study guide for test 1 CORRECTED
study guide for test 1 CORRECTED BSC1010
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This 14 page Study Guide was uploaded by Amanda Howard on Monday May 30, 2016. The Study Guide belongs to BSC1010 at University of North Florida taught by Dr. Michael R. Lentz in Summer 2016. Since its upload, it has received 23 views. For similar materials see General Biology I in Biology at University of North Florida.
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Date Created: 05/30/16
T est 1 review Chapter 1: Biology and the Tree of Life Main ideas: Organisms obtain and use energy, are made up of cells, process information, replicate, and evolve as a population o There is no single definition of life however there are five characteristics that all organisms share Energy: in order to stay alive, reproduce, maintain homeostasis, etc. organisms must use energy. In the case of animals energy is obtained through food and in the case of plants its obtained through sunlight Cells: organisms are made up of membrane bound cells Information: Organisms must have hereditary or genetic information which is stored in units called genes. The instructions for basic construction and information on basic biological processes are stored here Replication: organisms must have some way to reproduce Evolution: organisms are the product of evolution and the populations must continue to evolve The cell theory proposes that all organisms are made of cells and that all cells come from preexisting cells o The cell theory identified the fundamental structural unit common to all life o Hooke discovered cells which made up organisms and objects o Leeuwenhoek disprove spontaneous generation The theory of evolution by natural selection maintains that species change through time because individuals with certain heritable traits produce more offspring than other individuals do o All organisms are related by a common ancestry o Organisms evolve through natural selection Evolution occurs when heritable variation leads to differential success in reproduction Natural selection is a well-tested explanation for why species change through time and why they are so well adapted to their environment o If certain heritable traits lead to increased success in producing offspring then those traits will become more common in the population over time. In this way the populations characteristics change as a result of natural selection o Together the cell theory and theory of evolution provide two central unifying ideas: The cell is the fundamental unit of all organisms All species are related by common ancestry and have changed over time in response to natural selection A phylogenic tree is a graphical representation of the evolutionary relationships between species. These relationships can be estimated by analyzing similarities and differences in traits. Species that share distinctive traits are closely related and are placed close to each other on the tree of life o The cell theory and the theory of evolution predict that all organisms are part of a genealogy of species, and that all species trace back to a common ancestor o To reconstruct the phylogeny, biologists have analyzed the sequence of components in rRNA and other molecules found in cells In closely related organisms the RNA sequence is similar in comparison to less closely related organisms Species that are part of the same evolutionary lineages share certain changes in RNA that no other lineages share o A tree of life, based on similarities and differences in these molecules has three major lineages: Bacteria, Archaea, and Eukarya Just as a family tree shows relationships between individuals, a phylogenic tree shows relationships between species On a phylogenic tree branches that share a recent common ancestor represent closely related species o An organism’s genus and species make up its scientific name. scientific names are always italicized with the genus capitalized Biologists ask questions, generate hypotheses to answer them, and design experiments that test the predictions made by competing hypotheses o Biology is a hypothesis-driven, experimental science Good scientific hypotheses make testable predictions that can be supported or rejected by collecting and analyzing data A null hypothesis specifies what we should observe when the hypothesis being tested isn’t correct o Experiments are a powerful scientific tool because they allow researchers to test the effect of a single well defined factor on a particular phenomena Crucial to have a control group Experimental conditions must be kept as constant or equivalent as possible Repetition of the test is essential o Biologists practice evidence based decision making. They ask questions about how organisms work, pose a hypothesis, and use experimental or observational data to test these hypotheses Key terms: Organism- a life form Theory- an explanation for a very general class of phenomena or observations o Most scientific theories have two components: the first describes a pattern in the natural world, the second identifies a mechanism or process that is responsible for creating that pattern Cell- a highly organized compartment that is bounded by a thin flexible structure called a membrane and that contains concentrated chemicals in an aqueous solution. Chemical processes essential to life take place in the cell Cell theory- all organisms are made of cells and all cells come from preexisting cells Hypothesis- a proposed explanation Evolution- a change in the characteristics of a population over time