Overview of Photosynthesis

Most autotrophs (organisms that

create their own food), make organic

compounds (sugars/glucose) using a

process called photosynthesis.

This process occurs only in plants.

Overview of Photosynthesis

Photosynthesis is the process in which light

energy is converted into chemical energy and

can be shown by the following equation:

Overview of Photosynthesis

Photosynthesis occurs in two

stages:

Light-dependent reactions

(requires light)

Light-independent reactions

(does not require light)

Phase One: Light Reactions (Light-

Dependent)

Plants must first

capture light. They

have special organelles

called chloroplasts

located in the leaves of

a plant that help them

to capture light energy.

Phase One: Light Reactions (Light-Dependent)

Chloroplasts contain specialized structures to help

them carry out the two part process of

photosynthesis.

Thylakoid: flattened, sac-like

membranes that are arranged in

stacks

Grana (granum): stacks of

thylakoids

Stroma: the fluid-filled space that

is outside the grana

Phase One: Light Reactions (Light-

Dependent)

The thylakoid membranes of a

plant’s chloroplasts hold pigments,

which are special light absorbing

molecules.

Plants appear green because of

chlorophyll pigments found in the

chloroplasts.

Phase One: Light Reactions (Light-

Dependent)

When there’s a change in

temperature in certain parts

of the US, chlorophyll

pigments begin to break

down. Other pigments called

carotenoids may bring out

shades of yellow, red, and

orange.

Phase One: Light Reactions (Light-

Dependent)

Light reactions take place in the

thylakoids of a plant cell and consist of

the electron transport chain (or ETC).

At the end of the light reactions, we

have formed the energy-storage

molecules NADPH and ATP.

Phase One: Light Reactions (Light-Dependent)

Phase 2: The Calvin Cycle (Light-

Independent)

Plants must convert NADPH and ATP into organic

molecules called glucose (sugar), that can be

used by the plant.

At the end of the Calvin Cycle, the plant has

formed sugars, which can be used for energy and

as building blocks for complex carbs, which

make up cellulose and provide support for the

plant.

The Calvin Cycle

Overview of Cellular Respiration

The function of cellular respiration is

to take glucose and use the energy

stored there to make ATP, which can

then be used by the cells to carry out

essential processes.

This process occurs in BOTH plants and

animals.

Overview of Cellular Respiration

Cellular respiration occurs in the

mitochondria of the plant or animal

cell, and can be shown by the

following equation:

Overview of Cellular Respiration

Cellular respiration occurs in two main

parts: glycolysis and aerobic respiration

Stage one, glycolysis, is considered

anaerobic because it does not require

oxygen.

Stage two, which includes the Krebs Cycle

and ETC, is considered aerobic because it

does require oxygen.

Phase One: Glycolysis (Anaerobic)

Glycolysis occurs in the cytoplasm

of the cell and is the process of

breaking down the glucose.

At the end of glycolysis, we have

formed ATP and pyruvate

molecules.

Phase Two: Aerobic Respiration (Krebs

Cycle & ETC)

The Krebs Cycle is often referred to as the

Citric Acid Cycle.

In the Krebs Cycle, the pyruvate molecules

are broken down because they still hold

most of the energy.

At the end of the Krebs Cycle, we are left

with carbon dioxide molecules, ATP, NADH,

and FADH2

Phase Two: Aerobic Respiration (Krebs

Cycle & ETC)

The NADH and FADH2 go on to be used by

the ETC to convert ADP to ATP.

The ETC produces most of the energy, or

ATP.

Phase Two: Aerobic Respiration (Krebs

Cycle & ETC)

In eukaryotic organisms (those made up of

more than one cell), the ETC produces 36

ATP that the organism can use for essential

processes.

In prokaryotic organisms (those made up of

only one cell), the ETC produces 38 ATP

that the organism can use for essential

processes.

Anaerobic Respiration

In the event oxygen is not present for the cell to undergo the Krebs Cycle and ETC, it will than do an alternate process called fermentation.

Fermentation produces less ATP molecules than aerobic respiration, so it is not as efficient.

Anaerobic Respiration

There are two types of fermentation: lactic-

acid fermentation which produces lactic acid,

and alcohol fermentation which produces

alcohol.

Organisms such as yeast and bacteria undergo

fermentation to produce beer, wine, cheese,

and yogurt.