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Biology exam 3
Terms in this set (89)
•control of exchange of materials
•organization of cellular functions
•cellular communication and signal transduction
•cell to cell recognition
•transformation of energy
What are the molecular components that make up the plasma membrane?
-glycoproteins & glycolipids
*(protein or lipid+carbohydrate)
*found on exterior of cell only
•constructed from phospholipids
•bilayer is formed
•outside hydrophilic; inside hydrophobic
Steroids & glycolipids
•cholesterol increases or decreases membrane fluidity
•extracellular "sugar coat"
•includes some carbohydrates on proteins and lipids
•unique composition for each person
The fluid mosaic membrane model
•fluid phospholipid layers
•collage of proteins embedded in the matrix
•not completely homogenous; microdomains present (lipid rafts)
•tendency for molecules to move from areas of high concentration to areas of lower concentration
•based on kinetic energy intrinsic to molecules
Diffusion of water: osmosis
•diffusion of solvent (h2o)
•Tonicity of solutions
Toniticy of solutions
-water concentration=water concentration inside the cell
*or water concentration is the same on both sides of the semi-permeable membrane
-most cells contain about .9% dissolved salts
*an isotonic environment must contain about .9% dissolved salts (solutes)
•water concentration outside the cell is higher than inside the cell (solute concentration outside cell is lower than inside the cell)
•water moves into cell at a greater rate than it moves out
•solution with lowest concentration of solute
•water concentration outside cells is lower than inside cell (solute concentration outside cells is higher than inside)
•water moved out of cell at a greater rate than it moves in
•solution with highest concentration of solute
Movement of other small molecules
•three possible types of transport for molecules
*aka facilitated diffusion. Based on diffusion no energy is required
*requires an expenditure of energy
Concentration gradient, electrical gradient or both drive diffusion. No energy input required. Overall movement is from high concentration to low. Facilitated by channel or carrier protein. Channel proteins, open or gated channels (10 of millions of molecules transported/sec. carrier proteins, shape change (a thousand to a million molecules/sec.
Requires that a cell expand energy to move molecules across a membrane. A transport protein actively pumps a specific solute across a membrane against the solute's concentration gradient. Systems like this are common, coupling the passage of two solutes; they can transport ions as well as uncharged molecules. Usually us ATP as energy source. Transport protein uses energy to pump a solute across a cell membrane against concentration gradient, for example a calcium pump and sodium potassium pump.
Functions of active transport
Cell can uptake molecules against a concentration gradient. Molecules can be moved out of cell against concentration gradient. Cell can maintain optimal concentrations of ions
Transport of large molecules: bulk transport
Movement of large molecules or particles into or out of cell requires active transport. Two types are: exocytosis it exports molecules from the cell. And endocytosis brings molecules into the cell
Three types: pinocytosis, receptor-mediated endocytosis, and phagocytosis
What is Energy?
The capacity to do work
What is work?
Work is the ability to move matter in a direction it would not move if left alone. Energy is measured in calories, the amount of energy necessary to raise the temperature of 1 gram of water 1oC
Forms of energy
Potential energy: Stored energy, charged ions on one side of a membrane. Kinetic energy: energy of motion, ions moving through a membrane to charge an ATP molecule
The laws of thermodynamics: first law
In a closed system, energy can neither be created nor destroyed, only changed in form. The amount of energy present at the beginning of the universe and at the end will be the same. The form of the energy will be different
Second law of thermodynamics
Energy transformations result in increased disorder or entropy, some of the energy is no longer available to do work. Entropy is a measure of the amount of disorder or randomness in a system. Disorder is always increasing. Chemical reactions go to equilibrium
Why do cells need energy to survive
Cells are subject to becoming disordered due to to the second law of thermodynamics, they remain alive and healthy (ordered and active) only because they have a constant input of energy. Chemical reactions in a cell keep it in order.
Is a form of kinetic energy, consists of a spectrum of electromagnetic waves that differ in wavelength and energy content. Waves also have properties of a particle, called a photon and carries energy
Visible light is the part of the electromagnetic spectrum that our eyes can see
Photosynthesis is a process performed by plants that is capable of capturing the energy in the part of the electromagnetic spectrum that we see as visible light
Why do cells need energy to survive?
Cells are subject to becoming disordered due to the second law of thermodynamics, they remain alive and healthy (ordered and active) only because they have a constant input of energy. Chemical reactions in a cell keep it on order!
Two types: endergonic reactions require a net input of energy, think of as energy running "uphill". Exergonic reactions releases energy, energy following "downhill". Cellular metabolism is the sum total of all the reactions in a cell, at any instant, metabolism of a cell consists of thousands of individual chemical reactions, every reaction is mediated by an enzyme (biological catalysts that speed up reactions in a cell, without enzymes reactions on their own would be far too slow to keep a cell alive).
Orient substrate. Induce strain in substrate. Temporarily add chemical groups to substrate.
