Human Anatomy and Physiology

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Done by Fowsia Cabdulrahman
unit 5
Andrew Oldnall

Cell Membrane

The cell membrane is a thin semi-permeable membrane that surrounds the cytoplasm of a cell its function is to protect the honesty of cell by allowing certain substances into cells, while keeping other substances out. It also serves as a base of attachment for the cytoskeleton in some organisms and the cell wall in others. This the cell membrane also serves to help support the cell and help maintain its shape. ‘Animal cells, plant cells, prokaryotic cells, and fungal cells have cell membranes’. (Education biology book)

Cell membrane surrounds the cell, it is made up of lipid chains and phosphate heads, there are some protein which contain within the cell membrane, they are called, peripheral protein, glycol protein and integral protein, they often form channels for substances to pass in and out of the cell. Protein molecules is also known as ‘identity markers or ‘reception site’, they are called this because substances, e.g. hormones cannot pass them without their permission. The function of the cell membrane is that it supports, protects and controls movement in and out of the cell, it is also a barrier between the cell and its environment, for example, it protects the ribosomes and lysosomes from coming near each other and it also maintains homeostasis.

Cell Membrane Structure

The cell membrane is mainly calm of a mix of  and . Depending on the membrane’s location and role in the body, lipids can make up anywhere from 20 to 80 percent of the membrane, with the remainder being proteins. While lipids help to give membranes their flexibility, proteins monitor and maintain the cell's chemical climate and help to transfer of molecules across the membrane.

Cell membrane lipids

Phospholipids are major component of cell membranes. They form a lipid bilayer in which their attracted to water head areas suddenly arrange to face the aqueous cytosol and the extracellular fluid, their hydrophobic (repelled by water) tail areas face away from the cytosol and extracellular fluid. The lipid bilayer is semi-permeable, allowing only certain molecules to strew across the membrane.  is another lipid component of cell membranes. It helps to thicken cell membranes and is not found in the membranes of . Glycolipids are located on cell membrane surfaces and have a  sugar chain attached to them. They help the cell to recognize other cells of the body.


Cytoplasm is also known as ‘cell material’, it refers to anything between the nucleus and the cell membrane, a chemical reaction called ‘metabolism’ take place in the cytoplasm. Something called glycogen is stored in the cytoplasm, the glycogen is mainly stored in cells where we need energy the most and they are the muscle cells and the liver cells. For example, when we eat food the food breaks down into glucose, the glycogen then takes in some of the glucose and stores it until we need them. This is important because, if we ate food and used all the energy that it provides we would be tired immediately. Melanin is what makes up our skin colour and it is found in the cytoplasm, it protects from diseases, such as skin cancer. Cytoplasm supports and protects all the cell organelles; the cytoplasm is also storage for the glycogen and melanin. If there was not a cytoplasm, the substances would crush to each other and the cell its self would crush.


The nucleus usually is the largest structure inside the cell and is the one that gives the substances permission to come in and out of the cell. Some cells have more than one nucleus and this is called Multinucleate, the cells with no nucleus are called a nucleate. The nuclear is the heart of the cells and controls all the activities in the cell. Red blood cells have no nucleus, however they only live for a short period of time and eventually die; they usually live for 120 days. The function of the nucleus are many, for example, nothing can happen without the permission of the nucleus, for example, if a hormone wants to enter the cell, it also controls what is inside the nucleus, because if the cell did not have a heat which controls something, everyone would die because the viruses and the infections would come in without permission, the nucleus contains all heditary material of the cell.

The nucleus is bounded by a double membrane called the nuclear envelope. This membrane separates the contents of the nucleus from the . The envelope helps to maintain the shape of the nucleus and assists in variable the flow of molecules into and out of the nucleus through nuclear pores.  are also located in the nucleus for example when a cell is "resting" not , the chromosomes are organized into long tangled structures called  and not into individual chromosomes as we naturally think of them.

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Nuclear Membrane

Nuclear membrane is similar to the cell membrane, however the nuclear membrane has gaps which pores through which protein can pass, and the function of the nuclear is that it controls movement in and out of the nucleus. If there was not a nuclear membrane the nucleus would just move around the cell and crush other cell substance, which is why it is important to create a wall for the nucleus.


Mitochondria is a substance which locates in the cells, however it cannot be spotted because they very tiny, it has process in ...

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