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Describe (or draw a picture) the processes by which molecules move across membranes
There are two ways:
1-by PASSIVE TRANSPORT which may lead to one of the following: a-DIFFUSION of SMALL NONPOLAR MOLECULES b- FACILLATATED DIFFUSION of POLAR MOLECULES AND IONS which uses TRANSPORT PROTEINS c- or may move down to CONCENTRATION GRADIENT
2-by ACTIVE TRANSPORT which will a) move against CONCENTRATION GRADIENT b) use TRANSPORT PROTEINS thru FACILATATED DIFUSSION and requires ATP
Describe the catalytic cycle of an enzyme (or draw a picture)
Beginning with an ENZYME the ACTIVE SITE OF THE ENZYME is open (nothing is in it), then a SUBSTRATE enters the active site. When the SUBSTRATE IS IN THE ACTIVE SITE THE INDUCED FIT STRAINS THE SUBSTRATE BONDS; SUBSTRATE IS THEN CONVERTED TO PRODUCTS; and PRODUCT MOLECULES ARE RELEASED AND SUBSTRATE IS NOW READY FOR NEXT CATALYTIC CYCLE
Briefly describe the structure of a cell membrane
proteins embedded in a bilayer of phospholipids
Consider the following: chemical bonds in the gasoline in a car's gas tank and the movement of the car along the road; a climber at the top of a hill and the hike she took to get there. The first parts of these situations illustrate _______________, and the second parts illustrate _______________.
potential energy; kinetic energy
A plant cell placed in distilled water will ________; an animal cell placed in distilled water will __________
become turgid; burst
The sodium concentration in a cell is ten times less than the concentration in the surrounding fluid. How can the cell move sodium out of the cell?
active transport;only active transport can move solute against a concentration gradient
the synthesis of ATP from ADP and P does what?
stores energy in a form that can drive cellular work
Facilitated diffusion across a membrane requires ___________ and moves a solute ____________ its concentration gradient
transport proteins; down
What are aquaporins? where would you expect to find these structures?
Aquaporins are water transport channels that allow for very rapid diffusion of water through a cell membrane. They are found in cells that have high water transport needs, such as blood cells, kidney cells, and plant cells
how do the two laws of thermodynamics apply to living organisms?
Energy is neither created nor destroyed but can be transferred and transformed. Plants transform the energy of sunlight into chemical energy stored in organic molecules. Almost all organisms rely on the products of photosynthesis for the source of their energy. In every energy transfer or transformation, disorder increases as some energy is lost to the random motion of heat
what are the main types of cellular work? how does ATP provide the energy for this work?
The work of cells falls into three main categories: mechanical, chemical, and transport. ATP provides the energy for cellular work, usually by transferring a phosphate group to a protein (movement and transport) or a substrate (chemical)
why is the barrier of the energy of activation beneficial for organic molecules? Explain how enzymes lower Ea
Energy is stored in the chemical bonds of organic molecules. The barrier of Ea prevents these molecules from spontaneously breaking down and releasing that energy. When a substrate fits into an enzyme's active site with an induced fit, its bonds may be strained and thus easier to break, or the active site may orient two substrates in such a way as to facilitate the reaction
how do the components and structure of a cell membranes relate to the functions of membranes?
Cell membranes are composed of a lipid bilayer with embedded proteins. The bilayer creates the hydrophobic boundary between cells and their surroundings (or between organelles and the cytoplasm). The proteins perform the many functions of membranes, such as enzyme action, transport, attachment, and signaling
sometimes inhibitors can be harmful to a cell; often they are beneficial. Explain
Inhibitors that are toxins or poisons irreversibly inhibit key cellular enzymes. Inhibitors that are designed as drugs are beneficial if they interfere with the enzymes of bacterial or viral invaders or cancer cells. Cells use feedback inhibition of enzymes in metabolic pathways as important mechanisms that conserve resources
Explain how each of the following food preservation methods would interfere with a microbes enzyme activity and ability to break down food: canning (heating), freezing, pickling (soaking in acetic acid), salting
Heating, pickling, and salting denature enzymes, changing their shapes so they do not fit substrates. Freezing decreses the kinetic energy of molecules, so they lack energy of activation, even in the presence of enzymes.
biological membranes are composed of ______ and ________
What keeps the membrane in the phospholipids fluid?
