Photosynthesis and Respiration

Info to support what we have done in class

Written formulas

• Photosynthesis:6CO2 + 6H2O + Energy --> C6H12O6 + 6O2

• Cellular Respiration:C6H12O6 + 6O2 --> 6CO2 + 6H2O + Energy

What is Photosynthesis?

• Photosynthesis is a chemical process through which plants, some bacteria and algae, produce glucose and oxygen from carbon dioxide and water, using only light as a source of energy.

• The following slides are information taken from http://www.eschooltoday.com/photosynthesis/introduction-to-photosynthesis.html

Video and Additional Resources

• http://www.youtube.com/watch?v=hJFySkAi-ZA• http://

www.phschool.com/science/biology_place/biocoach/photosynth/overview.html

• http://www.biology4kids.com/files/plants_photosynthesis.html

• http://www.youtube.com/watch?v=g78utcLQrJ4• http://www.youtube.com/watch?v=QMgCziQgr

us

Why does a plant go through photosynthesis?

What does the plant need glucose (food) for?Just like humans and other living things, plants also need this food for many things. Let's see a few:

Glucose resulting from photosynthesis is used during respiration to release energy that the plant needs for other life processes.

The plant cells also convert some of the glucose into starch for storage. This can then be used when the plant needs them. This is why dead plants are a used as biomass, because they have stored chemical energy in them)

Glucose is also needed to make other chemicals such as proteins, fats and plant sugars that are all need for the plant to carry out essential growth and other life processes.

Light and Dark Reactions• Light reactions need light to produce

organic energy molecules (ATP and NADPH). They are initiated by colored pigments, mainly green colored chlorophylls.

• Dark reactions make use of these organic energy molecules (ATP and NADPH). This reaction cycle is also called Calvin Benison Cycle, and it occurs in the stroma. ATP provides the energy, while NADPH provides the electrons required to fix the CO2(carbon dioxide) into carbohydrates.

SIDE NOTES:This means Dark reactions will fail to continue if the plants are deprived of light for too long, since they use the output of the initial light-dependent reactions.

Basic Leaf Structure• The basic structure of a leaf

We cannot fully study photosynthesis without knowing more about the structure of a leaf. The leaf is adapted to play a vital role in the process of photosynthesis.

Wide surface area:Mosts green plants have leaves that are broad, flat and exposed to capture as much of the suns energy (sunlight) need for photosynthesis.

VeinsThe network of veins in the leaf also carry water from the stems to the leaves. Glucose produced is also sent to the other parts of the plant from the leaves through the veins. Additionally, the veins support and holds the leaf flat to capture sunlight

Pores (holes)The stomata (tiny holes underneath the leaf) allows air in and out of the leaf. Stomata (single is called stoma) is usually at the bottom surface of the leaf but some plant species have them on the upper surface whiles other have them on both sides. The stomata closes in the night to retain gases and moisture in the leaf cells, and opens during the day for gaseous exchange to continue.

Conditions for Photosynthesis

Conditions for photosynthesisBelow are things that plants need for photosynthesis:

1. Carbon dioxide (A colorless, naturally occuring odorless gas found in the air we breathe. It has a scientific symbol CO2. CO2 is produced by burning carbon and organic compounds. It is also produced when plants and animals breathe out during respiration)

2. Water

3. Light (Even though both natural and artificial light is OK for plants, natural sunlight is usually great for photosynthesis because they have other natural UV properties that help the plant)

4. Chlorophyll (This is the green pigment found in the leaves of plants)

5. Nutrients and minerals (Chemicals and organic compounds which the plant-roots absorb from the soil)

Products of PhotosynthesisSubstances that plants make

by photosynthesis:• Glucose• Oxygen

Where does Photosynthesis take place?

• Photosynthesis takes place inside plant cells in small things called chloroplasts.

• Chloroplasts (mostly found in the mesophyll layer) contain a green substance called chlorophyll. Chlorophyll absorbs the light energy needed to make photosynthesis happen.

Side Notes• It is important to note that

not all the color wavelengths of light are absorbed. Plants mostly absorb red and blue wavelengths; they do not absorb light from the green range.

• Other than glucose, which is an important source of carbohydrates, photosynthesis also produces proteins,fats and water soluble sugars.

Carbon Dioxide in Photosynthesis• Plants get carbon dioxide from the

air through their leaves.

• The carbon dioxide diffuses through small holes in the underside of the leaf called stomata (plural). (singular: stoma)

• The lower part of the leaf has loose-fitting cells to allow carbon dioxide to reach the other cells in the leaf. This also allow the oxygen produced in photosynthesis to leave the leaf easily.

Light for Photosynthesis• A leaf usually has a large surface

area, so that it can absorb a lot of light. Its top surface is protected from water loss, disease, and weather damage by a waxy layer.

• The upper part of the leaf is where the light falls and it contains a type of cell called a palisade cell. This is adapted to absorb a lot of light. Therefore, it has lots of chloroplasts.

Water for plants• Plants get the water they need

for photosynthesis through their roots.

• The roots have a type of cell called a root hair cell - these project out from the root into the soil.

• Roots have a big surface area and thin walls, which allow water to pass into them easily.

Side Notes

• Root cells do not contain chloroplasts, as they are normally in the dark and cannot photosynthesize.

• Plants need water for other important things such as:– Provide dissolved minerals

that keep the plants healthy– Provide a medium for

transporting minerals– Keep the plant firm and

upright– Keep the plant cool and

hydrated– Allow other chemical

reactions to occur in plant cells

ATP (Adenosine triphosphate)• Energy released from the

breakdown of food is stored in molecules of ATP.

• ATP is made of ribose (sugar), adenine (a nucleic acid), and phosphate groups (include PO4).

• Recall that nucleic acids are made of carbon, hydrogen, oxygen, nitrogen, and phosphorus.

• If an organism does not need it right away for growing, reproducing, responding to its environment the ATP can be stored long term as starch or fat.

ADP (Adenosine diphosphate)• ADP and ATP cycle back

and forth as energy is used and added.

• When energy is needed, a phosphate leaves the ATP and becomes ADP.

• When energy is created a phosphate group is added to ADP making it ATP.

Carbon Fixation

• Carbon fixing reactions use the products of the light dependent reactions to convert the CO2 and water into sugars.

• This is called the Calvin Cycle

• Plants that use only photosynthesis for this process are C3 plants. They are generally found in moderate climates

• Plants that live in more extreme conditions ,such as tropical or desert environments, fix carbon differently prior to entering the Calvin cycle.

Cellular Respiration

• This is the process by which food molecules are broken down to release energy to be able to do work.

• The written process of cellular respiration is the reverse of photosynthesis.

• There are two types of cellular respiration:– Aerobic that uses oxygen– Anaerobic that does not

use oxygen

• Glycolysis, the process where glucose is converted to pyruvate and energy is released, is the first process in both.

Aerobic Respiration• Aerobic Respiration

– Glycolysis: the process where glucose is broken down and energy is released. There are only two ATP created from each molecule of glucose.

– Krebs cycle: the second step which results in many electrons being released.

– Electron transport chain: The electrons that have been released are used to create more energy.

• The total amount of energy created by aerobic respiration is 36 molecules of ATP.

• This process is inefficient because this represents less than half of the energy available in one molecule of glucose. Mainly the waste is in the form of heat energy.

Anaerobic Respiration

• Alcoholic fermentation– Ethanol and carbon

dioxide are produced

• Lactic acid fermentation– Lactic acid is produced