NAME: Michael Timson

DATE:

FORM: L6-4

LAB: #6

SUBJECT: Biology

TEACHER’S NAME: Miss Sarjeant

TITLE: Drawing of a cross section of a ligustrum plant cell under a light microscope.

AIM: To draw a plan drawing of a ligustrum plant cell under a light microscope.

CALCULATION:

Magnification = ¿ image

real¿object

Size of image = cm

= x 10000

= μm

Real size of object = x 2.5

Magnification =

=

Cells are the basic building blocks of all organisms. They provide structure for the

body, take in nutrients from food, convert those nutrients into energy, and carry out

specialized functions. Within the cell are specialize structures known as organelles and these

organelles perform different and unique task within the cells. The organelles in a plant cells

varies in an animal cells. Organelles found in a plant cell may not be present in an animal cell

or may be structurally different such as the vacuole. Other organelles found in a “typical”

plant cell include the nucleus, chloroplast, cytoplasm, the smooth endoplasmic reticulum, the

rough endoplasmic reticulum (ribosomes present), the Golgi apparatus and the

mitochondrion. The cell membrane and cell wall is present in the plant cell but is not an

organelle as it is not inside of the cell.

The nucleus is a membrane enclosed organelle found in eukaryotic cells. It contains

most of the cell's genetic material, organized as multiple long linear DNA molecules in

complex with a large variety of proteins, such as histones, to form chromosomes.

The genes within these chromosomes are the cell's nuclear genome. The function of the

nucleus is to maintain the integrity of these genes and to control the activities of the cell by

regulating gene expression and thus is the control centre of the cell. The main structures

making up the nucleus are the nuclear envelope. It is a a double membrane that encloses the

entire organelle and separates its contents from the cellular cytoplasm, and the nuclear

lamina, a meshwork within the nucleus that adds mechanical support, much like

the cytoskeleton supports the cell as a whole. As a result of the nuclear membrane being

impermeable to most molecules, nuclear pores are required to allow movement of molecules

across the envelope. These pores cross both of the membranes, providing a channel that

allows free movement of small molecules and ions. The movement of larger molecules such

as proteins is carefully controlled, and requires active transport regulated by carrier proteins.

Nuclear transport is crucial to cell function, as movement through the pores is required for

both gene expression and chromosomal maintenance. Although the interior of the nucleus

does not contain any membrane-bound subcompartments, its contents are not uniform, and a

number of sub nuclear bodies exist, made up of unique proteins, RNA molecules, and

particular parts of the chromosomes. The best known of these is the nucleolus, which is

mainly involved in the assembly of ribosomes. After being produced in the nucleolus,

ribosomes are exported to the cytoplasm where they translate RNA.

The cell membrane also known as the plasma membrane is a thin semi-permeable

membrane that surrounds the cytoplasm of a cell. Its function is to protect the integrity of the

interior of the cell by allowing certain substances into the cell, while keeping other

substances out. It serves as a base of attachment for the cell wall in the plant cell. Thus the

cell membrane also serves to help support the cell and help maintain its shape. The cell

membrane is primarily composed of a mix of proteins and lipids. While lipids help to give

membranes their flexibility, proteins monitor and maintain the cell's chemical climate and

assist in the transfer of molecules across the membrane. Phospholipids are a major

component of cell membranes. They form a lipid bilayer in which their hydrophilic (attracted

to water) head areas spontaneously arrange to face the aqueous cytosol and the extracellular

fluid, while 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 diffuse across the membrane.

The cell wall is a tough layer locates outside the cell membrane that surrounds the

plant cells. It provides the cell with structural support and act as a pressure vessel,

preventing over-expansion when water enters the cell. Plant cell wall is made of long strands

of carbohydrate cellulose. These cellulose fibres are very strong and are arranged in a criss-

cross manner held together by a matrix that contains pectin. This composite structure has a

great resistance to stretching forces that might act on it.

The chloroplast are double membrane bound organelles and are the site of

photosynthesis. The chloroplasts have a system of three membranes: the outer membrane, the

inner membrane and the thylakoid system. The outer and the inner membrane of the

chloroplast enclose a semi-gel-like fluid known as the stroma. This stroma makes up much of

the volume of the chloroplast, the thylakoids system floats in the stroma. The thylakoid

system is suspended in the stroma. The thylakoid system is a collection of membranous sacks

called thylakoids. The chlorophyll is found in the thylakoids and is the sight for the process

of light reactions of photosynthesis to happen. The thylakoids are arranged in stacks known

as grana.

 The central vacuole is a membrane-bound organelle containing water and other

enzymes that function during the life of the plant. Structurally, the central vacuole is

surrounded by a phospholipid bilayer which align themselves in a certain manner and are

hence able to selectively allow certain molecules to enter and exit the cells or organelles they

surround. Central vacuoles are very versatile and can serve numerous important functions in

the cells of plants. They contribute to the rigidity of the plant using water to develop

hydrostatic pressure, store nutrient break down complex molecules. Central vacuoles can be

used to contain cellular waste and to isolate materials that may be harmful to the cell.

The Mitochondrion in plants cells play an essential role as the major producers of

ATP via oxidative phosphorylation (the metabolic pathway in which the mitochondria in

cells use their structure, enzymes, and energy released by the oxidation of nutrients to

reform ATP). They are the site of aerobic respiration in a cell. Oxygen and energy containing

molecules produced from glucose are used to make ATP. ATP is the energy currency of the

cell necessary for every energy-using process carried out.

There are two types of endoplasmic reticulum: rough endoplasmic reticulum (rough

ER) and smooth endoplasmic reticulum (smooth ER). Both types are present in plant and

animal cells. The two types of ER are separate entities and are not joined together. Cells

specialising in the production of proteins will tend to have a larger amount of rough ER

whilst cells producing lipids (fats) and steroid hormones will have a greater amount of

smooth ER. Part of the rough ER is continuous with the nuclear envelope. The Golgi

apparatus is also closely associated with the ER and recent observations suggest that parts of

the two organelles, i.e. the ER and the Golgi complex, are so close that some chemical

products probably pass directly between them instead of being packaged into vesicles

(droplets enclosed within a membrane) and transported to them through the cytoplasm. The

rough ER an extensive organelle composed of a greatly convoluted, sealed sac that is

continuous with the nuclear membrane. It is called ‘rough’ endoplasmic reticulum because it

is studded on its outer surface (the surface in contact with the cytosol) with

ribosomes. Smooth ER is more tubular than rough ER and forms a separate sealed

interconnecting network. It is found fairly evenly distributed throughout the cytoplasm and is

not studded with ribosomes hence giving the name smooth ER.