Cell Structure

Cells are the individual units that make life possible. Houses have bricks, we have cells.

Our cells give us structure, metabolise food, transport nutrients and waste, allow us to sense, see, hear and think.

These building blocks of life have very clever structures within them called organelles. We have organs, like our brain, heart and skin. Cells have organelles, like a nucleus, membrane and cytoplasm.

In this section we will explore these fascinating little units, under 4 headings: Animal cells, Plant cells, Fungal cells and Bacteria cells.

Animal Cells

Animals include you, me, chickens, donkeys, sea lions, lions and fish, to name a few. Our cells have particular structures within them that we need to learn in National 5 Biology.
Cell structures are called organelles:
**Cell Nucleus** - The brain of the cell which controls the activities within the cell and contains genetic information in chromosomes.
**Cell membrane** - The barrier around the cell that separates the interior of the cell from the outside environment while regulating the transportation of materials in and out of the cell.
**Cytoplasm** - A gel-like fluid in cells that acts as a medium for chemical reactions to occur. The cytoplasms contains organelles such as the nucleus, ribosomes and mitochondria.
**Ribosomes** - These aid in the synthesis of proteins.
**Mitochondria** - The organelle that generates chemical energy required to power the biochemical reactions within the cell.

Plant Cells
Bonzai trees, apples, grass, nettles, all have plant cells. Plant cells create energy from the sun through a process called photosynthesis. This will be talked about in more detail later, but for now you need to know about the organelle in charge of this job.
The cell organelles in plant cells:
**Cell Nucleus** - The brain of the cell which controls the activities within the cell and contains genetic information in chromosomes.
**Cell Membrane** - The barrier around the cell that separates the interior of the cell from the outside environment while regulating the transportation of materials in and out of the cell.
**Cytoplasm** - A gel-like fluid in cells that acts as a medium for chemical reactions to occur. The cytoplasms contains organelles such as the nucleus, ribosomes and mitochondria.
**Ribosome** - These aid in the synthesis of proteins.
**Mitochondria** - The organelle that generates chemical energy required to power the biochemical reactions within the cell.
**Cell wall** - A structural layer outside of the cell membrane that provides tensile strength and protection against mechanical and osmotic forces. This is made of **Cellulose** in plants. Cells walls of other cells are made of different chemicals and not cellulose.
**Chloroplast** - This organelle converts light energy into chemical energy via photosynthesis. These are little green structures that give many plants their green colour. They contain **Chlorophyll**, the chemical that allows light energy to be converted into chemical energy.
**Vacuole** - A compartment of plant cells containing sugars and salts. It is also in charge of water storage.

Fungal Cells
Fungal cells are very similar to plant cells. They contain a nucleus, cell wall, membrane, cytoplasm, ribosome, mitochondria and vacuole. However, fungal cells don’t photosynthesise, and so don’t have chloroplast.
Examples of fungi include yeast, mushrooms and moulds.

Bacterial Cells
Bacteria are all around us. They can be good and bad. Good bacteria populate our gut, allowing us to digest food effectively. Bacteria can also be harmful to us, causing infections. They are single-celled organisms.
It is very important that we understand bacterial cell structures, as knowing this allows us to fight them off with medications such as antibiotics.
Weirdly, bacterial cells don’t have a nucleus. Instead they have large circular chromosomes as well as plasmids, which are smaller rings of DNA.
The plasmids in bacterial cells carry extra genetic information for the bacteria. These are helpful for bacterial evolution and adaptation.
Other structures within bacterial cells include cytoplasm, cell wall, cell membrane, ribosomes and mitochondria.

Key Points!

Cells

Cells are the building blocks of life.
Cells have structures within them called organelles.
Animal Cells

Animal cells contain a nucleus, cytoplasms, cell membrane, ribosomes and mitochondria.
Plant cells

Plant cells contain a nucleus, cytoplasm, cell membrane, ribosomes, mitochondria, cell wall, vacuole and choroplast.
Fungal cells

Fungal cells are similar to plant cells, but don’t contain a vacuole or chloroplast.
Bacterial cells

Bacteria are single-celled organisms.
They contain DNA without a nucleus, plasmids, cytoplasm, cell membrane, cell wall, ribosomes and mitochondria.
Organelle functions

Nucleus - brain of cell containing DNA
Cytoplasm - fluid within the cell containing organelles and site of chemical reactions
Membrane - allows transport of molecules into and out of the cell
Ribosomes - allow protein production
Mitochondria - powerhouse of the cell
Cell wall - allows protection and structure to the cell
Chloroplast - site of photosynthesis
Vacuole - allows storage of water in plant cells
Plasmid - small rings of genetic information in bacterial cells.