Metabolism, Cellular Respiration, & Photosynthesis

Created by Bex28 

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All of the chemical reactions within a living organism.


Breakdown of more complex substances into simpler ones with release of energy, -G, Exergonic, Hydrolysis, spontaneous


The process that synthesizes a complex molecule from simpler compounds, thus requiring energy, +G, Endergonic, not spontaneous


A process that can occur without an input of energy.


the process of producing a chemical compound (usually by the union of simpler chemical compounds)


a chemical process in which a compound is broken down and changed into other compounds by taking up the elements of water.

What is energy?

The capacity to do work

What is Free energy-Gibb's free energy?

The portion of a system's energy that can perform work when temperature and pressure are uniform throughout the system, as in a living cell; a measure of a system's instability, meaning its tendency to change to a more stable state.

What does it mean to have a positive or negative Delta G?

+G = increases free energy, non spontaneous, unstable
-G = decreases free energy, spontaneous, stable

Delta G = Delta H - T Delta S

How the change in free energy can be calculated. Delta H = enthalpy (total energy)
Delta S = Change in system's entropy (randomness)
T = Absolute temperature in Kelvin (k) Units

Spontaneous Reaction

Term used to describe a reaction that will occur without additional energy

Non-spontaneous Reaction

A reaction that cannot occur without the input of work from an external source

Exergonic Reaction

A spontaneous chemical reaction in which there is a net release of free energy.

Endergonic Reaction

A non-spontaneous chemical reaction in which free energy is absorbed from the surroundings.

Chemical Work

The type of cellular work that includes the pushing of endergonic reactions, which would not occur spontaneously, such as the synthesis of polymers from monomers.

Transport Work

The type of cellular work that includes the pumping of substances across membranes against the direction of spontaneous movement.

Mechanical Work

The type of cellular work that includes the beating of cilia, the contraction of muscle cells, and the movement of chromosomes during reproduction.


The transfer of a phosphate group, usually from ATP, to a molecule. Nearly all cellular work depends on ATP energizing other molecules by phosphorylation.

Relationship of Catabolism in Regards to ATP

Catabolism releases energy (ATP).

Relationship of Anabolism in Regards to ATP

Anabolism requires energy (ATP).


A protein serving as a catalyst, a chemical agent that changes the rate of a reaction without being consumed by the reaction.

Active Site

The part of an enzyme molecule where a substrate molecule attaches (by means of weak chemical bonds); typically, a pocket or groove on the enzyme's surface.


The substance acted upon by an enzyme.

Specificity of an Enzyme

Attributed to a compatible fit between the shape of its active site and the shape of its substrate.; as a substrate enters the active site, interactions between its chemical groups and those on the R groups of the amino acids that form the active site of the protein cause the enzyme to change its shape slightly.

What causes an enzyme to denature?

Temperature, Salt Concentrations, and pH levels.

Optimal Enzymes

Particular temperature, salt concentration, or pH level that is the best possible condition that the enzyme will work in.


Any non protein molecule or ion that is required for the proper functioning of an enzyme. Cofactors can be permanently bound to the active site or may bind loosely with the substrate during catalysis.


An organic molecule serving as a cofactor. Most vitamins function as coenzymes in important metabolic reactions.

Induced Fit

Brings chemical groups of the active site into positions that enhance their ability to catalyze the reaction ("Clasping Handshake").


Substances that slow or stop enzymes.

Competitive Inhibitor

Reduce the product of enzymes by blocking substrates from entering active sites. (They try to BEAT the enzyme to the active site.)

Noncompetitive Inhibitor

They impede enzymatic reaction by binding to another part of the enzyme. This causes the enzyme to change shape in such a way that the active site is less effective.

Allosteric Regulation

The term used to describe any case in which a protein's function at one site is affected by the binding of a regulatory molecule to a separate site; oscillates between an inactive and active form; 3 to 4 enzymes together to form an allosteric.

Delta G (Enzymes)

Enzymes do NOT change Delta G.

Feedback Loops

Return of portion of output of a system, especially when used to maintain output within predetermined limits; it can alter or end the reaction (negative feedback) or to signal a need to modify system to produce more (positive feedback).

Cellular Compartmentalization

Organelles do specific functions; specialized organelles that have to perform certain functions.

Aerobic Respiration

Requires oxygen; Creates more ATP (more efficient); Krebs/Citric Acid Cycle; Cellular Respiration; Oxygen=Final Acceptor

Anaerobic Respiration

Does not require oxygen; Glycolysis Stage; Fermentation; Less efficient (less ATP); Final Acceptor=electron.

When does Fermentation occur?

It occurs if there is an absence of oxygen.

What is the chemical formula for Cellular Respiration?

C6 H12 O6+ 6O2= 6CO2+6H2O+Energy (Heat + ATP)

What is oxidized in Cellular Respiration?

Glucose is oxidized; loss of electrons.

What is reduced in Cellular Respiration?

Oxygen is reduced; adding of electrons.

What are the four phases of Cellular Respiration?

1. Glycolysis
2. Transition Reaction
3. Citric Acid Cycle
4. Electron Transport / Chemiosmosis

How do electron transport chains work?

