chapter 5

Question 1

membranes

Answer 1

• cells have to be highly organized since they have so many processes occurring in them at the same time (chaos would result and cell death)
• membranes organize many reactions (most organelles are bound by membranes)
• the outer layer of cells = plasma memrane

Question 2

plasma membrane

Answer 2

forms a boundary between living cells and their surroundings; controls traffic in and out of the cell (it is a double layer of molecules)

Question 3

phospholipids

Answer 3

membranes have a double layer of phospholipids (tail = hydrophobic; head = hydrophilic)

• two fatty acid chains; unsaturated chain (has a kink)
• the two ends act differently in water (hydrophilic head attracted to water and hydrophobic tail moves away from water)

Question 4

Phospholipids in water

Answer 4

they spontaneously form a stable two-layer sheet called a phospholipid bilayer

• hydrophilic heads face outward toward the water
• hydrophobic tails point inward, toward the tail of other phospholipids, sheilding themselves from the water

Question 5

plasma membrane

Answer 5

complex arrangement of phopholipids and other molecules (forms a barrier that regulates what can pass through the membrane because of hydrophobic/hydrophili interactions)
many proteins are attached to and extend through the membrane

Question 6

selective permeability

Answer 6

membranes allow some substances to cross more easily than others

• passive transport
• active transport

Question 7

passive transport

Answer 7

does not require energy to pass through (ex: small molecules can pass through (O2, C02), but not larger than molecules, and most molecules with a charge

Question 8

active transport

Answer 8

requires energy to move something (larger molecules and those with a charge need assistance to move across the membrane)

• usually require ATP (as energy); transport protein which only recognizes a particular solute
• usually moving the substance from lower to higher concentration (moving against the concentration gradient)

Question 9

types of passive transport

Answer 9

1. diffusion
   2, facilitated diffusion
2. osmosis

Question 10

diffusion

Answer 10

• the tendency for molecules to spread out into the available space; from higher to lower concentration (with or down the gradient, reaches equilibrium)
• does not require added energy
• ex: dye, sulfur from a match

Question 11

with a gradient

Answer 11

going with the flow

Question 12

against the gradient

Answer 12

not with the flow

Question 13

facilitated diffusion

Answer 13

• some molecules need assistance to diffuse across the membrane
• certain small molecules, too large to pass through the membrane, are assisted across the membrane through *transport proteins (does not require energy)
• still moving from higher to lower concentration (ex: sugars, amino acids, etc)

Question 14

osmosis

Answer 14

• the transport of water across a selectively permeable membrane (membrane will let water pass through, but not the solute)
• there is a higher concentration of “free” water molecules on the side with less solute (not associated with solute)
• water moves to the side with more solute (lower concentration of water)

Question 15

potential energy

Answer 15

stored energy
ex: sitting on top - PE
it takes almost no effort on your part to get to the bottom, gravity will “pull” you down

Question 16

first law of thermodynamics: law of consevation of energy

Answer 16

• energy can not be created or destroyed, but can be transferred or transformed
• ex: car’s engine burns the potential energy stored in hydrocarbons; the woman’s body burns the potential energy stored in the sugars in the soft drink

Question 17

chemical energy

Answer 17

the potential energy of molecules (energy is stored (PE) in the bonds within molecules, which can be used later for work (KE))
ex: plants store energy in the bonds of glucose

Question 18

ATP

Answer 18

• the primary energy carrier
• ATP = Adenosine triphosphate
• similar to the nucleic acid but adenine has two more phosphate groups added
• ATP carries the energy for almost all the work within cells
• in the bond between 2nd and 3rd phosphate groups
• when this bond is broken, energy is released (to do work) and ATP becomes ADP (adenosine diphosphate)

Question 19

ATP cycle

Answer 19

• bottom line = energy in the food we eat is used to generate ATP
• each ATP molecules contains about 1% of the chemical energy in a single glucose molecules
• analogy = if one molecule of glucose is a dollar ($1), then, each molecule of ATP is 1 penny ($.01)
• working muscle cells recycle all its ATP about one a minute (that amounts to about 10 million ATP molecules used and recycled each second, for each cell)

Question 20

enzymes

Answer 20

=are proteins

• proteins that serves as biological catalysts which increase the rate of reaction without itself being changed
• speed things up without causing change
• help chemical reactions happen quickly and precisely, at normal cell temperatures
• ex: heat will speed up the rate of reactions, but that would destroy our cells

Question 21

enzyme ability

Answer 21

• unique 3-d shape
• each enzyme only recognizes a particular substrate
• substrate fits precisely into the active site of the enzyme
• enzymes can break down substrates or bond them together
• **enzymes often end in “ase”
• ex: enzyme that breaks down lactose is lactase; sucrase breaks down sucrose

Question 22

substrate

Answer 22

what the enzyme acts on