Lesson 3

Photosynthesis and cellular respiration

How do you think this plant gets energy !!

https://www.youtube.com/watch?v=D1Ymc311XS8

Why do plants needs sunlight ?!

Plants needs to eat , but they can not make eat food lie the human . So they make there own food .

leaves are the major food producing organ in the plant.

Leaves gets the energy for making the food from the sunlight

That’s why you can notice in some plants the leaves are turned towards the sun light

Photosynthesis

Leaves are the sites of photosynthesis in plants.

Plants and some unicellular organisms such as algae , phytoplankton ( العوالق النباتية ) and other microorganisms obtain energy from the sunlight through a process we call it PHOTOSYNTHESIS .

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It is a series of chemical reactions that convert LIGHT ENERGY , WATER , AND CARBON DIOXIDE into the glucose ( sugar in the plant ) . And give off the oxygen .

The glucose can be used immediately or stored for growth or late use

Leaves contain many types of cells

1. EPIDERMAL : it is the cell that makes the top and the bottom layers of the leaf
2. it is flat , irregular shaped
3. On the bottom epidermal of most leaves are small openings called STOMATA

CARBON DIOXIDE , WATER VAPOR , AND OXYGEN pass through stomata

4) Epidermal cell can produce a waxy covering cell called cuticle

Most photosynthesis occurs in tow types of mesophyll (cells inside the leaf )

These cells contain chloroplast ( the organelles where photosynthesis occurs )

Near of top surface of the leaf are palisade mesophyll cell

They are packed together

This arrangement exposed the most cells to the light

Spongy mesophyll has open spaces between them because photosynthesis needs gas and the gas enters from these spaces

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Capturing light energy

1) first step of photosynthesis ,plants capture the energy in the light , this occur in chloroplasts , which contain plant pigments

Pigments are chemicals that can absorb and reflect the light

Most plants appear green because the chlorophyl reflects green light and absorbs other colors of light

2) During photosynthesis water molecules are split apart . This release oxygen in atmosphere

Making sugar

Sugar are made in the second step of photosynthesis , which can occur without light , in chloroplasts .

Carbon dioxide from the air is converted into sugars by using the energy stored and trapped by chlorophyll.

Carbon dioxide combines with hydrogen atoms from the splitting water molecules and form sugar molecules .

Plants can use this sugar as an immediate energy or can store it for later .

Potato and carrot are example for structures where sugar is stored

• Most chemical reactions requires input of energy
• In photosynthesis the light energy absorbed by chlorophyll
• When the light energy is absorbed ,it is used to splits water molecules

• Plants and other photosynthesis organisms absorb carbon dioxide and produce oxygen
• This is important for the ecosystem
• ECOSYSTEM: is all living or nonliving things in a given area

• How does the energy in food molecules become useable ?!

• all organisms requires energy to survive
• Energy is in the chemical bonds of food molecules

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• but how can the organism use this energy ?!

Cellular respiration

• When we breathe out we breath out carbon dioxide
• The carbon dioxide is a waste came from a process that release energy from molecules
• CELLULAR RESPIRATION : is a series of chemical reactions that convert energy in food molecules into useable form of energy called ATP
• Cellular respiration occur in tow parts of the cell 1) mitochondria 2)cytoplasm

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Glycolysis

• It is the first step of cellular respiration
• It occur in cytoplasm of all cells
• Glycolysis : it is a process by which glucose (sugar) is broken down into smaller molecules
• It produces some ATP

• The second step of cellular respiration occur in the mitochondria of eukaryotic cell
• This step requires oxygen
• The smaller molecules made from glucose during glycolysis are broken down into large amount of ATP
• cell use The ATP to power cellule processes
• In this step , tow waste products – water and carbon dioxide .
• The CO2 released by cells as a waste products is used by plants and some unicellular organisms during photosynthesis

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How are photosynthesis and cellular respiration are related ?

• Photosynthesis requires the reactants carbon dioxide and water . The products are oxygen and glucose

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• Photosynthesis is important to maintain the atmosphere we breath , it produce most of the oxygen in the atmosphere

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• Cellular respiration requires the reactants glucose and oxygen to produce carbon dioxide and water and release energy
• Most organisms perform cellular respiration , it is important because if your body didn’t break down and rearrange the food you eat, you wouldn’t have energy to do anything . Same for the other organisms .