Catalytic cycle of an enzyme
Enzyme, substrate, and active site
Enzymes can be damaged permanently by exposing them to extremes of temperature, pH or salt concentration. The enzyme's tertiary structure is destroyed so it will no longer function properly
How can the rate of an enzyme reaction be changed?
Temperature, pH, and salt concentration
Adenosine triphosphate. Main energy carrying molecule in a cell. Links endergonic and exergonic reactions
Metabolic pathways can be divided into two types: anabolic pathways
Link together simple molecules to form more complex molecules. The anabolic reactions Stores energy in the chemical bonds formed as molecules are built up. The reactions are primarily endergonic, non-spontaneous reactions and require free energy from the environment
Metabolic pathways can be divided into two types: catabolic pathways
Break down complex molecules to form simple ones. The catabolic reactions release energy that is stored in the bonds of the complex molecules. The reactions are primarily exergonic, spontaneous reactions and release free energy
Photosynthesis and respiration
Photosynthesis is a metabolic pathway that is primarily anabolic, CO2+H2O is used to form C6H12O6+O2. Respiration (glucose oxidation) is a metabolic pathway that is primarily catabolic, C6H12O6+O2 is used to produce CO2+H2O
How are anabolic and catabolic pathways linked?
The energy released by catabolic reactions is used to drive the anabolic reactions. Energy is transferred back and forth from the exergonic reactions to the endergonic ones through ATP
Enzyme activity can be regulated by inhibitors: irreversible inhibition and reversible inhibition
Types: competitive and non competitive
Energy is harvested through electrons that are moved from one molecule to the next. Electrons can carry energy, some of which will be transferred to intermediate molecules as the electrons travel a "downhill" journey. The basis for electron transfers down this energy hill is a series of reactions. Some substances more strongly attract electrons than do others. A substance that loses one or more electrons to another is said to be oxidized. A substance that gains electrons in this reaction is said to have undergone reduction. Oxidation and reduction reactions always occur in pairs in cells, known as a reduction-oxidation reaction or redox.
Electrons can be moved through molecules called intermediate electron carriers. NADP is found in photosynthesis. NAD is found in glucose oxidation
Situation in which the extracellular fluid has the same osmolarity as the fluid
Moves into a cell
Describe the general functions of cell membranes?
Selectively permeable means that the cell membrane allows some substances to pass through easily, while excluding other substances.
What does it mean when a plasma membrane is described as a "fluid mosaic"? Describe the model.
The Fluid Mosaic Model states that membranes are composed of a Phospholipid Bilayer with various protein molecules floating around within it. The 'Fluid' part represents how some parts of the membrane can move around freely, if they are not attached to other parts of the cell.
List and describe the functions of the classes of molecules that make up biological membranes
Phospholipids make up the basic structure of a cell membrane. A single phospholipid molecule has two different ends: a head and a tail. The head end contains a phosphate group and is hydrophilic. This means that it likes or is attracted to water molecules.
What is an integral protein? What is a peripheral protein?
Peripheral membrane proteins, or extrinsic proteins, do not interact with the hydrophobic core of the phospholipid bilayer. Instead they are usually bound to the membrane indirectly by interactions with integral membrane proteins or directly by interactions with lipid polar head groups.
Name the different classes of membrane proteins and describe their importance to the cell.
What is diffusion? How is it important to transport into or out of cells?
Diffusion is the passive(requiring no energy from the cell) transport of material from an area of high concentration to an area of low concentration. Diffusion allows water, carbon dioxide and other small uncharged particles into the cell.
Describe the two types of transport that move molecules into or out of cells.
Passive transport is the movement of molecules across the cell membrane and does not require energy. Active transport needs energy to move the molecules across the cell
What is meant when a membrane is described as "semi-permeable".
membrane that will allow certain molecules or ions to pass through it by diffusion
Compare and contrast simple diffusion and passive transport (facilitated diffusion).
Passive transport moves across a concentration gradient, or a gradual difference in solute concentration between two areas. Simple diffusion is the diffusion of small, uncharged, or hydrophobic molecules from an area of high concentration to an area of low concentration across the cell membrane
What is osmosis? Describe a situation where two solutions are isotonic, hypertonic and hypotonic.
a process by which molecules of a solvent tend to pass through a semipermeable membrane from a less concentrated solution into a more concentrated one, thus equalizing the concentrations on each side of the membrane.
What would happen to a red blood cell that was placed into a solution of 10% of NaCl? 0.1% NaCl? 0.8% NaCl? How would this differ (or be the same) with a plant cell?
Describe the sodium potassium pump? What type of transport system is it? Is a calcium transporter active or passive transport? Why?
Are endocytosis and exocytosis passive or active transport processes? Describe each of the processes and their function in cells.
The require active transport. Exocytosis exports molecules from cells. Endocytosis brings the molecules into the cell.