Natural selection- the process by which evolution occurs o Two conditions necessary for natural selection: individuals in a population vary in heritable traits and certain versions of those heritable traits are better suited to the environment than others Heritable- traits that can be passed on to offspring Population- a group of individuals of the same species living in the same area at the same time Artificial selection- changes in a population that occur when humans select certain individuals to produce the most offspring Fitness- the ability of an individual to produce offspring. Individuals with high fitness produce many surviving offspring Adaptation- a trait that increases the fitness of an individual in a particular environment Speciation- the divergence process causing the formation of new species Tree of life- a family tree of organisms Single common ancestor- the original life form back to which all organisms can trace their ancestors Phylogeny- the actual genealogical relationships of all organisms Ribonucleotides- rRNA is what biologists sequence in order to find common ancestry Prokaryotes- the vast majority of nucleus lacking organisms such as bacteria and archaea Taxonomy- the effort by scientists to name and classify organisms Taxon- a group Domain- a new taxonomic category proposed by Woese that includes Bacteria, Archaea, and Eukaryotes Prokaryote- no nucleus- bacteria and archaea Eukaryote- has a nucleus Phylum- major lineages in each domain Genus- the first part of the scientific name of an organism and indicates a group of closely related species Scientific name- an organisms genus and species designation, also referred to as its Latin name Null hypothesis- an outcome which supports the fact that the hypothesis being tested is incorrect Control group- a normal manipulated group Food competition theory- argues that long necks evolved because those with long necks can reach food unavailable to other mammals The sexual competition theory- an alternative hypothesis is that giraffes evolved long necks because longer-necked males win more fights than shorter-necked males Chapter 2: Water and Carbon: The Chemical Basis of Life Main Concepts: Molecules form when atoms bond to each other. Chemicals bonds are based on electron sharing. The degree of electron sharing varies from nonpolar covalent bonds to ionic bonds o When atoms participate in chemical bonds to form molecules, the shared electrons give the atoms full valence shells and thus contribute to the atoms’ stability Electrons are found in orbitals (which can each hold two electrons) grouped into electron shells The goal of bonds is to fill electron shells o The electrons in chemical bonds may be shared equally or unequally depending on the relative electronegativity of the two atoms involved o Nonpolar covalent bonds result from equal sharing; polar covalent bonds result from unequal sharing. Ionic bonds form when an electron is transferred completely from one atom to another Water is essential for life. Water is highly polar and readily forms hydrogen bonds. Hydrogen bonding makes water an extremely effective solvent Energy is the capacity to do work or supply heat and can be (1) a stored potential or (2) an active motion. Chemical energy is a form of potential energy, stored in chemical bonds o The chemical reactions required for life take place in water o Water is polar-meaning it has a partial positive and negative charges- because it is bent and has two polar covalent bonds o Polar molecules and charged substances, including ions, interact with water and stay in solutions via hydrogen bonding and electrostatic attraction Chemical reactions tend to be spontaneous if they lower potential energy and increase entropy (disorder). An input of energy is required for nonspontaneous reactions to occur o Energy comes in different forms. Although energy cannot be created or destroyed, one form of energy can be transformed into another o Experiments suggest that early in earth’s history the energy in sunlight and hot water drove chemical reactions between simple molecules, resulting in the formation of more complex compounds with higher potential energy. In this way energy in the form of sunlight was transformed into chemical energy Most of the important compounds in organisms contain carbon. Key carbon- containing molecules formed early in earth’s history o Organic molecules are critical to life because they have complex shapes provided by a framework of carbon atoms, along with complex chemical behavior due to the presence of functional groups Key Terms: Proton- positively charged particle with a mass of 1 Neutron- neutral particle with a mass of 1 Electron- negatively charged particles with no substantial mass Nucleus- contains the protons and neutrons in the center of the atom Element-an atom with a specific number of protons Atomic number- the number of protons in an atom of a specific element Mass number- the sum of the protons and neutrons Isotopes- an atom with a different number of neutrons than a standard atom of that element Orbitals- nuclei specific regions in with electrons move Electron shell- groups of orbitals Valence electrons- the electrons found in the outer shell Valence- the number of unpaired electrons Electron cloud- contains all the electron shells and takes up most of the space in an atom Chemical bonds- strong attraction that bonds atoms together in an attempt to pair valence electrons Covalent bond-sharing electrons Molecules- atoms linked by covalent bonds Electronegativity- how tightly atoms hold onto