energy processing - biology

photosynthesis and cellular respiration

exergonic

exergonic

change of Gibbs free energy is negative (Δg<0)

releases energy, occurs spontaneously

(think ex=exit)

endergonic

change of Gibbs free energy is positive (Δg>0)

uses energy, does not occur spontaneously

anabolic reactions

build molecules and store energy

anabolic pathways

build larger molecules from smaller molecules by creating chemical bonds

endergonic

catabolic reactions

break down molecules and releases energy

catabolic pathways

breaks down larger molecules into smaller molecules by breaking down chemical bonds

exergonic

-ase

enzyme suffix

enzyme

biological catalyst which speeds up chemical reactions in a cell

lowers activation energy (the energy needed to start a chemical reaction)

causes chemical reactions to occur faster

substrate

a molecule that the enzyme binds to cause a reaction to occur

active site

part of the enzyme that fits with the substrate in a “lock and key manner”

shaped to only be able to bond with the substrate

why are enzymes specific

enzyme only binds to a specific substrate

can only catalyze one type of reaction

enzymes are specific but reusable (does not change shape after chemical reaction)

fixation

a gaseous molecule that is taken from the atmosphere and “fixed” or put into a molecule consumable by plants and animals

(ex: carbon)

obligate anaerobe

cells that cannot survive in the presence of oxygen

obligate aerobe

cells that require oxygen

facultative anaerobe

cells that can survive in the presence or absence of oxygen

how do anabolic pathways and catabolic pathways work together

energy released from a catabolic pathway from breaking down chemical bonds is reused as a temporary energy storage molecule otherwise known as ATP, to be used in an anabolic reaction

how does a ATP molecule provide energy

energy stored in the bonds between the phosphate groups is broken down (via hydrolysis) which releases energy

how does an ATP molecule store energy

energy is stored in the bonds between the phosphate groups, built via dehydration hydrolysis

two types of enzyme inhibition

competitive inhibition

non-competitive inhibition

competitive inhibition

a competitive inhibitor molecule will bind at the active site and block the normal substrate from binding

non-competitive inhibition

a non-competitive inhibitor molecule binds at a site that is different from the active site

binding of the inhibitor changes the shape of the active site, making it unable to bind with the substrate

difference between enzyme inhibition and enzyme denaturing

enzyme inhibition: certain chemicals work to stop or inhibit the enzymes, thus blocking them from binding with the substrate

enzyme denaturing: past optimum temperature/outside optimal pH level enzyme begins to denature -> changes structure and shape of active site -> substrate can no longer bind

enzyme denaturation means an enzyme loses its function unlike enzyme inhibition

endergonic reaction graph

goes up

exergonic reaction graph

goes down

photosynthesis

uses energy to convert carbon dioxide and water into simple sugars through the creation of chemical bonds

anabolic

endergonic

cellular respiration

breaks down chemical bonds in glucose to release energy (ATP)

catabolic

exergonic

photosynthesis and cellular respiration work together to carry out metabolism in living things by

photosynthesis produces energy whereas cellular respiration consumes energy

(metabolism is the chemical reactions that occur within a living organism to maintain life)

photosynthesis equation

6 CO2 + 6 H2O + Light Energy ➜ C6H12O6 + 6O2

cellular respiration

C6H12O6 + 6O2➜ 6 CO2 + 6 H2O + ATP

two phases of photosynthesis

light-dependent reactions

light independent reactions (calvin cycle)

light-dependent reactions

requires sunlight

occurs in the thylakoid membranes

light energy trapped by chlorophyll and temporarily stored in NADPH and ATP molecules

light-dependent reaction equation

2 H2O + Light Energy ➜ O2 + NADPH + ATP

where does carbon fixation occur

in light-independent reactions

carbon fixation

carbon in carbon dioxide from the atmosphere that is “fixed” or put into a molecule of glucose during the Calvin Cycle

cellular respiration breaks down glucose and releases carbon back as gas (decarboxylation)

this is called the carbon cycle

light independent reactions (calvin cycle)

does NOT require sunlight

also conducts carbon fixation

occurs in the stroma

CO2 from the environment and ATP + NADPH created during light-dependent reactions used to produce glucose

light independent reactions equation

CO2 + ATP + NADPH ➜ C6H12O6

four phases of cellular respiration

glycolysis

pyruvate decarboxylation

citric acid cycle (Krebs cycle)

oxidative phosphorylation

glycolysis

occurs in the cytoplasm

glucose is split in half to form two molecules of pyruvate (a 3-carbon molecule)

2 ATP are needed to start glycolysis and 4 ATP are made, forming a +2 net ATP

produces 2 ATP

glycolysis equation

Glucose + 2 ATP ➜ 2 Pyruvate + 4 ATP

pyruvate decarboxylation

MUST occur because the next cycle (citric acid/Krebs cycle) CANNOT process 3 carbon molecules

removed carbon is given off as 2 CO2 molecules

produces 0 ATP

pyruvate decarboxylation equation

2 C3H6O3 ➜ 2 Acetyl CoA + 2 CO2

citric acid cycle (Krebs cycle)

completes the breakdown of the original glucose molecule

one acetyl-CoA can go through the cycle at a time

each produces 1 ATP and releases 2 carbons as 2 CO2 molecules

produces 2 ATP

citric acid cycle equation

2 Acetyl CoA ➜ 2 ATP + 4 CO2

oxidative phosphorylation

produces 34 ATP and H2O

oxygen is used and joined with hydrogen to form water

dehydration synthesis; anabolic

phosphates are added (phosphorylation) to ADP to produce ATP

why is the yield for oxidative phosphorylation 36-38 ATP molecules

some energy is used to move molecules around and into the mitochondria

photosynthesis and cellular respiration in the carbon cycle

photosynthesis takes gaseous carbon in the CO2 out of the atmosphere and makes it a solid in Glucose

cellular respiration breaks down glucose, releasing the carbon back into the atmosphere as a gas in CO2

fermentation

occurs when oxygen is not available

starts at glycolysis

obligate anaerobes and facultative anaerobes can still break down glucose and produce a small amount of ATP

produces 2 ATP

fermentation equation

Glucose + 2 NAD + 2 ATP ➜ 2 pyruvate +2 NADH + 4 ATP

why does fermentation occur

allows glycolysis to continue

(regeneration of NAD+ so glycolysis can continue)

not really for its ATP production

two types of fermentation

lactic acid

ethanol

lactic acid fermentation

pyruvate ➜ lactic acid + NAD+

ethanol fermentation

pyruvate ➜ ethanol + CO2 + NAD+

difference between cellular respiration and fermentation

aerobic cellular respiration yields

36 to 38 ATPs

fermentation yields only

2 ATPs