Energy and Life

Energy = the ability to do work

– Life on earth depends on a flow of energy

– Cells need energy constantly to continue functioning.

• Energy comes in many forms

– Examples:• Light• Heat• Energy stored in chemical compounds (like

glucose)

Most cellular processes require the input of energy.

Like what?

Examples:– Synthesis of new molecules

• proteins, enzymes, DNA etc.

– Breakdown of molecules • chemical digestion

– Build new structures • membranes, organelles, etc.

– Maintain Homeostasis • eliminate wastes, maintain body temp., active transport,

cell movement etc.

• Where do cells get this energy?

– From food we eat

– We measure the energy content of food in calories.

– Certain reactions break down these molecules to release energy.

• Energy released from a Gummy Bear

• http://www.youtube.com/watch?v=uj9D3mc7tVg&feature=related&safe=active

– Can’t use energy directly from food

– Need to store it and release it gradually.

– Store it in molecules of ATP.

ATP (Adenosine Triphosphate)– Source of cellular energy

– Stores energy as food is broken down so that it can be released slowly to cell when needed rather than all at once.

– A type of energy “currency”, that can be “paid out” as the cell needs it.

Structure of ATP (Adenosine triphosphate)– 1 adenine (type of nitrogenous base)– 1 ribose sugar (5 carbon ring)– 3 phosphate groups

How is ATP Formed?

– Energy is stored in high energy phosphate bonds

– Cells bond a third phosphate group to ADP

– ADP • (adenosine “di”phosphate)

– To release this energy again, the cell breaks off the 3rd phosphate group and energy is released.

– Can happen over and over again.

– Like recharging a battery!

IMPORTANT TO KNOW!!

• How does ADP and ATP differ?

• How is this related to energy?

Storing Energy

Add a phosphate to ADP

ADP + phosphate + energy → ATP

Releasing Energy

Remove a phosphate from ATP

ATP → ADP + phosphate + energy

Note:

The enzyme that catalyzes this reaction is called ATPase.

• Cells can regenerate ATP from ADP as needed by using the energy in foods like glucose.

ATP/ADP Cycle

How do organisms obtain food to make ATP?

• They eat it…

– Heterotrophs: obtain food

from consuming other living things.

• Ex: – Animals: herbivores, carnivores and omnivores– Fungi– Some protists– Some bacteria

• They make it themselves…

– Autotrophs: use light energy from the sun to make their own food through photosynthesis.

• Ex: – Plants– Algae– Some bacteria

Photosynthesis

• Process by which light energy is converted into the chemical energy of organic compounds (glucose).

• Occurs in the chloroplasts of plant cells (as wells as some single celled organisms, that can carry out photosynthesis.)

Chloroplast Structure• Stroma: protein containing fluid

• Grana: stacked membranes containing enzymes and chlorophyll.

Chlorophyll: – green pigment

necessary for photosynthesis.

– Absorbs red and blue wavelengths of light and reflects green light. (that’s why most plants look green)

• Note: – Other photosynthetic pigments exist besides

chlorophyll, but it is the main one used by autotrophs

• Ex: Carotenoids (orange/red colored pigment)

Equation for Photosynthesis

Photosynthesis Overview

• Plants Take In:– Carbon Dioxide Gas– Water– Sunlight (energy)

• Plants Produce:– Glucose (form of stored energy)– Oxygen Gas

The Process of Photosynthesis

• How Does the Chloroplast Work?– Light Dependant Reactions (Photochemical)– Light Independent Reactions (Carbon Fixation)

Light Reactions

Light Dependant Reactions (Photochemical)– Happen in the thylakoid membranes of grana– Directly involve chlorophyll and sunlight

– Produces oxygen– Converts ADP to ATP– Converts NADP+ to NADPH

• Chlorophyll absorbs sunlight– Creates high energy electrons– Electrons enter the electron transport chain– Eventually produce some ATP

• Photolysis– Water gets split inside grana

• Breaks into:– One oxygen atom– Two H+ ions– 2 electrons

• The Oxygen produced by splitting water gets released into the air

– Source of nearly all the oxygen in Earth’s atomosphere!

Thank you plants!!!

You make our lives possible.

• The H+ ions and electrons

– Join up with NADP+ an “electron carrier”

– It becomes NADPH

Making ATP

• H+ ions build up and cross the thylakoid membrane causing ATP to form as ATP synthase (an enzyme) turns ADP into ATP

Dark Reactions

Light Independent Reactions (Calvin Cycle)– Does not require light– Happens in stroma

– Carbon Fixation: • Carbon gets “Fixed” from a simple 1 carbon molecule

(CO2) to a complex 6 carbon one that holds stored energy (glucose/C6H12O6)

• Carbon Dioxide Molecules: (CO2)

– enters from atmosphere (through stomata)

– Combine to make PGAL a 3-carbon molecule– 2 PGAL combine to produce a 6-carbon

glucose

– Energy for these reactions to take place is provided by ATP and NADPH (from light reactions)

Photosynthesis Summary

Light vs. Dark Reactions

• Video Overview of Photosynthesis (5min)

• http://www.youtube.com/watch?v=mYbMPwmwx88&safe=active

• Factors Affecting Photosynthesis

– Temperature– Light Intensity– Water and Carbon Dioxide Availability

Tutor Vista:

http://www.youtube.com/watch?v=vmmWiJ3g9Cg&safe=active

• Temperature: – Enzymes are needed for photosynthesis– Function best between 0°C and 35°C.– Too hot or too cold and photosynthesis stops

• Intensity of Light:– More intensity = more photosynthesis– Remember blue and red wavelengths are

most useful for photosynthesis

• Availability of Water and CO2:

– One of the raw materials for photosynthesis– Split during photolysis reaction

– Water loss can kill plants– They have evolved strategies

• Waxy coatings on leaves

• Stomata: – small openings in plant

leaves that normally admit carbon dioxide

– Water can also escape through opening

• Guard Cells:– Can open or close

stomata to help prevent excess water loss from plant

Stomata and Guard Cells Video:

http://www.youtube.com/watch?v=cFX4JrsPaUs&safe=active