electrons Nonpolar covalent bond- the electrons are shared evenly Polar covalent bonds- unequal sharing of electrons Ionic bond- one atom gives or receives electrons to another Ion- an atom or molecule that carries a charge Cation- positively charged ion Anion- negatively charged ion Electron sharing continuum- refers to the degree which electrons are shared in a chemical bond with the greatest sharing found in nonpolar covalent bonds, the least sharing found in ionic bonds, and the middle ground being polar covalent Molecular formulas- indicate the number and types of atoms in a molecule Structural formula- indicate which atoms in a molecule are bonded together Ball and stick model- provide information on the 3d structure of molecules and the size of relative atoms Space filling molecules-more accurately depict special relationships between atoms Chemical reaction- when one substance is combined with others or broken down into another substance. Atoms are rearranged in molecules; in most cases, chemical bonds are broken and new bonds form 23 Mole- refers to the number 6.022x10 Molecular weight- the sum of the mass numbers of all atoms in a molecule Solution- a homogenous (uniform) mixture of one or more substances in a liquid Molarity- the number of moles of the substance present per liter of solution Coupled reaction- a common part of chemical reactions when chemical bonds are broken and new bonds form Solvent- an agent for breaking down a substance into a solution, water is a great solvent Hydrogen bond- the weak electrical attraction between the partial positive charge on the hydrogen that attracts the partial negative charge on oxygen Hydrophilic- substances that interact with water Hydrophobic- substances that don’t interact well with water Cohesion- binding between like molecules Adhesion- binding between unlike molecules Meniscus- the result of adhesion and cohesion in water when water molecules adhere to the glass pulling upwards at the perimeter while cohesion causes water molecules at the surface form hydrogen bonds with nearby water molecules and resist the upward pull of adhesion Surface tension- a property of water which gives the surface an elastic quality Specific heat- the amount of energy required to raise the temperature of 1gram of a substance by 1 degree Celsius Heat of vaporization- the energy required to change 1 gram of a substance from a liquid to a gas Hydrogen ion- H+ (formed when water dissociates) Hydroxide ion- OH- (formed when water dissociates) Acid- substances that give up protons during chemical reactions and raise the hydrogen ion concentration of water Base- substances that acquire protons and lower the hydrogen ion concentration of water pH- a scale which measures the acidity and basicness of a solution Buffers- compounds that minimize the pH changes Acid base reaction- a proton donor transfers a proton to a proton acceptor Homeostasis- constant conditions that need to be maintained in cells in order for survival Reactant- the initial atoms that go into a chemical reaction Products- the results of the reaction Chemical equilibrium- a dynamic but stable state when the forward and reverse reactions proceed at the same rate Endothermic- heat is absorbed in a reaction Exothermic- heat is released in a reaction Energy- the capacity to do work or to supply heat. The capacity exists in one of two ways: as stored potential energy or as an active motion Potential energy- stored energy normally found in chemical bonds Kinetic energy- the energy of motion Thermal energy- the kinetic energy of molecular motion Temperature- a measure of how much thermal energy its molecules possess. A low temperature means the molecules are moving slowly Heat- thermal energy transferred between objects Photons- high energy packs of light energy emitted by the sun Free radicles- particles which are highly unstable and contain unpaired electrons and are highly reactive The first law of thermodynamics- energy cannot be created or destroyed, but only transferred and transformed Entropy- the amount of disorder in a group of molecules The second law of thermodynamics- entropy always increases in an isolated system Chemical energy- the form of potential energy stored in chemical bonds Organic- molecules that contain carbon Functional groups- the critically important and unique H-, N-, and O- containing groups that affect the function of the protein, amino acid, etc in which it is contained o Amino and carboxyl groups- attract or drop a proton respectively, aminos act as bases, carboxyls act as acids o Carbonyl group- sites that link molecules into more complex compounds o Hydroxyl group- act as weak acids and are highly polar o Phosphate groups- have two negative charges, molecules with more than one phosphate linked together to store large amounts of energy o Sulfhydryl groups- link together via disulfide bonds, when present in proteins can form disulfide bonds that contribute to protein structure Prebiotic soup model- a model of chemical evolution in which certain molecules were synthesized from gases in the atmosphere or arrived via meteorites then condensed with rain and accumulated in oceans which would result in an “organic soup” that allowed for continued construction of larger, even more complex molecules Surface metabolism model- another model of chemical evolution which suggests that dissolved gases came in contact with minerals lining the walls of deep-sea vents and formed more complex, organic molecules Chapter 3: Protein Structure and Function Main Concepts: Most cell functions depend on