Cellular Biology study guide Chapter 5
carrier proteins
Bind a specific single solute and transport it across the lipid bilayer (uniport transport)
Membrane Spanning Carrier Proteins
Binds to specific substances and transport them across the membrane
Glycolipids
lipids with attached carbohydrate groups
Cholesterol
Main sterol in animal membranes, is important for keeping the membranes fluid
What do transport proteins do?
Move particular ions and molecules, including water, in a directed way across the membrane
Diffusion
Movement of molecules from an area of higher concentration to an area of lower concentration.
Calcium Pump (Ca2+)
Moves Ca2+ from the cytoplasm to the cell exterior, and from the cytoplasms into the vesicles of the endoplasmic reticulum (ER).
passive transport
Moves ions and molecules within the concentration gradient- higher to lower concentration
active transport
Moves ions or molecules against the concentration gradient- from lower to higher concentration
Primary Active Transport Pump
Moves positively charged ions (H+,CA2+, Na + and K+) across membranes
hypotonic solution
Strong walls prevent plant cells from bursting-osmotic pressure (turgor pressure) pushes cells tightly against their walls and supports soft tissues
Bulk endocytosis (pinocytosis)
Takes a drop of the aqueous extra cellular fluid (efc) surrounding the cells
receptor-mediated endocytosis
Target molecules are bound to receptor proteins on the outer surface cell
receptor-mediated endocytosis
Target molecules to be taken in are bound to receptor proteins on the outer cell surface
peripheral proteins
are held to membrane surfaces by non covalent bonds-hydrogen bonds and ionic bonds-formed with the polar parts of integral membrane proteins or membrane lipids
Proteins in cell-cell junctions
bind cells tightly together, as exemplified in gap junctions and tight junctions
cell adhesion proteins
bind cells together by recognizing and binding receptors or chemical groups on other cells
Osmosis
passive transport of water across a selectively permeable membrane
Where are proteins embedded?
phospholipid bilayer
Two major types of lipids in membranes
phospholipids and sterols
osmotic pressure
pressure that must be applied to prevent osmotic movement across a selectively permeable membrane
integral proteins
proteins embedded in the phospholipid bilayer.
H + Pumps
proton pump generates membrane potential and regulates pH in lysosomes and vacuoles
Receptor Proteins
recognize and bind molecules from other cells that act as chemical signals, such as hormones
Receptor proteins
recognize and bind molecules from other cells that act as chemical signals, such as hormones
What is the fluid mosaic model?
refers to the phospholipid molecules, which vibrate, flex back and forth, spin around their long axis, move sideways, and exchange places within the same bilayer half.
Antiport
solutes are transported in opposite directions
gated channels
switch between open, closed, or intermediate states
Three main functions of active transport
1. Uptake of essential nutrients from fluid surrounding cells, even when concentrations are higher in cells 2. Removal of secretory or waste materials from cells or organelles, even when concentrations are higher outside 3. Maintenance of intracellular concentrations of H+, Na+, K+, and Ca2+
low-density lipoprotein (LDL)
A complex of lipids and proteins, is the way cholesterol moves through the bloodstream
concentration gradient
A difference in the concentration of a substance across a distance.
Bulk endocytosis (pinocytosis) "cell drinking"
A drop of the aqueous fluid surrounding the cell- called extra cellular fluid (ECF) is taken into the cell together with any molecules that happen to be in the solution in the water.
Coated pit
A network of proteins (clathrin) coat and reinforce the cytoplasmic side
What do phospholipid molecules do?
Assemble into a bilayer (a later two molecules thick)
freeze fracture technique
Frozen cells were split into inner and outer halves, revealing the proteins embedded in the bilayers and their different patterns in the two halves
Phsopholipids
Have a polar electrically charged end containing a phosphate group, and a non polar uncharged end containing two non polar fatty acid tails
peripheral proteins
Held to membrane surfaces by non covalent bonds
If a solution surround a cell contains nonpenetrating solutes at higher concentrations than in the cell, the cell is what?
Hypertonic (water leaves and the cell shrinks)
If the solution surrounding a cell contains nonpenetrating solutes at lower concentrations than in the cell, the cell is what?
Hypotonic (water enters and the cells swell)
Phagocytes
In the bloodstream and protists such as amoeba, take in large particles or whole cells by phagocytosis
Cell-cell recognition proteins
In the plasma membrane identify a cell as part of the same individual or as a foreign, facilitate cell- cell linking, bind cells to the extracellular matrix (ECM) and link the ECM to the cytoskeleton
Na + K+ pump
In the plasma membrane of all animal cells moves 3 Na + out of the cell and 2 K+ into the cell in the same pumping cycle
channel proteins
Integral membrane proteins that form hydrophilic channels in the membrane through which water and ions can pass
What is phosphatidylcholine an example of?
Is an example of a phospholipid molecule
What does calcium pump regulate?
It regulates cellular activities such as secretion, microtubule assembly and muscle contraction
Transport of substances across a membrane against a concentration gradient requires what ?
