Bell Ringer 8-26-141. When you decide whether or not the data support the original hypothesis, you are

a. Making an inference

b. Making an observation

c. Drawing a conclusion

d. Posing a question

2. In a controlled experiment, a scientist is studying how long it takes parachutes of different sizes to fall to the ground. What is the independent variable?

a. The size of the parachute

b. The height from which the parachute is dropped

c. The size of the object carried by the parachute

d. The time it takes for the parachute to drop

3. Facts, figures, and other evidence learned through observations are called

a. Variables

b. Experiments

c. Questions

d. Data

Agenda

Finish Macromolecule Activity Photosynthesis Notes Photosynthesis Practice

Energy and Living Things

Photosynthesis is the process in which light energy is converted into chemical energy.

Autotrophs (plants and some bacteria) use the sun’s energy to carry out photosynthesis, and are therefore the foundation of all living systems.

Breaking Down Food For Energy Autotrophs are

organisms that use energy from sunlight or from chemical bonds in inorganic substances to make organic compounds.

Heterotrophs are organisms that must consume other organisms as food to get their energy.

Photosynthesis Photosynthesis is the process by which plants,

algae, and some bacteria use sunlight, carbon dioxide, and water to produce carbohydrates and oxygen.

Photosynthesis has 3 stages:Stage 1: absorption of light energy

Stage 2: conversion of light energy into chemical energy, temporarily stored in ATP and NADPH

Stage 3: storage of chemical energy in ATP and NADPH powers the formation of organic molecules

Photosynthesis Pigments are light-absorbing substances

that absorb only certain wavelengths of light and reflect all others.

Chlorophyll is the primary pigment involved in photosynthesis. Chlorophyll absorbs mostly blue and red light and reflects green and yellow light.

This reflection of green and yellow light makes many plants, especially their leaves, look green.

Photosynthesis occurs in the chloroplasts and uses the pigment chlorophyll.

Photosynthesis The following chemical equation

summarizes photosynthesis: 6H2O + 6CO2 + light C6H12O6 + 6O2

REACTANTS: water, carbon dioxide, light energy

PRODUCTS: glucose, oxygen

Stages of Photosynthesis:STAGE 1 - The Light-Dependent Reactions

These reactions are called the “light reactions,” or “light-dependent reactions” because the reactions absorb light energy to make glucose and oxygen.

Occurs in the chloroplasts on the thylakoid membrane where clusters of the pigment chlorophyll are embedded.

Photosynthesis: Where Does it Occur?

Thylakoid membrane

Photosynthesis: Thylakoids

Thylakoids are disk-shaped structures found in the chloroplasts of leaf cells that contain clusters of embedded pigments.

These pigment molecules in the thylakoids of chloroplasts absorb light energy.

Electrons in the pigments are “excited” by light, and jump from the chlorophyll molecules to other nearby molecules in the thylakoid membrane.

The series of molecules along the thylakoid membrane that excited electrons pass through as they jump along the chlorophyll molecules is called the electron transport chain.

Photosynthesis: Stage 1 Absorption of Light Energy

The excited electrons that leave chlorophyll molecules must be replaced by other electrons.

Plants get these replacement electrons from water molecules, H20.

The water molecules are split by an enzyme inside the thylakoid.

When water molecules are split, chlorophyll molecules take the electrons from the hydrogen atoms, H, leaving hydrogen ions, H+.

The remaining oxygen atoms, O, from the disassembled water molecules combine to form oxygen gas, O2.

Photosynthesis: Stage 2Conversion of Light Energy by Electron

Transport Chains Excited electrons lose some of their energy as they

pass through these proteins. The energy lost is used to pump hydrogen ions into the thylakoid.

As the process continues, hydrogen ions become more concentrated inside the thylakoid than outside, producing a concentration gradient across the thylakoid membrane.

The hydrogen ions will diffuse back out of the thylakoid down their concentration gradient through specialized carrier proteins, or proton pumps.

