A Level Biology: ATP Importance & Synthesis

• GCE A Level WJEC Biology Unit 3 Revision Guide, authored by experienced teachers, may not cover every specification aspect or represent the required knowledge depth.

Importance of ATP

• ATP is a nucleotide serving as the major energy currency for all cellular reactions

• ATP is inert, soluble, easily transported, and releases energy efficiently

• ATPase hydrolyzes the terminal bond of ATP, releasing usable energy with minimal heat waste

• ATP reforms through phosphorylation, which is the addition of a phosphate group (Pi) to ADP via a condensation reaction

• Most ATP synthesis occurs on the internal membranes of mitochondria and chloroplasts

• Protons must pass through ATP synthetase, found in the stalked particles of inner membranes

• This proton flow generates an electrochemical gradient, providing potential energy

• ADP phosphorylation, driven by the electrochemical gradient, forms ATP, which stores chemical energy, and the whole process is called chemiosmosis

• Chemiosmosis involves proton flow down an electrochemical gradient through ATP synthetase to facilitate ATP synthesis by phosphorylation

Mitochondrial and Chloroplast Membranes

• In mitochondria, protons flow from the intermembrane space into the matrix
• Chloroplasts facilitate proton flow across the thylakoid space and into the stroma
• Chloroplast structures: thylakoid space (A), stalked particles with ATP synthetase (B), outer membrane (C), thylakoid membrane (D), stroma (E)
• Mitochondrion structures: Intermembrane space (F), matrix (G), crista (inner membrane) (H), outer membrane (I), stalked particles with ATP synthetase (J)
• In chloroplasts and mitochondria, electron energy pump protons across membranes, creating a high concentration of hydrogen ions
• The electron flow down a concentration gradient provides energy for ATP synthesis
• Free electrons are taken up by a final electron acceptor
• In chloroplasts, Protons are pumped across the thylakoid membrane (D) and into the thylakoid space (A)
• In mitochondria, Protons are pumped across the crista (H) into the intermembrane space (F)
• The proton gradient drives ATP synthesis through stalked particles (B and J)

Electron Transport Chain and Proton Gradients

• The electron transport chain, located in inner mitochondrial or thylakoid membranes, uses proton pumps and electron carriers to generate a proton gradient
• High-energy electrons pass from carrier to carrier, driving proton pumps that move protons into the intermembrane space
• An electrochemical gradient allows protons to pass back into the matrix/stroma via ATP synthetase and facilitates ADP phosphorylation to form ATP, known as chemiosmosis

Photosynthesis and Chromatography

• Photosynthesis occurs in chloroplasts containing photosynthetic pigments absorbing light energy at specific wavelengths
• Pigment examples include chlorophyll a and b, carotene, and xanthophylls
• Chloroplasts orient for maximum light exposure and are mainly in mesophyll tissues, especially palisade cells
• Low light: Chloroplasts distribute evenly to maximize light absorption
• High light: Chloroplasts align to prevent overexposure damage
• Photosynthetic pigments can be separated via chromatography
• Rf values identify pigments with relative positions
• The line across the chromatogram should be drawn at the apex of each pigment curve to measure the distance between the origin and pigment
• The Rf value is calculated as the distance moved by pigment from the origin divided by the distance moved by the solvent front from origin.

Absorption and Action Spectra

• Absorption spectrum: graph showing light absorbed by a pigment at different wavelengths
• Chlorophyll a absorption peaks: 435 nm (blue) and 670-80 nm (red)
• Action spectrum: graph indicating the rate of photosynthesis at different wavelengths of light
• Overlapping an action spectrum shows a close correlation, suggesting wavelengths absorbed are used for photosynthesis

Thomas Englemann's Experiment

• Englemann's experiment determined which wavelengths of light were used most for photosynthesis
• He placed spirogyra algae in a suspension of motile aerobic bacteria and refracted white light into rainbow colors using a prism
• Oxygen, being a product of photosynthesis, is produced most at wavelengths where photosynthesis occurs most.
• Aerobic bacteria migrate to regions with the highest oxygen concentration
• Blue and red regions showed peak oxygen concentration, suggesting they cause the most photosynthetic activity

Light Harvesting

• Photosynthetic pigments harvest light energy via antenna complexes in thylakoid membranes
• Antenna complexes (A) have reaction centers (B), where Chlorophyll a, a primary pigment, resides
• Carotenes, xanthophylls, and chlorophyll b are accessory pigments, located in the antenna complex, absorb a variety of wavelengths.

