What is energy?
The capacity to cause change
kinetic energy
energy in motion
potential energy
stored energy
Conservation of Energy
- energy cannot be created or destroyed
2. energy can be converted from one form to another
entropy
measure of disorder or randomness in a system
heat
is a type of kinetic energy and product of all energy conversions
chemical energy
- arises from the arrangement of atoms and
* can be released by a chemical reaction.
cellular respiration
• the energy-releasing chemical breakdown of fuel
molecules (ie glucose)
• the storage of that energy in a form the cell can use to
perform work (ie ATP)
energy used by humans
- ~34% to do work
* ~66% as heat
calorie
– A calorie is the amount of energy that can raise
the temperature of one gram of water by 1 ⁰C.
• Food Calories are kilocalories, equal to 1,000 calories.
• The energy of calories in food is burned off by many
activities.
ATP
• acts like an energy shuttle
• stores energy obtained from food
• releases it later as needed
• consists of an organic molecule called adenosine plus a
tail of three phosphate groups and
• is broken down to ADP and a phosphate group, releasing
energy.
phosphate transfer
– ATP energizes other molecules by transferring phosphate groups. – This energy helps cells perform • mechanical work, • transport work, and • chemical work.
ATP cycle
– Cellular work spends ATP continuously.
– ATP is recycled from ADP and a phosphate group
through cellular respiration.
– A working muscle cell spends and recycles up to
10 million ATP molecules per second.
metabolism
total of all chemical reactions in an organism
activation energy
– Activation energy activates the reactants and
• triggers a chemical reaction.
– Enzymes reduce the amount of activation energy
required to break bonds of reactant molecules.
– Enzymes can function over and over again.
– Many enzymes are named for their substrates, but
with an –ase ending
induced fit
– An enzyme is very selective in the reaction it
catalyzes.
– Each enzyme recognizes a substrate, a specific
reactant molecule.
• The active site fits to the substrate, and the enzyme
changes shape slightly.
• This interaction is called induced because the entry of
the substrate induces the enzyme to change shape
slightly
feedback regulation
– Some products of a reaction may inhibit the
enzyme required for its production.
• This is called feedback regulation.
• It prevents the cell from wasting resources.
enzyme inhibitors
• Penicillin blocks the active site of an enzyme that bacteria
use in making cell walls.
• Ibuprofen inhibits an enzyme involved in pain signaling.
• Many cancer drugs inhibit enzymes that promote cell
division.
transport proteins
- are located in membranes and
* help move substances across a cell membrane
passive transports
- Diffusion
- Osmosis
- Facilitated diffusion
active transports
• ATPases (ie pumps)
concentration gradient
a region in which the substance’s density
changes.
diffusion
is the movement of molecules so that they spread
out evenly into the available space
osmosis
diffusion of water across a selectively permeable
membrane
