Introduction
A cell is a smallest unit of an organism that can live independently. There are two cell types: prokaryotic and eukaryotic cells. Prokaryotic cells include bacteria and a large group of other microorganisms with no nucleus. Eukaryotic cells include plant cell and animal cells, they have distinct nucleus and cell organelles.
Cell Structure Overview
The major parts of the cell are the nucleus, the control center; the cytoplasm, the space inside the cell; and the cell membrane, the protective skin of the cell.
The Nucleus
The nucleus contains the cell's DNA. Inside the nucleus is the nucleolus, the RNA container. The nucleus communicates using nuclear pores and is protected by a nuclear envelope. The DNA inside the nucleus is packaged into chromosomes. The nucleus controls the cell by deciding and acting on what the cell needs.
Cytoplasm and Cytoplasmic Organelles
The cell maintains life by assigning each responsibility to separate specialized machines. These machines are called organelles. An organelle is a compartmentalized structure that performs a specialized function within a cell. An animal cell contains a nucleus, ribosomes, mitochondria, rough endoplasmic reticulum, smooth endoplasmic reticulum, plasma membrane, Golgi apparatus and lysosomes. The nucleus controls the cell function.
Ribosomes: make proteins for the cell. Each ribosome is made of two protein subunits: the large subunit and the small subunit. The units clasp around a strand of nucleic acid instructions from the nucleus. The ribosome reads the strand instructions to make proteins for the cell to use in its normal activities.
Endoplasmic reticulum: Including rough ER and smooth ER. Rough ER is found attached to the outside of the nucleus. It appears rough because of the ribosomes on its surface. It helps the attached ribosomes in finishing protein synthesis. Smooth ER is NOT attached to the nucleus and DOES NOT have attached ribosomes (thus smooth). Smooth ER synthesizes carbohydrates and lipids.
The Golgi apparatus: made up of flattened, folded sacs, ships packages around the cell.
Mitochondria: converts carbohydrates taken from food into ATP -- produce energy to power the cell.
Lysosome: highly acidic, destroy waste to clean up the cell.
The Cell Membrane
A cell membrane is a selectively permeable structure that envelops the cell and protects the cell's internal environment. The cell’s membrane is made of phospholipids, which have carbohydrate heads and lipid tails. Proteins can be embedded or anchored on cell membrane. Cell membranes provides a stable environment for cells, perform communication function among cells via the surface proteins, and selectively exchange material between a cell and its environment.
Cell Membrane Transport
There are two types of transport through the cell membrane: passive and active transport. Passive transport requires no energy. Types of passive transport are osmosis, diffusion, and facilitated diffusion. Active transport requires energy from ATP.
