kuliah6a1 fotosintesis respirasi

8/6/2019 KULIAH6A1 FOTOSINTESIS RESPIRASI

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Photosynthesis All Materials © Cmassengale

I. Capturing the Energy of LifeA. All organisms require energy

B. Some organisms (autotrophs ) obtain energy directly from the sun

and store it in organic compounds ( glucose ) during a process

called photosynthesis

6CO2 + 6H2O + energy --> 6O2 + C6H12O6

II. Energy for Life Processes

A. Energy is the ability to do work

B. Work for a cell includes growth & repair, active transport

across cell membranes, reproduction, synthesis of cellular

products, etc.

C. Work is the ability to change or move matter against other

forces (W = F x D)

D. Autotrophs or producers convert sunlight, CO2, and H2O intoglucose (their food)

E. Plants, algae, and blue-green bacteria, some prokaryot es, are

producers or autotrophs

F. Only 10% of the Earth’s 40 million species are autotrophs



G. Other autotrophs use inorganic compounds instead of sunlight to

make food; process known as chemosynthesis

H. Producers make food for themselves and heterotrophs or

consumers that cannot make food for themselves

I. Heterotrophs include animals, fungi, & some bacteria, & protist s

III. Biochemical Pathways

A. Photosynthesis and cellular respiration are biochemical pathways B. Biochemical pathways are a series of reactions where the

product of one reaction is the reactant of the next C. Only autotrophs are capable of photosynthesis D. Both autotrophs & heterotrophs perform cellular respiration to

release energy to do work E. In photosynthesis, CO2(carbon dioxide) and H2O (water) are

combined to form C6H12O6 (glucose) & O2 (oxygen)

6CO2 + 6H2O + energy --> 6O2 + C6H12O6



F. In cellular respiration, O2 (oxygen) is used to burn C6H12O6

(glucose) & release CO2(carbon dioxide), H2O (water), and

energy

G. Usable energy released in cellular respiration is called adenosine

triphosphate or ATP

IV. Light Absorption in Chloroplasts

A. Chloroplasts in plant & algal cells absorb light energy from the

sun during the light dependent reactions B. Photosynthetic cells may have thousands of chloroplasts C. Chloroplasts are double membrane organelles with the an inner

membrane folded into disc-shaped sacs called thylakoids D. Thylakoids, containing chlorophyll and other accessory pigments ,

are in stacks called granum (grana, plural) E. Grana are connected to each other & surrounded by a gel-like

material called stroma F. Light-capturing pigments in the grana are organized into

photosystems



V. Pigments A. Light travels as waves & packets called photons

B. Wavelength of light is the distance between 2 consecutive peaks

or troughs

C.

Sunlight or white light is made of different wavelengths orcolors carrying different amounts of energy D. A prism separates white light into 7 colors (red, orange,

yellow, green, blue, indigo, & violet) ROY G. BIV E. These colors are called the visible spectrum



F. When light strikes an object, it is absorbed, transmitted, or

reflected G. When all colors are absorbed , the object appears black H. When all colors are reflected , the object appears white I. If only one color is reflected (green), the object appears that

color (e.g. Chlorophyll) VI. Pigments in the

Chloroplasts

A. Thylakoids contain a variety of pigments ( green red, orange,

yellow...) B. Chlorophyll (C55H70MgN4O6) is the most common pigment in

plants & algae C. Chlorophyll a & chlorophyll b are the 2 most common types of

chlorophyll in autotrophs D. Chlorophyll absorbs only red, blue, & violet light E. Chlorophyll b absorbs colors or light energy NOT absorbed by

chlorophyll a



F. The light energy absorbed by chlorophyll b is transferred to

chlorophyll a in the light reactions

G. Carotenoids are accessory pigments in the thylakoids & includeyellow, orange, & red



VII. Overview of Photosynthesis 6CO2 + 6H2O

C6H12O6 + 6O2

A. Photosynthesis is not a simple one step reaction but a

biochemical pathway involving many steps

B. This complex reaction can be broken down into two reaction

systems --- light dependent & light independent or dark

reactions

• Light Reaction: H2O O2 + ATP +

NADPH2 •

Water is split, giving off oxygen. • This system depends on sunlight for activation energy. • Light is absorbed by chlorophyll a which "excites" the

electrons in the chlorophyll molecule. • Electrons are passed through a series of carriers and

adenosine triphosphate or ATP (energy) is produced.

