photosynthesis & cellular respiration energy & living things, photosynthesis and cellular...
TRANSCRIPT
Photosynthesis&
Cellular Respiration
Energy & Living Things, Photosynthesis and Cellular Respiration
Chapter 5
Energy in Living Things Building Molecules That Store Energy
Metabolism: builds and breaks molecules Photosynthesis: conversion of light energy into
chemical energy Autotrophs: organisms that use sunlight or
inorganic molecules to produce organic matter These organisms include:
Plants – use sunlightProkaryotes – use chemicals flowing out
of earth vents on the ocean floor
Breaking Down Food for Energy Chemical energy can also be transferred
from one organic compound to another Ex. Hydrolysis using water to break bonds
Heterotrophs: organisms who receive chemical energy from consuming organic matter
Cellular respiration: releases energy that is contained in food to convert it to ATP (another form of energy)
ATP is the source of energy for cells to carry out their daily activities for an organism to survive
Transfer of Energy to ATP Similar to burning coal or wood for heat Food energy is released in a series of
enzyme-assisted chemical reactions The product from the previous reaction
becomes the reactant in the next reaction until ATP is created
Example: Starch is broken down into glucose and
glucose is broken down into Carbon Dioxide & Water
During the reaction: heat is released
ATP Adenosine triphosphate Removal of a phosphate group = energy Equation:
Photosynthesis All the energy used by organisms is traced
back to the sun Stages of Photosynthesis:
Energy is captured from the sun Light Energy → Chemical Energy: temporarily
stored in ATP and NADPH ATP and NADPH powers the formation of
organic compounds with the use of CO2
Equation:
Stage One: Absorption of Light Energy Light –Dependent Reactions Pigments
Light absorbing substances Absorb only certain wavelengths and reflect
all others Chlorophyll: absorbs blue & red, reflects green
& yellow Plants contain chlorophyll, chlorophyll a &
chlorophyll b Carotenoids: produce yellow and orange colors
Absorbs and reflect different wavelengths than chlorophyll
Enables plants to absorb more light during photosynthesis
Stage One: Continued Production of Oxygen
Thylakoids: disk-shaped structure containing of clusters of pigments in the chloroplast of the cell
Light strikes the thylakoids, energy is transferred to electrons and electrons move to higher levels
Electrons move from chlorophyll to nearby molecules to initiate stage two of photosynthesis.
These electrons are replaced by water molecules
Stage Two: The Conversion of Light Energy Electron Transport Chain (ETC): a series of
molecules that electrons pass through along the thylakoid membrane
Works around a concentration gradient – Hydrogen ions lose energy when they channel through a protein when the concentration builds within the cell, the ions diffuse out
The ions are “recharged” when they assist in adding a phosphate group to ADP to make ATP (first ETC)
In the 2nd ETC, electrons combine with hydrogen ions to create NADPH from NADP+
NADPH: electron carrier that provides high-energy electrons for stage three of photosynthesis
Stage Three: Storage of Energy Purpose: production of organic compounds
from carbon atoms Carbon Dioxide Fixation: transfer of carbon
dioxide to organic compounds (light-independent reaction)
Calvin Cycle A CO2 molecule added to a five-carbon
compound (3) Three 6-C compounds split into six 3-C
compounds One 3-C sugar is used to make organic
compound Five 3-C compounds are cycled through
Factors That Affect Photosynthesis Increase
Light Intensity Increases (until saturation) Carbon Dioxide concentration (until max)
Decrease Slowed by the Calvin Cycle Unfavorable conditions for enzymes
Cellular Respiration – Cellular Energy Aerobic: metabolic processes that require O2
Anaerobic: metabolic processes that do not require O2
Equation of Cellular Respiration:
𝑪𝟔𝑯𝟏𝟐𝑶𝟔+𝟔𝑶𝟐𝒆𝒏𝒛𝒚𝒎𝒆𝒔→
𝟔𝐂𝐎𝟐+𝟔𝑯𝟐𝑶+𝑨𝑻𝑷
Stage One: Breakdown of Glucose Glycolysis: enzyme assisted anaerobic process
that breaks down 6-C glucose into two 3-C pyruvate ions
Step 1: In 3 rxns, phosphate groups from 2 ATP are transferred to a glucose molecule
Stage One: Breakdown of Glucose Step 2: In 2 rxns, glucose broken down into two 3-
carbon compounds each with a phosphate
Stage One: Breakdown of Glucose Step 3: Two NADH molecules are produced and
one more phosphate group is transferred to each 3-C compound
Stage One: Breakdown of Glucose Step 4: In 4 rxns, each 3-C compound →→pyruvate
ion and four ATP molecules are produced
Summary of Glycolysis Uses 2 ATP to begin
Produces 4 ATP Net gain: 2 ATP
Glucose (6-Carbons) → Two 3-C pyruvate ions NADH and NAD+ are recycled
Stage Two: Production of ATP Oxygen present – pyruvate is converted to a 2-
carbon compound in the mitochondrion Reaction produces:
One molecule of CO2
One molecule of NADH One 2-C acetyl group attached to form acetyl-CoA
Krebs Cycle A cycle beginning with acetyl-CoA to produce ATP
Step 1: Acetyl-CoA attached to a 4-C compound to form a 6-C compound and release
CoA
Step 2: CO2 is released from 6-C compound forming a 5-C compound Electrons transferred to NAD+ to make NADH
Krebs Cycle - Continued Step 3: Another CO2 is released forming a 4-C
compound, an ATP molecule and NADH are produced
Step 4: 4-C compound converted to a different 4-C compound. Electrons transferred to FAD to produce FADH2
Step 5: 4-C compound converted to the original 4-C compound that started the cycle NADH produced
Electron Transport Chain Electrons are donated from NADH & FADH2
Located in the inner membrane of mitochondrion The energy of electrons are used to pump
out hydrogen ions Concentration gradient is created - causes
hydrogen ions to be pumped into the membrane
The energy created adds a phosphate group to ADP to form ATP
Products include: ATP and water molecules
Respiration in the Absence of Oxygen ETC cannot function – oxygen is the final electron
acceptor NAD+ is recycled in other ways Fermentation: recycling of NAD+ using
another form of organic hydrogen acceptor Lactic Acid Alcoholic
Lactic Acid Fermentation 3-C pyruvate converted to 3-C lactate Lactate: ion of its organic acid lactic acid
Formed during intense workouts During the conversion:
NAD+ and NADH are recycled No FADH2
Lactate expelled from muscles
Alcohol Fermentation 3-C pyruvate broken down to ethanol (2-C
compound) Step 1: Pyruvate is converted to 2-C compound
Carbon dioxide expelled Step 2: 2-C compound converted to ethanol During break down:
NAD+ and NADH are recycled Carbon dioxide expelled