BIO101 Ch. 6, 7, 8

energy

the ability to do work or cause change

chemical cycle

biomolecules cycle through the ecosystem from producers, to consumers, to decomposers

producers

produce organic nutrients via photosynthesis

consumers

obtains chemical energy from producers

decomposers

breakdown organic molecules and return inorganic molecules to the ecosystem

energy flows...

through an ecosystem, not cycle. eventually dissipates as heat

kinetic energy

the energy of motion

potential energy

stored energy

e.g. food, energy stored in chemical bonds can be converted to different types of kinetic energy

chemical energy

associated with the bonds between atoms in a molecule

mechanical energy

the energy possessed by an object as the result of its motion

1st law of thermodynamics

"law of conservation of energy"

-energy cannot be created or destroyed

-energy can be converted from one form into another

2nd law of thermodynamics

"law of entropy"

-energy cannot be converted from one form to another without loss of usable energy

entropy

the measurement of disorganization in an energy system

system with low entropy

organized, but less stable

system with high entropy

disorganized, but more stable, energy is dispersed

metabolism

sum of all chemical reactions that occur in a cell or organism

free energy (G)

the amount of energy remaining to do work after a chemical reaction has occurred

The difference in free energy (△G)

[G of reactants] - [G of products]

exergonic reactions

energy is released, spontaneous, favorable reaction

endergonic reactions

energy input is required, not spontaneous, unfavorable reaction

ATP composition

consists of nitrogenous base adenine, 5 carbon sugar ribose, and 3 phosphate groups

ATP cycle

continuous cycle of hydrolysis of ATP to ADP and synthesis ATP from ADP

hydrolysis of ATP to ADP

exergonic reaction

energy is released

phosphate groups can easily be removed

phosphorylation of ADP to ATP

endergonic reaction

energy input is required

functions of ATP

chemical work: supplies energy to synthesize macromolecules

transport work: supplies energy needed to pump substance across cell membrane

mechanical work: supplies mechanical energy

ATP coupled reactions

ATP hydrolysis (exergonic) is coupled with endergonic reactions so that both reactions can occur at the same time

enzymes

increase the rate of chemical reactions without being affected

ribozymes

enzymes composed of RNA and are involved with RNA synthesis and protein synthesis via ribosomes

substrates

the reactants in which enzymes interact with

enzymatic reactions

degrade or synthesize a product

active site

specific part of an enzyme that directly interacts with the substrate

energy of activation

the energy that must be added to cause molecules to react with one another

enzymes increase speed of chemical reactions because they lower the amount of activation energy needed

reaction rate

the amount of product produced per unit of time

factors affecting enzymatic rate

substrate/enzyme concentration, pH, temperature

substrate concentration

enzyme activity increases as substrate concentration increases

optimal pH

every enzyme functions better at optimal pH

any variation in pH can change the physical/chemical characteristics, decreasing energy or causing denaturation

increase in temperature =

increase in enzyme activity

high temperatures in enzymes

enzyme activity levels out then declines because high temperatures denature enzymes, loses its functional 3D shape, cannot interact with substrate

low temperatures in enzymes

decrease of enzyme activity, enzymes become inactive at freezing temperature but can restore activity when temp increases again

ectotherms

cold blooded animals that take on the temperature of their environment, must bask in sun for reactions to occur

e.g. reptiles, fish, amphibians

endotherms

warm blooded animals that maintain constant body temp, requires more energy

e.g. mammals, birds

cofactors

inorganic ions that assist an enzyme at active site

vitamins

small organic molecules that become part of a coenzymes molecular structure

pellagra

disease caused by deficiency of niacin (vitamin B3) resulting in deficiency of NAD+

enzyme activation

regulation of genes:

phosphorylation or dephosphorylation

phosphorylation

addition of a phosphate group via kinase enzymes

dephosphorylation

removal of a phosphate group via phosphate enzymes

enzyme inhibition

occurs when a molecule (inhibitor) binds to an enzyme and decreases its activity

noncompetitive inhibition

inhibitor binds an allosteric site and alters active site, substrate unable to bind

competitive inhibition

the substrate and inhibitor are both capable of binding the active site and compete with each other

a significant portion of pharmaceutical drugs

enzyme inhibitors that alter specific metabolic pathways

end product inhibition

the product of a reaction inhibits the enzyme

oxidation/reduction (redox)

