Chapter 5: The Working Cell Flashcards
amino acid R groups are
hydrophobic
membrane structure is made of what three structures?
- phospholipids arranged in a bilayer
- proteins inserted in the lipid bilayer
- a fluid mosaic model
what is the mosaic model?
a mosaic of proteins floating in or on the fluid lipid bilayer like boats on a pond
lipids DO NOT form
polymers
phospholipids are?
the most abundant lipid in the plasma membrane
the phospholipid bilayer contains both ——- regions.
- hydrophilic (phospho)
- hydrophobic (lipid)
membranes are fluid mosaics of
lipids and proteins
membranes form
spontaneously
membranes..
- have fatty acids on the inside
- have phosphate groups on both surfaces
membranes are NOT
solid structures
lipids have the ability to…
move to the cell surface
What are the 6 different types of membrane proteins?
- transporters
- enzymes
- cell-surface receptors
- cell-surface identity markers
- cell adhesion proteins
- attachments to the cytoskeleton
enzymes perform…
reactions
cell-surface receptors receive signal from outside activating and signaling what?
activating- protein inside cell
signaling- to nucleus
aquaporins are needed to..
maintain hydration
aquaporins are a mode of transportation of
H2O into cell
aquaporins are composed of..
cylinder of beta sheets form a structure called beta-barrel
How do aquaporins stay in-between the phospholipid bilayer?
nonpolar amino acid R-groups interact with the membrane
How does H2O pass through the aquaporin?
the polar interior allows water and small polar molecules through
What is membrane permeability?
the ability to pass a membrane
the process of a cell exchanging materials with its surroundings is controlled by the..
plasma membrane
plasma membranes regulate the cell’s molecular traffic b/c they are…
selectively permeable
3 characteristics of a hydrophobic lipid barrier
- nonpolar molecules pass through until concentrations are equal on both sides
- small polar molecules are extremely limited
- larger polar molecules and ions have the lowest permeability
types of passive transport include…
- diffusion
- osmosis
- facilitated diffusion
the word “passive” in passive transport means…
without energy
diffusion is…
the passive movement of molecules from an area of high concentration to low concentration
-spread out evenly into available space
diffusion is done to…
reach equilibrium
diffusion does not have a ____ present.
barrier
in diffusion individual molecules…
move randomly
once diffusion reaches equilibrium molecules are…
crossing the membrane at the same rate in both directions
in diffusion the concentrations will NEVER…
return to original concentrations
a solute is…
dissolved molecules or ions
a solvent is…
water or other diluent
solutes are usually…
solid molecules
a concentration gradient is..
areas of different solute concentration
osmosis is the…
net diffusion of water across a semipermeable membrane toward a higher solute concentration
What part of the cell is an aqueous solution? What is the solvent? What are the solutes?
the plasma membrane
solvent- H2O
solutes- dissolved substances
It is possible that H2O will —– during osmosis.
defy gravity due to the attraction of polar molecules
What is a hypertonic solution?
a solution that has a higher solute concentration
What is a hypotonic solution?
a solution that has a lower solute concentration
osmotic concentration is determined when..
2 solutions have different concentrations of dissolved solutes or particles
hypertonic solution has…
- high [solute] outside cell
- low [H2O] outside cell
in a hypertonic solution the net movement of water will be
out of the cell…the cell shrinks
hypotonic solutions has…
- low [solute] outside
- high [H2O] outside
in a hypotonic solution the net movement of water will be
into cell…the cell swells
-if no cell wall is present the cell could burst
what is an isotonic solution?
when the two solutions have the same osmotic concentration
isotonic solution has…
- equal [solute] outside and inside
- equal [H2O] outside and inside
in a isotonic solution the net movement of water will be
no where.. there will be no change
osmotic pressure is the ability of…
solutes to influence the movement of water
osmotic pressure is the force needed to stop…
osmotic flow
what is an example of a osmotic pressure?
a cell in a hypotonic solution gains water causing it to swell and build up pressure
osmotic pressure drives water…
into cell
hydrostatic pressure drives water…
out of cell
animal cells are vulnerable to extreme changes in concentration therefore they must be in…
isotonic environments
passive transport (passive diffusion) is the movement of molecules through a membrane where…
- no energy is required
- molecules move from higher to lower concentration
passive movement always moves….
down the concentration gradient
passive transport is mechanism for….
obtaining O2 and releasing CO2
facilitated diffusion does NOT require ____ but requires ____.