Photosynthesis: Stage 2 These proteins act as both ion

channels as well as enzymes. As H+ pass through the channel

portion of the protein, the protein catalyzes a reaction in which a phosphate group is added to ADP molecules to form ATP (ADP + P = ATP).

Thus, the movement of hydrogen ions across the thylakoid membranes through proton pumps provide the energy to produce ATP molecules.

inner thylakoid membrane

outer thylakoid membrane

Two Electron Transport Chains The first electron transport chain lies between two

large clusters of pigment molecules and is used to form ATP.

A second electron transport chain lies next to the sight of the first electron transport chain.

In this second chain, excited electrons combine with hydrogen ions (H+) and an electron acceptor called NADP+ to form NADPH.

NADPH is an electron carrier and is important in photosynthesis because it carries high energy electrons needed to produce organic molecules.

Photosynthesis: Stage 3The Light-Independent

Reactions The Storage of Chemical EnergyStage 3 of photosynthesis is known as the

Calvin cycle. The Calvin cycle creates complex carbohydrates

that store energy. Stage 3 of photosynthesis is also known as the

“light-independent reactions” or “dark reactions” because these series of reactions do not need light to occur.

Photosynthesis: The Light-Independent

Reactions Sometimes called carbon dioxide fixation because in a series of enzyme-assisted chemical reactions within the chloroplasts, CO2

molecules adhere to existing carbon compounds to form sugars for long-term energy storage.

The energy used in the Calvin cycle is supplied by ATP and NADPH that was made during Stage 2.

In a series of enzyme-assisted chemical reactions within the chloroplast called carbon dioxide fixation, CO2

molecules adhere to existing carbon compounds to form sugars for long-term energy storage.

This process called the Calvin Cycle uses the energy made in the 2nd stage of photosynthesis, and is often referred to as dark reactions, or light independent reactions.

Three Factors That Affect Photosynthesis 1.) amount of light – The rate of photosynthesis

increases as light intensity increases until all the pigments are being used. At this saturation point, the reactions of the Calvin cycle cannot proceed any faster.

2.) concentration of carbon dioxide – Once a certain concentration of carbon dioxide is present, photosynthesis cannot proceed any faster.

3.) range of temperature – Like all metabolic processes, photosynthesis involves many enzyme-assisted chemical reactions. Unfavorable temperatures may inactivate certain enzymes.

Bell Ringer 8-27-141. After scientists analyze the results of their experiments, they

a. Form hypothesesb. Include a controlc. Communicate those results to other peopled. Choose the variables they want to test

2. A factor in an experiment that can change is a(n) a. Observationb. Variablec. Controld. Hypothesis

3. What characteristic must be true of a good hypothesis?a. It must be correctb. It must have been observed many timesc. It must involve quantitative datad. It must be testable by observation or experiment

Get your macromolecules out!

Cellular Respiration Before energy from food can be utilized, it

must be transferred to ATP in a process called cellular respiration.

Cellular respiration is the set of metabolic reactions and processes that take place in the cells of organisms to convert biochemical energy from nutrients into adenosine triphosphate (ATP), and then release waste products.

To put it simply, cellular respiration is the process where cells produce energy from carbohydrates.

Cellular Respiration Cellular respiration is the opposite of

photosynthesis. The reactants of photosynthesis – carbon dioxide

and water – are the products of cellular respiration.

The products of photosynthesis – glucose and oxygen – are the reactants of cellular respiration.

Cellular respiration releases much of the energy in food to make ATP.

ATP provides cells with energy they need to carry out the activities of life.

Cells Transfer Energy From Food To ATP

When cells break down food molecules, some of the energy is released into the atmosphere as heat, while the rest is stored temporarily in molecules of ATP.

ATP molecules are often called the “energy currency” of a cell.

ATP Stores and Releases Energy

The energy from ATP is released when the bonds that hold the phosphate groups together are broken.

