Transcript
Part 1: ATP &Photosynthesis
Objectives
• Understand the energy carrying
molecules ATP & ADP, their structure and
model their cycle.
• Explain the importance of photosynthesis
to organisms on Earth.
• Recall the equation for photosynthesis.
• Discuss the structure of a chloroplast.
Autotrophs and Heterotrophs
• Autotrophs-Organisms,
plants, which make
their own food.
• Heterotrophs-
Organisms, animals,
that must obtain
energy from the foods
they consume.
Chemical Energy and ATP
–An important chemical compound
that cells use to store and release
energy is adenosine triphosphate,
ATP.
–ATP is used by all types of cells as
their basic energy source.
Chemical Energy and ATP
• ATP consists of:
– adenine
– ribose (a 5-carbon sugar)
– 3 phosphate groups
Adenine
ATP
Ribose 3 Phosphate groups
Chemical Energy and ATP•Storing Energy
– ADP has two
phosphate groups
instead of three.
– A cell can store small
amounts of energy by
adding a phosphate
group to ADP.
Energy
Energy
Chemical Energy and ADP
•Releasing Energy•Energy stored in ATP is released by
breaking the chemical bond between the
second and third phosphates.
P
ADP
2 Phosphate groups
ADP/ATP Cycle
In a Nut shell, ATP
• ATP is consumed in the cell by
energy-requiring processes and can
be generated by energy-releasing
processes. – In this way ATP transfers energy between separate biochemical
reactions in the cell.
• ATP is the main energy source for the
majority of cellular functions. – This includes the synthesis of organic molecules, including DNA
and, and proteins. ATP also plays a critical role in the transport of
organic molecules across cell membranes, for example during
exocytosis and endocytosis.
Energy Transformations
• All organisms need
constant energy
• Ultimate source of energy
for most life is the SUN
• Photosynthesis
– Chloroplasts of plants
– Solar energy is used to
convert water and carbon
dioxide into stored energy
in sugar
PHOTOSYNTHESIS An Overview
• The key cellular process
identified with energy
production is
photosynthesis.
• Photosynthesis is the
process in which green
plants use the energy of
sunlight to convert water
and carbon dioxide into
high-energy carbohydrates
and oxygen.
The Photosynthesis Equation
•The Photosynthesis Equation• The equation for photosynthesis is:
• Reactants Products
• 6CO2 + 6H2O C6H12O6 + 6O2
• carbon dioxide + water sugars +
oxygen
Light
Chloroplast Structure• Majority of chloroplasts are in the leaves
(million per square millimeter).
• Color of chloroplasts and leaves is
determined by chlorophyll (pigment that
collects light energy).
• Chloroplast is surrounded by a double membrane
(inner and outer)
• Inside the chloroplast are stacks of flat membrane
discs called thylakoids
• Stack of thylakoids = granum (multiple stacks are
called grana)
• Liquid portion that surrounds the grana= stroma
• Stomata – pores on
underside of leaf through
which gases pass
Pigments in Thylakoid• Chlorophyll is the main pigment that absorbs sunlight
• Blue and red wavelengths of light are absorbed and
green wavelengths are reflected (hence the green
color of plants)
• There are other pigments called accessory pigments
that can absorb light (red, yellow, orange- you see this
in the fall when the leaves change)
Inside a Chloroplast
•Inside a Chloroplast• In plants, photosynthesis takes place
inside chloroplasts.
Plant
Plant cells
Chloroplast
Inside a Chloroplast
• Chloroplasts contain thylakoids—saclike
photosynthetic membranes.
Chloroplast
Single
thylakoid
Inside a Chloroplast
• Thylakoids are arranged in stacks known
as grana. A singular stack is called a
granum.Granum
Chloroplast
Inside a Chloroplast
• The stroma is the area that surrounds the
Granum. It is like the cytoplasm in a cell. Stroma
Chloroplast
CHECK FOR UNDERSTANDING
What type of organism makes their own food?
What is the main source of Energy on earth?
Where does photosynthesis occur?
What are the overall reactants of photosynthesis?
What are the overall products of photosynthesis?
What pigments are found in a chloroplast?