Light-Dependent Stage

• Light energy is passed from accessory pigment to accessory pigment molecule towards the reaction center at the base
• Proteins associated with the antenna complex prevent light energy escaping
• Chlorophyll a molecules in the reaction center absorb light and emit high energy electrons
• Photosystem I (PSI) absorbs at 700nm (P700); Photosystem II (PSII) absorbs at 680nm (P680)
• Photons excite chlorophyll a, raising electrons to higher energy levels
• High-energy electrons are passed to electron acceptors/donors (A) for ATP synthesis via photophosphorylation or to reduce NADP

Cyclic Photophosphorylation

• Cyclic photophosphorylation involves only PSI (pathway Y), where high-energy electrons from PSI pass to an electron acceptor (A)
• These electrons help generate a proton gradient for chemiosmosis via the electron transport system
• The electron (now at a lower energy state) returns to PSI in a cyclic pathway

Non-Cyclic Photophosphorylation

• Non-cyclic photophosphorylation involves both PSI and PSII where high-energy electrons (pathway Z) from PSI are passed to NADP to form reduced NADP.
• PSI becomes electron-deficient and primed to take an electron from PSII, following PSII electron passing to a proton transport system and chemiosmosis
• The electron is passed to PSI in a non-cyclic pathway where PSII becomes electron-deficient

Photolysis and the Z Scheme

• Photolysis is the splitting of water by light, producing protons, electrons, and oxygen, and provides electrons for PSII

• Water molecules within the thylakoid space absorb light energy, and pass electrons to PSII

• Protons, used to reduce NADP, result in each molecule picking up two protons and two electrons to become reduced

• The products of the light dependent stage are ATP and reduced NADP, which power the light-independent stage (Calvin cycle)

• Non-cyclic photophosphorylation uses a Z scheme where Photosystems I and II are represented as I and II

• "p", Represents high-energy electrons passing to acceptors A, and the zigzag arrow between A2 and PSI indicates the electron transport system

• This generates a proton gradient necessary for phosphorylation and ATP synthesis that results in NADP and reduced NADP

• Water (Y) and oxygen (Z) represent the electron passing to PSII and the proton passing to NADP, respectively

• It's essential to remember that ATP energy and reduced NADP are necessarry to drive the calvin cycle

Light-Independent Stage (Calvin Cycle)

• The Calvin cycle fixes carbon dioxide into carbohydrates, with carbon dioxide taken up by RuBP

• This unstable 6C compound splits into two molecules of 3C glycerate-3-phosphate (GP) via rubisco

• ATP and reduced NADP (from the light-dependent stage) reduce GP to 3C triose phosphate (TP)

• TP is converted into glucose and then starch, TP is converted into RuBP using ATP for regeneration of the Calvin cycle

• After RuBP combines with carbon dioxide to form an unstable 6C compound and later GP, GP needs ATP energy from ATP, and reduced NADP to form 2 TP molecules

• Most TP is used to regenerate RuBP, which some is converted into glucose and starch

• Also, lipids, proteins and carbohydrates can be made from the products of the Calvin cycle, where Acetyl CoA and glycerol, and amino acids are synthesised

Interpreting Autoradiographs

• Remember to logically describe what you see in each autoradiograph
• When interpreting autoradiographs of experiments exposing chlorella algae to 14CO2 for 5–30 seconds, the darkness and size and the spot reflects the compound present
• GP is formed before TP, small amounts of sugar phosphates have been formed as they are produced
• There is more GP 30 seconds later, as the spot is larger and darker, while amino acids such as alanine and glycine have been formed, not present five second prior

Limiting Factors in Photosynthesis

• Efficient photosynthesis requires a suitable environment with water and carbon dioxide reactants, sufficient light at the appropriate wavelength, and optimal temperature for enzyme activity

• Photosynthesis will slow it any of these factors slow, and they becomes limiting Factors

• When increasing a limiting factor, such as light exposure, the rate of photosynthesis will increase until it reaches the saturation point then it will slows

• Temperature increasing kinetic energy affects transport rates and enzyme activity

• Light intensity is critical for exciting electrons in photosystems during the light-dependent stage

• The actual photosynthesis rate will be controlled by the factor close to it's minimum value

Mineral Nutrition Necessities

• Plants require inorganic ions which may be limiting in short supply such as macronutrients (sodium, magnesium, calcium, nitrate and phosphate)
• Tiny amounts of Micronutrients such as manganese and copper, are also needed
• Nitrogen, absorbed as nitrate, synthesizes amino acids and nucleotides; deficiency causes reduced growth and chlorosis.
• Chlorosis is yellowing of the leaves which appears in the older leaves first
• Magnesium (Mg2+) functions in chlorophyll production and ATPase activation in leaves; deficiency causes chlorosis starting between the veins of older leaves which is mobilized.