reactions that involve the exchange of electrons from one molecule to another

oxidation of photosynthesis

gain in oxygen, loss of hydrogen, loss of electrons

reduction of photosynthesis

loss of oxygen, gain of hydrogen, gain of electrons

during photosynthesis

-carbon dioxide is reduced to glucose

-water is oxidized to oxygen gas PS

during cellular respiration

-glucose is oxidized to carbon dioxide

-oxygen gas is reduced to water

photosynthesis

the process that captures solar energy and converts it to chemical energy

autotrophs

producers that make their own food

e.g. plants, algae, cyanobacteria

heterotrophs

consumers that must consume organic molecules and autotrophs

algae

simple nonflowering photosynthetic organisms of kingdom Protista, contain chlorophyll

phytoplankton

microscopic marine algae and bacterial autotrophs

ozone layer

oxygen gas layer in the atmosphere that filters radiation from the sun, life would be impossible without it

mesophyll tissue

tissue in green leaves where photosynthesis takes place

stomata

pores in plants that allow entry of carbon dioxide, release of 02 and water vapor

chloroplasts

organelles that carry out photosynthesis

plastid

plant organelles surrounded by double membrane

stroma

semifluid interior that contains thylakoids and enzymes

thylakoids

flattened sacs of thylakoid membrane where chlorophyll and other pigments are found

grana

stacks of thylakoids

2 stages of photosynthesis

1. light reactions

2. Calvin cycle reactions

light reactions

activated by solar energy, produces ATP and NADPH, occurs in thylakoids

Calvin cycle reactions

uses ATP and NADPH generated from light reactions to reduce CO2 into carbohydrates

visible light

electromagnetic waves visible to the human eye

pigments

light absorbing molecules

absorption spectrum

the range of a pigment's ability to absorb various wavelengths of light

chlorophyll (a and b)

dominant pigment involved with photosynthesis reactions

absorbs violet, blue, and red well

green light is not absorbed

carotenoids

accessory pigments that transfer energy to chlorophyll

absorbs violet, blue, green

reflects yellow, orange, red light

noticeable in fall when chlorophyll breaks down

photosystems

consists of pigment complex and electron acceptor molecules that absorb solar energy

noncyclic pathway

typical pathway used by electrons during light reactions, begins with photosystem II, involves PS I

cyclic pathway

only PS I is involved, used to produce additional ATP

How is oxygen gas produced in photosynthesis?

photolysis of water during cyclic pathway of light reactions

electron transport chain in photosynthesis

series of electron carrier proteins embedded within the thylakoid membrane, shuttles electrons from photosystem II to photosystem I and generate a hydrogen ion concentration

Calvin cycle

cyclic series of reactions that converts carbon dioxide into carbohydrates

3 stages-

1. carbon fixation

2. carbon dioxide reduction

3. RuBP regeneration

step 1 of Calvin cycle

Carbon Dioxide Fixation

carbon dioxide is fixed to ribulose-1,5,-bisphosphate (RuBP) via RuBP carboxylase (Rubsisco)

molecule then splits into (2) 3-phosphoglycerate (3PG) molecules

step 2 of Calvin cycle

Reduction of Carbon Dioxide

3-phosphoglycerate (3PG) is reduced to 1,3-bisphosphoglycerate (BPG)

BPG is reduced to glyceraldehyde-3-phosphate (G3P)

ATP and NADPH from light reactions are consumed

step 3 of Calvin cycle

RuBP used in carbon dioxide fixation must be regenerated for the Calvin cycle to continue

ATP is consumed during regeneration

G3P

glyceraldehyde 3-phosphate

end product of Calvin cycle

C3 plants

plants best adapted to cold temperatures and high moisture, 95% of green plants

photo respiration

when CO2 levels are low, and O2 levels are high, rubisco catalyzes RuBP and O2

C4 plants

plants better adapted to hot and dry climates, 5% of green plants

CAM plants

cacti, pineapple, orchids, snake plants

cellular respiration

the gradual cellular process that breaks down nutrient molecules to synthesize ATP

2. oxidation in cellular respiration

2. gain of oxygen, loss of hydrogen, loss of electrons

reduction in cellular respiration

loss of oxygen, gain of hydrogen, gain of electrons

cellular respiration redox reaction

glucose oxidized to carbon dioxide,

oxygen gas reduced to water

coenzymes

assist in redox reactions

NAD+ and FAD

NAD+

carries high energy electrons to the ETC

FAD

flavin adenine dinucleotide, can be used in place of NAD+

phases of cellular respiration

1. glycolysis

2. preparatory reaction

3. citric acid cycle

4. electron transport chain