Bio 240W Exam 1

Explain the significance of photosynthesis to other living organisms

\-It is the only biological process that can capture solar energy and convert it into chemical compounds that every organism uses to power its metabolism.

\-It is also a source of oxygen necessary for many living organisms

Describe short and long wavelengths of light

\-Red and below have long wavelengths, low frequency and low energy

\-Violet and above have short wavelengths, high frequency and high energy

Explain why organisms can only use a small portion of the electromagnetic spectrum for living processes

\-Energy levels lower than those represented by red light are insufficient to raise an orbital electron to an excited (quantum) state.

\-Energy levels higher than those in blue light will physically tear the molecules apart, in a process called bleaching.

\-Visible light/ useable energy has wavelengths between 400 nm and 700 nm.

Assess the roles of pigments in photosynthesis and in capturing light

\-Pigments absorb specific wavelengths of visible light

\-Different kinds of pigments exist and each absorbs only specific wavelengths of visible light, and reflects or transmits the wavelengths they cannot absorb.

\-Chlorophyll a is the main photosynthetic pigment

What is the main photosynthetic pigment in plants? What are the accessory pigments and what do they do?

\-Chlorophyll a is the main photosynthetic pigment

\- Chlorophyll b broadens the spectrum used for photosynthesis

\-Carotenoids absorb excessive light that would damage chlorophyll

Interpret the role of the thylakoid membranes in photosynthesis

\-Light reactions!!!

\-Where photosystem II and photosystem I are embedded

\-Split H2O and release O2

–Reduce NADP+ to NADPH

–Generate ATP from ADP and Pi by photophosphorylation

\-Thylakoids transform light energy into chemical energy in the form of ATP and NADPH

\-Where the electron transport chain takes place

Distinguish the flow of electrons and protons during linear electron transport and cyclic electron transport and evaluate their outcomes

Linear electron flow

\-the primary pathway

\-involves both photosystems (ETC)

\-produces ATP and NADPH using light energy

\-oxygen is released by the splitting of water

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Cyclic electron flow

\-uses only PS I

\-produces ATP, but not NADPH

\-No oxygen is released

\-generates surplus ATP, satisfying the higher demand in the Calvin cycle

Demonstrate how the hydrogen ion gradient across the thylakoid membrane is produced

As electrons move through the proteins that reside between PSII and PSI, they lose energy. This energy is used to move hydrogen atoms from the stromal side of the membrane to the thylakoid lumen.

\-will be used to synthesize ATP in a later step.

Explain how ATP is produced through photophosphorylation

light energy is used to pump protons across the thylakoid (mediated by flow of electrons through an electron transport chain) This stores energy in a proton gradient. As the protons flow back through an enzyme called ATP synthase, ATP is generated from ADP and inorganic phosphate.

Explain the importance of redox reactions in photosynthesis

Light + 6 CO2 + 6 H2O → C6 H12 O6 + 6 O2

CO2 is reduced to C6 H12 O6

H2O is oxidized to O2

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No free electrons!

Is what allows us to use and store solar energy for our lives

Describe the inputs and outputs for the carbon reactions/Calvin cycle

Inputs

\-ATP

\-NADPH

\-CO2

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Outputs

\-ADP + P

\-NADP+

\-sugar (G3P for C3 plants)

Explain the importance of Rubisco in the carbon reactions/Calvin cycle

\-Carbon fixation is catalyzed by Rubisco

\-accounts for 50% of soluble protein in leaves

\-also catalyzes RuBP + O2 reaction

\-nitrogen source?

Describe the relationship between the light reactions and the carbon reactions/Calvin cycle

Outputs of one are used as the Inputs of the other

Describe how the inputs of photosynthesis are related to the outputs/products, specifically the flow of carbon, hydrogen, and oxygen

The inputs go through redox reactions to make the outputs

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Light + 6 CO2 + 6 H2O → C6 H12 O6 + 6 O2

CO2 is reduced to C6 H12 O6

H2O is oxidized to O2

Explain how photosynthesis works in the energy cycle of all living organisms

Chloroplasts

\-collect energy from the sun

\-use carbon dioxide and water in the process called photosynthesis

\-produce sugars.

Animals

\-can make use of the sugars provided by the plants in their own cellular energy factories

So photosynthesis gives us and plants energy.

Define homeostasis and distinguish from homeodynamics.

homeostasis-maintenance of equilibrium around a specific value of some aspect of the organism or its cells ----keeps the body in dynamic equilibrium by constantly adjusting to the changes that the body’s systems encounter

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homeodynamics- A dynamic form of homeostasis involving the constantly changing interrelatedness of the body components while an overall equilibrium is maintained

Describe the different steps of the signal transduction pathway.

