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Complete Cell Structure

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Complete Cell Structure

Post by biologyisg8 on Fri Jan 30, 2009 1:11 pm

HISTORY



1. Robert Hooke – Use cork, pore-like regular structure

2. Schleiden (botanist) - plants made of cells

3. Schwan (zoologist) – same organism is cells





CELL
1. Basic unit of life
2. Every Structure/organism made of cells
3. All cells arise from pre-existing cells

4. Surrounded by thin layer of membrane (partially permeable)





MICROSCOPE

1. Light microscope

2. Electron Microscope


a) Transmission Electron Microscope

b) Scanning Microscope





LIGHT MICROSCOPE

1. Use glass lens

2. Use visible light as source of radiation

3. Resolution about 200nm

4. Visible light – 400 nm-700nm

5. Magnification – 1500 times


ELECTRON MICROSCOPE



1. Use electromagnetic lens

2. Use electron as source of radiation

3. Very short wavelength with high energy

4. Negatively charge
5. Specimen need to be stained with heavy metal atoms

6. Specimen must be in vacuum

7. Only dead specimen


a) Transmission Electron Microscope

I. The beam of electron passed through the specimen before being viewed


II. Only electron that transmitted are seen




b) Scanning Electron Microscope

I. The electron beam is used to scan the surfaces of structures


II. Only the reflected beam is observed

MAGNIFICATION AND RESOLUTION



1. Magnification- Number of times larger an image is compared with real size of the object



Magnification = size of image

Actual size of specimen




2. Resolution – the ability to distinguish between two separate points



MEASURING CELLS


1. Eye-piece graticule – transparent scale which placed in then microscope eye piece

2. Stage Micrometer Scale – miniature transparent ruler

3. Calibrating :


a) Check how much division on eye-piece graticule

b) Confirm the length of stage micrometer scale


c) Set the magnification


d) Measure the eye-piece graticule with stage micrometer scale under the microscope


e) Determine the value of each eye-piece graticule’s division

f) Determine size of specimen


ANIMAL CELL AND PLANT CELL UNDER MICROSCOPE

1. Features in common:


a) Surrounded by a very thin plasma membrane


b) Has nucleus


c) Has chromatin (mass of loosely coiled threads) – contains DNA (deoxyribonucleic acid)


d) Has nucleolus – made of loops of DNA


e) Has cytoplasm – aqueous material

f) Has mitochondria – carry out aerobic respiration

g) Has golgi apparatus- complex internal sorting and distribution system within the cell


2. Differences between animal and plant cells
(under light microscope):

a) Animal cell:

I. Has centriole (small structure close to the nucleus – involve in nuclear division)



b) Plant Cells:

I. Larger than plant cells


II. Surrounded by rigid cell wall outside plasma membrane

III. Linked to neighbouring cells by plasmodesmata

IV. Has large central vacuole surrounded by tonoplast

V. Has chloroplast (large organelles in green) – under high magnification; small grains~grana that absorb light in photosynthesis






