Biology Science 1

Cells

3 Structure of the Cell

1) Cell Membrane

2) Cytoplasm

3) Nucleus

Cell Membrane

- Also known as External Membrane / Plasma Membrane

- It act as a covering for the cell and encloses the contents of the cell

- It is semi-permeable membrane as it allows certain molecules and ions to enter or leave the cell

- Substance that enters : e.g. oxygen and nutrition

- Substance that leaves : e.g. carbon dioxide and waste products

Cytoplasm

- Its a watery solution that is found between the cell membrane and the nucleus

- It contains : minerals, gases, organic molecules and cell organelles

Nucleus

- It controls every organelles in the cytoplasm

- It contain fine network of strand known as Chromatin

- During cell division, the chromatin will form into chromosomes

- It contains chromosomes and there are 23 pairs of chromosomes - 1 pair from the mother and the other pair from the father. Total it has 46 chromosomes

- Chromosome are made up of strands of DNA [ Deoxyribonucleic Acid ] and it carries genes information such as (e.g. hair colour, height, skin colour etc.)

- Nucleolus is in the nucleus and it is mde up of DNA, RNA (Ribonucleic Acid) and Protein.

[ *Ribonucleic Acid : Transmit information from nucleus to the cytoplasm ]

Major Organelles of the Cell

1. Endoplasmic Reticulum [ ER ]

2. Ribosomes

3. Golgi Apparatus

4. Mitochondria

5. Lysosomes

6. Centriols

7. Vacuoles

Organelles & Rationales

1. Endoplasmic Retriculum (ER) : Passageway for the transportation of the materials

2. Ribosomes : Protein Synthesis

3. Golgi Apparatus : [ Packaging System ] Form secretory vesicle that are involved with secretory activities of a cell

4. Mitochondria : Produce ATP [ Adenosine Triphosphate ] to provide energy for the cells activities

5. Lysosomes : Contains enzymes that involve in digesting worn out cell structure

6. Centrioles : Involve in cell division

7. Vacuoles : Storage of secretions or waste products

Transport Across Cell Membrane

2 types of transportation :

1. Passive Transport > do not need to use energy

2. Active Transport > need to use energy

1. Passive Transport

2 types :

1. Diffusion : Is the movement of substances from High to Low concentration [ DHL = Diffusion, High to Low ] ( until equilibrium is met )

2. Osmosis : Is the movement of water from Low to High concentration [ OWLH = Osmosis, Water, Low to High ] ( until equilibrium is met )

2. Active Transport

- Is the movement of substances from Low to High concentration but need energy [ LHE = Low to High, needs Energy ]

Cell Division

2 types of division :

1. Mitosis : The division of ALL cells except reproductive cells

2. Meiosis : Reproductive cells

1. Mitosis

- A parent cell produces 2 daughter cells

- Each daughter cell contains 46 chromosomes ( both identical )

2. Meiosis

- Occurs in sperm or egg cells

- Go through 2 cells division

- A parent cell produces 4 daughter cells

- Each daughter cells contains 23 chromosomes ( half the number of diploid of chromosomes )

[ *diploid : having two similar complements of chromosomes ]

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