The cell membrane is composed of
phospholipid bilayer
phospholipids
-structural component of the membrane -amphipathic -selectively permeable
Cell membranes are also composed of
proteins, glycoproteins, glycolipids, cholesterol
Proteins are the ___________________ components of of membranes.
functional
Transporters, receptors, enzymes, anchors
examples of functional proteins
Cholesterol in cell membranes
maintains an optimum fluidity of the membrane in animal cells -prevents the membrane becoming too solid in cold temperatures or too fluid in high temperatures
Glycosylation
process of attaching a carbohydrate chain to a protein or lipid
glycolipid
lipid with carbohydrate attached
glycoprotein
protein with carbohydrate attached
The carbohydrate chain in cell membranes
-provides a distinctive cellular marker -helps protect proteins from damage
This type of model describes the cell membrane's structure
fluid-mosaic
The fluid mosaic model means that the cell membrane is
semi-flexible and a "tapestry" of several types of molecules
Since the cell membrane is semi-permeable, this allows the cell to maintain its internal conditions separate from the __________________
environment
Factors for molecules to cross membrane are
size, polarity, change
The membrane is MOST permeable to
small, hydrophobic molecules
The membrane is LEAST permeable to
large, hydrophilic, charged molecules.
Cells maintain
transmembrane gradients
chemical gradient
concentration of SOLUTE higher on one side than the other
electrochemical gradient
a chemical and electrical gradient (difference in electrical charges between the inside and outside of the cell)
Why is it important to maintain gradients?
-maintain water balance -transmission of nerve impulses -production of ATP
Ways that molecules move across cell membrane include
passive transport and active transport
passive transport
molecules move from area of HIGH concentration to an area of LOW concentration
Passive transport requires NO ___________ and movement is DOWN a gradient.
energy
The 3 types of passive transport
simple diffusion, facilitated diffusion, osmosis
simple diffusion
molecule passes across the membrane without help
facilitated diffusion
molecule passes across membrane with the help of membrane protein
osmosis
the net movement of a solvent (WATER) across a semi-permeable membrane into a solution with a higher solute concentration (SALT WATER)
_______________ molecules can NOT move across the membrane in osmosis.
solute
Osmosis _______________ the concentrations of solute on either side of the membrane
equalizes
Osmosis is responsible for
reabsorption of water in the kidneys uptake of water by plant roots dehydration resulting from cholera infection
Tonicity
relative solute concentration of one solution compared to another
HYPOtonic solution
solution has LOWER solute concentration than other solution
Isotonic
EQUAL solute concentration in both solutions net movement 0
HYPERtonic
HIGHER solute concentration than other solution
Water movement can make a cell _________ or _________ so cells must remain isotonic across the membrane
shrink, swell
crenation
shrinking of cell in a HYPERtonic solution
osmotic lysis
swelling and bursting of a cell in a hypotonic solution
osmosis in plants:
turgor pressure and plasmolysis
turgor pressure
pushes plasma membrane against cell wall and maintains shape and size; cell in a HYPOtonic solution
Plasmolysis
plants wilt because water leaves plant cells; cell in a HYPERtonic solution
active transport
molecule is transported from an area of LOW concentration to an area of HIGH concentration and requires ENERGY; moves AGAINST the gradient
Na+K+ ATPase- transmission of nerve impulses , H+/K+ ATPase- acidifies stomach juices required for digesting food.
active transport proteins
exocytosis
material inside cell is packages into vesicles and EXPORTED OUT of the cell; active transport
endocytosis
import of a molecule INTO cell through vesicle; active transport
cell communication AKA signal transduction
process of cells detecting and responding to signals in the extracellular environment
The 3 stage process of cell responsiveness
receptor activation 2. signal transductions 3. cellular response
receptor activation
receptor binds signaling molecule and becomes activated
signal transduction
signal gets transmitted through the cell; a series of proteins form a signal transduction pathway
cellular response
activity of target molecules is altered to change cell behavior
Target proteins:
enzyme-alter metabolism
structural proteins-alter cell shape or movement
transcription factor-alter gene expression
True or false: some signaling proteins and receptors travel a short distance and bind receptors on a nearby target
True
neurotransmitters
signaling protein that travels a short distance
FSH
signaling molecules (called hormones) are released in the bloodstream and travel long distances to bind their receptors on target cells
protein kinase
enzyme that adds a phosphate to a target protein to switch them on or off
protein phosphatases
Enzymes that can rapidly remove phosphate groups from proteins.
