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B1 G) Cell Differentiation
B1 G) Cell Differentiation
Human, animal and plant cells differentiate to become specialised to perform the role that they are responsible for undertaking. Cell differentiation occurs quite early on in the development of an organism. After specialising, human and animal cells will stay as that cell for the rest of their life; human and animal cells are unable to differentiate again to become another type of cell. Plant cells never lose their ability to differentiate again to become another type of plant cell.
Some cells in the human body are undifferentiated. These undifferentiated cells are known as stem cells in humans and animals, and meristems in plants. There is more information about stem cells in the stem cell section – click here to be taken to this section.
We are now going to look at a few different types of cells and the structures that they have in this section.
Some cells in the human body are undifferentiated. These undifferentiated cells are known as stem cells in humans and animals, and meristems in plants. There is more information about stem cells in the stem cell section – click here to be taken to this section.
We are now going to look at a few different types of cells and the structures that they have in this section.
Sperm Cells
Gametes are sex cells, and sperm cells are male gametes (female gametes are eggs). The role of sperm cells is to get the male DNA to the female DNA (in an egg) during sexual reproduction. Sperm cells contain half the normal number of chromosomes; human sperm cells have 23 chromosomes. Sperm cells have a long tail and a streamlined head so that they can swim to the egg. Sperm cells also have lots of mitochondria to give the sperm energy to move its tail, which allows the sperm to swim (the mitochondria obtain energy by undertaking respiration reactions). There are enzymes in the sperm’s head that digest through the membrane of an egg during fertilisation.
Gametes are sex cells, and sperm cells are male gametes (female gametes are eggs). The role of sperm cells is to get the male DNA to the female DNA (in an egg) during sexual reproduction. Sperm cells contain half the normal number of chromosomes; human sperm cells have 23 chromosomes. Sperm cells have a long tail and a streamlined head so that they can swim to the egg. Sperm cells also have lots of mitochondria to give the sperm energy to move its tail, which allows the sperm to swim (the mitochondria obtain energy by undertaking respiration reactions). There are enzymes in the sperm’s head that digest through the membrane of an egg during fertilisation.
Nerve Cells
Nerve cells send messages around the body via electrical impulses. There are a few different types of nerve cells/ neurones such as sensory neurones, relay neurones and motor neurones. Nerve cells are very long, which allows them to send electrical impulses from one part of the body to another part of the body. The ends of neurones have many different branches that connects the neurone to many other neurones who then take electrical impulses to other parts of the body.
Nerve cells send messages around the body via electrical impulses. There are a few different types of nerve cells/ neurones such as sensory neurones, relay neurones and motor neurones. Nerve cells are very long, which allows them to send electrical impulses from one part of the body to another part of the body. The ends of neurones have many different branches that connects the neurone to many other neurones who then take electrical impulses to other parts of the body.
Muscle Cells
Muscle cells contract and relax to allow parts of the body to move. Muscle cells are very long, which gives them space to contract. Muscle cells also contain lots of mitochondria who undertake respiration reactions, which provides the muscle cells with energy in order to contract.
Muscle cells contract and relax to allow parts of the body to move. Muscle cells are very long, which gives them space to contract. Muscle cells also contain lots of mitochondria who undertake respiration reactions, which provides the muscle cells with energy in order to contract.
Red Blood Cells
Red blood cells are responsible for taking oxygen around the body. They pick up oxygen in the lungs and take it to wherever it is needed in the body (such as a muscle cell). Here are some of the key characteristics of red blood cells:
Red blood cells are explored in more detail in the components of blood section – click here to be taken to this section.
Red blood cells are responsible for taking oxygen around the body. They pick up oxygen in the lungs and take it to wherever it is needed in the body (such as a muscle cell). Here are some of the key characteristics of red blood cells:
- Red blood cells are biconcave in shape (disc like or a filled in Cheerio). This shape gives them a very high surface area, which enables the efficient exchange of oxygen (both the loading and unloading of oxygen). This shape also means that they can carry as much oxygen as possible.
- They contain haemoglobin, which helps red blood cells to take oxygen around the body. Haemoglobin binds with oxygen in the lungs to create oxyhaemoglobin. Oxyhaemoglobin then splits up into haemoglobin and oxygen near body cells, which results in oxygen entering body cells.
- They do not have a nucleus. By not having a nucleus, red blood cells can contain more haemoglobin and can therefore carry more oxygen.
- Red blood cells are thin meaning that the distances for diffusion are short.
- Red blood cells are flexible, which enables them to squeeze through capillaries. The diameter of the capillaries is only slightly bigger than the diameter of red blood cells.
Red blood cells are explored in more detail in the components of blood section – click here to be taken to this section.
Root Hair Cells
Root hair cells are found on the roots of plants. They have a very large surface area to bring in water and mineral ions from the soil. The root hair cells also contain many mitochondria, which gives the root hair cells energy to undertake active transport to always bring in mineral ions from the soil into the root hair cells despite there being a lower concentration of mineral ions in the soil compared to inside the root hair cells (active transport is the net movement of particles against a concentration gradient [low to high] – click here for more information on active transport and root hair cells).
Root hair cells are found on the roots of plants. They have a very large surface area to bring in water and mineral ions from the soil. The root hair cells also contain many mitochondria, which gives the root hair cells energy to undertake active transport to always bring in mineral ions from the soil into the root hair cells despite there being a lower concentration of mineral ions in the soil compared to inside the root hair cells (active transport is the net movement of particles against a concentration gradient [low to high] – click here for more information on active transport and root hair cells).
Phloem & Xylem Cells
Phloem and xylem cells are responsible for transport in plants.
The phloem and xylem tubes are explored in more detail in the plant transport system section – click here to be taken to this section.
Phloem and xylem cells are responsible for transport in plants.
- Phloem cells create phloem tubes, which are hollow in the centre. Phloem tubes transport cell sap around plants; cell sap is a solution of food substances (sugars, amino acids and other soluble food molecules produced by photosynthesis). Phloem cells are living cells that have perforated ends. Cell sap can move in both directions through the phloem tubes. Energy is required in order for cell sap to move and this energy comes from mitochondria undertaking respiration reactions. Phloem cells have few subcellular structures to allow substances to move through easily. The process of cell sap moving through phloem tubes is known as translocation.
- Xylem cells create xylem tubes, which are hollow in the centre. Xylem tubes transport water and dissolved mineral ions from the roots to the stems, and then the leaves (water then exits the leaves into the atmosphere through the stomata). Water and dissolved mineral ions moving through the xylem tubes and then into the atmosphere is known as transpiration/ transpiration streams. Xylem cells are dead cells and there are no ends between the cells in xylem tubes.
The phloem and xylem tubes are explored in more detail in the plant transport system section – click here to be taken to this section.