Electrons removed from glucose are shuttled by NADH to the "top," higher energy end of the chain. At the "bottom," lower energy end, O2 captures these electrons along with hydrogen nuclei (H+), forming water.

Where does Glycolysis occur?

In the cytoplasm.

Where does Transition Reaction occur?

The matrix of the mitochondria.

Where does Citric Acid Cycle occur?

In the mitochondrial matrix.

Where does Electron Transport / Chemiosmosis occur?

Inner membrane of mitochondria.

What are the end products of Glycolysis for ONE glucose molecule?

2 Pyruvic Acids
2 ATPs

Where is the energy from the food transferred to during glycolysis?

Coenzymes, NADH+, FADH.

What occurs during the Transition Reaction?

Modifying pyruvates into Acetyl CoA.

What is the energy investment phase in Glycolysis?

The cell spends ATP. This investment is repaid with interest during the energy payoff phase.

How many enzymatic reactions occur during glycolysis?


What is necessary to enter into Kreb's cycle?

Acetyl CoA.

Oxaloacetate and Acetyl CoA combine to form what first during Kreb's cycle?


What are the end products of Kreb's cycle?


How many proteins are involved in the electron transport system?

3 Trans membrane Proteins.

What are the electron carriers during cellular respiration?

Through a series of reactions, the "high energy" electrons are passed to oxygen. In the process, a gradient is formed, and ultimately ATP is produced.

How much ATP total is produced?

38 ATP (Bacteria); 36 ATP (Eukaryotes)

How many ATP are created per NADH?


How many NADH are created during CR?


How many ATP are created per FADH?


How many FADH are created during CR?


Describe the process of alcohol fermentation?

Pyruvate is converted to ethanol in two steps. The first step releases CO2 from the pyruvate, which is converted to the two-carbon compound acetaldehyde. Then, that is reduced by NADH to ethanol.

Describe the process of lactic acid fermentation?

Pyruvate is reduced directly by NADH to form lactate as an end product, with no release of CO2.

How are fatty acids metabolized to enter into CR?

Beta oxidation -> Enter into Kreb's Cycle -> No Glycolysis

Chemical equation for photosynthesis.

6CO2 + 12H20 + Sunlight = C6H12O6 + 6O2 +6H20 + Heat


Process by which plants use the sun's energy to convert water and carbon dioxide into sugars; their way of making food.


These organisms use light energy to drive the synthesis of organic molecules from CO2 and (in most cases) water; Ex: algae, plants.


An organism that obtains organic food molecules without eating other organisms or substances derived from other organisms. Autotrophs use energy from the sun or from the oxidation of inorganic substances to make organic molecules from inorganic ones.


Organisms that obtain food by consuming other living things. "self-feeders"

Are there any prokaryotic photoautotrophs or are all photoautotrophs always plants?

There are some Prokaryotes.

Describe the structure of chloroplasts.

-More complex than mitochondria
-Inner membranes form disc-like structures called Thylakoid
-Stack is called Granum
-Cytoplasm (matrix) is called Stroma

Purpose of stomata.

Gas exchange.

What are the two main phases of photosynthesis?

Light reactions (the Photo part of PS) & Calvin cycle (the synthesis part of PS)

What do Photosystem I and Photosystem II do during the light reactions during PS?

PSI = loads up electrons onto NADPH
PSII = Water molecules split to form and release oxygen.

What is reduced during PS?

Carbon Dioxide is reduced during PS. (It gains electrons.)

What is oxidized during PS?

Water is oxidized during PS. (It loses electrons.)

What are the end products of light reactions?

(1) ATP, (2) NADPH + H+ (Hydrogen Ions), (3) O2

Why are the end products necessary for the Calvin Cycle?

To split water, release oxygen, produce ATP, and form NADPH.

What is the spectrum within visible light?

The segment most important to life is the narrow band from about 380 nm to 750 nm in wavelength.

What wavelengths are the most effective during PS?

Ultra-Violet and Red.

What wavelength is the least effective?

Green = 500 nm.

Why are leaves green?

Interaction of light with chloroplasts; green light is reflected or transmitted and all other colors are absorbed in the chloroplasts; very little green light absorbed by chlorophyll.

What are the pigments involved in photon absorption?

Chlorophyll a, chlorophyll b, and carotenoids.

How does an electron get to an excited stage?

Pigment's electron gains energy.

What does the reaction center within a photosystem do?

Splits water to make molecular oxygen - releases hydrogen ions.

What else do light reactions produce?

Oxygen & ATP

Why is this called chemiosmosis?

It is the movement of ions.

What is needed to start the Calvin cycle?

Carbon dioxide.

What are the steps of the Calvin Cycle?

1. Carbon Fixation
2. Reduction
3. Regeneration of the CO2 Acceptor (RuBP)

What is actually produced at the end of the Calvin Cycle?


What are C3 plants?

Plants that enter the Calvin cycle and are fixed into 3-phosphoglycrate by the enzyme Rubisco.

What are C4 plants?

Corn, Crabgrass, & Sugar cane.

What are CAM plants?

carry out a form of photosynthesis that adapts them to dry conditions known as crassulacean acid metabolism. plants keep their stomatas closed during the day and open at night. the reverse of how other plants work. (Pineapples and Cactus)

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