Download Chapter 8

Chapter 8
Cellular
Energy
*Photosynthesis
*Cellular Respiration
ENERGY - is
the ability to do work
ALL ORGANISMS –
need and use energy!!!!
Where do organisms get the
energy that they need?
it comes from food,
however, the
ultimate source of
most of our
energy is the SUN
Law of Thermodynamics

Energy cannot be created or
destroyed, but it can be converted
into other forms
Metabolism


The sum of a cell’s chemical reactions
Metabolism = Catabolism + Anabolism

Catabolism: to break down


Ex: cellular respiration
Anabolism: to build up

Ex: photosynthesis
*This results in a continuous flow of energy within
an organism.
organisms meet their energy needs
in different ways
AUTOTROPHS – plants, some bacteria & protists
produce their own food
 chemoautotrophs go through chemosynthesis
 photoautotrophs go through photosynthesis
HETEROTROPHS – fungi, animals, some bacteria &
protists cannot produce their own food
 must obtain energy from the foods they consume
ENERGY


energy comes in many forms – light, heat, electricity,
nuclear, kinetic,…
Some organisms consume foods in order to get the
stored energy out of them
ATP


cellular activities require the use of energy
one of the main chemical compounds that cells use
to store energy is ATP (adenosine triphosphate)
ATP consists of :
 1. a N-containing part – called adenine

2. a 5-Carbon sugar - called ribose

3. three phosphate groups (P and O)
Metabolic Pathway of
ATP and ADP

form a cycle of releasing and absorbing energy
ATP
requires (absorbs) energy
ADP
releases
Energy
ATP and Glucose

most cells have only a small amount of ATP
(enough to last for a few seconds of activity)

more is made as needed by using the stored
energy (glycogen)
2 processes of great importance
that enable living things to
meet their energy needs –
1. PHOTOSYNTHESIS –
the production of organic compounds
2. CELLULAR RESPIRATION –
the break down of organic compounds
Light Energy
PHOTOSYNTHESIS
Chemical Energy
(organic compounds)
CELLULAR
RESPIRATION
ATP’s
ATP- ADP CYCLE
ADP’s + P groups +
energy (that can be used
to do cellular activities)
Photosynthesis
process by which a cell captures light energy
(photons) and uses it to make food
(usually carbohydrates, like glucose)
photosynthesis occurs in photoautotrophs:
 plants
 algae
 some bacteria (prokaryotes)
PHOTOSYNTHESIS - process in which water,
carbon dioxide, and light energy are converted into
oxygen and organic compounds
the ORGANIC COMPOUNDS made
during photosynthesis are usually
carbohydrates (sugars and starches)
PHOTOSYNTHESIS – general equation
6 CO2 + 6 H2O + light (energy)
C6H12O6 + 6 O2
What are the reactants?
What are the products?
Where does the light energy come from?
Where does the H2O come from?
Where does the CO2 come from?
Photosynthesis - Overview
most photosynthetic organisms are
eukaryotes, therefore, photosynthesis
occurs inside the CHLOROPLAST
prokaryotes lack chloroplasts,
in these organisms, photosynthesis
occurs in the cytoplasm
PIGMENTS
ALL photosynthetic organisms contain PIGMENTS
(light absorbing substances)
the principal photosynthetic pigment is (green)
CHLOROPHYLL
in addition to chlorophyll there are other pigments
called ACCESSORY PIGMENTS (ex. Carotenoids)
Chloroplast Structure
chloroplasts contain disc like
structures called
THYLAKOID DISKS
these are arranged in stacks
called GRANA
PIGMENTS are found inside the
thylakoid disks
a fluid called STROMA surrounds
the thylakoid disks
PHOTOSYNTHESIS –
consists of 2 major sets of reactions
1. LIGHT DEPENDENT REACTIONS
2. LIGHT INDEPENDENT REACTIONS
(or CALVIN CYCLE)
What do the names indicate
about these reactions?
Light
Dependent
Reactions
(occur in thylakoid disk
containing chlorophyll)
Light
Independent
Reactions
(occur in stroma)
Light dependent reaction:
What are the reactants? products?
Light independent reaction (Calvin Cycle)?
What are the reactants? products?
Alternative Pathways


