Animal and plant cells (AQA GCSE Biology Combined Science): Revision Notes
Animal and plant cells
Both animal and plant cells are made up of tiny structures inside them. These structures are called organelles and they each have different jobs to help the cell work properly.
Structures found in both animal and plant cells
Cell membrane
The cell membrane works like a security guard at the cell's entrance. It decides what can come in and what can go out of the cell. Important substances like oxygen, carbon dioxide and glucose can pass through it.
Think of the cell membrane as a selective barrier - it's not just a simple wall, but an intelligent gatekeeper that actively controls what substances can enter and leave the cell.
Nucleus
The nucleus is like the cell's control centre. It's a large structure that holds all the genes. These genes contain instructions that tell the cell what to do and how to behave.
Cytoplasm
Cytoplasm is a jelly-like substance that fills up the inside of the cell. Think of it like the cell's workspace where many important chemical reactions happen.
Mitochondria
Mitochondria are tiny structures that work like power stations. They carry out respiration, which releases energy that the cell needs to do all its jobs. The singular form is mitochondrion.
Cells that need lots of energy, like muscle cells, contain many more mitochondria than cells that don't need as much energy. This is a perfect example of how structure relates to function in biology.
Ribosomes
Ribosomes are very small structures that make proteins. This process is called protein synthesis. You can't see them clearly under a normal microscope because they're so tiny.
Extra structures found only in plant cells
Plant cells have all the same structures as animal cells, plus three additional ones that help plants survive in their own special way.
This is the key difference between animal and plant cells: plants have three extra structures that animal cells don't have. Remember this - it's often tested!
Cell wall
The cell wall is like a strong outer jacket made from a substance called cellulose. It gives the plant cell extra strength and helps it keep its shape. This is different from the cell membrane - don't get them confused!
Permanent vacuole
The permanent vacuole is a large space filled with a watery liquid called cell sap. It helps keep the plant cell firm and rigid, a bit like inflating a balloon to make it hard.
Chloroplasts
Chloroplasts are green structures where photosynthesis takes place. This is the process where plants make their own food using sunlight. That's why most plants are green - because of all the chloroplasts in their cells.
Key differences to remember
The fundamental difference:
Animal cells have:
- Cell membrane, nucleus, cytoplasm, mitochondria, and ribosomes
Plant cells have:
- All the animal cell structures PLUS cell wall, permanent vacuole, and chloroplasts
The three structures that plant cells have but animal cells don't are the cell wall, permanent vacuole, and chloroplasts. These extra structures help plants stay upright, store water, and make their own food.
Examples in action
Real-world Examples: Structure and Function
Example 1: Muscle cells Muscle cells contain lots of mitochondria because they need plenty of energy to contract and move the body. More mitochondria = more energy production.
Example 2: Plant root cells Plant root cells often don't have chloroplasts because they're underground and don't get sunlight for photosynthesis. No light = no need for chloroplasts.
Key Points to Remember:
- Both animal and plant cells share five basic structures: cell membrane, nucleus, cytoplasm, mitochondria, and ribosomes
- Plant cells have three extra structures that animal cells don't have: cell wall, permanent vacuole, and chloroplasts
- Each structure has a specific job - the cell membrane controls what goes in and out, the nucleus controls cell activities, and mitochondria provide energy
- The cell wall is made of cellulose and gives plants strength, while chloroplasts allow plants to make food through photosynthesis
- Don't confuse the cell wall with the cell membrane - they're completely different structures