IB Biology HL C1

enzyme

biological catalyst made by living cells

substrate

reactants converted into products by enzymes

globular proteins

enzyme-substrate specificity

substrates correspond to the shape of the enzyme’s active site

enzymes have absolute or broad specify

factors that affect enzyme activity

substrate concentration

temperature

pH

anabolic

reactions that build larger molecules

requires energy input

catabolic

reactions that break down larger molecules

releases energy

reaction pathways

linear and cyclic

non competitive inhibition

enzymes with allosteric site

when non-substrates bind to allosteric, it causes change in enzyme shape, inhibiting substrate binding

competitive inhibition (2)

competitive inhibitors have a similar shape to enzyme substrates

they temporarily bind to active site, blocking substrate from binding

irreversible inhibition (2)

bond covalently to allosteric or active site, which permantely stops function

considered toxic to biological systems

ATP (2)

adenosine triphosphate

supplied energy for almost all cell processes

synthesized in endergonic reactions

how does ATP produce energy

ATP splits into inorganic phosphate and ADP (exergonic reaction) to release energy

cell respiration (3)

process of breaking down glucose to create ATP

performed by all cells

most energy is used to make ATP, other is lost as heat

phosphorylation

addition of a phosphate group to a mole to destabilize it

makes it more reactive

aerobic respiration (5)

occurs with oxygen

breaks down glucose, fatty acids, amino acids

yields 30 ATP

CO2 is waste product, oxygen + glucose → carbon dioxide + water

occurs in cytoplasm and mitochondria

aerobic vs anaerobic respiration (5)

oxygen use

use of macromolecules

ATP yield

products

where reaction occurs

anaerobic respiration

occurs with no oxygen

breaks down only carbs

produces lactate or ethanol and carbon dioxide

yields 2 ATP

occurs in cytoplasm

lactate fermentation mechanism

1. glycolysis → produces 2 ATP and 2 NADH

2. NADH cannot convert back to NAD without oxygen, so pyruvate is fermented into lactate to fulfill redox reaction

lactate

lactic acid

when it builds up, it is toxic to cells (mostly muscles)

causes soreness/stiffness

requires extra oxygen to convert back to pyruvate

yeast fermentation

anaerobic respiration

yeast undergoes glycolysis to produce pyruvate

pyruvate → ethanal + carbon dioxide → ethanol

bread and alcohol

stages of aerobic cell respiration

1. glycolysis

2. link reaction

3. Krebs cycle

4. ETC and chemiosmosis

carbs vs lipids for respiration

anaerobic ATP production: yes; no

substrate for aerobic: glucose and fructose; fats and oils

energy yield: 17kJ/g; 34 kJ/g

glycolysis

occurs in cytoplasm

1 glucose molecule converts into 2 pyruvate

glucose + 2P + 2ADP + 2NAD → 2pyruvate + 2NADH + 2ATP

link reaction

begins in cytoplasm and in mitochondria

pyruvate converts into acetyl-CoA by oxidative decarboxylation

2 pyruvate + 2NAD +CoA → 2acetyl-CoA + 2NADH +2H + 2CO2

acetyl-coa

all nutrients can be converted to this

if ATP is required, it is used in Krebs

if ATP is not needed, it is stored as fatty acids

Krebs cycle

occurs in mitochondria

C-4 + acetyl-CoA → citrate → C-5 (cycle)

per 1 glucose = 6NADH, 2ATP, 2FADH, 4CO2

use of NADH and FADH

transports H+ to ETC

ETC

electron transport chain

pumps electrons in intermembrane space

NADH goes through 3 pumps: the first two pump 4H+, last pumps 2H+

FADH skips the first pump: pumps 6H+ total

chemiosmosis

channel protein that allows H+ to pass back into matrix

uses build-up of H+ to produce ATP

4H+:1ATP

chemiosmosis structure

transmembrane subunit - drum shape (rotor) with binding sites for H+

large stalk - knob that extends into matrix. active sites that combine ADP and Pi

