cels 3 Flashcards
What must a cell do?
Manufacture cellular materials, obtain raw materials, remove waste, generate the required energy, and control all of the above.
What is the function of the plasma membrane at the boundary of each cell?
Provides special conditions within the cell and acts as a semi-permeable barrier.
What are the characteristics of the plasma membrane?
A semi-permeable barrier that allows passage of oxygen, nutrients, and waste; controls movement of substances in and out of the cell.
How does cell size relate to the plasma membrane?
Interaction with the environment limits the maximum size of a cell; a small cell has a greater surface to volume ratio than a larger cell.
What is the structure of the plasma membrane?
A double layer of phospholipids with various embedded or attached proteins.
How does saturation affect the plasma membrane?
Saturated membranes are packed tightly together, leading to less fluidity; unsaturated membranes have tails that prevent tight packing, allowing more fluidity.
How does temperature affect the plasma membrane?
High temperatures increase fluidity (lipids are more fluid), while low temperatures decrease fluidity.
What role does cholesterol play in the plasma membrane?
Stabilizes membrane fluidity, raises melting point, and prevents phospholipids from packing too tightly.
What is the role of membrane proteins?
Facilitate the transport of molecules across the membrane, act at receptors for signaling, maintains cell shape, enables cell to cell adhesion
What are the functions of membrane proteins?
Involved in signal transduction, cell recognition, intercellular joining, linking cytoskeleton & extracellular matrix, and membrane transport.
What is diffusion?
A passive transport process where membranes are permeable to lipid-soluble molecules that move down their concentration gradient without energy.
What is facilitated diffusion?
Movement of hydrophilic molecules that requires membrane proteins called channels and carriers, aiding movement down their concentration gradient without energy.
What is facilitated diffusion for water?
Movement of water across a cell membrane requires channels called aquaporins, occurring via osmosis from high water concentration to low water concentration.
What is active transport?
Requires transport proteins that use energy (ATP) to move specific substances against their concentration gradient.
What is co-transport?
Indirect active transport where one substance is pumped across the membrane and its concentration gradient powers the movement of a second substance against its gradient.
What are organelles?
Cellular structures that provide special conditions for specific processes, keep incompatible processes apart, and allow specific substances to be concentrated.
How are cellular organelles structured?
Cellular organelles are bounded by membranes, each providing its own special conditions.
