Understanding Animal Cell Structure for GCSE

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 learnt later in the course. Throughout my 12 years of teaching, I have seen first hand how important it has been for my students to develop a solid understanding of animal cell structure and function in order to succeed in their Biology studies.

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

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 your understanding of many topics throughout the course, such as protein synthesis, movement in and out of cells, and respiration.

The diagram below shows the key components of an animal cell:

• Cell membrane

• Nucleus

• Mitochondria

• Cytoplasm

• Ribosomes

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

The Structure of Animal Cells

Cell membrane

The cell membrane 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.

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 mitochondria are therefore sometimes termed the powerhouse of the cell. Cells that specifically require large amounts of energy will have many mitochondria (for example, 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, including 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 and functions 

Comparison Between Animal and Plant cells

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

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

• Plant cells contain chloroplasts, and they photosynthesise. Animal cells do not contain chloroplasts, and they do not photosynthesise

• Animal cells 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

Cells are the building blocks of all organisms, and therefore provide the key to understanding all the processes of life.

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

• Cilia cells are specialised epithelial cells with hair-like structures that 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

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 the 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 while 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

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, nucleus, mitochondria, cytoplasm and ribosomes. 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, including defending against pathogens, transporting oxygen, respiration and cell division.

Key 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 being the site of protein synthesis. Understanding how each of these cellular structures contributes to cell processes and how cells interact, is crucial for providing insights into the functioning of living organisms.

Many students that I have worked with find it useful to practise drawing and labelling animal and plant cells from memory. I like to use a wipeable white board initially so that my students can make mistakes and learn from them without worrying about their work becoming messy. This topic lends itself particularly well to being displayed on a mind map, so once you are more confident with the structures, why not produce a large mindmap all about animal and plant cell organelles and their functions?

My top tip for consolidating your knowledge of animal cells would be to work through some example questions on this topic and familiarise yourself with the expectations of the exam board by looking carefully at the mark scheme. You can find exam-board specific 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

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