Adding/removing a phosphate group is a way to ________________ and ________________ alter protein activity
quickly, reversibly
second messenger
amplify signal throughout the cell
cyclic AMP
second messenger
cell communication steps
signaling molecule binds to receptor
signal is transmitted via a series of proteins in the cell
activity of target proteins is altered to bring about cellular response
target proteins
ultimately receive a message to alter cell activity
energy
the ability to do work
the two basic forms of energy
kinetic and potential
kinetic energy
associated with movement
potential energy
stored energy
chemical energy
Energy stored in chemical bonds (form of potential energy)
chemical reaction
when one or more substances change into one or more new substances REACTANTS to PRODUCTS
True or False: In chemical reactions, existing chemical bonds are broken and new ones are formed
True
exergonic reaction
A chemical reaction that RELEASES energy
Gibbs free energy
the difference in energy stored in the chemical bonds of reactants and products
If the energy stored in products is less than the energy stored in the old bonds THEN
products have LESS energy than reactants Reaction is exergonic Reaction is spontaneous
a NEGATIVE gibbs free energy indicates a
exergonic reaction
endergonic reaction
A non-spontaneous chemical reaction in which energy is ABSORBED and REQUIRED for use of reaction
If the energy stored in the products is more than the reactants THEN
products have more energy than reactants reaction is endergonic reaction is NOT spontaneous
Metabolism
All of the chemical reactions that occur within an organism
catabolic reactions
breakdown of molecules used to RELEASE energy recycle monomers (building blocks) EXERGONIC bonds
anabolic reactions
build molecules and macromolecules ENDERGONIC reactions
endergonic reactions
REQUIRE ENERGY
In exergonic reaction because products have less energy than reactants, there is a net _______________ of energy
release
In endergonic reactions because products have more energy than reactants, there is a net ______________ of energy
input
The energy source for many endergonic cellular reactions is
ATP
ATP is a product, what is it converted from?
ADP
catalyst
substance that speeds up the rate of a chemical reaction; is not consumed and remains unchanged at the end of the reaction
enzymes
protein catlysts
ribozymes
RNA molecules that function as catalysts.
activation energy
Energy needed to get a reaction started and to transition state
True or False: Activation energy is only needed for endergonic reactions
FALSE- it is needed for BOTH endergonic and exergonic reactions
transition state
intermediate state between reactants and products
common ways to OVERCOME activation energy
large amounts of heat
using enzymes to lower activation energy
________________ lowers activation energy
enzymes
active site
location where chemical reaction occurs
substrates
reactants, that are first affected by enzyme, that bind to active site
enzyme-substrate complex
formed when enzyme and substrate bind
Products
molecules that are formed after the reaction
The steps of an enzyme catalyzed reaction are
substrates bind
enzyme undergoes conformational change that binds substrates more tightly
substrates are converted to products
products are released
induced fit model
explains conformational change an enzyme undergoes after binding substrate.
prosthetic group
small, non-protein helper molecule permanently attached to the enzyme
cofactor/coenzymes
non-protein helper molecules NOT permanently attached to the enzyme
Coenzymes are _______________ like vitamins, but cofactors are -__________ like Sulphur phosphate
organic, non-organic
True or False: ALL chemical reactions in the body are catalyzed reactions
True
factors that affect the rate of enzyme catalyzed reactions
substrate concentration, pH, temperature, and inhibitors