Biology- plasma membrane
What kind of role do proteins have?
A functional role
What kind of role do phospholipids have?
A structural role
What do rip and rib stand for?
All plasma membrane functions R reaction site(cellular Chem reactions) I insulation P protection R recognition I in and out B boundary
What is a gLyco protein
Any protein that has carbohydrates attached to phospholipids
Why do scientists describe the plasma membrane as a fluid mosaic
Because the proteins embedded in the lipid bilayer can move around or float amount the lipids and because so many different kinds of molecules make up the plasma membrane
What occurs when these lipids are mixed with water
Fatty acid tails cluster together Heads attracted to water Lipid bilayer =result
Describe the two parts of a lipid bilayer.
Fatty acid tails- hydrophobic "water-hating" Phosphate head-hydrophilic "water-loving"
What do some of the proteins do?
Form channels and pumps that help move material across the cell membrane
What does the lipid bilayer do?
Gives plasma membrane flexible structure and forms a strong barrier between the cell and its surroundig
What are the two parts of phospholipids?
Head (glycerol and phosphate group) and tails
What is the function of transport proteins
Help transport ions, macromolecules, and other substances incapable of entering a cell by themselves across plasma membrane -charged particles, small polar -large molecules need special processes to get through
What is the function of proteins in the membrane?
Hormone binding sites Election carriers Pumps for active transport Channels for passive transport Enzymes Cel signaling Cell adhesion
Membrane acts as an attachment point for ...
Intracellular cytoskeleton and if present cell wall
What kind of cells produce a plasma membrane and cell wall?
Prokaryotes(plants) Algae Fungi Not animals
What do most plasma membranes contain?
Protein molecules that are embedded in the lipid bilayer
What are channels in plant cells?
Pits
What do pits contain?
Plasmodesmata (continuous strands of cytoplasm) that Connect cytoplasm of neighboring cells slowing movement of water soluble materials from cell to cell
The cell wall is ______ enough to allow____,____,___, to pass through easily
Porous Water,oxygen,carbon dioxide, and certain other substances
What else does cholesterol do?
Prevents cells from freezing when your body temp gets very low. That's why animals in post areas have larger amounts of cholesterol
Do all cells have a plasma membrane? What does it do?
Yes Regulates what enters/exits cell Protects and supports cells
Are organelles also composed of phospholidpids
Yes. Mitochondria are bounded by double membrane
What is plasma membrane analogous for?
Our skin
Where is the cell wall located?
Outside the cell membrane
Structure of lipid bilayer
-Head groups of lipids in bilayer exposed to water -fatty acid tails form oily layer inside membrane from which water is excluded
What is the function of the cell wall?
-provide support and protection for the cell
What is the function of the plasma membrane?
-regulate what enters and exits the cell -protects and supports the cell -acts as wall to keep organelles inside -helps cell control chemical and electrical properties -help maintain cell hlmeostasis
What are gap junctions
Channels formed by embedded proteins in the plasma membrane of adjacent cells Allows small water soluble substances to pass directly from cell to cell
What do carbohydrates molecules act like?
Chemical identification cards, allowing individual cells to identify one another
What is the plasma membrane composed of?
Double-layered sheet called a lipid bilayer
What are Desmosomes?
Links intermediate filaments of neighboring cells Acts as rivets but allows passage of substances through spaces between cells
What do carb chains do?
Located outside bilayer Used to identify the cell -Determines blood type depending on which type is bonded to membrane
What is the function of cholesterol in plasma membranes?
Make the membrane more rigid but still flexible - too much can cause hardened arteries
What are the properties of lipids?
Many have oily fatty acid chains attached to chemical groups that interact strongly with water
Can all substances cross biological membranes?
No, some re too large or too strongly charged to cross lipid bilayer
Most biological membranes are _____ meaning some substances can pass across them and others cannot
Selectively permeable
Selectively permeable membranes are also called...
Semi permeable membranes
What kind of molecules pass through the plasma membrane easily?
Small, uncharged molecules Water, glycerol, ethanol Small, nonpolar has molecules Nitrogen, oxygen,carbon dioxide
What is an extra cellular matrix
Solution of macromolecules outside the cell (extra cellular space) - may help regulate behavior of cell in contact with matrix
What are junctions?
Specialized regions in plasma membranes where cells can be connected to one another
What are phospholipids called phospholipids
The lipid has only two fatty acids, the third being replaced by a phosphate group
What happens if substance is able to cross membrane
The membrane is determined as permeable to it - membrane is impermeable to substances that cannot pass across it
What are tight junctions
When plasma membranes are fused Substances cannot move through spaces between cells