Respiration and Glycolysis

• In respiration, high-energy bonds in glucose and fatty acids break, releasing energy for ATP production by phosphorylation, catalyzed by enzymes
• Aerobic respiration completely breaks down of glucose with oxygen with large ATPs released by oxidative phosphorylation
• Anaerobic respiration incompletely breaks down glucose without oxygen with small ATPs released by level phosphorylation

Glycolysis Explained

• Without oxygen, glycolysis occurs in the cytoplasm where unstable hexose phosphate molecules splits into 2, 3C triose phosphate molecules after which, dehydrogenation occurs
• Hydrogen atoms is picked up by NAD to form reduced NAD, and two ATP molecules are produced by substrate level phosphorylation, forming pyruvate (3C)
• Glycolysis produced are pyruvate, reduced NAD, and ATP
• This is also called (net)

The Link Reaction

• Pyruvate diffuses into the mitochondrial matrix and undergoes decarboxylation which is the enzymatically releasing of CO2 and dehydrogenation- for reduced NAD formation
• This forms 2C acetate/acetyl, attaching it to coenzyme A, and forms and acetyl CA, and with further H atoms and NAD reduced
• Dehydrogenation: removal of H atoms by enzyme dehydrogenase
• Decarboxylation: removal of carboxyl group, releasing CO2

Krebs Cycle

• Acetyl CoA enters the Krebs cycle (mitochondrial matrix) and combines with a 4C compound, regenerating CoA.
• Key coenzymes are NAD, FAD, and A which represents substrate level phosphorylation
• The Krebs cycle is a series of oxidation-reduction reactions, where the dehydrogenation of the 6 carbon compound releases 2 H atoms in order to reduce NAD
• Decarboxylation releases CO2 into a 5 carbon compound
• Failure to regenerate 4C compouns stops Krebs cycle

Products of The Krebs Cycle

• 2 CoA molecules are regenerated and go back to the link reaction
• Two 4C molecules are regenerated to allow the Krebs cycle to continue
• 4 CO2 is released as waste and into the atmosphere
• 2 ATP is produced through substrate level phosphorylation
• 6 Reduced NAD pass to the the ETC and donates electrons and protons
• 2 Reduced FAD pass to the ETC and and donates electrons and protons

Electron Transport Chain

• The ETC is inner mitochondrial membrane (cristae) with NAD, FAD transporting H atoms the ETC
• Oxygen is essential as the final electron acceptor where a proton accumulation destroys the proton gradient
• ATP is not produced and the cell dies
• Reduced NAD, associated with three ETC proton pumps, generates 3 ATP molecules, and reduced FAD, associated with two pumps, generates 2 ATP molecules by oxidative phosphorylation
• H atoms derive through chemisomosis

Anaerobic Respiraation

• Anaerobic respiration uses the final electron acceptor as the link reaction and Krebs cycle stop with NAD and FAD unavailable to pick up any more atoms.
• The process is that it is produced and in animals/cytoplasm
• This lactate/lactic acid is pyruvate's electron receptor, which allows 2% energy efficiency over all in the presence of oxygen.

Cyanide

• Cyanide is an final elctron respiratoty that prevents a forming protein through an intermember and which reduces chain

Anaerobic Respiration Explained

• Yeast pyruvate is a released and and is reoxidized through C, H, and O, allowing you to identify the diagram

Aerobic And Manmaluam energy usage

• Glucose molecules are a depleted 4- 2ATPS/ cell, by the inner membrane and the and

Alternative Uses

• During severe and lipid molecule usage

Alternate Respitory System

• Used as the enzyme with other ATP molecules in the end
• In the respitiry, in 2,35 and 21

Respiratory Quotients

• The amount of oxygen used to calculate respiration such as 1 as an average.

Section 3.4 - Basic Microbiology

• Classification for corkscrews and spirallium and a classification system through

Basic Bacteria And Walls

• A bacteria must stain to be gram positive or negative, with color as well as cell structure,
• Gram positive: thick pouter wall and 8 mm
• Gram negative: Has peptidoglycan and 2mm

Gram Stain Procedure

• Culture is needed on either nutrient agar jelly and broth/
• Requires that you have a carbon nitrogen source as we as sulfur and phosphorous

Proper Media for Growth

• There is different temperatures and optimum ranges that species grow in

Bacteria Oxygen Requirements

• Obligated aerobes need oxygen or they can't grow
• Obligated anaerobes are inhibited with oxygen
• Facultative anaerobes thrive with it, but when needed don't require it

Aseptic Technique

• This is a technique used to control bacterial cultures by contamination sterilizing equipment/
• Sterile techniques include metal transfer through Bunsen flame
• Glassware under pressure

Setting Up an Equipment

• Aseptic techniques are need and a bacteria cultures use techniques in order to grow

Estimating Bacteria And Colonies And Populations

• A bacteria must be estimated by direct and indirect light to check accuracy of bacteria
• The direct counts includes total amounts of live bacteria
• The indirect counts includes a the the the the total volume and population sizes

Section 3.5 Population Size and Ecosystems

Factors affecting population size

• A population is a group of a single species in one defined area
• Influenced by (increase or decrease): birth, death, immigration, emigration

Population growth strategies

• Fugitive: reproduce quickly and spread which results in invading many colonies to help prevent
• Equilibrium controls population by completing within stable habitat. Usually growth is s- shaped

Phases Of Bacterial Populi

• Lag: prepare by making enzymes
• Exponential replication and double per unit time
• Stationary number of new cells equals cell division with growth slowed
• Nutrient loss
• Environment control, no new cells

Tip

When listing the step, be mindful of the number on earth

Resistance, Biotic and Abiotic