Cell Structures and Functions

Learning outcomes:

•  Explain that the basic unit of all living things is the cell.
•   Identify structure and state the function of the main organelles in the cell such as nucleus, nucleus membrane, chromatin, cytoplasm, vacuole, mitochondria, ER, ribosomes, golgi apparatus, lysosomes, chloroplast, cell wall

Cell Theory

• All living things are made up of cells
• Cells are the smallest working units of all living things
• All cells come from pre-existing cells through cell division

A cell is the smallest unit that is capable of performing life functions.

Examples of cells: Amoeba proteus, Plant stem, Bacteria, nerve cell, red blood cell

Two types of cells

• Prokaryotic

1.     Do not have organelles (specialized structures in cells) surrounded by membranes

2.     Few internal structures

3.     One-celled organisms eg. bacteria

•  Eukaryotic

1.     Contain organelles surrounded by membranes

2.     Most living organisms eg. Plant, animal, fungi 

Plant Eukaryotic Cell

Animal Eukaryotic cell

Cell Wall

• Most commonly found in plant cells and bacteria
• Surrounds the cell membrane
• Rigid structure that maintains the shape, supports & protects cells
• Permeable to small molecules and small proteins only

Cell Membrane

• Selectively permeable membrane of cell that controls movement of substances in and out of the cell

Inside the cell…

Nucleus

• ·      Contain chromatins that control cell activities
• ·      Chromatin contain DNA which is the genetic material
• ·      DNA contain instructions for traits & characteristics and to carry out the cell’s function
• ·      Separated fro cytoplasm by nuclear membrane       

   Cytoplasm

• Gel-like mixture
• Surrounded by cell membrane
• Contains organelles

Mitochondria

• referred to as the powerhouse of the cell
• the food we eat is transformed into energy (ATP) for the cell and our bodies

Endoplasmic Reticulum 

• An interconected network of tubes and vesicles
• Synthesis of proteins, fats, steroid
• Transports materials around in cell
• Smooth type: Lacks ribosomes
• Rough type: RIbosomes embedded in surface 

Ribosomes

• Each cell contains thousands
• Make proteins
• Found on endoplasmic reticulum & floating throughout the cell

s  Golgi Bodies (smaller versions of the Golgi Apparatus)

•      - Works closely with the ER
•      - Primary function is to process and package complex molecules such as proteins and  fats that are made by the cell
•      - Brings these products to the surface of the cell where they can be secreted
•      other secretions include hormones, antibodies and enzymes

   Lyosome

•  Contain digestice enzymes
•  Digest excess or worn-out organelles, food particles and engulf bacteria or       viruses
•  Also help repair worn-out plasma membrane
•  They also provide sugars, amino acids and bases which are the function of macromolecules
•  Cell breaks down if lyosome explodes

Vacuoles 

•  - Membrane - bound sacs for storage, digestion and waste removal
•  - Central large vacuole-help plant vells matintain shape
•  - Food vacuoles: formed by phagocytosis 
•  - Contractile vacuoles (in freshwater protists): pump excess water out of the cell
• 
  

       

       Chloroplasts

         

         - Usually found in plant cells

         - Contains green chlorophyll

         - Where ohotosynthesis takesm place

         - Converts light energy to chemical energy in glucose