- energy
- help
what are two examples of facilitated diffusion?
- channel proteins
2. carrier proteins
What to ions use to diffuse?
channel proteins
What do proteins use to diffuse?
carrier proteins
channel proteins are also known as…
ion channels
ion channels are ____ and open and close __ _____ __ ______
gated
in response to stimulus (chemical or electrical)
what three conditions determine the direction of diffusion in ion channels?
- concentration on either side of membrane
- voltage differences across membrane
- if channel is opened or closed
carrier proteins DO NOT
open like channels
carrier proteins have..
a pocket or binding spot
carrier proteins help transport…
ions and some sugars and amino acids
carrier proteins require a…
concentration difference across the membrane
carrier proteins MUST..
bind to the molecule before they transport
Active Transport requires…
ENERGY
What is used to fuel active transport?
ATP which is directly or indirectly used
active transport moves substances from…
low to high concentrations
against the concentration gradient
Active transport requires the use of…
highly selective carrier proteins
active transport is NOT..
diffusion
The Na+–K+ pump is used to…
maintain isotonic solution
the Na+–K+ pump is a good example of a ____ use of ATP
direct
the Na+–K+ pump moves ____ Na+ ____ and ____ K+ _____ the cell.
3-out
2-into
in the Na+–K+ pump ATP is used to?
change the shape of the carrier protein
Explain what happens with the carrier protein in a Na+–K+ pump.
the carrier protein binds Na+ or K+ as its shape changes so the ions can be carries across the memebrane
the Na+–K+ pump is a classic example of?
shape determines function
isotonic DOES NOT mean?
everything is in solution
bulk transport requires…
ENERGY
large molecules (polysaccharides and proteins) cross the membrane in ____ via _____.
bulk
vesicles
small molecules and water can cross the lipid bilayer…
directly or via transport proteins
what is endocytosis?
movement of large molecules and other substances into the cell
what is receptor-mediated endocytosis?
specific molecules (like cholesterol) are taken in after they bind to a receptor
exocytosis requires…
ENERGY
exocytosis is the movement..
of materials out of the cell
exocytosis is used in plants to
export cell wall material
exocytosis is used in animals to secrete…
hormones, neurotransmitters, and digestive enzymes
what is the cycle of energy of life?
energy enters the biological world from the sun –> photosynthetic organisms captures this energy and stores it in chemical bonds –> cells extract stored energy and use it to do work
EVERYTHING gets energy from..
the sun
Where does the energy cycle start?
organisms that carry out photosynthesis
the capacity to do work of to change derives from?
chemical transformations in cells
What are the two types of energy?
kinetic and potential
what is kinetic energy?
energy in motion
what is potential energy?
energy that matter possesses b/c of its location or structure (stored energy)
kinetic energy can be ____ b/c it ______ _____ and ____
seen
produces light, heat
Thermal energy is?
kinetic energy associated with random movement of atoms or molecules
chemical energy is?
potential energy stored in chemical bonds
chemical energy is available for?
release in a chemical reaction
the heat produced in thermal reactions is a result of:
- rapid movement of atoms
- rapid chemical reactions
energy =
electricity found in the electrons of chemical bonds
LIVING ORGANISMS ARE…
OPEN SYSTEMS
the laws of thermodynamics is the study of…
energy transformations
what is an open system?
energy and matter can be transferred between the system and its surroundings
energy transformations is the movement of
electrons
energy is required to…
maintain order
What is the first law of thermodynamics?
“the energy of the universe is constant - it is neither created nor destroyed”
When energy is converted from one form to another…
the total energy before and after the conversion is the same
What is the second law of thermodynamics?
“during every energy transformation, some energy is unusable”
“unusable energy” is often lost as
heat
energy transformations increase the…
entropy (disorder) of the universe
what is an example of an energy transformation that can no longer be used as a source of energy?
body heat
during biological order and disorder cells can?