ULTRASTRUCTURE OF AN ANIMAL CELL



NUCLEUS



1. Largest cell organelle

2. Surrounded by two membrane – nuclear envelope

3. Outer membrane is continuous with endoplasmic reticulum

4. Nuclear envelope conspicuously perforated by nuclear pores

5. Chromosomes in loosely coiled state (chromatin)
6. Has nucleolus that manufactures ribosome



CENTRIOLES


1. Two centriole per cell

2. Lie closely together

3. Is a hollow cylinder (0.4µm)

4. Formed from a ring of microtubules

5. Are used to grow the spindle fibers for nuclear division





ENDOPLASMIC RETICULUM


1. An extensive system of membranes

2. Membranes form as system of flattened sacs (cisternae) that can go on to form golgi apparatus

3. ER that covered with ribosomes called rough ER

4. ER that lacks of ribosomes and appears smooth called smoother

5. Rough ER transport proteins throughout the cells

6. Smooth ER produce lipids and steroids





RIBOSOMES

1. Site of protein synthesis

2. Found free on cytoplasm or on the rough ER

3. Very small organelles (about 22 nm in diameter)

4. Made of RNA(ribonucleic acid) and protein


GOLGI APPARATUS

1. A stack of flattened sacs (cisternae)


2. The apparatus collects, processes and sort molecules (particularly proteins from the rough ER)


3. Golgi vesicles transport molecules to other parts of cell or out of the cell


4. Golgi vesicles also used to makes lysosomes






LYSOSOMES


1. Spherical sacs surrounded by single membrane
2. No internal structure

3. 0.1-0.5 µm diameter

4. Contain hydrolytic (digestive enzyme)

5. Breakdown (digest) unwanted structure






MITOCHONDRIA



1. Larger than lysosomes, surrounded by two membranes

2. The inner is folded to form finger-like cristae which project into the interior solution or matrix

3. carry out the later stage of aerobic respiration (make ATP, the universal energy carrier in cells)

4. Involved in synthesis of lipids



CILIA



1. A thin extensions that can move in a wave-like manner

2. A few/single – flagella/flagellum (relatively long)

3. Many- cilia/ cilium ( 3-4 µm long)

4. Covered by an extension of plasma membrane

5. Contains microtubules arise from structure called basal body

6. Microtubules arranged in an outer cylinder of 9 pairs, surrounding two central microtubules

7. How its move?
i. Caused by microtubules
ii. Slide against each other causing the whole structure to bend
iii. If in group, they all moved in coordinated manner






ULTRASTRUCTURE OF A PLANT CELL




-
All structures found in animal cells are also found in plant cells except centrioles and rarely cilia

- Some structures cannot be found in animal cells





CELL WALL


1. Gives definite shape
2. Prevent cell from bursting when water enters by osmosis

3. allowing large pressures to develop inside the cell






PLASMODESMATA (PLASMODESMA)


1. As a connector between cells

2. Pore like structure in the cell walls

3. Movement of materials controlled by their structure





CENTRAL VACUOLE



1. Surrounded by a membrane (tonoplast – controlled exchange between vacuole and cytoplasm)
2. Fluid in vacuole is solution of minerals (salts, sugars), oxygen, carbon dioxide, pigments, enzymes-including waste product
3. Help regulates the osmotic properties of cells)



CHLOROPLAST

1. Large organelles in green colour
2. Contain grains/grana that absorb light in photosynthesis
3. Grain consist of stacks of membranes
4. Mainly in the leaves



TWO FUNDAMENTALLY DIFFERENT TYPES OF CELL



1. Prokaryotes

i. pro means before; karyon means nucleus

ii. e.g.; bacteria

iii. nuclei lies free in cytoplasm

2. Eukaryotes

i. eu means true

ii. e.g.; animals, plants, fungi

iii. DNA lies inside nucleus



Prokaryotes


Eukaryotes

Average diameter of cell 0.5-5 µm


Cells commonly up to 40µm diameter and commonly 1000-10000 times volume of prokaryotic cells

DNA is circular and lies free in the cytoplasm


DNA is not circular and its contained in a nucleus. The nucleus is surrounded by an envelope of two membranes

DNA is naked


DNA is associated with protein, forming structures called chromosomes

Slightly smaller ribosomes (about 18nm diameter)


Slightly larger ribosomes (about 22 nm diameter)

No ER present


ER present, to which ribosomes may be attached

Very few cell organelles; none are surrounded by an envelope of two membranes


Many types of cell organelle present (extensive compartmentalisation and division of labour). Some of them bounded by single membrane and some of them by two membranes

Cell wall present


Cell wall sometimes present (plants)



TISSUES AND ORGANS

- Specialised cells show division of labour by being grouped into tissues

- Tissues may be further grouped into organs

- Organs grouped into system



1. Tissue

i. A collection of cells together with any intercellular secretion produced by them

ii. May be in the same type or mixed type of cells

2. Organ

i. A part of body which form structural and functional unit and its composed of more than one tissue

3. System

i. Collection of organs with particular function

ii. E.g.: excretory, reproductive, cardiovascular and digestive



Examples in dicotyledonous leaf.
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