Organisms that live in fresh water are almost always hypertonic to their environment. In which way is this a serious problem? How do you think the organisms cope with this problem?
What is receptor mediated endocytosis? Describe an example.
During receptor-mediated endocytosis, ligands are found out in the extracellular fluid. They will find and bind to proteins located in clusters in the cell membrane. ... A lysosome will attach to the vesicle, and using acidic enzymes, it will breakdown the ligands for use as energy elsewhere in the cell.
Extensive irrigation in arid regions causes salts to accumulate in the soil. Based on what you have learned about water balance in plant cells, explain why increasing soil salinity has an adverse effect on agriculture.
extensive salinity in the soil makes it hypertonic to the walls of the plants. This causes water to move out of the cells and causes the plant cells to plasmolyze (shrivel up and die). Introduction of water can help change the high salts in the soil by dissolving them and not causing the plant cells to plasmolyze.
Describes chemical reactions that require energy input.
Energy associated with objects or particles in motion
Energy that has the potential to do work, stores energy
Gibbs free energy is the the usable energy or energy that is available to do work
All the chemical reactions that take place inside cells, including anabolism and catabolism
Describes chemical reactions that release free energy
Transfers energy from catabolism to anabolism, transfer from exergonic to endergonic
Molecule on which the enzyme acts
Specific region of the enzyme to which substrate binds
Energy necessary for reaction to occur
A substance produced by living organism that acts as a catalyst to bring about a specific bio chemical reaction
Inorganic ion, such as iron and magnesium ions, that are required for optimal regulation of enzyme activity.
a nonprotein compound that is necessary for the functioning of an enzyme
Describe the difference between anabolic and catabolic pathways and give an example of each. How are anabolic and catabolic reactions linked?
Anabolic require input of energy to synthesize molecules from simpler ones, for example synthesizing sugar from CO2. Catabolic involves breakdown of molecules into simpler ones, for example like breaking down food
Describe each of the laws of thermodynamics and give an example that illustrates each of them.
The first law is energy can not be created or destroyed only in a changed form. Second law is energy transformations results in increased disorder or entropy, there is some of the energy that can not do work
How does the ATP molecule carry energy.
ATP is used to power the majority of energy requiring cellular reactions
Describe how ATP couples exergonic and endergonic reactions.
ADP is combined with a phosphate to form ATP in the reaction ADP+Pi+free energy→ATP+H2O. The energy released from the hydrolysis of ATP into ADP is used to perform cellular work, usually by coupling the exergonic reaction of ATP hydrolysis with endergonic reactions
Describe the steps in the process of how an enzyme catalyzes a reaction.
1. substrate and enzyme bind
2. enzyme undergoes conformational change
3. substrates are converted to products
4. products are released
What is activation energy? How do enzymes lower activation energy?
Enzymes are large proteins that bind small molecules. When bound to an enzyme, the bonds in the reactants can be strained (that is stretched) thereby making it easier for them to achieve the transition state
How does substrate concentration affect reaction rate?
By increasing the enzyme concentration, the maximum reaction rate greatly increases. Conclusions: The rate of a chemical reaction increases as the substrate concentration increases. Enzymes can greatly speed up the rate of a reaction. However, enzymes become saturated when the substrate concentration is high.
Describe the generic groups that are used to classify enzymes.
Describe how molecular structure determines the function of an enzyme.
All enzymes display specificity to different substrates. This means that each, individual enzyme has its own unique substrate to react with
What factors can affect the rate of an enzyme catalyzed reaction? How does each work?
Several factors affect the rate at which enzymatic reactions proceed - temperature, pH, enzyme concentration, substrate concentration. Increasing temperature increases the Kinetic Energy that molecules possess. pH measures the Acidity and Basicity of a solution
What is meant by enzyme denaturation? What types of conditions will denature an enzyme?
When enzymes denature, they are no longer active and cannot function. A shift in pH level affects hydrogen bonds, a weak type of bond that connect parts of the enzyme to one another
What is a metabolic pathway? How are enzymes involved in metabolic pathways?
The process of glycolysis is used to create energy via the catabolic pathway. While enzymes in catabolic pathways break down molecules and release energy, enzymes in anabolic pathways, or biosynthetic reactions, need energy to change or convert molecules into more complex molecules or macromolecules
Compare and contrast the action of a competitive enzyme inhibitor and non-competitive inhibitor.
A competitive inhibitor will block the enzyme's active site. A non-competitive inhibitor will bind to the enzyme somewhere other than the active site of the enzyme
What is an allosteric enzyme? How do these enzymes function?
Allosteric enzymes are enzymes that change their conformational ensemble upon binding of an effector, which results in an apparent change in binding affinity at a different ligand binding site.
What are the effects of the extremes in pH, temperature or salt concentrations on an enzyme?
Temperature increases enzyme activity until it peaks, at which point further increases decrease activity by denaturing
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