Getting to Know Your Cells
Cell Biology
You may have heard people describe their body as a machine. Typically, the response to this statement would be to roll your eyes and zone out of the conversation. And while some of these comments are made in vain, the individuals making them are not wrong. But they are not unique; all humans are ‘machines’. Your body works like a finely-tuned instrument; constantly performing highly complex jobs right under your nose. Even when you are curled up hungover in a ball on the couch on a Sunday morning, your body is grinding away to keep you feeling that horrendous. The main cogs in the human body responsible for this hard work are your cells. Every inch of skin, lock of hair and piece of heart is composed of these tiny little machines which work together to create tissues, organs and collectively, a fully working human. The average sized adult has over 37 trillion cells, of which there are around 200 different types. It is crazy to think that we all start out as a single cell and develop into a highly complex, ordered device. So learning about what makes a cell a cell and some of the specific workers responsible for distinct bodily functions can teach us a bit more about ourselves.
You may have heard people describe their body as a machine. Typically, the response to this statement would be to roll your eyes and zone out of the conversation. And while some of these comments are made in vain, the individuals making them are not wrong. But they are not unique; all humans are ‘machines’. Your body works like a finely-tuned instrument; constantly performing highly complex jobs right under your nose. Even when you are curled up hungover in a ball on the couch on a Sunday morning, your body is grinding away to keep you feeling that horrendous. The main cogs in the human body responsible for this hard work are your cells. Every inch of skin, lock of hair and piece of heart is composed of these tiny little machines which work together to create tissues, organs and collectively, a fully working human. The average sized adult has over 37 trillion cells, of which there are around 200 different types. It is crazy to think that we all start out as a single cell and develop into a highly complex, ordered device. So learning about what makes a cell a cell and some of the specific workers responsible for distinct bodily functions can teach us a bit more about ourselves.
Look inside your cells
Look inside your cells
Every organ is made up of tissues, and every tissue is made up of cells. While cells are the smallest entity in this system, they are the most complex and their function can determine how well an entire organ functions. Each cell acts as its own little machine, containing individual components to ensure it runs efficiently. Flash back to GCSE biology and you may remember learning the differences between an animal and plant cell. Whether you enjoyed biology or not, some vocab about cell structure have probably been engraved in your head forever. Learning about these structures (called organelles) can allow us to understand the intricate processes which make a cell such a powerful unit.
Cell Membrane, Cytoplasm and Nucleus
1. Cell Membrane
Each cell has a defined border separating their interior from the external environment. This border is called a cell membrane and contains many different pores, channels and receptors. These contraptions allow signals from the outside of a cell to pass to the inside without completely disrupting the contained environment.
2. Cytoplasm
The inside of a cell is described as the cytoplasm. This is a broad term for the many proteins and structures which are contained within a cell. The cytoplasm is normally a distinct environment compared to the space surrounding the cell as it has different levels and types of molecules like ions. Structures called microtubules act as train tracks in the cytoplasm to transport proteins around the cell.
3. Nucleus and Nucleolus
At school, the nucleus would have been described to you as the ‘brain of the cell’. While the nucleus doesn’t make memories or have higher functions, it possesses every instruction on how to make a cell run correctly. The nucleus holds your DNA, the genetic material which codes for every protein you need to survive. This material is extremely precious, and the nucleus enables the protection of this material by separating it from the rest of the cell. Certain sections of the DNA are bound to the nucleolus.
Endoplasmic Reticulum and Ribosomes
Surrounding the nucleus is the endoplasmic reticulum (ER). This is the area where the proteins coded by the DNA are created. The actual construction of these proteins happens in ribosomes; the small puncta on the ER. The areas of ER with ribosomes is described as ‘rough’ whereas areas without ribosomes are called ‘smooth’. Together, the proximity of the ER to the nucleus and the machinery within the ribosomes make the perfect environment for the synthesis of new proteins.
Golgi Apparatus, Vesicles and Lysosomes
Once proteins have been synthesised in the cell, they need to be sorted and sent to their correct location to perform their specific job. New proteins are packed into vesicles; small compartments which can travel through the cytoplasm, as they leave the ER. These vesicles are sent to the golgi apparatus, sometimes referred to as the ‘post office of the cell’, which organises and packages up proteins into new vesicles to be delivered to their new home. The golgi apparatus also generates lysosomes; a vesicle containing digestive proteins. Lysosomes are known as the ‘stomach’ of the cell as they absorb waste in the cytoplasm and break it down, so it can easily be recycled or disposed of.
Mitochondria
All of the above processes require energy, and this energy is generated by bean-shaped organelles called mitochondria. Mitochondria generate a substance called ATP using oxygen. This is known a cell respiration. Very active cells require high numbers of mitochondria, therefore high numbers are found in muscle and heart cells.
Express your cells
Although most cells contain the basic features listed above, different types of cells have been adapted for their specific function.
Red Blood Cell
Location: Blood
Size: 8.2um diameter
Role: To transport oxygen around the body
Adaptation: Red blood cells have no nucleus (enucleated), meaning they have a concave shape. This gives them flexibility to pass through very narrow blood vessels and absorb as much oxygen as possible.
Cardiac Myocyte Cell
Location: The Heart
Size: 25um diameter
Role: Cardiac myocyte cells make up the muscle of the heart. These cells are responsible for the pumping action of the heart to move all the blood around your entire body.
Adaptation: These cells are extremely strong and durable as they have to work continuously. They are all connected by gap junctions which allows them to contract in a wave-like pattern to synchronously pump blood and alter the hearts pace. The rhythm of this pumping is intrinsically determined by pacemaker cells and the cardiac cells adapt to new rhythms rapidly.
Skeletal Muscle Cell
Location: Muscles (eg. Biceps, Quadraceps etc)
Size: 1-40mm length
Role: To aid the voluntarily movement of limbs through contraction. The by-product of this actions also produces heat.
Adaptation: Skeletal muscle cells are long fibres containing many nuclei as they are generated by the fusion of many smaller muscle cells during development. They also contain high numbers of mitochondria and contractile filaments (called actin and myosin).
Neuron
Location: The Brain
Size: less than an inch to several feet (length)
Role: To process and transmit signals rapidly to permit voluntary and involuntary action.
Adaptation: Neurons have long processes for receiving signals called dendrites. These signals are condensed into a single signal and transmitted down their axon to other neuron’s dendrites. Signal transmission occurs at a chemical junction called a synapse.
Keratinocyte
Location: The epidermis
Size: up to 30um diameter (when no longer dividing)
Role: To protect the inner layers of the skin from contaminants (bacteria, viruses etc) and mutagens (UV radiation) by forming a barrier
Adaptation: These cells can produce and release lots of inflammatory proteins if a contaminant enters the skin. They also contain melanin granules, which give your skin colour, and can produce high levels of keratin, which make the cells harden and form the top layers of your skin.
Now you have an idea of what your cells are made of and some of their adaptations. These small changes to structure allow your cells to carry out such a diverse range of functions, all vital for keeping you alive. So, appreciate your cells for making you yourself!
