Cell Structure Explained: A Beginner's Guide for Access to HE Science Students

Cells are the basic unit of life

Starting an Access to HE Science course this September?

If it's been a while since you last studied science, don't worry—you're not expected to remember everything from school.

Many students feel nervous about returning to Biology, especially if it's been several years since they last looked down a microscope or thought about cells. The good news is that the course starts by building on the basics, and that's exactly what we're going to do here.

Let's begin with one of the most important topics in biology...

What is a cell?

Cells are microscopic structures

A cell is the smallest living unit of an organism. Think of a cell as a tiny building block. Every living thing is made up of cells, from the bacteria living in the soil to the tallest trees and the human body. Your body contains around 30 trillion cells, all working together to keep you alive. Some organisms, such as bacteria, consist of just one cell. These are called unicellular organisms.

Humans, animals and plants are made up of many cells, so they are known as multicellular organisms. Although cells are incredibly small (most can only be seen using a microscope), each one carries out all the essential processes needed for life.

What does a cell do?

Cells perform many important functions, including:

• Producing energy

• Making proteins

• Removing waste products

• Growing and dividing to produce new cells

• Responding to changes in their environment

Different types of cells have different jobs. For example:

• Muscle cells contract to produce movement.

• Nerve cells carry electrical signals.

• Red blood cells transport oxygen.

• White blood cells help fight infection.

Despite their different roles, most human cells contain the same basic structures.

The main parts of an animal cell

An animal cell contains several important structures called organelles. Each organelle has its own specific job.

Parts of an animal cell

1 - Cell membrane

The cell membrane forms the outer boundary of the cell. It controls what enters and leaves the cell, rather like a security gate. Small substances such as oxygen and nutrients can move into the cell, while waste products leave through the membrane.

2 - Nucleus

The nucleus is often described as the control centre of the cell. It contains the cell's DNA (genetic material), which acts as the instructions for building and operating the cell.

The nucleus controls activities such as growth, protein production and cell division.

3 - Mitochondria

Mitochondria are often called the powerhouses of the cell. They release energy from food during a process called aerobic respiration. Cells that require lots of energy, such as muscle cells, contain large numbers of mitochondria.

4 - Ribosomes

Ribosomes are tiny structures responsible for making proteins. Proteins are needed for growth, repair and many important chemical reactions inside the body.

5 - Cytoplasm

The cytoplasm is a jelly-like substance that fills most of the cell. It holds the organelles in place and is where many of the chemical reactions needed for life take place.

How are plant cells different?

Plant cells contain all of the structures found in animal cells, but they also have three additional features.

Parts of a plant cell

6 - Chloroplasts

Chloroplasts contain a green pigment called chlorophyll. They absorb light energy so the plant can carry out photosynthesis, producing its own food. Animal cells do not have chloroplasts because animals cannot photosynthesise.

7 - Permanent vacuole

Plant cells usually contain one large permanent vacuole filled with cell sap.

The vacuole stores water and dissolved substances and helps keep the cell firm.

8 - Cell wall

The cell wall surrounds the cell membrane. Unlike the flexible membrane, the cell wall is rigid and made from cellulose. It provides strength and support to help plants stay upright

Animal cells vs plant cells

Animal Cell	Plant Cell
Cell membrane	Cell membrane
Cytoplasm	Cytoplasm
Nucleus	Nucleus
Mitochondria	Mitochondria
Ribosomes	Ribosomes
No cell wall	Cell wall
No chloroplasts	Chloroplasts
Small temporary vacuoles (if present)	Large permanent vacuole

Why is cell structure important?

Understanding cells is the foundation of biology. As you progress through your Access to HE Science course, you'll build on this knowledge to learn about topics such as:

• Cell transport (diffusion, osmosis and active transport)

• Cell division (mitosis and meiosis)

• DNA and genetics

• Human body systems

• Microbiology

• Disease and immunity

Having a good understanding of cell structure will make these later topics much easier to understand.

Top Tip for Access Students

Don't worry about memorising every detail straight away. Instead, focus on understanding what each organelle does and why it is important. Once you understand the function of each part of the cell, remembering their names becomes much easier.

Remember, every healthcare professional, scientist and researcher started by learning the basics—and this is where your journey begins.

Ready for September?

If you're preparing to start an Access to HE Science course and would like extra support with Biology, Chemistry or Physics, we're here to help.

At Applied Science Tutoring, we provide one-to-one online tuition to support students studying Access to HE Science courses. Whether you're returning to education after a few years—or a few decades—we'll help you build confidence, strengthen your understanding and prepare for success.