Chapter5 Flashcards
briefly describe the reactions that occur within cells
thousands of chemical reactions happen in the microscopic space of cells, and different reactions have different purposes. Life requires energy and cells use energy to manufacture and move things.
what is energy
the capacity to perform work and move an object against an opposing force
name and describe the types of energy
kinetic energy is the energy of motion. potential energy is stored energy that an object possesses as a result o its location or structure
how does potential energy work in molecules
chemical energy is potential energy in molecules that is released to power the work of the cell. if we couldn’t convert energy from one form to another we couldn’t survive
what is the first law of thermodynamics?
the total amount of energy in this world is constant; energy can be transferred and transformed but not destroyed. This is also known as the law of energy conservation
what is the second law of thermodynamics
energy conversions reduce the order of the universe and increase its ntropy (disorder). basically means energy tends to go towards transformations that aren’t very useful
what are the two main types of chemical reactions
endergomic and exergonic reactions. endergomic- products are rich in PE. energy is absorbed from surroundings as the reaction occurs, so the products store (typically in covalnt bonds) more energy than the reactants did. exergonic- a chemical reaction that releases energy. it begins with reactants whose covalent bonds contain more enrgy than those in the products
what are examples of exergonic and endergomic reactions
endergonic: energy-poor reactants like CO2 and H2O, using energy from sunlight, produce energy-rich sugar molecules (ex C6H12)6) exergonic- when burning wood, PE o lucose in cellulose molecules is released as heat and light producing carbon dioxide and water. In cellular respiration, oxygen is used to convert chemical energy stored in fuel molecules like glucose to form chemical energy cell can use to perform work.
what is cellular metabolism and energy coupling?
cellular metabolism is the sum of all endergonic and exergonic reactions carried out by the cell. energy coupling is the use of energy released from exergonic reactions to drive essential endergonic reactions, is critical for cells, ATP is key for this
what is ATP
adenosine triphosphate. adenosine is adenine, a nitrogenous base and ribose. triphosphate is three negatively charged phosphate groups. these bonds are unstable and can be easily broken down by hydrolysis
how does the structue of ATP correlate to its energy-storage abilities
the triphosphate, because it has like charges crowded together contributes to the potential energy stored in ATP. Most cellular work depends on ATP energizing molecules by phosphorylating them.
what type of reaction is the hydrolysis of ATP, what kind of reaction is it coupled to, and how?
the hydrolysis of ATP is an exergonic reaction or one that releases energy (ATP —-> ADP + P) they hydrolysis of ATP is coupled to an endergonic reaction by a phosphate group from ATP being transferred to some other molecule. thiis called phosphorylation
what is the ceullular work driven by ATP?
there is chemical work, or the phosphorylation of reactant molecules drives the endergonic synthesis of protein molecules. then there is mechanical work. An example would be the transfer of phosphate group to special motot proteins in muscle cells causes the proteins to change and pull on actin filaments causing cells to contract
how does the dephosphorylation of ATP work?
energy is released in exergonic reactions, such as glucose breaking down during cellular respiration is used to regenerate ATP form ADP. When ADP is phosphorylated, ATP is formed. (an endergonic or energy-storing reaction)
what is activation energy?
most of cell’s molecules are rich in PE but will not spontantously break down into simpler molecules bc there is an energy barrier that must be overcome for reaction to begin. activation energy is the energy barrier, or the amount of energy that must be absorbed by reactants to become activated and start chemical reactions
what is an enzyme
a protein molecules that functions as a biological catalyst, increasing the rate of reaction without itself being changed into a different molecule
what is the shape and parts of an enzyme
enzymes have a unique 3D shape that determines which chemical reaction it can catalyze. it has a substrate, which is the specific reactant that an enzyme acts on. It aso has an active sire, which is a region of the enzyme, typically a pocket or groove, where it fits.
how is the enzyme specific?
an active site only fits one kind of substrate molecule, so the cell has many different kinds of enzymes to catalyze all its reactions
what happens as the enzyme is working and what happens after a reaction is catalyzed
the active site changes shape slightly when a substrate binds to an enzyme so that it embraces the substrate more snugly. this induced fit may strain substrate bonds or place chemical groups of the active site in position to catalyze the reaction. After catalysis, the enzyme releases the products and emerges unchanged from the reaction; the active site can now be used for another substrate.
what are some examples of ideal enzyme conditions
few enzymes can tolerate extremely salty ocnditions, few enzymes can tolerate pHs out of range 6-8, higher temperatures denature enzyme
what are enzyme helpers?
many enzymes will not functions without nonprotein helpers called cofacters ex ions of zinc, iron, or copper. a coenzyme is a cofacter, that’s an organic molecule, ex: vitamins
what are inhibitors
chemicals that attach to enzymes by covalent bonds and interfere with enzyme’s activity. they are sometimes irreversible (ex toxins and poisons) The main two types are competitive and noncompetitive.