High Energy Electrons
• High energy electrons
produced by chlorophyll
require carriers to transfer
them (with their energy)
• NADP+ is a carrier
• When full with electrons it is
NADPH
Photosynthesis• 2 Stages:
– Light-dependent reactions
– Light-independent reactions (Calvin Cycle)
Photosystems
• Areas on thylakoids that contain clusters of chlorophyll and protein
• Absorb sunlight
• Generate high energy electrons
• Photosystem II and Photosystem I
LIGHT-DEPENDENTREACTIONS OVERVIEW
• Requires sunlight
• Location: thylakoid membranes
• Reactants: sunlight, water, NADP+
(electron acceptor), ADP• Products: oxygen, NADPH (energy
carrying molecule), and ATP• Main function : generate energy carrying
molecules (ATP and NADPH) for the next stageof photosynthesis
Light Dependent Reactions
• Photosystem II
– Light energy absorbed by
photosystem II produces high
energy electrons
– Water molecules are split to
replace those electrons
(releasing H+ ions and oxygen)
Light Dependent Reactions
• Electron Transport
Chain
– High-energy electrons
move down the electron
transport chain (to
photosystem I)
– Energy made is used to
pump H+ ions across
the thylakoid membrane
and into the thylakoid
space
Light Dependent Reactions
• Photosystem I
– Electrons are reenergized in photosystem I
– Second electron transport chain transfers these
electrons to NADP+ to form NADPH
– NADP+ is final electron acceptor
Light Dependent Reactions
• Hydrogen Ion Movement and ATP Formation
– H+ now highly concentrated in thylakoid space
– H+ move out of thylakoid to get to more negative
area
• Move through ATP synthase which rotates and the
energy is used to convert ADP into ATP
• Called Chemiosmosis
CFU
• What is made in light dependent
reactions?
• What is used in light dependent
reactions?
• Where do these reactions occur?
• What travels into the thylakoid?
CFU continued
• What happens when the H+ build up?
• What makes the ATP?
• What happens to the electrons at the
end of the chain?
• What happens to the ATP and NADPH
made?
LIGHT-INDEPENDENTREACTIONS OVERVIEW
• DOES NOT require sunlight (dark reactions or Calvin cycle)
• Location: stroma
• Reactants: NADPH, ATP, and CO2
• Products: ADP and unhooked phosphate group,NADP+, and glucose
• Main Function: to make glucose
Light-Independent Reactions• occurs in the stroma of the chloroplast
• uses the ATP and NADPH from the light
reactions
• uses CO2 from environment (often called
carbon fixation) to make sugar
• AKA – Calvin Cycle
CO2 Enters the Cycle
• 6 carbon dioxide molecules are taken in
through the stomata (openings in bottom
of a leaf)
• Combine with six 5-carbon molecules to
make twelve 3-carbon compounds
Sugar Production
• Energy from ATP and NADPH convert
the 3-carbon molecules to higher energy
forms
• 2 of the 3-carbon molecules are removed
from cycle to form glucose, starch, and
cellulose
• Remaining 3-carbon molecules (most of
them) are converted back to 5-carbon
forms that started the cycle (to keep it
going)
Sugar Production
• Glucose can be used for energy to make
ATP or it can be converted to
starch/cellulose
• Sugars made also provide carbon
skeleton to interact with elements like
nitrogen, sulfur, and phosphorous to
make other organic molecules
– Amino acids, lipids, or nucleic acids
Chloroplast
LightH2O
O2
CO2
Sugars
NADP+
ADP +
PLight-
dependent
reactions
Calvin
Cycle
–Factors Affecting Photosynthesis • Many factors affect the rate of photosynthesis,
including:
• Water
• Temperature
• Intensity of light
• Water- a shortage can slow or stop photosynthesis
• Temperature-photosynthesis depends on enzymes
that work best between 0o and 35o C. Temps above
or below will slow photosynthesis.
• Intensity of light- increasing light intensity increases
the rate of photosynthesis. The rate will level off.
• Stomata- used for gas exchange.
• Guard cells- control the opening and closing of the
stomata.
CHECK FOR UNDERSTANDING
1. What is used in Calvin Cycle?
2. What is made in Calvin Cycle?
3. Where does the Calvin Cycle occur?
4. What leaves the Calvin Cycle?
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