proteins o In organisms, proteins function in catalysis, defense, movement, signaling, structural support, and transport of materials o Proteins can have diverse functions in cells because they have such diverse structures and chemical properties Amino acids are the building blocks of proteins. Amino acids vary in structure and function because their side chains vary in composition o Amino acids have a central carbon bonded to an amino group, a hydrogen atom, a carboxyl group, and an R-group o The structure of the R-group affects the chemical reactivity and the solubility of the amino acid o In proteins, amino acids are joined by a peptide bond between the carboxyl group of one amino acid and the amino group of a second amino acid Proteins vary widely in structure. The structure of a protein can by analyzed at four levels that form a hierarchy- the amino acid sequence, substructures called alpha-helices or beta-pleated sheets, interactions between amino acids that dictate a protein’s overall shape, and combinations of individual proteins that make larger multiunit molecules o A protein’s primary structure, or sequence of amino acids, is responsible for most of its chemical properties o Interactions that take place between carbonyl and amino groups in the peptide-bonded backbone create secondary structures, which are stabilized primarily by hydrogen bonding o Interactions between R-groups found in the same polypeptide and between R-groups and the peptide bonded backbone allow the protein to fold into a characteristic overall shape- its tertiary structure o In many cases, a complete protein consists of several different polypeptides, bonded together. The combination of polypeptides represents the protein’s quaternary structure In cells, most proteins are enzymes that function as catalysts. Chemicals reactions occur much faster when they are catalyzed by enzymes. During enzyme catalysis, the reactants bind to an enzyme’s active site in a way that allows the reaction to proceed efficiently o Enzymes are protein catalysts that lower activation energy by stabilizing the transition state of the reaction. This speeds reaction rates. The enzyme itself is unchanged by the reaction o Catalysis takes place at the enzyme’s active site, which has unique chemical properties and a distinctive size and shape. As a result, most enzymes catalyze a specific reaction o As a group, enzymes are able to catalyze many types of reactions because the chemical and physical structures of their active sites are so diverse. This diversity is due to the variety of amino acids and the four levels of protein structure o Many enzymes function only with the help of cofactors o Virtually all enzyme activity in cells is regulated. In most cases, regulation occurs when molecules bind at the active site or at locations on the protein that induce a change in the size or shape of the active site o The rate at which enzymes work depends on substrate concentration, their affinity for the substrate, temperature, and pH Key Terms: Amino acids- the building blocks of proteins, only about 20 Monomer- a molecular subunit Polymerization- the process of linking monomers Macromolecules- a very large molecule that is made up of smaller molecules Protein-a macromolecule, a polymer, that consists of linked amino acids Condensation reactions-condensation reactions- the way in which monomers are polymerized by a loss of a water molecule Hydrolysis- the reverse of dehydration reaction Peptide bond- the C-N bond that results from the condensation reaction Polypeptide- the resulting macromolecule when amino acids are linked in a chain by peptide bonds o R-group orientation: Side chains can interact with each other or water o Directionality: Free amino group, on the left, is called the N-terminus while the free carboxyl group, on the right, is called the o C-terminus o Flexibility: Single bonds on either side of the peptide bond can rotate, these bonds make the entire structure flexible Oligopeptides- peptides- polypeptides containing fewer than 50 amino acids Proteins- polypeptides containing more than 50 amino acids Catalyze- speed up chemical reactions Enzyme- a protein that functions as a catalysis Side chain- the unique part of the amino acids that differentiate amino acids from each other, differ in their size, shape, reactivity, and interactions with water o Does the side chain have a negative charge? If so, it has lost a proton, so it must be acidic o Does the side chain have a positive charge? If so, it has taken on a proton, so it must be basic o If side chain is uncharged, does it have an oxygen atom? If so, the highly electronegative oxygen will result in a polar covalent bond and thus is uncharged polar o If the answers to all three questions are no Then you are looking at a nonpolar amino acid o Nonpolar R-groups: hydrophobic Do not form hydrogen bonds Coalesce in water Lack charged or highly electronegative atoms capable of forming hydrogen bonds with water o Polar R-groups: hydrophilic Form hydrogen bonds Readily dissolve in water Primary structure- the basic sequence of amino acids in a protein Secondary structure- distinctively shaped sections of the proteins that are stabilized largely by hydrogen bonding that occurs between the carbonyl oxygen of one amino acid residue and the hydrogen on the amino acid of another o Alpha helix- one possible secondary protein structure in the form of a coil o Beta pleated structure- another possible secondary protein structure in which a peptide chain bends 180 degrees and then folds in the same plane