Download CELLULAR ENERGY – CH. 8 • All cellular activities require energy

CELLULAR ENERGY – CH. 8
 All cellular activities require energy to live.
 Nearly all energy for life comes from the Sun.
 Autotrophs – make their own food
 Heterotrophs – ingest food to obtain energy.
 Metabolism – all chemical reactions in a cell.
ALL organisms use a 2-step process to get the energy they
need:
1. Chemical energy from organic molecules (i.e.
glucose) is used to make ATP (this is cellular
respiration)
2. ATP provides the energy we need (for muscle
contraction, synthesizing molecules, etc.)
On average, each ATP molecule in our body is used and resynthesized more than 30 times per minute when we are at
rest and more than 500 times per minute during strenuous
exercise.
ATP (adenosine triphosphate) –
 most important biological molecule that provides energy.
Any time the cell needs energy the bonds of the ATP
molecule are broken to release energy.
 triphosphate = 3 phosphate groups (PO43-) Remember PO43is a charged ion.
 Since each PO43- ion is negative and like charges repel each
other, it takes a lot of energy to put the 3 PO43- groups
together.
ATP
ADP (adenosine diphosphate)
 when a bond is broken and energy is released ADP can then
bond with another phosphate group and form ATP again.
This is a renewable cycle so energy is always available for
cells to use.
1. PHOTOSYNTHESIS – Energy Storage
-anabolic pathway that uses energy to make larger
molecules from smaller ones
 Light energy from the sun is converted into chemical energy.
Plants use the sun’s energy to make simple sugars. These
simple sugars are converted to complex carbohydrates, like
starches, which store energy.
6CO2 + 6H2O + ☼  C6H12O6 + 6O2
 NOTE: products are glucose and oxygen!
 Occurs in chloroplasts
TWO PHASES of Photosynthesis:
Light Energy
Light – Dependent reactions (phase 1)
Light – Independent reactions (phase 2)
Glucose
A. PHASE 1. Light-dependent reactions –
 convert light energy into chemical energy
 ATP produced in these reactions is used to fuel lightindependent reactions.
 Light is captured in the chloroplasts
B. PHASE 2. Light-independent reactions (Calvin Cycle) –
 Does not require light
 ATP formed in phase 1 is not stable enough to provide all
energy needs so phase 2 converts energy into organic
molecules such as glucose.
 Takes the products made in the light-dependent reactions to
make sugars.
 Occurs in the chloroplasts.
2. CELLULAR RESPIRATION – Energy Releasing
-catabolic pathway in which energy is released as
larger molecules are broken into smaller ones
C6H12O6 + 6O2  6CO2 + 6H2O + energy (ATP)
 occurs in both plant and animal cells
 Purpose
make ATP for energy
 NOTE: products of photosynthesis are reactants of cellular
respiration.
3 Parts of cellular respiration:
1. Glycolysis – anaerobic (does not require oxygen)
 Occurs in cytoplasm
 Breaks down glucose
 Fermentation - follows glycolysis when oxygen is not
present.
o Lactic Acid fermentation – continues glycolysis to
continue production of ADP. (muscle fatigue, cheese
making)
o Alcoholic fermentation – used by some types of
bacteria (like yeast) to make CO2 and ethyl alcohol
--- used to make bread and alcoholic beverages.
2 - Kreb’s cycle – aerobic (requires oxygen)
 citric acid cycle
 Occurs in mitochondria
3 - Electron transport – aerobic
 Most ATP produced here (~32)
 Occurs in mitochondria