Used when water and/or carbon dioxide are
not present or in insufficient amounts
2 types:

The C4 pathway


Sugar cane, corn
The CAM pathway

Pineapple, cacti, orchids
Factors Affecting Photosynthesis




availability of water
availability of carbon dioxide
temperature
light intensity
Biochemical (Metabolic) Pathway
Light Energy
PHOTOSYNTHESIS
Chemical Energy
(organic compounds)
CELLULAR
RESPIRATION
ATP’s
ATP- ADP CYCLE
ADP’s + P groups + energy
(that can be used to do cellular
activities)
Cellular Respiration
process that releases energy
(in the form of ATP’s)
from food (organic compounds)
All living things undergo some form of
cellular respiration, but remember living
things differ so this process may differ
There are 2 possible ways in which a cell can
accomplish cellular respiration and harvest energy
from food….
(aerobic) Cellular Respiration =
oxidative respiration
or
Fermentation (anaerobic
respiration)
*both start with the same first step
GLYCOLYSIS
(aerobic) Cellular Respiration or
Oxidative Respiration
releases energy
(in the form of ATP’s)
from food
(organic compounds)
~in the presence of oxygen~
3 steps of
(aerobic) Cellular Respiration
1. Glycolysis
2. Kreb’s Cycle
3. Electron Transport Chain
1. Glycolysis




occurs in the cytoplasm
anaerobic
“splitting of glucose” into pyruvic acid (pyruvate)
net gain of 2 ATP and 2 pyruvate
2. Kreb’s Cycle




occurs in mitochondrion (of eukaryotes)
aerobic
breaks down pyruvic acid
produces CO2 and a net gain of 2 ATP
3. Electron Transport Chain




occurs in mitochondria(of eukaryotes)
aerobic
uses electrons to release energy and produce ATP
produces H2O and up to 34 ATP
How many ATP’s from
(aerobic) Cellular Respiration?
Glycolysis (2)
Kreb’s Cycle (2)
Electron Transport Chain (maximum 34)
possible 38 ATP’s


the actual number of ATP’s varies from cell to cell
most eukaryotic cells produce 36 ATP’s
General Equation for
(aerobic) Cellular Respiration
C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP (energy)
What are the reactants?
What are the products?
if no oxygen is present…..
glycolysis is followed by
fermentation
Fermentation (anaerobic respiration)
releases energy (in the form of ATP)
from food (organic compounds)
~in the absence of oxygen~
2 steps of
Fermentation
(anaerobic respiration)
1. Glycolysis
2. Fermentation
1. Glycolysis




occurs in the cytoplasm
anaerobic
“splitting of glucose” into pyruvic acid (pyruvate)
net gain of 2 ATP and 2 pyruvate
2. Fermentation




occurs in the cytoplasm
anaerobic
the break down of pyruvic acid in the absence of
oxygen
net gain of 0 ATP
How many ATP’s from
FERMENTATION?
Glycolysis (2)
Fermentation (0)
possible 2 ATP
* fermentation is not nearly as efficient in releasing
energy from food as is (aerobic) Cellular Respiration
2 common types
of Fermentation
LACTIC ACID FERMENTATION
 converts pyruvic acid into lactic acid
 process used to make yogurt, cheese, sour cream
 occurs in some fungi and some bacteria
 occurs in skeletal muscle cells of animals = lactic acid
or sore muscles
2 common types
of Fermentation
ALCOHOLIC FERMENTATION
 converts pyruvic acid into ethanol (ethyl alcohol)
 process used in the making of bread and alcoholic
beverages - wine, beer,…
 occurs in yeasts, some bacteria, some plants
 ethanol is added to gasoline to make gasohol
Visualizing Cellular Respiration
Let’s see the process again…
Photosynthesis
and
Cellular Respiration
are a metabolic (biochemical) pathways
BECAUSE…..
The products of photosynthesis
are used as the reactants in
cellular respiration
 The products of cellular
respiration are used as the
reactants in photosynthesis


Cellular Respiration Virtual Lab