Chapter5

Question 1

briefly describe the reactions that occur within cells

Answer 1

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.

Question 2

what is energy

Answer 2

the capacity to perform work and move an object against an opposing force

Question 3

name and describe the types of energy

Answer 3

kinetic energy is the energy of motion. potential energy is stored energy that an object possesses as a result o its location or structure

Question 4

how does potential energy work in molecules

Answer 4

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

Question 5

what is the first law of thermodynamics?

Answer 5

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

Question 6

what is the second law of thermodynamics

Answer 6

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

Question 7

what are the two main types of chemical reactions

Answer 7

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

Question 8

what are examples of exergonic and endergomic reactions

Answer 8

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.

Question 9

what is cellular metabolism and energy coupling?

Answer 9

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

Question 10

what is ATP

Answer 10

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

Question 11

how does the structue of ATP correlate to its energy-storage abilities

Answer 11

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.

Question 12

what type of reaction is the hydrolysis of ATP, what kind of reaction is it coupled to, and how?

Answer 12

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

Question 13

what is the ceullular work driven by ATP?

Answer 13

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

Question 14

how does the dephosphorylation of ATP work?

Answer 14

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)

Question 15

what is activation energy?

Answer 15

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

Question 16

what is an enzyme

Answer 16

a protein molecules that functions as a biological catalyst, increasing the rate of reaction without itself being changed into a different molecule

Question 17

what is the shape and parts of an enzyme

Answer 17

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.

Question 18

how is the enzyme specific?

Answer 18

an active site only fits one kind of substrate molecule, so the cell has many different kinds of enzymes to catalyze all its reactions

Question 19

what happens as the enzyme is working and what happens after a reaction is catalyzed

Answer 19

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.

Question 20

what are some examples of ideal enzyme conditions

Answer 20

few enzymes can tolerate extremely salty ocnditions, few enzymes can tolerate pHs out of range 6-8, higher temperatures denature enzyme

Question 21

what are enzyme helpers?

Answer 21

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

Question 22

what are inhibitors

Answer 22

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.

Question 23

describe a competitive inhibitor

Answer 23

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

Question 24

describe a noncompetive inhibtor

Answer 24

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

Question 25

are all inhibitors harmful

Answer 25

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

Question 26

what are some examples of inhibitors

Answer 26

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

Question 27

what do membranes do because of which wuality

Answer 27

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.

Question 28

what is the structure of a fat molecule?

Answer 28

triglyceride tri: 3 fatty acids glyceride: 1 glycerol molecule

Question 29

briefly describe phospholipid bilayer structure

Answer 29

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.

Question 30

what do membrane proteins do

Answer 30

1. enzyme 2. receptors for chemical messengers from other cells. receptor proteins have specialized shapes that fit their messenger

Question 31

what is signal transduction

Answer 31

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

Question 32

what is passive transport

Answer 32

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

Question 33

what is the concentration gradient and what is down/against it?

Answer 33

it's a difference in the concentratuon of a substance. down is from high to low. against is low to high.

Question 34

what is equilibrium

Answer 34

condition ot which concentration of a substance is equal throughout space, moeves down concentration graient to reach equilibrium.

Question 35

what happens at equilibrium?

Answer 35

molecules continue to move back and forth but there is no ne change in concentration on either side of the membrane

Question 36

what is diffusion

Answer 36

diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration gradient to reach equilibrium

Question 37

does diffusion require work

Answer 37

no. it results from the random motion (kinetic energy of atoms and molecules. so it is an example of passive transport.

Question 38

what are some reasons things can't diffuse across the membrane

Answer 38

size, polarity, charge

Question 39

what is the hope for things that can';t pass across the membrane

Answer 39

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

Question 40

what are some examples of things that require facilitated diffusion

Answer 40

many sugars, amino acids, and ions, and even water

Question 41

explain why/how facilitated diffusion works with water

Answer 41

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

Question 42

what is osmosis

Answer 42

diffusion water across a selectively permeable membrane

Question 43

how does osmosis work

Answer 43

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.

Question 44

what is osmoregulation

Answer 44

in order to survive in a hypertonic or hypotonic environment, cells must prevent excessive uptake or loss of water

Question 45

what are some examples of osmoregulation

Answer 45

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

Question 46

what is tonicity

Answer 46

the tendency of a cell in a give solution to gain or lose water

Question 47

briefly describe an isotonic solution

Answer 47

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.

Question 48

briefly describe hypertonic solution

Answer 48

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

Question 49

briefly describe a hypotonic solution

Answer 49

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.

Question 50

what is turgidity

Answer 50

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

Question 51

what is active transport

Answer 51

the movement of molecules across am embrace from low to high

Question 52

describe how transport protein operates

Answer 52

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

Question 53

what is endocytosis

Answer 53

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

Question 54

name and describe the three types of endocytosis

Answer 54

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

Question 55

what is exocytosis

Answer 55

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

Question 56

what are example reasons for exocytosis

Answer 56

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.