Tertiary structure-the three dimensional shape of a polypeptide/ protein Quaternary structure- a structure present in many proteins in which several distinct polypeptides that interact to form a single structure Van der Walls interaction- weak electrical interactions between hydrophobic side chains Covalent disulfide bonds- bonds between sulfur containing Rgroups Multienzyme complex- a group of enzymes, each of which catalyzes one reaction, that are physically joined to each other Denatures- an unfolded protein Molecular chaperones- proteins which help proteins fold correctly in cells Prions- improperly folded proteins Chapter 4: Nucleic Acids and the RNA World Main Concepts: Nucleotides consist of a sugar, a phosphate group, and a nitrogen-containing base. Ribonucleotides polymerize to form RNA. Deoxyribonucleotides polymerize to form DNA o Ribonucleotides have a hydroxyl (-OH) group on their 2’ carbon. Deoxiribonucleotides do not o Nucleic acids form when nucleotides polymerized. Polymerization occurs via phosphodiester linkages between the 3’ carbon on one nucleotide and the phosphate group on another o Nucleic acids have a sugar-phosphate backbone with nitrogenous bases attached o Nucleic acids are directional- they have a 5’ end and a 3’ end o During polymerization new nucleotides are added to the 3’ end DNA’s primary structure consists of a sequence of nitrogen containing bases. Its secondary structure consists of two DNA strands, running in opposite directions, which are held together by complimentary base pairing and twisted into a double helix. DNA’s structure allows organisms to store and replicate the information needed to grow and reproduce o DNA is an extremely stable molecule that serves as a superb archive for information in the form of base sequences o DNA is stable because deoxyribonucleotides lack a reactive 2’ hydroxyl group and because antiparallel DNA strands form a secondary structure called a double helix. The DNA double helix is stabilized by hydrogen bonds that form between complementary purine and pyrimidine bases and by hydrophobic interactions between bases stacked on the inside of the spiral o DNA’s structural stability and regularity make it ineffective at catalysis o DNA is readily copied via complimentary base pairing. Complimentary base pairing occurs between A-T and G-C pairs in DNA RNA’s primary structure consists of a sequence of nitrogen containing bases. Its secondary structure includes short regions of double helices and structures called hairpins o RNA molecules can have secondary structure because complimentary base pairing occurs between A-U and G-C on the same strand. Some tertiary and Quaternary structure also occurs, because hydrogen bonding allows RNA molecules to fold in precise ways, and thus interact with each other Because RNA molecules can carry information as well as catalyze chemical reactions, it is likely that RNA was the first self-replicating molecule and a forerunner to the first life forms Key Terms: Nucleic acids- polymers similar to proteins, however instead of being made of amino acids they are made of nucleotides Nucleotides- monomer that made up nucleic acids Ribonucleotides- a form of nucleotides which contains the sugar ribose Deoxyribonucleotides- a form of nucleotide which contains the sugar deoxyribose Purines and pyrimidines- the 4 ribonucleotides contained in cells today, each of which contains a nitrogenous base Phosphodiester linkages- the result of condensation reactions between the phosphate group of one nucleotide and the hydroxyl group of the sugar of another, also called a phosphodiester bond Ribonucleic acid- RNA Deoxynucleic acid- DNA Phosphorylated- the addition of one or more phosphate groups raises the potential energy of substrate molecules enough to make an otherwise endergonic reaction possible Gel electrophoresis and autoradiography- techniques used to analyze DNA Antiparallel-in DNA one strand is oriented 5’ 3’ and the other is oriented 3’ 5’ Complimentary base pairing- each nucleic acid has a match to which it pairs in the double helix Template strand- in DNA replication when the strands separate free nucleotides match up on the original strand, also called the template strand DNA replicase- is a ribozyme that can catalyze the addition of the ribonucleotides to a complementary RNA strand and can replicate DNA Complementary strand-the new strand formed when free nucleotides match the base pairs on the template strand Hairpin- the secondary structure of RNA also called a stem and loop configuration Ribozymes- the catalytic, enzyme-like RNA RNA replicase- is a ribozyme that can catalyze the addition of the ribonucleotides to a complementary RNA strand and can replicate RNA Chapter 6: Lipids, Membranes, and the First Cells Main Concepts: Phospholipids are amphipathic molecules- they have a hydrophilic region and a hydrophobic region. In solutions, phospholipids spontaneously form bilayers that are selective and permeable- meaning that only certain substances cross them readily o The plasma membrane forms a physical barrier between the internal and external environment, often between life and nonlife o The basic structure of plasma membranes is created by a phospholipid bilayer o Phospholipids have a polar head and a nonpolar tail. The nonpolar tail consists of a lipid, usually a fatty acid or isoprene. Lipids do not dissolve in water o Small nonpolar molecules tend to move across membranes readily; ions and other charged compounds cross rarely if at all o The permeability and fluidity of lipid bilayers depend on