls exchange with its surroundings, cytosol in which reactions occur, ribosomes that make proteins, and DNA as its genetic material. These shared features reflect a common evolutionary origin. All cells must also exchange nutrients, gases and wastes with their immediate environment, which is why membrane structure and surface-area-to-volume ratio matter for every cell.
Q3: Describe the structure and function of a mitochondrion.
A mitochondrion has a double membrane. The inner membrane is folded into cristae, which increase the surface area for the enzymes of the electron transport chain, and it encloses a fluid matrix where the Krebs cycle occurs. Mitochondria are the site of the aerobic stages of cellular respiration and produce most of the cell's ATP. They contain their own circular DNA and ribosomes, evidence of their endosymbiotic origin.
Q4: Describe the structure and function of a chloroplast.
Chloroplasts, found in plant and algal cells, have a double membrane surrounding a fluid stroma. Inside are stacks of flattened membrane sacs called thylakoids (grana) that contain chlorophyll, where the light-dependent reactions of photosynthesis occur. The light-independent reactions (Calvin cycle) take place in the stroma, producing glucose. Like mitochondria, chloroplasts contain their own circular DNA and ribosomes.
Q5: How do the rough ER, Golgi apparatus and vesicles work together to export a protein?
Ribosomes on the rough endoplasmic reticulum synthesise the protein, which enters the ER to be folded. Transport vesicles carry it to the Golgi apparatus, where it is modified (for example, by adding carbohydrate groups), sorted and packaged into secretory vesicles. These vesicles move to the plasma membrane and fuse with it, releasing the protein by exocytosis. Smooth ER, which lacks ribosomes, synthesises lipids.
Sample Quiz Questions
Q1: Prokaryotic cells have a membrane-bound nucleus.
Answer: FALSE
Prokaryotic cells lack a membrane-bound nucleus. Their DNA is in a nucleoid region.
Q2: Both prokaryotic and eukaryotic cells contain ribosomes.
Answer: TRUE
Ribosomes are found in all cells — prokaryotic (70S) and eukaryotic (80S) — for protein synthesis.
Revision Tip
Organelle structure-function pairs are classic flashcard content — drill a Revizi deck with the 6–8 major organelles until recall is automatic.
Related Concepts
Last updated: 9 October 2026 · 6 sample flashcards · 2 sample quiz questions