Embed Size (px)
Citation preview
1
Energy Flow Through Living Things: Photosynthesis & Cellular
Respiration
Chapter 8&9
2
8-1 Energy and Life• Living things need energy to survive
– comes from food– energy in most food comes from the sun
• Plants use light energy from the sun to produce food
• autotrophs organisms that make their own food– Ex - plants
• heterotrophs organisms that must obtain energy from the foods they consume
– animals
3
Chemical Energy and ATP• Energy – the ability to do work
– Forms: light, heat, electricity, chemical compounds
• chemical compound that cells use to store and release energy is adenosine triphosphate (ATP)– ATP - basic energy source for all cells
4
Chemical Energy and ATP
• ATP consists of:
– adenine
– ribose (a 5-carbon sugar)
– 3 phosphate groups
Adenine
ATP
Ribose 3 Phosphate groups
The three phosphate groups are the key to ATP's ability to store and release energy.
5
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.
ADPATP
Energy
Energy
Partiallycharged battery
Fullycharged battery
+
Adenosine Diphosphate (ADP) + Phosphate
Adenosine Triphosphate (ATP)
6
Chemical Energy and ATP
– Releasing Energy• Energy stored in ATP is released by breaking the
chemical bond between the second and third phosphates.
P
ADP
2 Phosphate groups
7
ATP energy uses: - cellular activities: active transport,
protein synthesis - muscle contraction
• Most cells have only a small amount of ATP, because it is not a good way to store large amounts of energy.
• Cells can regenerate ATP from ADP as needed by using the energy in foods like glucose.
Chemical Energy and ATP
8
8-2 Photosynthesis
• Photosynthesis - the process in which green plants use the energy of sunlight to convert water and carbon dioxide into high-energy carbohydrates and oxygen
9
The Photosynthesis Equation
• The Photosynthesis Equation• The equation for photosynthesis is:
• 6CO2 + 6H2O C6H12O6 + 6O2
• carbon dioxide + water sugars + oxygen
Light
Light
10
The Photosynthesis Equation
O2
CO2
+H20
Sugar
ADPNADP+
Light-Dependent Light-Dependent Reactions Reactions
(thylakoids)(thylakoids)
H2O
ATPNADPH
Calvin Cycle (stroma)
Light energy
11
Light and Pigments
• photosynthesis requires chlorophyll– pigments - light-absorbing molecules that
gather the sun's energy• The main pigment in plants is chlorophyll.• There are two main types of chlorophyll:
– chlorophyll a – chlorophyll b
12
Light and Pigments• Chlorophyll absorbs light well in the blue-violet and
red regions of the visible spectrum.
Wavelength (nm)
Est
imat
ed A
bso
rpti
on
(%
) 100
80
60
40
20
0400 450 500 550 600 650 700 750
Chlorophyll b
Chlorophyll a
Wavelength (nm)
13
Light and Pigments• Chlorophyll does not absorb light will in the green
region of the spectrum. Green light is reflected by leaves, which is why plants look green.
Est
imat
ed A
bso
rpti
on
(%
) 100
80
60
40
20
0400 450 500 550 600 650 700 750
Chlorophyll b
Chlorophyll a
Wavelength (nm)
14
Light Energy
• Light is a form of energy– compound that absorbs light also absorbs
energy from that light– chlorophyll absorbs light the energy is
transferred directly to electrons in the chlorophyll molecule raising the energy levels of these electrons
– high-energy electrons are what make photosynthesis work
15
Pop Quiz1. This molecule is called _____.
2. Energy in this molecule is stored in the _____.
3.
4.
5.
Word Bank
ADP
Ribose
Phosphate groups
Bonds
ATP
Adenine
Adenosine
16
8-3 Inside a Chloroplast• Inside a Chloroplast
• In plants, photosynthesis takes place inside chloroplasts.
Plant
Plant cells
Chloroplast
17
Inside a Chloroplast
• Chloroplasts contain thylakoids—saclike photosynthetic membranes.
Chloroplast
Singlethylakoid
18
Inside a Chloroplast• Thylakoids are arranged in stacks known as grana.
A singular stack is called a granum.• Stroma – space outside of the thylakoids
Granum
Chloroplast
Stroma
19
Inside a Chloroplast• Proteins in the thylakoid membrane organize
chlorophyll and other pigments into clusters called photosystems, which are the light-collecting units of the chloroplast.
Chloroplast
Photosystems
20
Photosynthesis Reactions
• reactions of photosystems include: – light-dependent reactions (requires light)
• take place within the thylakoid membranes• uses water, ADP, and NADP+
• produces oxygen, ATP, and NADPH
– light-independent reactions (Calvin cycle)• takes place in the stroma • ATP and NADPH not stable enough to store the
energy they carry for more than a few minutes• uses ATP and NADPH energy to build high-energy
sugars for long term storage
21
Photosynthesis Reactions
• The two sets of photosynthetic reactions work together.– The light-dependent reactions trap sunlight
energy in chemical form. – The light-independent reactions use that
chemical energy to produce stable, high-energy sugars from carbon dioxide and water.