temperature and on the types of phospholipids present. Phospholipids that contain long saturated fatty acids form a dense and highly hydrophobic membrane interior that lowers permeability, relative to phospholipids containing shorter, unsaturated fatty acids Ions and molecules diffuse spontaneously from regions of high concentration to regions of low concentration. Water moves across lipid bilayers from regions of high water concentration to regions of low water concentration via osmosis- a special kind of diffusion o Diffusion is movement of ions or molecules owing to their kinetic energy o Solutes move via diffusion from a region of high concentration to a region of lower concentration. This is a spontaneous process driven by an increase in entropy o Water moves across membranes spontaneously if a molecule or an ion that cannot cross the membrane is found in different concentrations on the two sides. In osmosis, water moves from the region of higher concentration of water to a lower concentration of water. o Osmosis is a passive process driven by an increase in entropy In cells, membrane proteins are responsible for the passage of ions, polar molecules, and large molecules that can’t cross the membrane on their own because they are not soluble in lipids. Some membrane proteins form channels, some facilitate diffusion by binding to substrates, and some use energy from ATP to actively pump ions or molecules o The permeability of lipid bilayer can be altered significantly by membrane transport proteins o Channel proteins provide holes in the membrane and facilitate the diffusion of specific ions into or out of the cell o Transport proteins are enzyme like proteins that facilitate the diffusion of specific molecules into or out of the cell o Energy demanding pumps actively move ions or molecules against their electrochemical gradient o In combination the selective permeability of phospholipid bilayers and the specificity of transport proteins make it possible to create an environment inside a cell that is radically different from the exterior Key terms: Plasma membrane- cell membrane- a layer of molecules that surrounds the cells interior and separates it from the external environment Hydrocarbons-molecules that only contain hydrogen and carbon Fatty acid- a hydrocarbon chain bonded to a carboxyl functional group Fats- three fatty acids linked to a three carbon atom called glycerol Glycerol- three carbon atom Ester linkage- the bond which join the fatty acids to the glycerol Steroids- a family of lipids distinguished by the bulky four ring structure Phospholipids- consists of a glycerol that is linked to a phosphate group and to either two chains of isoprene or two fatty acids Amphipathic- compounds that contain both hydrophilic and hydrophobic elements Lipid bilayers- when two layers of phospholipids molecules align with the hydrophilic head on the outside and the hydrophobic tail on the inside Permeability- the tendency to allow a given substance to pass across it Selective permeability- some substances cross easily and others don’t Saturated- has the maximum number of hydrogen bonds possible Unsaturated- has one or more double bonds Waxes-partially liquid and partially solid at room temperature fats Oils- liquid triacylglycerols Solutes- the dissolved molecules and ions which have thermal energy and are in constant random motion Diffusion- movement of molecules and ions that results from their kinetic energy Concentration gradient- a difference in solute concentration Osmosis- diffusion of water Hypertonic- when there is a higher concentration of water in the cell then outside which will cause the cell to shrivel Hypotonic- there is a lower concentration of water inside the cell then outside causing water to flow in and causing the cell to burst Isotonic- when the concentration of water inside the cell is equal to the concentration of water outside the cell Fluid mosaic model- the suggestion that membranes are a mosaic of phospholipids and different types of proteins, and that the overall structure was proposed to be dynamic and fluid Scanning electron microscope- used in freeze fracture electron microscopy Integral membrane proteins- proteins that span the membrane and have segments facing both the interior and exterior surfaces Peripheral membrane proteins- only found on one side of the membrane Detergent- a small amphipathic molecule that helps to make fats and lipids water soluble Transport proteins- membrane proteins that affect permeability Ion channels- specialized proteins that help move ions in and out of cells Electrochemical gradient- ions move in response to a combined concentration and electrical gradient Channel proteins- selective proteins which assist in the admission of certain ions and/ or molecules Aquaporins- channels that allow water to cross the membrane Passive transport- energy is not required Facilitated diffusion- the passive transport of substances that otherwise would not cross the membrane using proteins and channels Carrier proteins- transporters- proteins that bind to the ions in order to help them cross the membrane Active transport-transport across the electrochemical gradient Pumps- membrane proteins that help facilitate movement in active transport Sodium potassium pump- a pump that uses ATP to move Na+ and K+ across the membrane Secondary active transport- cotransport- a gradient set up by the pump provides the potential energy required to power the movement of a different molecule against its particular gradient
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