- create ordered structures from less ordered materials
- transform ordered form of matter and energy into less ordered forms
(ex: of metabolism)
two characteristics of metabolism are?
- sum of all chemical reactions
2. transforms matter into energy
anabolic reactions are AKA..
endergonic
catabolic reactions are AKA
exergonic
during anabolic reactions?
complex molecules are made from simple molecules
how does energy play a role during anabolic reaction?
energy is required
during catabolic reactions?
complex molecules are broken down to simpler ones
What role does energy play during catabolic reactions?
energy is released
______ fuels ______ reactions
catabolic
anabolic
EXergonic =
energy existing
What do cells use for energy to drive the reactions of cellular work?
ATP
what does ATP stand for?
Adenosine TriPhosphate
ATP is a
nucleotide
ATP is the chief
“currency” all cells use
ATP is composed of?
- ribose -5 carbon sugar
- adenine (a nitrogenous base)
- chain of 3 phosphates
the chain of 3 phosphates are key to
- energy storage
- bonds are unstable (easy to use for energy)
the 3 phosphates are…
“super” charged electrostatic molecules that are very electronegative
How does ATP power cellular work?
by coupling exergonic reactions to endergonic reactions
What are the three types of cellular work?
- chemical
- transport
- mechanical
cells manage energy by
energy coupling, fueled by ATP
ATP hydrolysis powers
endergonic reactions
coupled reaction results in a
net energy gain (exergonic )
ATP is not for
long term energy storage
how much ATP do cells store?
only a few seconds worth
What are better ATP storage molecules?
fat, and carbohydrates
human are in a constant stage of…
metabolism
energy is required to started a
chemical reaction
What does the rate of reaction depend on?
the activation energy required
larger activation energy..
proceeds more slowly
What are the two ways rate can be increased?
- increase energy (temp.) of reactants
- lower activation energy
activation energy prevents..
spontaneous metabolic reactions
What are the two enzymes that speed up metabolic reactions?
- catalyst
- enzymes
how do these enzymes speed up the metabolic reactions?
by lowering energy barriers
What is a catalyst?
a chemical agent that speeds up a reaction without being consumed
What is an enzyme?
catabolic proteins
sucrase is an enzyme that…
catalyzes the hydrolysis of sucrose
catalyst “jump start”
organic reactions
NOT all proteins are
enzymes
“ase” =
enzyme
catalysts influence chemical bonds by…
lowering the activation energy
enzymes are not a part of
chemical reactions
catalysts CAN NOT make…
an endergonic reaction spontaneous
catalysts do NOT alter…
the amount of product made
most enzymes are
proteins
the shape of an enzyme….
brings substrates (reactants) together initiating their reaction
the shape of the enzyme is critical to its…
function
Note the difference between the molecules formed in a carbonic anhydrase with and without an enzyme.
without enzyme- 200 molecules/hour
with enzyme- 600,000 molecules/second
enzymes are…
highly specific
enzymes apply stress to..
particular bonds to lower acitivation energy
reactants=
substrates to product
sugar a form of..
good, fast, short energy
the rate of enzyme-catalyzed reaction depends on
concentrations of substrate and enzyme
any condition affecting an enzymes 3-d shape will also affect
the rate
two conditions that will affect the rate of an enzyme is
optimum temperature
optimum pH
an inhibitor is?
a substance that binds to enzyme and decreases its activity
a competitive inhibitor..
competes with substrate for active site
a noncompetitive inhibitor..
- binds to enzyme at a site other than the active site
- causes shape change that makes enzyme unable to bind substrate
many chemical compounds are
enzyme inhibitors
competitive and noncompetitive inhibitors are AKA
active or inactive enzymes
two characteristics of biochemical pathways are…
- reactions occur in a sequence
- product of one reaction is substrate for the next
two characteristics of feedback inhibition are…
- end-product binds to inhibitory site on the first enzyme
- shuts down pathway to conserve energy
feedback inhibition is AKA
negative feedback
most metabolic products are carried out by
multiple enzymes
glucose goes through about
8 metabolic processes
the three types of bulk transport are?
phagocytosis, endocytosis, exocytosis
