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Cell Structure.

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Cell Structure S Hoyland Furness College Channelside Barrow-in-Furness Cumbria LA14 2PJ Introduction The human body is made up of trillions of cells; these cells are the body's living building blocks. The cells themselves, as with the human body, are highly organised and within their interior have many highly specialized organelles. Through the coordinated actions of these cellular components each cell has the ability to perform certain basic functions essential to its own survival and specialized tasks that contribute to the maintenance of homeostasis. The cellular components within the cell (organelles) reflect the metabolism of the cell and dictate the bodily system it will be associated with, these cellular variations are essential for the whole body's survival. All body functions ultimately depend on the activities of the individual cells that compose the body. A Basic Human Cell Organelles within A Human Cell Nucleus The nucleus is one of the major parts of any individual cell and is also typically the largest, usually spherical in appearance and located towards the centre of the cell. Within the nucleus is the cells genetic material, deoxyribonucleic acid (DNA), which has two important functions. First, the DNA provides instructions for directing the synthesis of proteins and enzymes within the cell. By directing the kinds and amounts of various proteins and enzymes that are produced, the nucleus indirectly governs most of the cellular activities and is therefore commonly known as the control centre. ...read more.


Each mitochondrion is enclosed in two phospholipid bilayers called the inner and outer mitochondrial membranes. The outer membrane is smooth while the inner membrane is folded into convolutions called cristae. The cristae are responsible for providing the mitochondrion with a large surface area that enhances the productivity of respiration. The two membranes divide the mitochondria into two internal compartments. The space located between the outer and inner mitochondrial membranes is called the intermembrane space. The space enclosed by the inner membrane is termed the mitochondrial matrix; it is here that the metabolic steps of cellular respiration occur. Figure 4 (Human Physiology From Cells to Systems) Ribosomes. Ribosomes are involved in the assembly of proteins according to cell's genetic instructions. They are most predominant in cells that have high rates of protein synthesis. A functional ribosome consists of two non-membranous subunits; these subunits are constructed in the nucleolus of the cell, which join together in the presence of messenger RNA (ribonucleic acid). It is these ribosomes that give the ER its rough appearance although not all ribosomes are attached to the ER. Free ribosomes are suspended in the cytoplasm and are involved in the synthesis of proteins that remain in the cytoplasm. Although they produce proteins destined for different fates the ribosomes are structurally identical and interchangeable. ...read more.


High Power Drawing of the stained Onion Cells (mag x400) The table below outlines the general differences between the human cell and the plant cell observed under the light microscope. Nucleus Cytoplasm Cell Membrane Vacuole Chromatin Granules Cell Wall Cheek cells Yes, tends to be towards the centre of the cell Yes, makes up most of the cell Yes, encases the cell Yes, but very small Yes No Onion cells Yes, more likely to be found towards the edge of the cell Yes, found in a thin layer around the edge of the cell Yes, found inside the cell wall of the cell Yes, large important in the turgor pressure of the cell Yes Yes From the table above we can see the two main differences between the human and plant cells. 1. Vacuole, A membrane bound sac that plays a role in intercellular digestion and the release of cellular waste products, small in the animal cell but large in the plant cell. In the plant cell the vacuole plays a part in the turgor pressure of the cell, when the plant is well watered the water collects in the cell vacuoles producing rigidity; if the water pressure in the vacuole is reduced the plant wilts. 2. Cell wall, this structure is made of a substance called cellulose and provides the cells with both protection and rigidity, it's this structure that gives the plant the ability to remain upright (not present in animal cells). ...read more.

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