Chapter 9: Photosynthesis and Cellular Respirationmissmccormic.weebly.com/uploads/1/0/1/2/10125307/...Photosynthesis is a pathway in which light energy from the Sun is converted to

Photosynthesis and Cellular Respiration Unit

All cellular activities require energy.

Directly or indirectly nearly all energy for life comes from the sun.

Autotrophs: organisms that can make their own food. Plants convert light energy from the sun into chemical energy.

Hetertrophs: organisms that need to ingest food to obtain energy.

All of the chemical reactions in a cell are referred to as the cell’s metabolism.

Photosynthesis is a pathway in which light energy from the Sun is converted to chemical energy for use by the cell.

CO2 + H2O + light C6H12O6 + O2

Cellular respiration is a pathway in which organic molecules are broken down to release energy for use by the cell. C6H12O6 + O2 CO2 + H2O + about 38 ATP

Adenosine triphosphate – ATP- is the most important biological molecule that provides chemical energy.

ATP is the most abundant energy-carrier molecule in cells and is found in all types of organisms.

ATP is made of an adenine base, a ribose sugar, and three phosphate groups. Adenosine = Adenine + ribose sugar Triphosphate – 3 phosphate groups

Where energy is “found”

ATP releases energy when the bond between the second and third phosphate groups is broken forming a molecules called adenosine diphosphate- ADP

Cells use ATP to perform 3 types of work Chemical, mechanical, and transport

ATP is continuously converted to ADP as cells do work ADP can be converted back to ATP

Organisms break down carbon-based molecules to produce ATP.

Carbohydrates are the molecules most commonly broken down to make ATP.

• not stored in large amounts

• up to 36 ATP from one

glucose molecule

triphosphateadenosine

adenosine diphosphate

tri=3

di=2

Photosynthesis and Cellular Respiration Unit

Photosynthesis occurs in two phases. Phase 1(Light reactions): light-dependent reactions, light

energy is absorbed and then converted into chemical energy in the form of ATP and NADPH.

Phase 2 (Calvin Cycle): light –independent reactions, the ATP and NADPH that were formed in phase one are used to make glucose. Once glucose is produced, it can be jointed to other simple

carbohydrates and form larger molecules = STARCH!

Two steps in the process of photosynthesis Phase 1: Light Reactions

Phase 2: Calvin Cycle

6CO2 + 6H2O + light C6H12O6 + 6O2

Chloroplasts-large organelles that capture light energy in photosynthetic organisms (mainly found in leaf cells)

Two main compartments essential for photosynthesis: #1: Thylakoids- flattened saclike

membranes that are arranged in stacks. Light-dependent reactions take place

within the thylakoids.

Thylakoids form stacks called grana.

#2: Stroma- the fluid-filled space that is outside the grana. Light-independent reactions in phase 2 of

photosynthesis occur here.

chloroplast

stroma

grana (thylakoids)

Pigment: light-absorbing colored molecules found in the thylakoidmembranes of chloroplasts. Pigments differ in their ability to absorb

specific wavelengths of light.

Major light-absorbing pigments in plants are chlorophylls. Chlorophyll absorbs red & blue light and

reflects green light. This is why leaves appear green!

Also contain accessory pigments which allow plants to trap additional light energy from other areas of the visible spectrum. Carotenoids reflect yellow, orange, and red.

Give carrots and sweet potatoes their color. Also visible in fall when leaves are changing

colors.

chloroplast

leaf cell

leaf

The light-dependent reactions capture energy from sunlight

• take place in thylakoids

• water and sunlight are needed Water molecule is split using captured energy

• chlorophyll absorbs energy

• energy is transferred along thylakoid membrane then to light-independent reactions

• oxygen is released

• H+ ion is used later in Calvin Cycle

The light-independent reactions make sugars

Occurs in the Stroma

Uses CO2 absorbed from atmosphere

Uses ATP and H+ from Light reactions to build sugar Forms sugars (glucose)

(C6H12O6)

Photosynthesis and Cellular Respiration Unit

The function of cellular respiration is to harvest electrons from carbon compounds such as glucose, and use that energy to make ATP. Occurs in mitochondria

Structure of mitochondria aids with this process

Inner and outer membrane (many folds)

Lots of surface area allows for many reactions to occur at once

C6H12O6 + 6O2 6CO2 + 6H2O + ATP

2 main parts to cellular respiration: Glycolysis- is an anaerobic process

Anaerobic= NO OXYGEN REQUIRED

Aerobic respiration- includes the Krebs cycle and electron transport. Aerobic= REQUIRES OXYGEN

Step 1: Glycolysis (splitting sugar) Breakdown of glucose

Takes place in the cytoplasm

Must use 2 ATP molecules to start

Electrons are passed to carriers NAD+ & NADH

4 ATP molecules produced

Pyruvic Acid molecule is produced Most of the energy is still in this

Glucose + 2 ATP 4 ATP + 2 Pyruvic Acid + 2 NADH

Step 2 – The Krebs Cycle (TCA Cycle) Finishes the breakdown of glucose

Occurs inside the mitochondria

Pyruvic Acid is broken down using an enzyme (Acetyl CoA)

Followed quickly by the Electron Transport Chain (O2

is used)

2 Acetyl CoA + O2 6 NADH + 2 FADH2 + 2ATP

The electron transport chain uses NADH and FADH2 to make ATP. high-energy electrons enter electron transport chain

energy is used to transport hydrogen ions across the inner membrane

hydrogen ionsflow through achannel in themembrane

The breakdown of one glucose molecule produces up to38 molecules of ATP.

• ATP synthase produces ATP

• oxygen picks up electrons and hydrogen ions

• water is released as a waste product

After glycolysis, if O2 is not present, fermentation will occur

Fermentation – process of making ATP without oxygen No extra ATP is produced

Only what is made in glycolysis

Fermentation is Anaerobic Anaerobic = without oxygen

2 common types of fermentation Both break down the 2 Pyruvic Acids left over from glycolysis

Lactic Acid Fermentation Commonly done by fungi & bacteria

Produces some food (cheeses, yogurt, bread, soy sauce)

Can be done in the human body Produces Lactic Acid

Sore muscles after hard work?

Alcoholic Fermentation Commonly done by yeasts

Produces many foods that we eat

Produces Alcohol & CO2

Food is Digested

Glucose extracted, sent to cells

Glycolysis Breaks down Glucose

Anaerobic (no O2)

Fermentation

Lactic Acid

Fermentation

Alcoholic

FermentationKrebs Cycle

4 ATP + 2 Pyruvic Acid

6 NADH + 2 FADH2

+ 2ATP

Aerobic (O2)

Alcohol &CO2Lactic Acid

Equation for cellular respiration is the opposite of photosynthesis.