unit 3 - cellular energetics

bioenergetics

the study of how energy from the sun is transformed into energy in living things

first law of thermodynamics

energy can’t be created or destroyed // sum of energy in the universe is constant

exergonic reaction

products have less energy than reactants; energy is given off

endergonic reactions

require an input of energy; products have more energy than the reactants

transition state

a high energy molecule that reactants must turn into before becoming products; difficult to achieve

activation energy

certain amount of energy required to reach the transition state

how does activation energy work

chemical bonds must be broken before new ones can form

enzymes

biological catalysts that speed up reactions

enzyme specificity

each enzyme catalyzes only one kind of reaction

substrates

targeted molecules

enzyme-substrate complex

enzymes make the transition state happen by helping substrates get into position

active site

special region on the enzyme where substrates go

how do the structures and active sites relate?

structure (shape and charge) must be compatible with active site of an enzymea

what happens to an enzyme after a reaction

it’s released and goes back to its original state

induced fit

enzyme has to slightly change its shape to fit the substrate

cofactors

factors that sometimes help enzymes catalyze reactions

conenzyme

a type of cofactor; organic molecule, inorganic molecule, ion

what can affect an enzymatic reaction

temperature and pH

what determines reaction speed

concentration of an enzyme and substrate

at what temperature are enzymes denatured?

42 degrees celsius

denatured

what happens when an enzyme is denatured by heat and isn’t able to catalyze reactions anymore

what is the optimum temperature for most human enzymes to function

37 degrees celsius

how does pH alter enzymes

hydrogen bonds are disrupted and structure is altered

what is the optimum pH for most enzymes

7

when there is a high concentration of substrates, what happens to a reaction?

initially speeds up, once all of the enzymes are bound to a substrate, reaction can’t speed up any longer

saturation point

the point where all enzyme are bound to substrates

how does a cell regulate enzyme activity

regulating conditions that influence enzyme shape

allosteric sites

somewhere on the enzyme that substrates can bind to that isn’t the active site

competitive inhibition

a substance binds to the active site in place of the substrate

noncompetitive inhibitor

when an allosteric inhibitor binds to allosteric site

what happens to ATP when a cell needs energy?

the third phosphate is broken off: ATP → ADP + P + energy

how can endergonic reactions be powered

by organisms using exergonic processes that increase energy

cellular respiration

breaking down sugar and making ATP

photosynthesis

how autotrophs get sugar for ATP

what was the earliest photosynthesis done by

prokaryotic cyanobacteria

what is the formula for photosynthesis?

6CO2 + 6H2O → C6H12O6 + 6O2

what happens when light initially strikes a leaf

chlorophyll is activated, electrons are excited

what happens after chlorophyll is activated

sends electrons down electron carriers, which makes ATP and NADPH

What happens to ATP, NADPH, and CO2 during dark reactions

used to make carbs, H2O is split and O2 is released

stroma

fluid filled region

grana

structures in the chloroplasts that look like coin stacks

thylakoids

individual discs within granum; have chlorophyll

chlorophyll

light-absorbing pigment that drives photosynthesis

thylakoid lumen

interior thylakoid

what are the types of reaction centers

photosystem I and photosystem II

photophosphorylation

when light is used to make ATP

absorption spectrum

shows how well a certain pigment can absorb electromagnetic radiation

what happens right after a leaf captures sunlight

energy is sent to P680 and forms active electrons

what is P680

reaction center of PS II

what is P700

reaction center of PS I

photolysis

H2O is split into O2, H2, ions, electrons

where do the electrons from photolysis go

replace missing ones in PS II and replenish those from the thylakoid

what establishes a proton gradient in the ETC

H+ ions being pumped into thylakoid lumen as energized e- from PS II

How is ATP produced during PS II

H+ ions move back into the stroma through ATP synthase

where do e- go after leaving PS II

PS I; they’re passed through a second ETC

when do e- stop on the second ETC

when they reach NADP+ to make NADPH

cyclic electron flow

makes only ATP, no NADPH

what mainly happens during the light independent reactions

use products of light reactions (NADPH and ATP) to make sugar

carbon fixation

CO2 from air is converted into carbs

where does carbon fixation occur?

stroma

what is another term for dark reactions/light independent reactions?

Calvins cycle

stomata

pores on the leaf that allow CO2 to enter the leaf, and O2 and H2O to exit

what do plants do on hot and dry days to their stomata

close them to prevent water loss → limits CO2 access / reduces photosynthetic yield

photorespiration

uses ATP and O2, produces more CO2, doesn’t make sugars

what is the formula for cellular respiration

C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP

aerobic respiration

when ATP is made in the presence of O2

anaerobic respiration

when ATP is made without O2

what are the four stages of aerobic respiration

glycolysis, formation of acetyl-coA, krebs/citric acid cycle (CAC), oxidative phosphorylation

pyruvic acid

3 C molecules that form when glucose (6C) splits, one glucose breaking down results in 2 pyruvic acid and 2 ATP

how is ATp made in glycolysis

combining ADP and an inorganic phosphate (using an enzyme)

how many NADH does glycolysis make?

2; comes from e- transfer to carrier NAD+ (turns to NADH)

where does glycolysis occur

cytoplasm

where does the formation of acetyl co-A occur?

mitochondrion

what types of C molecules are present in the beginning of the formation of acetyl-coA

two 2-C molecules, extras left as CO2

acetyl coA

2C molecule

how many NADH are made for every initial glucose

2

where does the kreb’s cycle occur

matrix of the mitochondria

what happens to both acetyl-coA molecules as soon as they enter the Kreb’s cycle

turned into CO2

electron transport chain

e- take energy from glucose and carry it with themthe

at the start of oxidative phosphorylation, how many NADH, FADH2 have been produced?

10 NADH, 2 FADH2

what do NADH and FADH do

shuttle e- to ETC → forms NAD+, FADH, can be reused

electron transport chain

a series of protein carrier molecules embedded in cristae

what is the final acceptor in the ETC

O2

what happens when the e- get to the final acceptor

O2 + e- + H+ → H2O

what would happen if there weren’t O2 in the ETC

e- wouldn’t move down it, shuts down electron transport

chemiosmosis

H+ ions from original H atom are pumped across inner mitochondrial membrane from the matrix into inner membrane space; pumping/diffusion of ions

when does chemiosmosis happen

at the same time as electron transport, uses energy released from ETC

pH/proton gradient

caused by the pumping of H+ ions; difference of the concentration of H+ across a membrane

\

what is the only way H+ ions diffuse across a membrane

ATP synthase

oxidative phosphorylation

when e- are given up, it’s ‘oxidation’ and ADP is phosphorylated to make ADP

what must be maintained about an enzyme

the tertiary shape

negative control

not exposed to experimental treatment or any treatment known to have effect

positive control

exposed to treatment that is known to have an affect / no exposed to experimental treatment

controlled variable

aspects of an experiment that could be changed but aren’t intentionally

what does a decrease in temperature do to reaction rate

slows it down; fewer enzyme-substrate collisions

what is the only way reaction rate will stay constant

saturation levels are maintained

how do cells manage energy resources

energy coupling; energy releasing processes drive energy storing processes

what does it mean for pathways in biological systems to be sequential

product of one reaction can be a reactant in the next; allows for more controlled and efficient energy transfer

where is chemical energy temporarily stored during light dependent reactions

NADPH

what transfers stored chemical energy to power production of organic molecules in light dependent reactions

ATP and NADPH