2. Living things transform energy
Energy makes things happen
• Energy-the capacity to do work, to make things happen
• Forms of energy
– Radiant-solar energy
– Chemical-food
– Mechanical-motion
– Electrical
– Nuclear
• Heat
– Motion of atoms, ions, or molecules (mechanical)
– Low quality energy because it is too dispersed to do useful work
3. • Potential energy-stored energy
• Kinetic energy-energy in action
• Ex. Person climbing ladder to diving board and
diving into water.
– Chemical-food
– Kinetic-climbing ladder
– Potential-higher altitude
– Kinetic-diving to the water
• Measuring energy
– Calorie-amount of heat required to raise the
temperature of 1g of water by 1
o
C
– Kilocalorie
• 1,000 calories
• Calories listed on nutrition labels
4. Two laws apply to energy and its
use
• The first law of thermodynamics
– The law of conservation of energy-states that energy
cannot be created or destroyed, but it can be changed
from one form to another
• The second law of thermodynamics
– States that energy cannot be changed from one form
to another without a loss of usable energy
• Energy flows through living things, it does not
cycle
• The second law of thermodynamics tells us that
as energy conversion occurs, disorder (entropy)
increases because it is difficult to use heat to
perform more work
5. Cellular work is powered by ATP
(adenosine triphosphate)
• ATP is a nucleotide-a monomer for DNA and
RNA
• Phosphate groups are unstable
• ATP can break down into ADP+P
• ADP can break down into AMP+P
• ATP beakdown and regeneration is the ATP
cycle
• Exergonic reaction-releasing energy, performing
work
• Endergonic reaction-energy is required,
constructing a building
6. ATP breakdown is coupled to
energy-requiring reactions
• Coupled reactions occur in the same
place, at the same time, and is such a way
that an energy-releasing (exergonic)
reaction drives an energy-requiring
(endergonic) reaction
• Energy releasing reaction-hydrolysis of
ATP
7. Enzymes speed chemical reactions
Enzymes speed reactions by lowering activation
barriers
• Enzyme-typically a protein molecule that
functions as an organic catalyst to speed a
chemical reaction without itself being affected by
the reaction
• A certain amount of energy (energy of activation)
has to be put into a reaction and then the
reaction will occur. An enzyme will lower the
amount of energy required to start the reaction.
• Each enzyme has a specific reaction it speeds
8. • Substrate-reactants in an enzymatic reaction
• Active site-part of the enzyme where substrate
forms an enzyme-substrate complex
• Induced fit model-enzyme slightly changes
shape to achieve optimum fit with the substrate
• Products are released after reaction is complete
• Active site is then ready to bind with another
substrate molecule
9. Enzyme speed is affected by local
conditions
• Substrate concentration-enzyme activity
increases as substrate concentration
increases
• Temperature-enzyme activity increases as
temperature increases. If temperature is
too high, the enzyme denatures and can
no longer bind with substrate.
• pH-enzymes have optimal pH for
reactions. Extreme pH can denature the
enzyme
10. • Cofactors
– Inorganic ions or nonprotein organic
molecules required by enzyme in order to be
active
– Inorganic ions-copper, zinc, iron
– Nonprotein organic molecules-coenzymes-
assist the enzyme and may accept or
contribute atoms to the reaction
• Vitamins are required for synthesis of coenzymes.
If vitamin is not available, enxymatic activity
decreases.
– Inhibitor-reduces amount of product produced
by an enzyme per unit time
11. Enzymes can be inhibited
noncompetitively and competitively
• Metabolic pathway-series of
linked reactions
• Noncompetitive inhibition-
inhibitor binds to the enzyme
at a location other than the
active site
• Competitive inhibition-inhibitor
and substrate compete for the
active site of an enzyme
• Inhibition is benefitial because
once sufficient end product of
a metabolic pathway is
present, it is best to inhibit
further production to conserve
raw materials and energy.
12. The plasma membrane has many
and various functions
The plasma membrane is a phospholipid bilayer
with embedded proteins
• Plasma membrane in both bacteria and
eukaryotes are phospholipid bilayer
• Proteins are found within and along the
membrane
• Cholesterol-supports the membrane
• Phospholipids and proteins can have
cabohydrates attached. These are glycolipids
and glycoproteins.
13.
14. Proteins in the plasma membrane
have numerous functions
•Channel proteins-allow molecule to move
across the membrane
•Carrier proteins-combine with substance and
help it move across the protein
•Cell recognition proteins-glycoproteins (have
carbohydrates attached)-foreign cells have their
own glycoproteins that enable the immune
system to recognize them and mound a
defense
15. •Receptor proteins-have a binding site for a
specific molecule, protein then changes
shape and causes a cellular response
•Enzymatic proteins-carry out metabolic
reactions directly
•Junction proteins-form junctions between
cells, assist cell-to-cell communications
16. Malfunctioning plasma membrane
proteins
• Type 2 Diabetes-not enough carrier
proteins for the amount of glucose in the
blood
• Color blindness-lack functional red or
green photopigment protein
• Cystic fybrosis-channel proteins that are
not properly regulated
17. The plasma membrane regulates the
passage of molecules into and out of cells
Diffusion across a membrane requires no
energy
• Diffusion-molecules move from a high
concentration to a low concentration. The
molecules follow the concentration
gradient until equilibrium is reached
– Passive transport since no energy is required
– Small molecules, such as CO2 and O2, can
diffuse through the plasma membrane
18. • Facilitated diffusion-water, glucose, amino
acids, Na+, Cl-, and Ca2+
facilitated passage
through membrane
– Requires a transporter but no energy since it’s
moving down its concentration gradient
– Transporter moves specific substances
Carrier proteins are slower than channel proteins
19. • Osmosis-diffusion of water from low solute to
high solute
– Isotonic solutions-solute concentration is the same on
both sides
– Hypotonic solution-higher solute inside cell so water
moves into the cell
• Lysis-cells bursting when in hypotonic solution
• Plant cells-experience turgor pressure, which allows plants to
stand up
– Hypertonic solution-solute concentration higher
outside cell, water moves out
Figure 5.10C
20. Active transport across a membrane
requires a transporter and energy
• Active transport-molecules more across plasma
membrane accumulating on one side of the cell.
Moving against the concentration gradient so
energy is required
21. Bulk transport involves the use of
vesicles
• Endocytosis or exocytosis
• Moves molecules too large to
be moved by carrier proteins
such as polypeptides,
polysaccharides, or
polynucleotides
• Phagocytosis-large particle
(like food) is taken in, common
in unicellular organisms
• Pinocytosis-take in very small
particles
• Receptor-mediated
endocytosis. Allows bulk
transport of specific
substances.
22.
23. In multicellular organisms, cells
communicate
Extracellular material allows cells to join
together and communicate
• Plant cells-
– Plasmodesmata-numerous channels that
pass through the cell wall. This allows direct
exchange of some materials between adjunct
plant cells and, ultimately, all the cells of a
plant.
24. • Animal cells
– Anchoring junctions-
connect cells in tissues
that stretch
– Tight junctions-prevent
digestive juices from
leaking
– Gap junctions-plasma
membrane channels
join
– Extra-cellular matrix-
where junctions are
not present
• Cartilage and bone
