Organelles – Part I

Organelles Organelles are ‘tiny organs.’ Organs are to humans as organelles are to cells.

Nucleus Function: The nucleus is the cell’s genetic control center. Stores DNA Makes RNA Makes ribosomes Directs the synthesis of proteins

Nucleus Structure: The nucleus has 3 parts: Nuclear envelope – membrane surrounding genetic material DNA Chromatin: DNA stretched out and skinny Chromosomes: DNA coiled up for replication Nucleolus – center of nucleus, produces ribosomes

Nucleus Chromatin Nucleolus Pore Ribosomes Rough endoplasmic reticulum Two membranes of nuclear envelope

Ribosomes Function: Structure: Ribosomes manufacture proteins based on instructions they get from the DNA in the nucleus. Structure: Ribosomes are small spherical structures. They float in the cytoplasm OR are connected to the rough ER. They are composed of proteins & RNA.

Ribosomes

Endoplasmic Reticulum (ER) There are two types of ER: Smooth ER Rough ER

Smooth ER Function: Structure: The smooth endoplasmic reticulum has a variety of functions: Synthesizes lipids Processes toxins and drugs in liver cells Stores and releases calcium ions in muscle cells Structure: Smooth endoplasmic reticulum is composed of flattened sacs that often extend throughout the entire cytoplasm

Rough ER Function: Structure: The rough ER has three functions: Synthesis of proteins (in the attached ribosomes) Modification of proteins. Packing of proteins. Structure: Rough endoplasmic reticulum is the same as the smooth but it is dotted with ribosomes which make it bumpy.

Golgi Apparatus (Golgi Bodies) Function: They receive and modify ER products then modify, sort, package and ship them to other organelles or the cell surface. Structure: The Golgi apparatus looks like stacks of membranous sacs.

Lysosomes Function: Structure: They contain enzymes that break down: Food Damaged organelles Bacteria with which they fuse. Structure: Lysosomes are made by the Golgi Apparatus. They are tiny spheres of enzymes

Interesting Facts… Abnormal lysosomes can cause fatal diseases. When a cell is damaged the nucleus sends a message to the lysosome telling it to explode – the enzymes inside eat the cell – for this reason we also call lysosomes ‘suicide sacs’

Huntingdon’s disease

Pompe’s disease

Tay-sachs disease

Vacuoles Function: Vacuoles can do all kinds of things. They can contain pigment (color) They can contain poison. They have contain food or water. Plants have central vacuoles that function store large amounts of water

Vacuoles Structure: Vacuole is the general term given to any other membrane sac in the cell. Animal cells have small vacuoles called vesicles