Structure and Function Relationships in Cells Revision Notes | GCSE OCR Foundation Biology

What this lesson covers

Understand how the structure of key organelles relates to their function, including nucleus, cell membranes, mitochondria and chloroplasts. Learn to est...

• Explain how the structure of the nucleus, cell membrane, mitochondria, chloroplasts and plasmids relates to their specific functions
• Compare the relative sizes of different sub-cellular structures using appropriate estimations
• Describe the key features of plant, animal and bacterial cells and their adaptations
• Calculate magnification and actual size of cellular structures from microscope images

Key ideas to keep in view

Use this lesson to stay inside B1.1 Cell structures while connecting the detail back to the wider B1: Cell level systems topic.

• B1: Cell level systems
• B1.1 Cell structures
• GCSE OCR Foundation Biology

Lesson notes preview

Read the core explanations from Structure and Function Relationships in Cells before testing yourself from memory.

• Your phone works because each component has the right shape for its job - the camera lens focuses light, the speaker vibrates to make sound. Cells work exactly the same way. Every part of a cell has a specific structure that makes it perfect for its particular function.
• This isn't coincidence - it's the fundamental rule of biology. Structure determines function. A mitochondrion looks completely different from a nucleus because they do completely different jobs. Understanding this connection is your key to making sense of cell biology.
• 2. The Control Centre - Nucleus Structure and Function
• The control centre of the cell that contains DNA and controls all cellular activities. Surrounded by a nuclear membrane with pores.
• Picture the nucleus as the cell's headquarters. It's large and spherical - roughly 10 micrometers across in most cells. This size matters because it needs to house all the cell's DNA, which would stretch 2 metres if unravelled.
• The nuclear membrane isn't solid - it's punctured with thousands of tiny pores. These aren't random holes. They're precisely controlled gateways that let messenger molecules pass in and out whilst keeping the precious DNA safely inside.
• Trap: Many students think the nucleus 'makes' proteins. Actually, it makes the instructions (mRNA) that tell ribosomes how to make proteins. The nucleus is the architect, not the builder.
• 3. The Powerhouses - Mitochondria Structure and Function
• The powerhouses of the cell that release energy from glucose through respiration. Have a folded inner membrane called cristae.
• Mitochondria look like tiny sausages under the microscope, but their internal structure is what makes them special. They have two membranes - an outer smooth one and an inner membrane that's folded into structures called cristae.

Continue through the topic

Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.