Exam 3 BSCI 170 keller

Light Reactions

The first of two major stages in photosynthesis (preceding the Calvin cycle). These reactions, which occur on the thylakoid membranes of the chloroplast or on membranes of certain prokaryotes, convert solar energy to the chemical energy of ATP and NADPH, releasing oxygen in the process.

Photosynthesis can be thought of two ways:

- Transforming light energy into stored chemical energy; or

- Making the first carbon backbones that form nearly ALL other organic molecules

What is the product of photosynthesis.

G3P

Global Catabolic-Anabolic cycle

with complementary pathways in photosynthesis and respiration. The constant input of new energy from sunlight makes up for the constant loss of energy to entropy through heat.

photocynthesis occurs in the/ What are the compartments

the chloroplast, requiring three compartments: the stroma, thylakoid membrane, and thylakoid lumen

Two phases of photosynthesis

light dependent and light independent/Calvin cycle

The light reactions capture energy from... and convert it into ...

Energy stored in the form of...

Light and convert it into chemical enrgy

AtP and NADPH

Flow of electrons in Photosynthesis light reactions

PSII--->PQ--->Cytochrome Complex--->PC--->PSI--->Fd--->NADP+

What does light do at PSII

Light excites electrons in chlorophyl of PSII, and these high energy electrons are used to reduce PQ to PQH2 in the thylakoid membrane.

What does water do in photosynthesis

The electrons from chlorophyl are replaced by electrons from water molecules, split by the process of photolysis (this is where oxygen gas comes from)

What powers the cytochrome complex

The high energy electrons from PQH2 power the proton pump Cytochrome complex, which moves H+ across the thylakoid membrane creating a high concentration in the thylakoid lumen.

What powers ATP synthase in photosynthesis

The H+ gradient generated by PQ-Cytochrome complex-PC (electron transport chain) powers the enzyme complex ATP synthase to make ATP in the stroma.

Is PC a high of low electron carrier

Low energy electrons leave the Cytochrome complex in the low energy carrier PC.

What occurs at PSI

Electrons from PC are delivered to PSI, where they are re-excited by light. The high energy electrons from PSI go to Fd, and then are transferred to NADP+ by the enzyme NADP+ reductase, making NADPH.

Dark reactions

The energy from the light reactions is used to power the Calvin cycle.

The Calvin cycle uses carbon fixation to trap CO2 and build G3P.

Carbon fixation

CO2 is attached to RuBP by the enzyme Rubisco, generating two 3-carbon molecules

Reduction

the 3-carbon molecules are modified to make glyceraldehyde-3-phosphate (G3P).

Regeneration

five molecules of G3P are use to rebuild (regenrate) three molecules of RUBP.

how many G3P is generated from CO2

For every three CO2 molecules fixed, one G3P is made

Calvin Cycle net reactants and products

3CO2 + 9ATP + 6NADPH + 3RuBP (5C)

goes to

1G3P (3C) + 9ADP + 6NADP + 9pi + 3 RuBP (5C)

Carbohydrates are made of

carbon, hydrogen, oxygen

Carbohydrates are used for

-Fuel

-Structural elements

Monosaccharides

simple sugars (glucose, fructose, galactose)

Glucose and Fructose

most common and are structural isomers. Glucose isn't special

Monosaccharides diversity

Length

Structural isomers

Geometric isomers (Cis vs. Trans)

Disaccharide

double sugars (sucrose, lactose)

Polysaccharides

sugar polymers

metabolism and and monosaccharides

monosaccharides are Fundamental tools for metabolism

storage polyaccharides

Starch (plants)

Glycogen (Animals)

Monomers and polymers are connected by (carbohydrates)

glycosidic linkages formed through dehydration synthesis

Cellulose

structural carbohydrate (repeat glucose)

beta glycosidic linkage

ex. Cellulose

Not digestible

Promote hydrogen bonds

alpha glycosidic linkage

Starch and Glycogen

Digestable

Helical Sugars

unbranched (1-4 glycosidic linkage)

Branched (1-6 glycosidic linkage)

Chitin

Structural carbohydrate some animals have (animals need to shed this)

Starch Metabolism

G3P from photosynthesis may be made into starch or sucrose.