Double bonds in the unsaturated fatty acid tails produce kinks
In ________ cells, the steroid cholesterol, wedged into the bilayer, helps stabilize the membrane at worm temperatures but also helps keep the mambrane fluid at lower temperatures.
The word mosaic refers to...
the position of proteins in the phospholipid bilayer and also to the varied functions of the proteins.
what is the function of integrins?
they span the membrane and attach to the cytoskeleton on the inside and the extracellular matrix (ECM) on the outside giving the membrane a stronger framework
what is the function of glycoproteins?
cell to cell recognition
What function of membrane proteins is specific to plasma membrane proteins?
forming junctions between cells
Many proteins are ________
________ proteins function as chemical messengers from other cells.
receptors; its shape is specific to the cell the message is to be rec'd
The message transfer process performed by receptors is called...
What makes a membrane be selectively permeable?
Their hydrophobic interior; non polar, hydrophobic molecules can easily pass through membranes. polar molecules and ions are not soluble in lipids.
Many essential molecules such as ______ and _____, require transport proteins to enter or leave the cell
________, the key ingredients of biological membranes, were probably among the first organic molecules that formed from chemical reactions on early Earth
The formation of ______________ collections of molecules was a critical step in the evolution of the first cells.
A _____________ that allows cells to regulate their chemical exchanges with the environment is a basic requirement for life.
plasma membrane; one of the features that illustrates the evolutionary unit of life
Diffusion requires ________, and results from ________
no work; thermal motion of atoms and molecules
Most of the traffic across cell membranes occurs by _______
diffusion by passive transport
One of the most important molecules that crosses membranes by passive transport is ______
The direction of osmosis is determined by...
the differnce in total solute concentration, not by the nature of the solutes
The tonicity of a solution mainly depends on....
its concentration of solutes that cannot cross t he plasma membrane relative to the concentrations of solutes in the cell
when an animal cell such as a red blood cell is immersed in a solution that is _________ to the cell, the cell's volume remains constant
describe animal cells when in an isotonic solution; hypotonic solution; hypertonic solution
isotonic-water comes and goes and is normal
hypotonic- water only comes n and cell fills up w/ too much water nd becomes lysed (bursts)
hypertonic- water only goes out and the cell shriveles up
describe plant cells when in an isotonic solution; hypotonic solution; hypertonic solution
isotonic-water comes and goes and cell is flaccid
hypotonic-water only comes in and cell becomes turgid
hypertonic-water only goes out and plant cell shrivels up (plasmolyzed)
_______ and ______ molecules can dissolve in lipid bilayer of a membrane and cross it with ease
The greater the number of ____________ for a particular solute present in a membrane, the faster the solutes rate of diffusion across the membrane
name substances that use facilitated diffusion for crossing cell membranes
sugars, amino acids, ions and water
The very rapid diffusion of water into and out of certain cells, such as plant cells, kidney cells, and red blood cells is made possible by transport proteins called _______
In active transport a cell must expend energy to move a solute _________ its concentratio gradient--that is across a membrane toward the side where the solute is more concentrated
Describe the process of an active transport system that moves a solute out of the cell against its concentration gradient
1-Solute binding-the solute on the cytoplasmic side of the plasma membrane attaches to a specific binding site on the transport protein 2- Phosphorylation-ATP then transfers one of its phosphate groups to the transport protein 3- Transport-the shape changes in sucha a way that the solute is released on the other side of the membrane 4- Protein reversion- the phosphate group detaches, and the transport protein returns to its original shape, ready for a new round of active transport
___________ allows a cell to maintain concentrations of small molecules that are different from concentrations in its surroundings
A cell uses the process of ________ to export bulky materials such as proteins or polysaccharides
exocytosis; tears or insulun the pancreas
In ________ a cell takes in substances.
name 3 types of endocytosis and describe
Phagocytosis; cellular eating by engulfing a particle with pseudopodia and packaging it within a membrane enclosed sac large enough to be called a vacuole
pinocytosis; cellular drinking by gulping droplets of fluid into tiny vesicles; not specific as it takes any and all solutes dissolved in the droplets
receptor mediated endocytosis;highly specific. Receptor proteins for specific molecules are embedded in regions of the membrane that are lined by a layer of coat proteins. The coated pit then pinches closed to form a vesicle that carries the molecules into the cytoplasm
Our cells use _____________ to take in chlesterol from the blood for synthesis of membranes and as a precursor for other steroids
receptor mediated endocytosis
Energy is _________
the capacity to perform work
heat and light are a form of what kind of energy?
