AP Bio

• Cells are typically small.
• Moving materials in and out of cells becomes more difficult as the cell size increases.
• Smaller cells allow for more efficient exchange of materials with the environment.
• Surface area (SA) is the amount of surface covering the outer part of the cell.
• The larger the SA:V ratio (Surface Area to Volume Ratio), the more efficient the cell.
• Smaller cells typically have a higher SA:V ratio and are more efficient in material exchange.
• Larger cells have a lower relative SA, making it difficult to meet the demand for internal resources and the demand to remove waste sufficiently.
• These limitations restrict cell size and shape.
• • The surface area of the plasma membrane must be large enough to adequately exchange materials
• Membrane folding increases surface area.
• More folds result in more surface area.
• As organisms increase in size, the surface area to volume ratio decreases, affecting properties like heat exchange with the environment.
• In the small intestine, there are folded structures called villi that greatly increase the surface area.
• Loss of folding in cells can lead to decreased efficiency in nutrient absorption.
• Elephants have large, flat ears that allow for increased thermal energy dissipation.
• A Cell is life’s basic unit of structure and function
• There are two distinct types of cells: prokaryotic cells and eukaryotic cells.
• Light microscopes are used to study stained or living cells. They can magnify the size of an organism up to 1,000 times.
• Electron microscopes are used to study detailed structures of a cell that cannot be easily seen or observed by light microscopy.
• Prokaryotic cells are a lot smaller and simpler than a eukaryotic cell
• Bacteria and archaea are examples of prokaryotes.
• The inside of the cell is filled with a substance called cytoplasm
• Eukaryotic cells are more complex than prokaryotes
• Fungi, protists, plants, and animals are examples of eukaryotes
• Eukaryotic cells have many smaller structures called organelles
• Some of these organelles are the same structures seen in prokaryotic cells, but many are uniquely eukaryotic.
• The plasma/cell membrane is the outer envelope or layer of the cell, made up of mostly phospholipids and proteins.
• Cell membranes control the transport of materials in and out of the cell
• Phospholipids are amphipathic meaning they are both a Hydrophobic(Non-polar) and Hydrophilic(Polar)
• Embedded proteins are found in the cell membrane and can be hydrophilic or hydrophobic
• Peripheral & Integral proteins are types of embedded proteins
• Peripheral proteins are loosely bound to the surface of the membrane
• Integral proteins span the membrane
• Embedded proteins can be hydrophilic or hydrophobic
• Embedded proteins can be hydrophilic or hydrophobic
• The framework of the cell membranes is described as the Fluid Mosaic Model
• The structure(cell membrane) is not static and is held together primarily by hydrophobic interactions which are weaker than covalent bonds
• Most lipids and some proteins can shift and flow along the surface of the membrane or across the bilayer
• Cholesterol (a type of steroid) is randomly distributed and wedged between the phospholipids in the cell membrane of eukaryotic cells
• Cholesterol regulate bilayer fluidity under different environmental conditions