chapter 5 Flashcards
membranes
- 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
plasma membrane
forms a boundary between living cells and their surroundings; controls traffic in and out of the cell (it is a double layer of molecules)
phospholipids
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)
Phospholipids in water
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
plasma membrane
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
selective permeability
membranes allow some substances to cross more easily than others
- passive transport
- active transport
passive transport
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
active transport
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)
types of passive transport
- diffusion
2, facilitated diffusion - osmosis
diffusion
- 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
with a gradient
going with the flow
against the gradient
not with the flow
facilitated diffusion
- 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)
osmosis
- 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)
potential energy
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
first law of thermodynamics: law of consevation of energy
- 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
chemical energy
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
ATP
- 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)
ATP cycle
- 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)
enzymes
=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
enzyme ability
- 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
substrate
what the enzyme acts on