chemiosmosis mechanism

H+ binds to drum subunit, causing it turn like a turbine

rotation of drum rotates stalk

active sites for ADP and P binding are exposed and bond forms

ejection of ATP

photosynthesis

CO2 + H2O → glucose + O2

occurs in plants to produce oxygen

converts light energy into into chemical energy stored in complex carbon compounds

free air CO2 enrichment experiments (face)

determines effect of CO2 on dependent variable in plantations or forests

CO2 monitored in circular area

electromagnetic radiation

energy that travels in waves

discrete amounts of energies known as photons

human visible range is between 400-700nm

pigments

chemicals that appear coloured

absorb some and reflect other wavelengths

absorption spectrum

graph showing percentage of light absorbed at each wavelength

action spectrum

graph showing rate of photosynthesis at each wavelength

stages of photosynthesis

1. absorption of sunlight (mostly red and blue)

2. light dependent reactions

3. light independent reactions

photosystems

light absorbing proteins in thylakoid membrane

structured arrangement of pigments to absorb larger range of wavelengths

photosystem structure

light harvesting arrays - contains chlorophyll and accessory pigments to absorb light and transfer to reaction centre

reaction centre -contains chlorophyll a molecules. absorbs energy to excite (photoactivation) chlorophyll a molecules. donates excited electrons to electron acceptor.

types of photosystems

PII/P(680) - receives electrons from water, excites, passes to plastoquinone

PI/P(700) - receives electrons from plastocyanin, excites, passes to NADP

PII → plastoquinone → plastocyanin → PI → NADP

photoactivation

absorption of photons to produce excited electrons

occurs in PSII in chlorophyll a of reaction center

photolysis

the splitting of water molecules using light energy into oxygen, protons (H+H+), and electrons (e−e−)

2H2O→4e−+4H++O2

electrons travel to PSII

chemiosmosis and ATP synthase in photosynthesis

same as cellular respiration

light independent reactions

calvin cycle

occurs in stroma

converts CO2 into carbohydrates with ATP and NADPH

phases of calvin cycle

1. carbon fixation - CO2 reactions with RuBP to produce 3C (catalysed by rubisco)

2. reduction - using H+ from NADPH, reactant is reduced to triose phosphate

3. regeneration of RuBP - converts 3c (triose phosphate) into 5c (RuBP) with 3 ATP

synthesis of triose phosphate

two triose phosphate create glucose → two glucose create fructose then sucrose (most soluble for transport)

can make acetyl-coa for cellular respiration

bright light cyclic photophosphorylation

in bright light, NADPH doesn’t oxidize into NADP fast enough

energy from electrons in PSI get used ad increases H gradient so chemiosmosis is faster

reduction of NADP

occurs with NADP reductase

electrons in plastocyanin replace those lost and give potential energy to photoactivation.

electrons are transferred to ferredoxina dn then NADP reductase

thylakoid membrane structure

grana - stacked thylakoid discs

stroma lamellae - unstacked between grana that increase SA:V ratio, more PS I and ATP synthase exposed (faster ATP synthesis and NADPH production)

intracellular enzymes

come from free ribosomes

ex. glycolysis, Krebs

extracellular enzymes

made by ribosomes embedded in endoplasmic reticulum

eg. digestive enzymes

formation of products in enzymes

1. substrate successfully collides with enzyme active site

2. when the substrate binds, it induces change in active site, causing bond to destabilize. this favours bond formation of products

3. product bond forms and release from active site

light-dependent reactions

uses light directly

involves photolysis of water

converts light energy into chemical energy in form of ATP and NADP

limited at low CO2 and low light environments (PSII needs right levels of CO2 to have right shape to pass electrons to plastocyanin)

light-independent

calvin cycle

does not use light directly, but is limited since ATP and NADPH can’t be produced

occurs in stroma

results in carbon fixation