Cell BiologyDeep Dive

Animal Cell: Organelles and Their Functions

Part of Cell Organelles · GCSE GCSE Biology revision

This deep dive covers Animal Cell: Organelles and Their Functions within Cell Organelles for GCSE Biology. Revise Cell Organelles in Cell Biology for GCSE Biology with 12 exam-style questions and 15 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 3 of 13 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.

Topic position

Section 3 of 13

Practice

12 questions

Recall

15 flashcards

🏗️ Animal Cell: Organelles and Their Functions

🧬 Nucleus

Controls all cell activities — the "control centre"
Contains chromosomes made of DNA
Surrounded by double nuclear membrane with pores
Contains the nucleolus where ribosomes are assembled
Sends instructions to ribosomes via mRNA

⚡ Mitochondria (singular: mitochondrion)

Site of aerobic respiration
Transfer energy from glucose, producing ATP
Double membrane — inner membrane folded into cristae (increase surface area)
Have their own DNA and ribosomes
Cells with high energy demands (e.g. muscle cells) have many mitochondria

🏭 Ribosomes

Site of protein synthesis
Made of rRNA and protein
Found free in cytoplasm (make cytoplasmic proteins) OR attached to rough ER (make proteins for export)
Present in ALL cells, including prokaryotic cells
Translate mRNA code into a sequence of amino acids

🌐 Rough Endoplasmic Reticulum (Rough ER)

Network of membrane-bound sacs covered in ribosomes
Ribosomes on its surface synthesise proteins
Folds and processes newly made proteins
Transports proteins to the Golgi apparatus
"Rough" = rough appearance due to ribosomes

📬 Golgi Apparatus

Stack of flattened membrane sacs (cisternae)
Receives proteins from rough ER
Modifies and packages proteins (e.g. adds sugar chains)
Sends finished proteins in vesicles to cell membrane for export OR to lysosomes
Also makes lysosomes

🗑️ Lysosomes

Membrane-bound sacs containing hydrolytic (digestive) enzymes
Digest worn-out organelles (autophagy)
Destroy engulfed bacteria in white blood cells
Release their contents when cells are damaged or worn out

🧱 Cell Membrane

Controls what enters and leaves the cell (selectively permeable)
Made of a phospholipid bilayer with proteins embedded
Site of cell signalling and receptor proteins

🌊 Cytoplasm

Gel-like fluid filling the cell
Site of many chemical reactions (e.g. glycolysis)
Suspends and connects all organelles
Contains dissolved chemicals needed for chemical reactions

Practice Questions for Cell Organelles

Scientists studying mitochondria use electron microscopes rather than light microscopes. Which statement correctly explains why electron microscopes are more useful for studying cell ultrastructure?

A. Electron microscopes produce a coloured image that makes organelles easier to identify
B. Electron microscopes have a higher resolution, so finer details of organelles can be seen
C. Electron microscopes allow scientists to study living cells in real time
D. Electron microscopes are cheaper and easier to use than light microscopes

1 markfoundation

A researcher is isolating mitochondria from liver cells using cell fractionation. The protocol states the homogenisation solution must be: (i) cold, (ii) isotonic, and (iii) buffered. Explain why each of these three conditions is necessary.

3 marksstandard

Quick Recall Flashcards

What is cell fractionation and what is it used for?

Cell fractionation is a technique that separates organelles from a cell homogenate using differential centrifugation. It allows individual organelle types to be isolated in a pure form so their structure and function can be studied in detail.

What does the term 'ultrastructure' mean in cell biology?

Ultrastructure refers to the fine internal structural detail of cells and organelles — features too small to be seen with a light microscope. Ultrastructure is revealed by electron microscopy. Examples: cristae of mitochondria, thylakoids of chloroplasts, nuclear pores, rough ER ribosomes.