\-Environmental or developmental signal (can be internal or external)

\-Receptor (or sensor)

\-Signal transmission/transduction

\-Response (by an effector)

Compare and contrast negative feedback and positive feedback loops

Positive feedback

\-Keeps a process going that has a cutoff point

\-does NOT maintain homeostasis

\-An effector (provides response or effect) continues to stimulate a sensor/receptor so that a greater change occurs in the internal environment

Negative feedback

\-Primary homeostatic mechanism

\-Keeps variable close to set point

Give an example of positive feedback and negative feedback

Positive feedback

\-Childbirth

Negative feedback

\- Body temperature

\-Water potential in plants

Provide examples of receptors, control centers, and effectors in a negative feedback loop.

In terms of body temperature

Receptors: Temperature-sensitive cells in the skin and brain

Control Center: thermoregulatory center in the brain

Effectors: Sweat glands (hot) or Skeletal muscles (cold)

What are reduction and oxidation

Reduction—gain an electron Oxidation—lose an electron

Early investigators thought the oxygen produced by photosynthesis came from carbon dioxide. We now know it comes from…

Water

The primary function of the light reactions of photosynthesis is

to produce energy-rich ATP and NADPH, and oxygen

Which color light is the least effective in photosynthesis

Green light

As electrons are passed down the ETC associated with PS II, they lose energy. What happens to this energy?

It is used to establish and maintain a proton gradient

Which of the following are directly associated with Photosystem I?

A) receiving electrons from the thylakoid membrane electron transport chain

B) generation of molecular oxygen

C) extraction of hydrogen electrons from the splitting of water

D) passing electrons to the cytochrome complex

A) receiving electrons from the thylakoid membrane electron transport chain

The ATP synthase in the thylakoid membrane is sometimes called a “coupling factor.” What is this enzyme coupling?

ATP synthesis with the proton gradient

Why is no NADPH produced in cyclic electron flow?

Electrons flow from ferredoxin to the cytochrome c complex instead of to NADP+ reductase

Discuss the role of ATP in energy transfer in the cell

\-allows the cell to store energy briefly and transport it within the cell to support endergonic chemical reactions.

\-Energy derived from glucose catabolism is used to convert ADP into ATP.

\-Two processes of ATP regeneration are substrate-level phosphorylation and oxidative phosphorylation through the process of chemiosmosis.

\-Energy must be infused into the system to regenerate ATP.

Describe the two major types of phosphorylation: substrate and oxidative

Substrate:

\-Only a few ATP molecules are made

\-a direct result of the chemical reactions that occur in the catabolic pathways

\-A phosphate group is removed from an intermediate reactant

\-the free energy of the reaction is used to add the third phosphate to an available ADP

\-very direct method of phosphorylation

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Oxidative:

\-Many ATP molecules are made

\-much more complex process, chemiosmosis,

\-takes place in mitochondria.

\-involvement of oxygen in the process

Describe the overall result in terms of molecules produced during the chemical breakdown of glucose by glycolysis

\-the first pathway used in the breakdown of glucose to extract energy.

\-Glycolysis consists of two parts

* prepares the six-carbon ring of glucose for cleavage into two three-carbon sugars. 2 ATP are used in the process
* extracts ATP and high-energy electrons from hydrogen atoms and attaches them to NAD+. Four ATP molecules are formed by substrate phosphorylation

Compare the output of glycolysis in terms of ATP molecules and NADH molecules produced

Inputs

\-2 ATP

\-2 NAD+

\-1 glucose

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Outputs

\-4 ATP (2 net)

\-2 NADH

\-2 pyruvate

Describe how electrons move through the electron transport chain and explain what happens to their energy levels during this process

\-The electron transport chain is the last component of aerobic respiration

\-The electrons are passed through a series of redox reactions, with a small amount of free energy used for proton gradient

\-The electrons gradually lose energy

\-High-energy electrons are donated by either NADH or FADH2

\-End the chain, as low-energy electrons reduce oxygen molecules and form water.

Describe how a proton (H+) gradient is established and maintained by the electron transport chain and used in the process of chemiosmosis

\-a series of redox reactions is used to pump hydrogen ions across the mitochondrial membrane.

\-The uneven distribution of H+ ions establishes both concentration and electrical gradients

\-hydrogen ions pass through the inner mitochondrial membrane by an integral membrane protein called ATP synthase.

\-the proton gradient is used for the addition of a phosphate to ADP, forming ATP

Discuss the process of metabolism used by organisms when oxygen is unavailable.

\-If NADH cannot be oxidized through aerobic respiration, another electron acceptor is used.

\-use some form of fermentation to accomplish the regeneration of NAD+

\-NADH to produce ATP using an electron transport chain is not utilized.

Lactic acid fermentation

\-used routinely in mammalian red blood cells, and in skeletal muscle that has an insufficient oxygen supply

Alcohol Fermentation

\-produces ethanol

\-fermentation of pyruvic acid by yeast produces the ethanol found in alcoholic beverages

What happens during the Citric Acid cycle/Krebs cycle?

\-pyruvate oxidized completely to CO2 and acetyl CoA

•2 ATP

•6 NADH + 2 FADH2 for electron transport

•per 1 glucose