22
Inside a Chloroplast
Chloroplast
Light
H2O
O2
CO2
Sugars
NADP+
ADP + P
Calvin Cycle
Light- dependent reactions
Calvin cycle
23
Electron Carriers
• electrons in chlorophyll absorb sunlight electrons gain energy– Cells use electron carriers to transport these
high-energy electrons from chlorophyll to other molecules
– One carrier molecule is NADP+.• transport electrons• NADP+ accepts and holds 2 high-energy electrons
along with a hydrogen ion (H+) - NADP+ NADPH• energy of sunlight can be trapped in chemical form• NADPH carries high-energy electrons to chemical
reactions elsewhere in the cell to make carbohydrates
24
Factors Affecting Photosynthesis
• Many factors affect the rate of photosynthesis, including:•Water• Temperature• Intensity of light
25
9-1 Chemical Pathways• Food serves as a source of raw materials for the
cells in the body and as a source of energy.
Animal
Plant
Animal Cells
Plant Cells
Mitochondrion
26
• Both plant and animal cells carry out the final stages of cellular respiration in the mitochondria.
Animal Cells
Plant Cells
MitochondrionOuter membrane Intermembrane
space
Inner membrane
Matrix
27
Chemical Energy and Food• Chemical Energy and Food
– One gram of the sugar glucose (C6H12O6), when burned in the presence of oxygen, releases 3811 calories of heat energy
– calorie - the amount of energy needed to raise the temperature of 1 gram of water 1 degree Celsius
• Cells gradually release the energy from glucose and other food compounds beginning with glycolysis - releases a small amount of energy.
28
Overview of Cellular Respiration• If oxygen is present:
– cellular respiration - the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen
– glycolysis Krebs cycle electron transport chain
• equation:– 6O2 + C6H12O6 → 6CO2 + 6H2O + Energy– oxygen + glucose → carbon dioxide + water + Energy
29
Overview of Cellular Respiration
Cytoplasm
Pyruvicacid
Mitochondrion
Electrons carried in NADH
Electrons carried in NADH and FADH2
Glucose Glycolysis
30
Overview of Cellular Respiration• Glycolysis – cytoplasm• Krebs cycle and electron transport - mitochondria
CytoplasmMitochondrion
Glycolysis
31
Stretch break
You have 2 minutes to talk, stretch, stand up…
32
Glycolysis• the process in which one molecule of glucose is
broken in half, producing two molecules of pyruvic acid, a 3-carbon compound– ATP Production
• cell uses up 2 molecules of ATP to start the reaction
• When glycolysis is complete, 4 ATP molecules have been produced a net gain of 2 ATP molecules
– NADH Production• removes 4 high-energy electrons electron carrier
called NAD+ becomes an NADH molecule.
• The NADH molecule holds the electrons until they can be transferred to other molecules.
33
Glycolysis
2 ADP 4 ADP 4 ATP
2 Pyruvicacid
2 ATP
Glucose
34
Glycolysis
2 ADP 4 ADP 4 ATP2 ATP
Glucose2 Pyruvicacid
35
Glycolysis
4 ADP 4 ATP
Glucose
2 ADP2 ATP
2 Pyruvicacid
36
Glycolysis
Glucose2 Pyruvicacid
4 ADP 4 ATP2 ADP2 ATP
2NAD+
37
Glycolysis
Glucose2 Pyruvicacid
4 ADP 4 ATP2 ADP2 ATP
2NAD+2
38
Glycolysis
To the electrontransport chain
2NAD+ 2 Pyruvicacid
4 ADP 4 ATP2 ADP2 ATP
2
39
Glycolysis
– The Advantages of Glycolysis• very fast - cells can produce thousands of ATP
molecules in a few milliseconds• does not require oxygen
40
Fermentation
• oxygen is not present glycolysis is followed by a different pathway - fermentation– Fermentation – release of energy (ATP) from
food in the absence of oxygen– cells convert NADH to NAD+ by passing high-
energy electrons back to pyruvic acid– Anaerobic – does not require oxygen
41
Fermentation
– Alcoholic Fermentation• Yeasts and a few other microorganisms use
alcoholic fermentation • Forms ethyl alcohol and carbon dioxide as wastes
– equation: • pyruvic acid + NADH → alcohol + CO2 + NAD+
42
Fermentation
– Lactic Acid Fermentation• pyruvic acid that accumulates from glycolysis
converted to lactic acid• regenerates NAD+ so that glycolysis can continue
– converts glucose into lactic acid– equation:
• pyruvic acid + NADH → lactic acid + NAD+
43
Fermentation• The first part of the equation is glycolysis.
44
Fermentation
• The second part shows the conversion of pyruvic acid to lactic acid.
45
The Totals
46
Comparing Photosynthesis and Cellular Respiration
• The energy flows in photosynthesis and cellular respiration take place in opposite directions.
47
Comparing Photosynthesis and Cellular Respiration
• On a global level, photosynthesis and cellular respiration are also opposites. – Photosynthesis removes carbon dioxide from
the atmosphere and cellular respiration puts it back.
– Photosynthesis releases oxygen into the atmosphere and cellular respiration uses that oxygen to release energy from food.