describe a competitive inhibitor
a competitive inhibitor resembles the enzyme’s normal substrate for the enzym’s active site. it blocks substrates forom entering the active site which may be overcome by increasing the concentration of substrate molecules (making it more likely that the substrate mmolecule will be nearby when an active site becomes vacant
describe a noncompetive inhibtor
does not enter active site but binds to the enzyme somewhere else. its binding changes shape of enzyme os active site no longer fits substrate
are all inhibitors harmful
no, for example feedback inhibition is when a metabolicc reaction is blocked by its products. for instance, a cell could be producing more product than it needs to the product may inhibit one of the enzymes in the pathway
what are some examples of inhibitors
when an inhibitor stops an enzyme from catalyzing a crucial metabolic reaction, an organism may be poisoned. some beneficial drugs inhibt enzymes for survival of disease-causing bacteris. Aspirin inhibits enzymes involved in inducing pain. cancer drugs are inhibitors of enzymes that promote cell division
what do membranes do because of which wuality
membranes provide structural basis for metabolic order. allow partitioning of cell into functional compartments containing specific enzymes. the membrane has a selective permeability, meaning some substances pass through more easily than others do.
what is the structure of a fat molecule?
triglyceride
tri: 3 fatty acids
glyceride: 1 glycerol molecule
briefly describe phospholipid bilayer structure
2 layers of hydrophobic molecules can easily pass through membranes since they are soluble in lipids. polar molecules and ions are not soluble in lipids so they rely on proreins embedded in the phosopholipid bilayer to determine whether or not they can pass through.
what do membrane proteins do
- enzyme 2. receptors for chemical messengers from other cells. receptor proteins have specialized shapes that fit their messenger
what is signal transduction
the idea that typically the messenger to the receptor bond triggers a chain reaction involving other proteins so eventually a molecules that performs a specific activity inside the cell is “told” to carry out this activity
what is passive transport
membrane helps maintain homeostasis by controlling what substances enter/leave cells, passive transport- cell transports something across cell membrane but doesn’t use ATP for this to happen
what is the concentration gradient and what is down/against it?
it’s a difference in the concentratuon of a substance. down is from high to low. against is low to high.
what is equilibrium
condition ot which concentration of a substance is equal throughout space, moeves down concentration graient to reach equilibrium.
what happens at equilibrium?
molecules continue to move back and forth but there is no ne change in concentration on either side of the membrane
what is diffusion
diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration gradient to reach equilibrium
does diffusion require work
no. it results from the random motion (kinetic energy of atoms and molecules. so it is an example of passive transport.
what are some reasons things can’t diffuse across the membrane
size, polarity, charge
what is the hope for things that can’;t pass across the membrane
they can do it with the help of specific transport proteins in the membrane. facilitated diffusion is diffusion made possible by carrier/transport proteins. without the protein, the substance would cross too slowly to be useful or not at all
what are some examples of things that require facilitated diffusion
many sugars, amino acids, and ions, and even water
explain why/how facilitated diffusion works with water
since water is polar, it moves through hydrophobic interior of the cell membrane very slowly in unaided diffusion. aquaporins are transport proteins that allow diffusion into and out of cell
what is osmosis
diffusion water across a selectively permeable membrane
how does osmosis work
water molecules cross a membrane until solute concentrations are equal on both sides, water moves from high to low but because it is polar it will form weak bonds with solute molecules, the free water molecule, some more likely to move.
what is osmoregulation
in order to survive in a hypertonic or hypotonic environment, cells must prevent excessive uptake or loss of water
what are some examples of osmoregulation
organisms that live their entire life in environment that is not ideal. ex: fresh water fish live in hypotonic environment so they have gills and kidneys that prevent excessive water buildup
what is tonicity
the tendency of a cell in a give solution to gain or lose water
briefly describe an isotonic solution
the solute concentration of cell and environment are essentially equal so cell gains water at the same rate it loses it. it is ideal for animal cells. it makes plant cells flaccid, and they may wilt. equilibrium.
briefly describe hypertonic solution
animal cell shrivels and can die from water loss because environment has higher solute concentration, causing it to lose water. plant cells also shrivel and die in a process called plasmolysis where cell membrane peels away from cell wall. water leaves, solute comes in
briefly describe a hypotonic solution
animal cell may lyse because its environment has a lower solute concentration, causing it to gain water and solute to move out. plant cells like net flow of water so this is ideal environment, they become turgid.
what is turgidity
main pressure of cell contents against cell wall that allow plants to be firm, determined by ware content of central vacuole. cell walls expand some but keep plant cell from bursting
what is active transport
the movement of molecules across am embrace from low to high
describe how transport protein operates
solute on cytoplasmic side of plasma membrane attaches to specific binding site on transport protein. then, ATP phosphorylates the transport protein. the transport’ protein’s shape changes in such a way that the solute is released to the other side of the membrane. the phosphate group detaches and the transport protein returns to original shape cand can do its job again
what is endocytosis
process by which cells ingest external fluid, macromolecules and large particles including other cells. a portion of the cell membrane forms a pouch around particle that is then pinched off into the cell as vesicle or vacuole from plasma membrane
name and describe the three types of endocytosis
phagocytosis- movement of large particles or whole cells
pinocytosis- transport of solutes or fluids
receptor mediated endocytosis- cell membrane has indeted self to become a pit, which is lined with receptor protons that pick up specific molecules ,form vesicle, and then carry to cytoplasm
what is exocytosis
reverse of endocytosis. macromolecules are released from cell through a vesicle that transports substance to cell membrane and fuses with it to let substance out of cell
what are example reasons for exocytosis
proteins made on ribosomes are packaged by Golgi into vesicles, which move to membrane and deliver protein out side cell. cells in pancreas manufacture insulin and get it to blood stream thru exocytosis.