• Takes place in the thylakoids.

• Dark Reaction: ATP + NADPH2 + CO2

C6H12O6 • Carbon dioxide is split, providing carbon to make sugars. • The ultimate product is glucose. • While this system depends on the products from the light

reactions, it does not directly require light energy.

• Includes the Calvin Cycle .

• Takes place in the stroma.



VIII. Calvin Cycle A. Carbon atoms from CO2 are bonded or "fixed" into organic

compounds during a process called carbon fixation B. The energy stored in ATP and NADPH during the Light Reactions

is used in the Calvin cycle

C. The Calvin cycle has 3 main steps occurring within the stroma of

the Chloroplast

STEP 1

•

CO2 diffuses into the stroma from surrounding cytosol• An enzyme combines a CO2 molecule with a five-carbon

carbohydrate called RuBP

• The six-carbon molecule produced then splits immediately into a

pair of three-carbon molecules known as PGA



STEP 2

• Each PGA molecule receives a phosphate group from a molecule

of ATP

• This compound then receives a proton from NADPH and releases

a phosphate group producing PGAL

• These reactions produce ADP, NADP+, and phosphate which are

used again in the Light Reactions.

STEP 3

• Most PGAL is converted back to RuBP to keep the Calvin cycle

going• Some PGAL leaves the Calvin Cycle and is used to make other

organic compounds including amino acids, lipids, and

carbohydrates

• PGAL serves as the starting material for the synthesis of

glucose and fructose

• Glucose and fructose make the disaccharide sucrose, which

travels in solution to other parts of the plant (e.g., fruit, roots)

• Glucose is also the monomer used in the synthesis of the

polysaccharides starch and cellulose



D. Each turn of the Calvin cycle fixes One CO2 molecule so it takes

six turns to make one molecule of glucose IX. Photosystems & Electron Transport Chain

A. Only 1 in 250 chlorophyll molecules (chlorophyll a ) actuallyconverts light energy into usable energy

B. These molecules are called reaction-center chlorophyll



C. The other molecules (chlorophyll b, c, & d and carotenoids)

absorb light energy and deliver it to the reaction-center

molecule

D. These chlorophyll molecules are known as antenna pigments E. A unit of several hundred antenna pigment molecules plus a

reaction center is called a photosynthetic unit or photosystem

F. There are 2 types of photosystems --- Photosystem I &

Photosystem II

G. Light is absorbed by the antenna pigments of photosystems II

and I

H. The absorbed energy is transferred to the reaction center

pigment, P680 in photosystem II, P700 in photosystem I

I. P680 in Photosystem II loses an electron and becomes positively

charged so it can now split water & release electrons

(2H2O 4H+ + 4e- + O2)

J. Electrons from water are transferred to the cytochrome

complex of Photosystem I

K. These excited electrons activate P700 in photosystem I which

helps reduce NADP+ to NADPH

L.

NADPH is used in the Calvin cycleM. Electrons from Photosystem II replace the electrons that leavechlorophyll molecules in Photosystem I



X. Chemiosmosis (KEM-ee-ahz-MOH-suhs) A.Synthesis or making of ATP (energy)

B. Depends on the concentration gradient of protons ( H+) across

the thylakoid membrane

C. Protons (H+) are produced from the splitting of water in

Photosystem II D. Concentration of Protons is HIGHER in the thylakoid than in the

stroma

E. Enzyme, ATP synthetase in the thylakoid membrane, makes ATP

by adding a phosphate group to ADP



XI. Alternate Pathways A. The Calvin cycle is the most common pathway used by autotrophs

called C3 Plants

B. Plants in hot, dry climates use alternate pathways to fix carbon

& then transfer it to the Calvin cycle

C. Stomata are small openings on the underside of leaves for gas

exchange (O2 & CO2)

