Biology Exam #2

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The cell membrane is composed of
phospholipid bilayer
-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.
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
process of attaching a carbohydrate chain to a protein or lipid
lipid with carbohydrate attached
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
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 __________________
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
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Passive transport requires NO ___________ and movement is DOWN a gradient.
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
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.
Osmosis _______________ the concentrations of solute on either side of the membrane
Osmosis is responsible for
reabsorption of water in the kidneys uptake of water by plant roots dehydration resulting from cholera infection
relative solute concentration of one solution compared to another
HYPOtonic solution
solution has LOWER solute concentration than other solution
EQUAL solute concentration in both solutions net movement 0
HIGHER solute concentration than other solution
Water movement can make a cell _________ or _________ so cells must remain isotonic across the membrane
shrink, swell
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
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
material inside cell is packages into vesicles and EXPORTED OUT of the cell; active transport
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
1. 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:
1. enzyme-alter metabolism 2. structural proteins-alter cell shape or movement 3. transcription factor-alter gene expression
True or false: some signaling proteins and receptors travel a short distance and bind receptors on a nearby target
signaling protein that travels a short distance
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
1. signaling molecule binds to receptor 2. signal is transmitted via a series of proteins in the cell 3. activity of target proteins is altered to bring about cellular response
target proteins
ultimately receive a message to alter cell activity
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
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
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
In exergonic reaction because products have less energy than reactants, there is a net _______________ of energy
In endergonic reactions because products have more energy than reactants, there is a net ______________ of energy
The energy source for many endergonic cellular reactions is
ATP is a product, what is it converted from?
substance that speeds up the rate of a chemical reaction; is not consumed and remains unchanged at the end of the reaction
protein catlysts
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
1. large amounts of heat 2. using enzymes to lower activation energy
________________ lowers activation energy
active site
location where chemical reaction occurs
reactants, that are first affected by enzyme, that bind to active site
enzyme-substrate complex
formed when enzyme and substrate bind
molecules that are formed after the reaction
The steps of an enzyme catalyzed reaction are
1. substrates bind 2. enzyme undergoes conformational change that binds substrates more tightly 3. substrates are converted to products 4. 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
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
factors that affect the rate of enzyme catalyzed reactions
substrate concentration, pH, temperature, and inhibitors
substrate concentration increases reaction until ____________________ is reached
all enzyme active sites are occupied by substrate
velocity (speed) of reaction at maximum rate
measure of the ability that an enzyme has to its substrate -substrate concentration needed to reach half Vmax
________ Km value means a HIGH affinity for substrate, while a _________ Km value means a LOW affinity for substrate
pH affects ionic bonds that are important for _______________________ and interactions with substrate
protein folding
a LOW temperature means the rate of reaction is __________ as molecules collide less often
a HIGH temperature ___________________ enzymes by breaking chemical bonds
used to slow down a chemical reaction
The two types of inhibitors
competitive and noncompetitive
Competitive inhibitors
bind at enzyme active site which prevents the substrate from binding -Vmax STAYS THE SAME but more substrate is needed to reach it
noncompetitive inhibitor
binds to an allosteric site NOT the active site -prevents the enzyme from working properly by affecting its SHAPE -LOWERS Vmax
allosteric site
A specific receptor site on some part of an enzyme molecule remote from the active site.
Competitive inhibitors are usually
reversible inhibitors are ________________ and irreversible inhibitors are ___________________
temporary, permanent
Reversible inhibitors usually
leave active site and the level depends on concentrations of substrate and inhibitors
Noncompetitive inhibitors can be
reversible (TEMPORARY) OR irreversible (PERMANENT
enzyme inhibitors examples include
drugs, poisons, pesticides, or naturally occurring molecules used to regulate metabolic pathways
Methotrexate, Penicillin, Cyanide
enzyme inhibitors
All living things require energy for:
-daily life processes (growth, reproduction, nerve impulses) -daily activities (running, studying, driving)
The typical energy expenditure of humans is
60-75% basal metabolic functions 20-35% lifestyle activities 5-10% digestion of food
energy is contained within
organic foods
heterotrophs (humans, animals, some prokaryotes) must
consume food to obtain energy
autotrophs (plants, some prokaryotes) can
make their own food to obtain energy
Energy stored in ______________ must be converted to a useable form
The chemical formula for cellular respiration is
C6H12O6 +6O2 = 6CO2 + 6H2O
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aerobic cellular respiration (OXYGEN)
process of converting energy stored in organic food molecules into energy stored in ATP -exergonic reaction. 40% ATP 60% Heat
________ is the form of energy that can be directly used by cells
ADP + P ----->
Mitochondria are cell's _____________ _______________
energy factories
____________ is the primary site of ATP synthesis in eukaryotes
Organelles of the mitochondria are
alter membrane, inner membrane, crista-folds of mitochondria, matrix-cytosol of mitochondria , and ribosomes
__________ reactions play a central role in cellular respiration
Redox reactions
electrons transferred from one molecule to another
loss of electrons
gain of electrons
oxidation is loss, reduction is gain
True or False: Electrons are often transferred in the form of oxygen
FALSE- they are often transferred in the form or HYDROGEN
Glucose is _______________ into carbon dioxide, and oxygen is ______________ to water in cellular respiration
electron carriers
transfer electrons
electron carriers in cellular respiration
The Four stages of cellular respiration are
glycolysis, pyruvate to acetyl CoA, citric acid cycle, oxidative phosphorylation
Glycolysis takes place in
Is glycolysis aerobic or anaerobic?
