For whom would an appreciation of the structural characteristics of the human heart come more easily: an alien who lands on Earth, abducts a human, and dissects his heart, or an anatomy and physiology student performing a dissection of the heart on her very first day of class? Why?
Lesson 4: Cell Structure 4.1 Cell Theory 1. All organisms are composed of one or more cells and life processes of metabolism and hereditary occur in these cells 2. Cells are the smallest living things- basic units of all organisms 3. Cells arise only by division of a previously existing cell Rate of diffusion is affected by: Surface area available Temperature Concentration gradient Distance Surface Area-to-Volume ratio: as a cells size increases its volume increases Increased size means diffusion is harder to do 4 Major features of all cells: 1. Nucleoid/ Nucleus- o Where genetic information is stored 2. Cytoplasm- o A semifluid matrix that fills the interior o Cytosol: contains organic molecules and ions 3. Ribosomes- o Protein Synthesis 4. Plasma membrane o Encloses the cell and seperates its contents from its surroundings o Phospholipid bilayer: Tails- non polar; hydrophobic Head- polar; hydrophilic o Receptor proteins o Transport Proteins Prokaryotes- (simplest) 1 singular circular molecule of DNA in the center of the nucleoid Eukaryotes- (more complex) DNA found in the nucleus which is surrounded by the nuclear envelope 4.2 Prokaryotic Cells Simplest organisms- small Consists of cytoplasm surrounded by a plasma membrane encased within a cell wall Ribosomes: Carry out protein synthesis Bacterial cell walls