• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

The cell may be regarded as the basic unit of an organism it carries out the essential processes that make the organism a living entity. All cells share certain structyral and functional features and they are of almost universal occurance in living organi

Extracts from this document...

Introduction

GIVE AN ACCOUNT OF THE DISTRIBUTION & FUNCTIONS OF THE MEMBRANES OF EUKARYOTIC CELLS The cell may be regarded as the basic unit of an organism, it carries out the essential processes that make the organism a living entity. All cells share certain structural and functional features and they are of almost universal occurrence in living organisms. Biologists have devoted a great deal of attention to its structure and the processes that go on inside it. They have recognised a major distinction between two types of cells, Eukaryotic cells that have a nucleus and Prokaryotic cells that do not have a nucleus. There are many other differences between these two cells, in particular eukaryotic cells have a full complement of membrane bound organelles in their cytoplasm and are characterised by the possession of these organelles. Eukaryotic cells are typical of a great majority of organisms including all animal and plant cells and it is this type of cell that we will be looking at. They are multicellular which means they are composed of groups of specialised cells each performing a particular function. They also show a high level of structural complexity that allows an elaborate division of labour, which has enabled them to reach high orders of functional complexity. The biological membrane and the various molecular complexes embedded in them must now be viewed as playing a central role in both cell structure and its functions All cells whether animal or plant has a cell surface that is known as the plasma membrane. ...read more.

Middle

This forms the bulk of the ER and consists of flattened cavities, its function is to isolate and transport the proteins that have been synthesised by the ribosome's. The major function of ribosome's is protein synthesis, RER allows the conveyance of the finished product via other organelles to the plasma membrane for export. Smooth ER consists of tubular cavities and does not have ribosome's attached, it is concerned with synthesis and transport of lipids and steroids. Proteins produced by the ribosome's are believed to move to the Golgi Apparatus via Rough ER The Golgi Apparatus is an assembly point through which raw materials for secretion are funnelled before being shed from the cell. It consists of a stack of flattened membrane bound sacs continuously being formed at one end and budded off as vesicles at the other. At times the Golgi modifies the cell products it contains, the protein received from the RER has polysaccharides added to it producing glycoproteins. Similarly it modifies lipids into Glycolipids, these products are then wrapped into various types of ecretary vesicles for movement to the cell membrane so they can discharge their contents. After which the membranes of the vesicles become fused with the plasma membrane thereby providing the cell with additional surface area. The vesicles also contain digestive enzymes and become Lysosomes. ...read more.

Conclusion

The nuclear envelope is perforated by pores through which certain substances may pass from the nucleus into the cytoplasm and vice versa. The pores are thought to be surrounded by protein and lined with hydrophilic groups which make them readily penetrated by water soluble substances. The pores are partly plugged by complexes of ribonucleic acids and proteins which regulate the passage of molecules between the nucleus and the cytoplasm. The outer membrane is continuous with the endoplasmic reticulum. Chloroplasts are unique to plants and are found in the green cells, they are urrounded by a double membrane and have an elaborate internal membrane system called Lamellae which consist of two membranes. At certain points these form sac like structures called Thylakoids, each thylakoid consists of a pair of membranes close to each other with a narrow space between. In places the thylakoids are arranged in neat stacks and form a Granum and this is where the green pigment Chlorophyll is found. These membranes are embedded in a fluid Stroma which contains the enzyme involved in light independent reaction. The function of the thylakoid membranes is to hold the chlorophyll molecules in a suitable position for trapping the maximum amount of light energy. The internal organisation of the chloroplast provides a large surface area without taking up too much room. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Molecules & Cells section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Molecules & Cells essays

  1. A Level Biology revision notes

    same antigen o Most differentiate into plasma cells * Secrete large amounts of antibodies * Bind to antigens and mark them for destruction o Some differentiate into memory cells * Secondary response o Exposure of same antigen causes activation of memory cells o They immediately recognize the antigen o Antibodies

  2. Explain why the structure and function of proteins is essential to living organisms.

    length hydrogen bonds affect the shape of the molecules however this time it causes it to fold rather than twist. This provides a flat folded structure that is very strong, i.e. silk, which is produced naturally by silk worms. Secondary structure proteins are generally fibrous proteins.

  1. Liver and its role

    concentration of the bile salt has a direct impact on the rate of the reaction. The beginning of the reaction will give me the best results, as there will be same amount of enzymes no matter on which experiment (as volume of lipase has been kept constant)

  2. Four organelles or structures that all eukaryotic cells have in common.Introduction.The cell as it ...

    In other words, every neutral atom has a number of electrons equal to its number of protons; however, if there is an imbalance, the atom will have an electric charge and is called an ion .This is when an atom losses an electron or acquire more of them.

  1. Follicular development

    (Welt et al, 2003), consists of a ?-subunit and ?-subunit, which are linked by a disulfide bridge. There are two homologous ?-subunits, which bind to the ?-subunit to form either inhibin A (??A) or inhibin B (??B). Inhibin specifically inhibits the synthesis and secretion of FSH, which has been demonstrated by many experiments, carried out in vitro and in vivo.

  2. The Origin of the Mitochondrion.

    "Endosymbiosis" refers to the relationship in which one cell lives inside a larger cell while the two exchange resources such as food, shelter or energy (Cooper 1997). According to the endosymbiotic theory for the origin of mitochondria, the organism that became the mitochondrion, the endosymbiont, had the ability to carry out oxidative phosphorylation to obtain energy.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work