It requires active transport - a process that requires energy output
Pinocytosis is nonspecific
It takes any solutes present in efc because the membrane lacks surface receptors for specific molecules
phospholipids and sterols are the two major types of what?
Lipid Membranes
primary active transport
The protein that transports a substance also hydrolyzes ATP to power the transport directly
secondary active transport
Uses an ion concentration gradient established by a primary pump as an energy source
Phagocytosis "cell eating"
Begins when surface receptors bind molecules on the substances to be taken in
Receptors with target molecules collect in a depression in the plasma membrane called
Coated pit
Transport
Controlled movement of specific ions and molecules across a membrane by membrane proteins
Membrane functions
Define the boundaries of cells and, in eukaryotes, the boundaries of compartments (organelles)
What do membranes do?
Defines the boundaries of cells and in eukaryotes, the boundaries of compartments Ex. Nucleus, mitochondria and chloroplasts
Molecular Insights
Describes the discovery of receptor- mediated endocytosis
Membranes are asymmetric
Different arrangements of membrane lipids and proteins occur in the two bilayer halves
What is passive transport a form of?
Diffusion
Fascilated Diffusion
Diffusion of polar and charged molecules through transport proteins in the hydrophobic lipid bilayer
Osmosis
Diffusion of water through a selectively permeable membrane
simple diffusion
Diffusion through the lipid part of a biological membrane
organelles of the endomembrane system
ER, Golgi Complex, lysosome, mitochondrion and chloroplast
What do membranes consist of?
Electrical properties and conduct signals when a cell receives an electrical, chemical, or mechanical stimulus
The differences in concentration ions and in electrical charge on the two sides of the membrane, constitutes a what?
Electrochemical gradient- form of potential energy
Where are integral proteins embedded?
Embedded deeply in the bilayer, whereas peripheral membrane proteins associate with membrane surfaces
Both Exocytosis and endocytosis require
Energy (ATP)
What does simple diffusion transport?
Non polar inorganic gases and organic molecules
Hydrophobic tail
Nonpolar, hates water
kiss and run mechanism
Occurs when a vesicles fuses with the plasma membrane, the vehicle contents are released from the cell, and then the vehicle reforms and moves back into the cell
Hydrophilic head
Polar end is hydrophilic and loves water
The concentration difference that drives diffusion, a concentration gradient is a form of what?
Potential energy
Tonicity
Property of a solution with respect to a particular membrane
fluid mosaic model
Proposes that the membrane consists of a fluid phospholipid bilayer in which proteins are embedded and float freely
Fluid Mosaic Model
Proposes that the membrane consists of a fluid phospholipid bilayer in which proteins are embedded and float freely.
Glycoproteins
Protein molecules with carbohydrate groups attached. Found on outer surface of cell membranes
nonpenetrating solutes
Proteins and other molecules that cannot pass through a membrane that is impermeable to them but freely permeable to water
Endocytosis
Proteins and other substances are trapped in pitlike depressions that bulge inward from the plasma membrane and pinch off as an endocytic vesicle
The "mosaic" part of the fluid mosaic model
Refers to membrane proteins, most of which float individually in the fluid lipid bilayer, like icebergs in the sea.
Mosiac
Refers to membrane proteins-most float individually in the lipid bilayer, some are attached to the cytoskeleton
fluid
Refers to the phospholipid molecules, that constantly move and exchange places within the same layer
Exocytosis
Secretory vesicles bud from the golgi complex move through the cytoplasm and contact the plasma membrane
Membrane Spanning Channel Proteins
Selectively regulate transport of specific ions or water through the membrane
polar molecule
Small enough to slip between the hydrocarbon tails of phospholipid molecules in a fluid bilayer
hypertonic solution
Stems and leaves wilt- in extreme cases, plant cells shrink so much that they retract from their walls (plasmolysis)
The lipid bilayers form what?
The lipid bilayer forms the structural framework of membranes and is a barrier to the passage of most water-soluble molecules
What is the glycocalyxes function?
The main function is to protect cells against chemical and mechanical damage
osmotic pressure
The term for pressure that must be applied to a solution to prevent water movement across a membrane
membrane potential
The voltage across a cell's plasma membrane.
What do glycolipids and glycoproteins do?
They form a surface coat called the glycocalyx
plasma membrane
Thin layer of lipids and proteins, seperates cells from its surroundings
secondary active transport
Transport is indirectly driven by ATP hydrolysis
enzymatic proteins
confer specific properties on the membranes with them
biological membranes
consist of lipids and proteins assembled into a thin film
recognition proteins
in the plasma membrane identify a cell as part of the same individual or as foreign
integral proteins
embedded in the phospholipid bilayer
ion channels
facilitate the transport of ions
transport proteins
form channels that allow selected polar molecules and ions to pass across a membrane
symport
the solute moves through the membrane channel in the same direction as the driving ion
Aquaporins
water channel proteins
Isotonic
when the concentration of two solutions is the same