_______________ is a term that refers to the potential energy available for release in a chemical reaction
why is chemical energy the most important type of energy for living organisms?
it is the energy that is available to do the work of the cell. Just as the potential energy of the cyclist can be converted to kinetic energy in the speedy ride downhill, the chemical energy of molecules can be released to power the work of the cell. Life depends on the fact that energy can be converted from one form to another
what is thermodynamics?
the study of energy transformations that occur in a collection of matter
What are the laws of thermodynamics?
First Law-the law of energy conversavation; the energy in the universe is constant. Energy can be transfered and transformed but can not be destroyed.
Second Law-entropy (a measure of disorder, or randomness)
During every energy transfer some energy becomes _______. In most energy transfer some energy is converted to ________, the energy associated with random molecular motion
__________ is a disordered form of energy, and its release makes the universe more random
According to the second law of thermodynamics, energy conversions increase the ___________ of the universe
Only about ________ of the chemical energy stored in gasoline is converted to the ____________ of the cars movement; the rest is lost as heat energy
25%; kinetic energy
Because the second law of thermodynamics states that energy transformations result in the universe becoming more disordered (entropy), how then can one explain bilogical order?
A cell creates its structures from less organized materials. For example, amino acids are ordered into the specific sequences of polypeptides. Although this increase in order corresponds to a decrease in entropy, it is accomplished at the expense of ordered forms of energy taken in from the surroundings
An _____________ is a chemical reaction that releases energy
exergonic reaction which begins with reactants whose covalent bonds contain more energy than those in the products. The reaction releases to the surroundings an amount of energy equal to the difference in potential energy between the reactants and the products. Ex the burning of wood
________________ is a chemical process that uses oxygen to convert the chemical energy stored in fuel molecules to a form of chemical energy that the cell can use to perform work
burning and cellular respiration are alike in being _______ but differ because....
exergonic; they differ in that burning is essentially a one-step process that releases all of a substance's energy at once, while cellular respiration involves many steps, each a separate chemical reaction (think of it as a slow burn)
________ yield products that are rich in potential energy
Describe an endergonic reaction
Endergonic reactions start out with reactant molecules that contain relatively little potential energy. Energy is absorbed from the surroundings as the reaction occurs, so the products of an endergonic reaction store more energy than the reactants did. The energy is potential energy stored in the covalent bonds of the product molecules. Ex: photosynthesis
All cells use ___________ in the process of building the macromolecules that form the structure and perform the functions of the cell
A _______________ is a series of chemical reactions that either builds a complex molecule or breaks down a complex molecule into simpler compounds.
metabolic pathway; ex. cellular respiration
All of an organisms activities require energy, which is obtained from sugar and other molecules by the _________ of cellular respiration
____________ are the key to energy coupling.
_________ shuttles chemical energy and drives cellular work
ATP stands for ________ and consists of what?
the adenosine part consist of: adenine, a nitrogenouse base, and ribose, a five carbon sugar.
the triphosphate part is a chain of three phosphate groups that are negatively charged and crowded together; their mutual repulsion (since they are all the same charge of negative) makes the triphosphate chain of ATP the chemical equivalent of a compressed spring
Name 3 main types of cellular work
chemical, mechanical, and transport---ATP drives them all to work
In __________ the phosphorylation of reactants provides energy to drive the endergonic sysnthesis of products
In _________ the transfer of phosphate groups to special motor proteins in muscle cells causes the proteins to change shape and pull on actin filamens, in turn causing the cells to contract
in _______ ATP drives the active transport of solutes across a membrane against their concentration gradient by phosphorylating certain membrane proteins
Work can be sustained because ATP is a ______
renewable resource that cells regenerate
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