Biology Chapter: Cells and Organelles

Cells

• Cells are the basic living units of organisms.
• All cells share three fundamental components: a cell membrane, cytoplasm, and DNA.
• The cell membrane separates the cell's interior from its surroundings.
• Cytoplasm is a jelly-like substance within the cell.
• DNA is the cell's genetic material.
• Two major cell types exist: eukaryotic and prokaryotic.
• Eukaryotic cells are complex, possess organelles (specialized parts), and are found in plants and animals.
• Prokaryotic cells lack a nucleus and membrane-bound organelles, and are always part of single-celled organisms.

Organelles

• Organelles are specialized cell parts, analogous to organs in a body.
• The nucleus is the cell's control center, containing DNA that directs cellular activities.
• DNA exists as chromatin when not dividing; during division, it condenses into chromosomes.
• The nucleolus, within the nucleus, produces ribosomes.
• Ribosomes synthesize proteins.
• Ribosomes can be attached to the endoplasmic reticulum (ER).
• The ER comes in two forms: rough (with ribosomes) and smooth (without ribosomes).
• The ER transports substances to the Golgi apparatus.
• The Golgi apparatus modifies proteins.
• Vacuoles store materials.
• Lysosomes are cellular "garbage collectors," containing enzymes to break down waste.
• Mitochondria are the cell's energy producers, creating ATP during cellular respiration.
• The cytoskeleton includes microfilaments (protein threads) and microtubules (hollow tubes).
• Plant cells uniquely possess a cell wall.

Second Line of Defense

• The body employs general strategies to combat pathogens.
• Maintaining a higher body temperature (fever) slows or eliminates some pathogens.
• Inflammation brings more blood cells to a site of infection, aiding in pathogen destruction.
• Phagocytes, a type of white blood cell, engulf and destroy pathogens.