The removal of a phosphate group from ATP (3 phosphates) produces ADP (adenosine diphosphate -- 2 phosphates), which releases energy in a way that enables cells to use the energy.

Cells use energy released by this reaction to power metabolism.

Cellular Respiration Cellular respiration can

be aerobic respiration (with oxygen) or anaerobic respiration (without oxygen).

Cellular respiration begins in the cytoplasm, and ends in the mitochondria.

Cellular Respiration

The chemical formula for cellular respiration is:C6H12O6 + 6O2 6CO2 + 6H2O + energy

REACTANTS: glucose, oxygen PRODUCTS: carbon dioxide, water,

energy (ATP)

Cellular Respiration: Stage 1

Glycolysis Stage 1 of cellular respiration is called

glycolysis. Glycolysis is the stage of cellular

respiration where glucose is broken down in the cytoplasm, converted to pyruvate, and produces a small amount of ATP and NADPH.

Glycolysis – uses 2 ATP, but produces 4 ATP – net gain = 2 ATP

Cellular Respiration: Stage 2

The Krebs Cycle Stage 2 of cellular respiration is known as

the Krebs cycle (also called the Citric Acid Cycle) and is aerobic respiration.

Pyruvic acid produced during glycolysis enters the mitochondria and is converted into carbon dioxide and water.

ATP and NADPH are produced. The Krebs cycle produces 2 ATP for each

molecule of pyruvic acid broken down.

Cellular Respiration: The Electron Transport Chain

If enough O2 is present, up to 34 ATP molecules can be formed from a single glucose molecule!

At the end of the electron transport chain, oxygen (O2) acts as the final electron acceptor and combines with H+ ions to form water molecules (H2O).

Fermentation

If oxygen (O2) is not present in sufficient amounts, the electron transport chain in the mitochondrial membrane cannot function.

Energy molecules (ATP and NADPH) cannot be created in abundance.

So, what does the cell do to continue to break down organic compounds and release energy if not enough oxygen is present?

Fermentation:

Fermentation is the anaerobic process that continues the breakdown of carbohydrates when there is not enough oxygen for aerobic respiration.

There are two types of fermentation: 1.) lactic acid fermentation and 2.) alcoholic fermentation.

Lactic acid and/or ethanol (alcohol) are the by-products of fermentation.

Lactic Acid Fermentation In lactic acid fermentation, NAD+, an

electron acceptor, is recycled and glycolysis can continue to produce ATP.

Fermentation enables glycolysis to continue producing ATP as long as the glucose supply lasts.

Lactate, an ion of lactic acid, can build up in muscle cells if not removed quickly enough and can cause “muscle burn” or muscle fatigue.

Alcoholic Fermentation

Carbon dioxide is released during alcoholic fermentation by yeast.

Carbon dioxide gas released by the yeast is what causes the rising of bread dough and the carbonation of some alcoholic beverages.

Alcoholic Fermentation Alcoholic fermentation is a two-step process: First,

pyruvate is converted, releasing carbon dioxide. Second, electrons are transferred from a molecule of NADH to the two-carbon compound, producing ethanol.

Alcoholic fermentation by yeast can be used to produce food and beverages such as bread, cheese, beer, and wine.

Production of ATP The total amount of ATP a cell is able to

harvest from each glucose molecule that enters glycolysis depends on the presence or absence of oxygen.

When oxygen is present, aerobic respiration occurs.

When oxygen is not present, anaerobic respiration, or fermentation, occurs instead.

Production of ATP Most ATP is made during aerobic respiration.

Glycolysis (Stage 1 of cellular respiration) can occur with or without oxygen, and produces a net gain of 2 ATP molecules.

The Krebs cycle (Stage 2 of cellular respiration) produces 2 ATP molecules for each glucose molecule broken down.

The electron transport chain can produce up to 34 ATP molecules from a single glucose molecule.

Cytoplasm

CO2

H2O