Chapter 4 - Energy and LIfe PDF

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Chapter 4 - Energy and LIfe - Dr. Lutterschmidt...

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BIOL 1408 – Contemporary Biology Dr. Lutterschmidt

Chapter 4 – Energy and Life 4.1 Living things use energy to power life 

All living things need energy to survive

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Work = force x distance

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Energy is defined as the capacity to do work o E=mc2

Energy is converted from one form to another 

Does the rider at the top of the slide contain energy o Potential energy is the energy an object has due to its location or structure

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What happens when the rider goes down the slide? o Kinetic energy is the energy of motion

Potential energy is stored in the bonds that hold atoms together into molecules 

In cells, ATP is a common energy currency molecule

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Breaking a bond in ATP releases energy that can be used to drive other processes

Conservation of energy 

Energy can be converted but cannot be created or destroyed o Solar energy warms the lizard o Heat energy dissipates o Chemical energy in lizard’s food is stored and later converted to kinetic energy

Heat is a by-product of energy conversion 

At each conversion some energy is lost to living things in the form of heat

Living things must work to counter entropy 

With each energy conversion heat is released, so the disorder in a system increases

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Entropy is the amount of disorder in a system

4.2 energy flows through ecosystems 

Solar energy is inputted daily

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Energy therefore flows through living systems

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Life on Earth is powered by the sun

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Producers and consumers 

Producers can absorb the sun’s energy and convert it to chemical energy (make their own food)

Producers capture solar energy and convert it to chemical energy (sugars)

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The process of Photosynthesis

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Overall inputs and output of photosynthesis

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Sugar production is the goal of photosynthesis 

Photosynthesis takes place inside the cells of plants and algae in organelles called chloroplasts

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Plants and algae produce oxygen gas as a by-product

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The Earth’s atmosphere was low in O2 prior to the evolution of photosynthesis

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Consumers obtain energy by eating producers

Cellular respiration allows plants and animals to power life 

The potential energy in the chemical bonds of sugar is converted to chemical energy

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The kinetic energy can now be used for work

4.3 so why are plants green? 

Chlorophyll is the primary pigment (light absorbing molecule) in chloroplasts

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Light in blue/violet and orange/red ranges are absorbed

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Light in the green/yellow range is reflected

Plants look green because chlorophyll reflects green light 

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The leaves of many deciduous trees change color in the fall

4.4 Photosynthesis: overall reaction 

The chemical inputs/output for photosynthesis:

Photosynthesis occurs in 2 linked stages 

Photosynthesis captures the energy in sunlight and stores it in the form of sugar molecules 1. the light reactions capture sunlight and store it in high-energy molecules 2. the Calvin cycle (dark reactions) uses those high-energy molecules to produce sugar

4.5 what happens to the water molecule 

Water is used during the light reaction as a source of electrons

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What remains of the water molecule (oxygen) is released and exits the leaf

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Photosynthesis proceeds in 2 stages: overview 1. Light reactions a. Convert light energy to chemical energy 2. Calvin Cycle a. Uses high-energy molecules (ATP, NADH) to produce sugars 

Inside a leaf both stages of photosynthesis are occurring

4.6 A closer look at the Calvin cycle: making sugars 

Calvin cycle uses high-energy molecules from the light reactions to construct sugars

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The plant can use sugars in a variety of ways

Plants are built of sugars 

Plants store glucose in 2 ways

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Both ways represent many glucose molecules stitched together

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4.7 in Cellular Respiration, oxygen is used to harvest the energy stored in sugar 

Cellular respiration releases the chemical energy stored in sugars

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All organisms – both producers and consumers – use cellular respiration

Aerobic respiration 

Aerobic respiration requires oxygen

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It takes place inside the mitochondria

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Aerobic respiration happens in both producers and consumers

The Ins and Outs of aerobic respiration 

O2 travels from lungs to the mitochondria

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Food travels from digestive system to the mitochondria

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CO2 leaves the cell and is expelled from the lungs

3 body systems play a role in cellular respiration

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Energy stored in ATP 

Cellular respiration produces an energy-carrying molecule acalled ATP

Kilocalories 

A calorie is the amount of chemical energy stored in food

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A nutrition label is really showing you kilocalories, or thousands of Calories

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A calories also can describe the amount of energy burned

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Weight gain/loss is result of Calories in versus out

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220 calories = 2,200

4.8 Cellular respiration is how life gets energy to power work 

Cell ular respiration uses O2 to “burn” sugar (glucose)

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Energy is then used to generate ATP

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By-products are CO2 AND H2O

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Both plants and animals depend on cellular respiration 24 hours a day, every second, in every cell

Cellular respiration: overall reaction 

The chemical inputs/output for cellular respiration are:

Study Tip 

The chemical inputs for cellular respiration and photosynthesis are reciprocal

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Photosynthesis is the most important equation in biology then cellular respiration

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Cellular respiration has 3 stages 1. Glycolysis (glucose oxidation → burning glucose) 2. Citric Acid Cycle – Kreb Cycle 3. Electron Transport Chain (produces the most ATP)

Cellular respiration overview

Glycolysis 

Takes place in cytoplasm

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Splits glucose into 2 pyruvic acids

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Small amount of ATP produced

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Citric Acid Cycle 

Takes place in the mitochondrial fluid

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Uses O2

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Pyruvic acid broken to CO2

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High energy electrons produced

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Small amount of ATP produced

Electron Transport Chain 

Takes place in the inner membranes of mitochondria

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High-energy electrons move through chain

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Electrons combine with O2 to form H2O

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Lots of ATP produced

4.9 In fermentation, energy is harvested from sugar without oxygen 

Aerobic respiration

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Anaerobic respiration

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Fermentation is anaerobic 

Fermentation harvests the energy from glucose without O2

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Only a small bit of ATP is produced

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Fermentation produces much less ATP than aerobic respiration

4.9 Lactic acid fermentation in muscles 

When cells can’t get O2, lactic acid fermentation is an “emergency” mode

4.10 Cellular respiration is a central hub of many of life’s metabolic processes 

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Many types of molecules can feed into cellular respiration

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In addition to sugar, we can process o Carbohydrates = sugars o Fats o Proteins

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This means we can generate ATP from many different food inputs

All food provides energy

Energy use by living things 

Your metabolism is the sum total of all the chemical reactions that occur in your body

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Anabolism – build macromolecules

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Catabolism – break-down macromolecules

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ATP produced by cellular respiration powers nearly all of life’s processes

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