two phases of glycolysis
energy investment phase and energy payoff phase
The components that go into glycolysis are
glucose, ADP, NAD
the products of glycolysis are
pyruvate, ATP, and NADH
the conversion of pyruvate to acetyl CoA takes place in
matrix of mitochondria
The components that go into the second stage of cellular respiration are
The products of the second stage of cellular respiration are
acetyl CoA, CO2, and NADH
the citric acid cycle takes place in
matrix of mitochondria
The components that go into the citric acid cycle are
acetyl CoA, ADP, 6NAD, FAD
the products of the citric acid cycle are
At the citric acid cycle, glucose has been completely
the oxidative phosphorylation phase takes place in
inner membrane of mitochondria
two parts of oxidative phosphorylation
electron transport chain and ATP synthesis
True or False: High energy electrons are donated to the electron transport chain
The electron transport chain has how many protein complexes
electrons are donated to the chain by these electron carriers
Electrons are transferred down the chain to
the terminal electron acceptor AKA OXYGEN
Energy is released with each electron transfer and is used to ______________ _______________ H ions across inner membrane to create an ______________________________
actively transport, electrochemical gradient
ATP synthase
The enzyme that make ATP from ADPand inorganic phosphate.
ATP synthase makes ATP by
A process for synthesizing ATP using the energy of an electrochemical gradient and the ATP synthase enzyme.
ATP synthase provides a _________ for H ions to diffuse down their gradient which releases the stored energy
ATP synthase has ________ active sites
One complete turn produces _____ ATP in chemiosmosis
The end products of oxidative phosphorylation are
Process by which cells release/create energy in the absence of oxygen
True or False: The electron transport chain will remain active without oxygen
FALSE- the chain will shut down
Fermentation occurs in
humans, animals, plants, yeasts, and some bacteria
The two types of fermentation are
ethanol fermentation and lactic acid fermentation
Lactic acid fermentation takes place in
humans, animals, and some bacteria
lactic acid equation
pyruvate + NADH -->2 molecules lactate +ATP
ethanol fermentation takes place in
plants, yeasts, and some bacteria
ethanol fermentation equation
2pyruvate ------> ethanol+CO2 + ATP
anaerobic respiration
Respiration that does not require oxygen
Fermentation stops at which cellular respiration phases
2nd (conversion of pyruvate to Acetyl CoA)
Molecules OTHER THAN _________ are used as the terminal electron receptor in anaerobic respiration
other molecules besides glucose can be broken down to supply energy. these include:
proteins, complex carbohydrates, fats
True or False: In equal amounts of glucose and fats there will be more energy in the fats.
In aerobic cellular respiration, the products are
H2O and CO2 and a LARGE amount of ATP
In fermentation, the products are
Lactate and a very SMALL amount of ATP OR ethanol and CO2 with a very SMALL amount of ATP
In anaerobic cellular respiration, the products are
CO2 and variable element (ex NO3) and a LARGE amount of ATP
the process of using light energy to make glucose from CO2 and H2O
What is the purpose of photosynthesis?
to make food and in turn energy
the equation for photosynthesis is
6CO2 + 6H2O ------> C6H12O6 + 6O2
knowt flashcard image
In photosynthesis, CO2 is _________ to glucose
In photosynthesis, Water is __________ to oxygen
How is photosynthesis important to life?
-provides autotrophs and heterotrophs with organic food for cellular respiration -Provides organisms with oxygen for aerobic cellular respiration
Photosynthesis takes place in
green structures EX: leaves and stems
Mesophyll cells
cells that contain many chloroplasts and host the majority of photosynthesis
Site of gas exchange under the leaf
leaves also contain
epidermal cells
The main cell organelle that photosynthesis takes place in is
chloroplasts contain the pigment
Structures of the chloroplast include
outer membrane, intermembrane space, inner membrane, STROMA, THYLAKOID, GRANUM, lumen (inside thylakoid)
Light-absorbing molecule
Why does chlorophyll appear green?
reflects green light
Light energy is absorbed by
boosting electrons to a higher energy level
ground state
The lowest energy state of an atom
When an atom is in its ground state and it absorbs light energy it get converted to
the excited state
excited state
a state in which an atom has more energy than it does at its ground state
to become stable again, and atom can:
-by releasing excess energy as heat or light -by transferring excess energy to another molecule (resonance energy transfer) -by passing the excited electron to another molecule
chlorophyll is found in
thylakoid membrane
Other pigment molecules in photosynthesis
accessory pigment molecules
Accessory pigment that enables a plant to absorb additional light energy and maximize photosynthesis.
two stages of photosynthesis
light reactions and calvin cycle
light reactions take place in
thylakoid membrane
the light reactions phase produces
ATP, NADPH, and O2