Understanding Animal Cell Structure for GCSE Students

All GCSE and iGCSE Biology courses require you to recall the structure of an animal cell including all the organelles and their functions. You are expected to be able to identify these organelles in diagrams and to compare structures found in animal cells with those found in other cells such as plant cells. 

The cell structure topic is taught early in the GCSE course as much of the information studied will underpin other ideas learned later in the course. This means, in order for you to really succeed in your Biology studies, it is important that you develop a really solid understanding of animal cell structure and function.

In this article, I will break down the key information that you will need to know about the structure and function of animal cells.

Overview of animal cells for GCSE

Animal cells are considered the basic building blocks of animal organisms. The cells are eukaryotic which means that they contain a nucleus and other membrane-bound organelles, such as mitochondria.

In-depth knowledge of animal cell structure and function will support understanding of many topics throughout the course such as protein synthesis, movement in and out of cells, and respiration amongst others.

The diagram below shows the key components of an animal cell to include the following structures:

• Cell membrane

• Nucleus

• Mitochondria

• Ribosomes

• Cytoplasm

You should be able to identify these organelles in a diagram of an animal cell.

Comparison between animal and plant cells

You must be able to compare animal and plant cells in terms of their structure and functional similarities and differences.

Remember that both plant and animal cells are eukaryotic and are building blocks are larger organisms. They also both contain key organelles including the cell membrane, cytoplasm, nucleus, mitochondria and ribosomes.

However, there are also differences:

• Plant cells have cell walls made of cellulose which provide support to the cells giving them a much more regular shape compared to animal cells. 

• Animal cells do not photosynthesize and so they do not contain chloroplasts like plant cells do.

• Animal cells also do not have a large permanent vacuole which plant cells use as a way of storing water. When full, the vacuole also provides support to the cell by pushing the cell membrane against the cell wall.

The importance of animal cells

Due to the role of cells as the building blocks of all organisms, they provide the key to understanding all processes of life.

• Cells can be specialised to carry out specific functions for example:

  • Cilia cells are specialised epithelial cells with hair-like structures which waft mucous containing trapped pathogens away from the lungs, this prevents infections

  • Red blood cells lack nuclei so that they can be packed full of haemoglobin for carrying oxygen to respiring cells of the body

  • Some white blood cells have many ribosomes to give capacity for the production of huge quantities of antibody proteins to fight pathogens

Specialised cells diagram

Groups of similar cells, work together to form particular functions of an organism for example

• Muscle tissue contracts to allow movement

• Nervous tissue transmits electrical impulses to allow responses to stimuli

• Fat tissue insulates and protects

Cellular organisation is therefore key in ensuring functionality of organs where different tissue types allow certain processes to occur for example

• The heart is made up of muscle tissue, nervous tissue, fatty tissue and connective tissue. Together, these tissues support the constant pumping of blood around the body to deliver oxygen and glucose to respiring cells whilst removing waste products such as carbon dioxide.

Cells have the capacity to divide through mitosis and meiosis.

• In mitosis, body cells are replicated when a parent cell divides to produce two daughter cells which are genetically identical to the original cell. This is important to allow growth of an organism but also to repair damaged tissues.

• Sex cells are produced via a different form of cell division, meiosis. In meiosis a parent cell divides twice resulting in the production of four haploid daughter cells, called gametes. In animals, the gametes are the egg and sperm cells which fuse at fertilisation to produce a zygote. This super potent stem cell is able to develop into an entire new organism through mitotic cell division and differentiation of cells into all of the specialised cells of the body.

The structure of animal cells

Cell membrane

The cell surface membrane surrounds all other structures in an animal cell. It is a semi-permeable barrier which controls the exchange of substances between the inside and outside environment.

As the most external structure of a cell, the membrane is also responsible for interacting with other cells, such as neighbouring cells or immune cells. Molecules, such as hormones, can bind to receptors on the membrane initiating specific responses within the cell.

The nucleus

The nucleus is a large organelle containing cellular DNA within a membrane. Nuclei are found in all eukaryotic cells, apart from red blood cells. The DNA in the nucleus provides the instructions for all of the different proteins that can be made by the cell and therefore is responsible for cell function.

During cell division, the genetic material inside the nucleus copies itself so that there are two sets of chromosomes. The nucleus then breaks down and the genetic material is separated into two new cells.

• In mitosis, the daughter cells produced have diploid nuclei, which means they have the same number of chromosomes as the parent cell. 

• In meiosis, the daughter cells produced have haploid nuclei which contain half the number of chromosomes as the parent cell. These are the gametes (egg and sperm). In fertilisation, two gametes fuse, each providing half of the DNA required for the resulting zygote.

Mitochondria

The mitochondria are the site of aerobic respiration in all eukaryotic cells (including animal cells and plant cells). In respiration, glucose reacts with oxygen to release energy in the form of ATP (adenosine triphosphate), carbon dioxide and water are produced as waste products.

Cellular respiration provides the energy required for cell processes and is therefore mitochondria are sometimes termed the powerhouse of the cell. Cells which specifically require large amounts of energy will have many mitochondria e.g. muscle cells.

Cytoplasm

The cytoplasm is a gel-like substance made up of water and dissolved solutes, found inside the cell membrane. All organelles are suspended in the cytoplasm. 

Many of the metabolic reactions within a cell take place in the cytoplasm, this includes anaerobic respiration. Substances, such as proteins and other biological molecules are also transported around the cell in the cytoplasm.

Ribosomes

Ribosomes are small organelles found in all cells. In eukaryotic cells, ribosomes are found either free in the cytoplasm of the cell, or attached to other organelles such as the rough endoplasmic reticulum.

Ribosomes are the site of the translation stage of protein synthesis. In protein synthesis, information from the DNA in the nucleus is transferred to the ribosomes where it is translated into functional proteins. 

Cellular structures & functions table

Ace your biology exam by understanding animal cells

In summary, animal cells are eukaryotic cells with membrane-bound organelles and a nucleus. They have several shared features with plant cells including the cell membrane, ribosomes, nucleus, mitochondria and cytoplasm. However, unlike plant cells, animal cells do not have chloroplasts, a cell wall or a large permanent vacuole.

Animal cells are the building blocks of multicellular eukaryotic animal organisms and play key roles in the body, from defending against pathogens to transporting oxygen as well as through cellular processes, such as respiration and cell division.

Important organelles have specific functions such as the cell membrane regulating substances entering and leaving the cell, the nucleus containing DNA, mitochondria providing the site of respiration and ribosomes as the site of protein synthesis. Understanding how each of these cellular structures contribute to cell processes and how cells interact, is crucial for providing insights into the functioning of living organisms.

My top tip for consolidating your knowledge of animal cells would be to work through as example topic questions and familiarise yourself with the expectations of the exam board through the accepted mark points. You can find exam-board specific topic questions on cell structure through these links:

• AQA GCSE Cell Structure

• Edexcel GCSE Cell Structure

• OCR GCSE Cell Structures

• Edexcel IGCSE Cell Structure

• CIE IGCSE Cell Structure