CELL STRUCTURE & FUNCTIONS

Cell Theory

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

Definition

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

Examples

Amoeba proteus

Red blood cell etc...

Types

1. Prokaryotic
2. Eukaryotic

Prokaryotic

• Do not have organelles surrounded by membranes
• Few internal structure
• One-celled organisms (bacteria)

Eukaryotic

Animal 

• Contain organelles surrounded by membranes
• Most living organisms eg. plant, animal, fungi

http://waynesword.palomar.edu/images/plant3.gif
(Not accurate)

Cell Wall

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

Cell Membrane

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

Nucleus

• Contain chromatins that control cell activities
• Chromatins contain DNA which is the genetic material
• DNA contain instructions for traits & characteristics & carry out the cell's function
• Separated from cytoplasm by nuclues membrane

Cytoplasm

• Gel-like mixture
• Surrounded by cell membrane
• Contains organelles (nucleus)

Mitochondria

• Refer to the "powerhouse" of the cell
• The food we eat is transformed into energy (ATP) for the cells & our bodies

Endoplasmic Reticulum

• An interconnected 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 cells contain thousands
• Make proteins
• Found on endoplasmic reticulum & floating throughout the cell

Golgi Bodies/ Apparatus

• Work closely with 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 & enzymes

Lysosome

• Contain digestive enzymes
• Digest excess or worn-put 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 foundation of macromolecules
• Cell breaks down if lysosome explodes

Vacuoles

http://www.biologycorner.com/resources/paramecium.gif

• Membrane-bound sacs for storage, digestion, and waste removal
• Central large vacuole-help plant cells maintain shape
• Food vacuoles: formed by phagocytes
• Contractile vacuoles (in freshwater protists): pump excess water out of the cell-------------->not in syllabus!

Chloroplasts (Absent in Animals)

• Usually found in plant cells
• Contain green chlorophyll
• Where photosynthesis takes place
• Converts light energy into chemical energy in glucose

Differences in Plants & Animals:

• Plant cell has cell wall while animal doesn't
• Plant cells has a large vacuole while animal cells has numeral small cells
• Plant cell has a fixed shape while animal cell has an irregular shape
• Plant cell has chloroplasts but animal cell doesn't