Cells, Tissues, Organs and Organ Systems Review Chapter 2

What are cells? Prokaryotic vs. Eukaryotic (expanded definition) Basic cell parts – – Plasma membrane – Cytoplasm – Nucleus

Why are most cells small? Easier for nucleus to control Cell volume to cell surface area ratio – If cell volume is too large, its more difficult to move nutrients and waste around efficiently

Fluid Mosaic Model of the Cell Membrane Phospholipids are polar. Membrane has hydrophobic interior and hydrophilic exterior. Cholesterol is embedded throughout to give the membrane structural support. Proteins are attached to or embedded in the membrane and serve to help move molecules in and out of the cell. Carbohydrates bonding with lipids and proteins on the outside of the cell make up the glycocalyx, or the cell coat. The cell coat is used for cell to cell communication and as a fingerprint (important with bacteria). The membrane is selectively permeable, keeping undesirable molecules out.

Movement Across a Membrane Simple Diffusion – the free movement of molecules from an area of high concentration to an area of low concentration (no energy required) Facilitated Diffusion – the movement of molecules down the concentration gradient with the help of a transport protein (no energy required) Osmosis – the movement of water down the concentration gradient (no energy required) Active transport – the movement of molecules UP the concentration gradient, usually with the help of proteins (energy required)

Bulk Transport Endocytosis – absorption of molecules – Pinocytosis – cell drinking – Phagocytosis – cell eating – Receptor-mediated endocytosis – involves receptor proteins Exocytosis – secretion of molecules

Structure and Movement Cytoskeleton – lattice frame made of microtubules, microfilaments and intermediate filaments that supports the cytoplasm Cilia and Flagella – elongated appendages that cells use to move, starting with the basal body and consisting of microfilaments

Newly Discovered Vaults