D. Guard cells on each side of the stoma help open & close thestomata

E. Plants also lose H2O through stoma so they are closed during the

hottest part of the day



F. C4 plants fix CO2 into 4-Carbon Compounds during the hottestpart of the day when their stomata are partially closed

G. C4 plants include corn, sugar cane and crabgrass H. CAM plants include cactus & pineapples I. CAM plants open their stomata at night and close during the day

so CO2 is fixed at night J. During the day, the CO2 is released from these compounds and

enters the Calvin Cycle XII. Factors Determining the Rate of

Photosynthesis A. Light intensity - As light intensity increases, the rate of

photosynthesis initially increases and then levels off to a plateau

B. Temperature - Only the dark, not the light reactions are

temperature dependent because of the enzymes they use (25 oC

to 37oC)

C. Length of day

D. Increasing the amount of carbon dioxide available improves the

photosynthesis rate

E. Level of air pollution



BACK

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Cellular Respiration All Materials © Cmassengale

C6H12O6 + 6O2 -----> 6CO2 + 6H20 + energy (heat

and ATP)

Energy

• Capacity to move or change matter

• Forms of energy are important to life include Chemical, radiant(heat & light), mechanical, and electrical

• Energy can be transformed from one form to another

• Chemical energy is the energy contained in the chemical bonds

of molecules

• Radiant energy travels in waves and is sometimes called

electromagnetic energy. An example is visible light

• Photosynthesis converts light energy to chemical energy

•

Energy that is stored is called potential energy

Laws of Thermodynamics

• 1st law- Energy cannot be created or destroyed.



Energy can be converted from one form to another. The

sum of the energy before the conversion is equal to the

sum of the energy after the conversion.

• 2nd law- Some usable energy is lost during transformations.

During changes from one form of energy to another, some

usable energy is lost, usually as heat. The amount of

usable energy therefore decreases.

Adenosine triphosphate (ATP) • Energy carrying molecule used by cells to fuel their cellular

processes • ATP is composed of an adenine base, ribose sugar, & 3

phosphate (PO4) groups

• The PO4 bonds are high-energy bonds that require energy to be

made & release energy when broken



• ATP is made & used continuously by cells • Every minute all of an organism's ATP is recycled • Phosphorylation refers to the chemical reactions that make ATP by

adding Pi to ADP ADP + Pi + energy « ATP + H2O

• Enzymes (ATP synthetase& ATPase) help break & reform these

high energy PO4 bonds in a process called substrate-levelphosphorylation

• When the high-energy phosphate bond is broken, it releases

energy, a free phosphate group, & adenosine diphosphate (ADP)



Enzymes in Metabolic Pathways:

• Biological catalysts

• Speeds up chemical reactions

• Lowers the amount of activation energy needed by weakening

existing bonds in substrates



• Highly specific protein molecules

• Have an area called the active site where substrates temporarily

join

• Form an enzyme-substrate complex to stress bonds

• Enzyme usable

enzyme substrate complex



Energy Carriers During Respiration: NADH: A second energy carrying molecule in the mitochondria;

produces 3 ATP

FADH2: A third energy carrying molecule in the mitochondria;produces 2 ATP

Mitochondria:

• Has outer smooth, outer membrane & folded inner membrane

• Folds are called cristae



• Space inside cristae is called the matrix & contains DNA &

ribosomes

• Site of aerobic respiration

• Krebs cycle takes place in matrix

• Electron Transport Chain takes place in cristae

Cellular Respiration Overview: C6H12O6 + 6O2 -----> 6CO2 + 6H20 + energy (heat and

ATP)• Controlled release of energy from organic molecules (most often

glucose) • Glucose is oxidized (loses e-) & oxygen is reduced (gains e-)

• The carbon atoms of glucose (C6H12O6) are released as CO2

• Generates ATP (adenosine triphosphate)