Starch synthesis occurs in the stroma of the chloroplast.

Fructose and Glucose make Starch which is multiple sucrose molecules

Sucrose Metabolism

G3P from photosynthesis may be made into starch or sucrose.

G3P exported to the cytoplasm may become sucrose.

Fructose and Glucose make Sucrose

Catabolism of Glucose

Two ways:

Break bonds

Substrate level phosphorylation

Taking electrons

Oxidative Phosphorylation

Cell respiration pathways

Glycolysis

Transition step

Citric Acid Cycle

Oxidative Phosphorylation

substrate-level phosphorylation

Glycolysis

Citric Acid cycle

Glycolysis

substrates: Glucose, NAD+, ADP, Pi

Products: 2 Pyruvate, 2NADH, 2ATP, 2 H2O

2Phases

Transition step

Pyruvate to Acetyl-CoA in matrix (mediated by pyruvate dehydrogenase complex)

Pyruvate is decarboxylated (removing CO2) uses redox which also reduces NAD+ to NADH

The resulting 2 2 carbon acetate molecules has Co enzyme A via an unstable sulfide bond, making Acetyl CoA

Citric Acid Cycle

Acetyl-CoA enters citric acid cycle, dropping Coenzyme A to be recycled back to transition step.

2C acetate is added to a prexisting 4C molecule, that will be regenerated at end of cycle.

Products of Citric acid cyle for 2 Acetyl-CoA: 2 ATP, 6 NADH, 2 FADH2, 4 CO2

oxidative phosphorylation

powered by NADH and FADH2

10NADH and 2 FADH2 from prior stages

Two entry points complex 1 and complex 2

Oxygen is final Electron acceptor

Path1: Oxidative phosporylation

NADH -> Complex I -> Q -> Complex III -> cyt C -> Complex IV -> O2

Path2: Oxidative phosporylation

FADH2 -> Complex II -> Q -> Complex III -> cyt C -> Complex IV -> O2

Pumps in Oxidative phosphorylation

Complex1, Complex3, and complex 4

ETC makes (Oxidative phosphorylation)

ETC generates an H+ gradient by moving H+ from matrix across the inner membrane into the intermembrane space. This generates the Proton Motive Force

What powers the production of ATP

The facilitated diffusion of H+ back into the matrix through ATP Synthase powers the production of ATP. This process is Chemiosmosis.

PMF and ATP synthase

Oxidative Phosphorylation

Complexes

ETC

ATP synthase

Chemiosmosis

Substrate Level Phosphorylation makes... (ATP)

4 ATP per glucose

NADH makes... (ATP)

3ATP per molecule

FADH2 Makes (ATP)

2ATP per molecule

Oxidative phosphorylation makes (ATP)

38

Net ATP of Cell Respiration

36 ATP

DNP

makes inner membrane permeable to H+ ions

(LOW PMF and LOW Chemiosmosis)

Thermogenin

Uncoupler protein

allows H+ ions to move freely back into the matrix

(LOW PMF and LOW Chemiosmosis)

How can you disable the whole ETC

Prevent any redox reactions after Q

Antimycin

Blocks oxidation of Q by complex 3

(NO PMF or Chemiosmosis)

Cyanide

Blocks reduction of O2

(NO PMF or Chemiosmosis)

Oligomycin

Blocks Transport of H+ through ATP Synthase

(PMF but NO Chemiosmosis)

Hill Reagents

Artificial electron acceptors

(PMF and Chemiosmosis, NO NADPH)

Preventing movement of electrons in photosynthesis ETC

prevents ATP and NADPH from being produced

Preventing the production of NADPH may not holt ATP production

Fermentation

NADH is oxidized by the mitochondrial ETC, regenerating NAD+ needed by the citric acid cycle and glycolysis.

Alternative pathway to regenerate NAD+ when its not working in the Mitochondria

Creates Lactic Acid in Humans and Ethanol in Yeast

Human and Yeast Fermentation

Both consume pyruvate and regenerate NAD+ for glycolysis