Flashcards in Chapter 3: Chemical Level of Organization: Cells And Homeostasis Deck (120)
What is a plasma membrane?
Cell's outer surface surrounding the cell internal's and external organs
What is the cytoplasm?
Consists of all the cell's cellular contents between the plasma membrane and nucleus. Contains 2 parts: Cytosol (fluid portion of cytoplasm, contains water, dissolved solvents, suspended particles), and organelles (Characteristic shape and function).
What is the nucleus?
Contains most of cell's DNA. Each chromasome within has thousands of genes that control most aspects of a cell's structure and function.
What is the fluid-mosaic model?
The molecular arrangement of the plasma membrane resembles a continually moving sea of fluid lipids that contain a mosaic of different proteins
What are the 4 functions of the plasma membrane?
1) Acts as a barrier separating inside or outside of cell. 2) Controls the flow of substances into and out of cell. 3) Helps identify the cell to other cells (eg immune cells) and 4) Participates in intercellular signalling
Describe the basic structure of the lipid bilayer
2 back-to-back layers made up of 3 types of lipid molecules: Phospholipids (75%... contains phosphorus), cholesterol (20%... steriod with attached OH group) and glycolipids (5%... attahched carbohydrate group)
How do phospholipids orient themselves in the lipid bilayer?
Their hydrophilic heads face outward... the heads face a watery fluid on either side (cytosol on the inside and EC fluid on the outside). Hydrophobic fatty acid tails in each half of the bilayer point toward one another forming a nonpolar hydrophobic region in the membrane's interior
What are integral proteins?
Extended into or through the lipid bilayer and firmly embedded in it. Most are transmembrane proteins so extend the entire width of the bilayer and portrude into both the cytosol and the EC fluid. Example are glycoproteins (proteins with carbohydrate groups attached to the ends that protrude into the EC fluid. The carbohydrates are oligosaccharides)
What is peripheral proteins?
Not as firmly embedded in the membrane. Attached to the polar heads of membrane lipids or integral proteins at the inner or outer surface of the membrane.
What is Glycocalyx?
Carbohydrate portions of glycolipids and glycoproteins that form an extensive sugary glyccalyx. Enables cells to recognize one another (ie WBCs ability to detect a foreign glycocalyx).
What are the 5 functions of integral proteins?
1) ion channels (pores/holes that specific ions can flow through to can into/out of cell). 2) Carriers (Selectively moving a polar substance or ion from one side of the memebrane to the other). 3) Receptors (Recognizes and binds a specific types of molecules. Insulin receptors bind insulin. A molecule that binds to a receptor is called a LIGAND). 4) Enzymes (catalyze specific chemical reactions). 5) Linkers (Anchor proteins in plasma membranes of nearby cells to one another or to protein filaments inside and outside of cell)
What's a main function of glycoproteins and glycolipids?
Serve as identity markers. May enable a cell to 1) recognize other cells of the same kind during tissue formation and 2) Recognize and respond to foreign dangerous cells. Eg blood cells must be compatible or RBCs will clump together.
Functions of peripheral proteins?
1) Support plasma membrane. 2) Anchor integral proteins. 3)Move materials and organelles within cells. 4) Attach cells to one another.
What does membrane fluidity depend on?
The number of double bonds in the fatty acid tails of the lipids in the bilayer. Each double bond puts a kink in the fatty acid tail which increases membrane fluidity by preventing lipid molecules from packing together
Why is membrane fluidity important?
Enables movement of membrane materials responsible for important cell processes like cell movement, growth, division, and secretion. It also allows it to self-seal when punctured or torn (ie intracytoplasmic sperm injection).
How does cholesterol's affect on the lipid bilayer vary based on temperature?
Makes lipid bilayer stronger (and less fluidity) at normal temperature and weaker (and more fluidity) at lower temperature
What is selective permeability?
The plasma membrane allows some substances t pass more readily than others. Nonpolar molecules (CO2, O2, steriods) are highly permeable, moderately permeable to small uncharged polar molecules (water and urea) and impermeable to large uncharged polar molecules (like glucose). Transmembrane proteins that act as channels and carriers can increase the plasma membrane's permeability to a variety of selective ions and uncharged polar molecules.
What's a concentration gradient?
A difference in the concentration of a chemical from one place to another. Like from outside the cell to inside.
What is ELECTRICAL GRADIENT and MEMBRANE POTENTIAL?
The inner surface of the plasma membrane is more negatively charged and the outer surface is more positively charged. This difference in electrical charges is called an electrical gradient. The charge difference is termed membrane potential.
What's the electrochemical gradient?
A substance will move downhill from where it's more concentrated to where it's less concentrated to reach equilibrium. A positively charged substance will move towards a negatively charged substance and vice versa. The combined influence of the concentration gradient and electrical gradient is the electrochemical gradient.
WHat are passive processes?
A substance moves down its concentration / electrical. Gradient to cross the membrane using only its own kinetic energy (energy of motion) no input from cell's energy. Example is simple diffusion
What are active processes?
Cellular energy is used to drive the substance uphill against its concentration or electrical gradient. ATP is used. Example is active transport.
What are endocytosis and exocytosis?
They are active processes using the vesicles. In endocytosis, vesicles detach from the plasma membrane while bringing materials into a cell0. In exocytosis vesicles merge with the plasma membrane to release materials from the cell.
WHat is diffusion?
A passive process. Random mixing of particles occurs in a solution because of the particles' kinetic energy. Both solutes and solvents undergo diffusion. Solute molecules will diffuse towards an area of low concetration (think about the dye example)... eventually they become evenly distributed and reach equilibrium
Factors that influence the diffusion rate of substances across a membrane
1) Steepness of concentration gradient (greater the difference in concentration between tthe 2 sides of the membrane the higher the rate of diffusion). 2) Temperature (the higher the temp the faster the rate of diffusion). 3) Mass of the diffusing substance (the larger the mass of the diffusing particle the slower the diffusion rate). 4) Surface area (The larger the membrane SA available for diffusion the faster the rate of diffusion... air sacs of lungs). 5) Diffusion distance (The greater the distance over which diffusion must occur the longer it takes... pneumonia).
What is simple diffusion?
Passive process. Substances move freely through the lipid bilayer of the plasma membrane of cells without the help of membrane transport proteins. Like nonpolar hydrophobic molecules. O, CO2, N gases, steriods, fatty acids, fat soluble vitamins, small uncharged polar molecules like water and urea
What is facilitated diffusion?
An integral membrane protein (either a membrane channel or carrier) assists a specific substance across a membrane. Usually solutes that are too polar or highly charged
What's channel-mediated facilitated diffusion?
A solute moves down its concentration gradient across the lipid bilayer through a membrane channel (likely an ion channel)... passage of small inorganic molecules too hydrophilic to penetrate the nonpolar interior of the lipid bilayer
What's a gated channel?
When a part of the channel acts as a gate or a plug, changing shape in one way to open to pore and another to close