• The energy in one glucose molecule may be used to produce 36

ATP

• Involves a series of 3 reactions --- Glycolysis, Kreb's Cycle, &

Electron Transport Chain

Glycolysis:

• Occurs in the cytoplasm

• Summary of the steps of Glycolysis :

a. 2 ATP added to glucose (6C) to energize it.

b. Glucose split to 2 PGAL (3C). (PGAL = phosphoglyceraldehyde)

c. H+ and e- (e- = electron) taken from each PGAL & given to

make 2 NADH.

d. NADH is energy and e- carrier.

e. Each PGAL rearranged into pyruvate (3C), with energy

transferred to make 4 ATP (substrate phosphorylation).

f. Although glycolysis makes 4 ATP, the net ATP production bythis step is 2 ATP (because 2 ATP were used to start

glycolysis). The 2 net ATP are available for cell use.

g. If oxygen is available to the cell, the pyruvate will move into

the mitochondria & aerobic respiration will begin.



Net Yield from Glycolysis

4 NADH2

2 CO2

4 ATP ( 2 used to start reaction)

h. If no oxygen is available to the cell (anaerobic), the pyruvate will

be fermented by addition of 2 H from the NADH (to alcohol + CO2 in



yeast or lactic acid in muscle cells). This changes NADH back to

NAD+ so it is available for step c above. This keeps glycolysis going!

Alcoholic Fermentation

Lactic Acid Fermentation

Aerobic Respiration:

• Occurs in the mitochondria • Includes the Krebs Cycle & the Electron Transport Chain • Pyruvic acid from glycolysis diffuses into matrix of mitochondria

& reacts with coenzyme A to for acetyl-CoA (2-carbon

compound) • CO2 and NADH are also produced



Kreb's Cycle:

• Named for biochemist Hans Krebs • Metabolic pathway that indirectly requires O2

• Kreb's Cycle is also known as the Citric acid Cycle • Requires 2 cycles to metabolize glucose • Acetyl Co-A (2C) enters the Kreb's Cycle & joins with

Oxaloacetic Acid (4C) to make Citric Acid (6C) • Citric acid is oxidized releasing CO2 , free H+, & e- and forming

ketoglutaric acid (5C) • Free e- reduce the energy carriers NAD+ to NADH2 and FAD+ to

FADH2

• Ketoglutaric acid is also oxidized releasing more CO2 , free H+,

& e- • The cycle continues oxidizing the carbon compounds formed

(succinic acid, fumaric acid, malic acid, etc.) producing more

CO2, NADH2, FADH2, & ATP • H2O is added to supply more H+

• CO2 is a waste product that diffuses out of cells • Oxaloacetic acid is regenerated to start the cycle again • NADH2 and FADH2 produced migrate to the Electron Transport

Chain (ETC)



Net Yield from Kreb's

Cycle (2 turns) 6 NADH2

2 FADH2

4 CO2

2 ATP

Electron Transport Chain:

•

Found in the inner mitochondrial membrane or cristae • Contains 4 protein-based complexes that work in sequence

moving H+ from the matrix across the inner membrane (proton

pumps) • A concentration gradient of H+ between the inner & outer

mitochondrial membrane occurs



• H+ concentration gradient causes the synthesis of ATP by

chemiosmosis

• Energized e- & H+ from the 10 NADH2 and 2 FADH2 (produced

during glycolysis & Krebs cycle) are transferred to O2 to

produce H2O (redox reaction) O2 + 4e- + 4H+ 2H2O

Energy Yield from Aerobic Respiration

Glycolysis Kreb's Cycle Total4 NADH2 6 NADH2 10 NADH2 x 3 = 30 ATP

0 FADH2 2 FADH2 2 FADH2 x 2 = 4 ATP

2 ATP 2 ATP 4ATP

38 ATP

• Most cells produce 36- 38 molecules of ATP per glucose (66%

efficient)



• Actual number of ATP's produced by aerobic respiration varies

among cells


kuliah6a1 fotosintesis respirasi

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