Photosynthesis

TEKS

• 4.B: Students will…

investigate and explain cellular processes

including energy conversions

• 9.B: Students will…

compare the reactants and products of

photosynthesis and cellular respiration in

terms of matter and energy

Photosynthesis

• Autotrophic Process – plants and plant-like

organisms (ex: some protists) make their food

from sunlight (radiant energy)

• Heterotrophs get their food by EATING it

• Chemotrophs get their food from CHEMICALS

• This energy is stored in the bonds of glucose

(sugar) in their bodies – which biomolecule?

» Anabolic – it builds glucose

» The energy in glucose is a kind of chemical energy

» ATP is also a type of chemical energy

Photosynthesis Formula

6CO2 + 6H2O + light C6H12O6 + 6O2

Photosynthesis

Why is Photosynthesis Important?

• Makes organic molecules (glucose) out of

inorganic molecules (water and carbon

dioxide)

– Organic is anything containing carbon AND

hydrogen

• Beginning of all food chains – therefore

ALL life is supported by photosynthesis

• It makes the oxygen gas and food we

need to survive

Basic Photosynthesis

Leaves

Structure of Leaves

• Cuticle – Outer waxy layer that protects the leaf

and prevents water loss

– Transpiration: the loss of water through a plant’s

stomata

• Upper Epidermis – no chloroplasts; protects the

inner tissues

Structure of Leaves

• Mesophyll (middle)

– ***Palisade layer – filled with chloroplasts

(where photosynthesis actually occurs)***

– Spongy layer – allows CO2 to reach

chloroplasts and O2 to escape; filled with

these gases, which makes the leaf buoyant

Structure of Leaves

• Lower Epidermis

– Stomata – pores on the underside of leaves where

gases move in and out of the plant. They are

open during the day and typically closed at night

(why?)

– Guard cells – regulate the opening and closing of

the stomata to control gas exchange

Structure of Leaves

• Vascular Tissue: similar to our arteries and

veins

– Xylem: carries water UP the plant, from the

roots to the leaves

– Phloem: carries food (glucose) DOWN the plant

for storage

Structure of Leaves

Steps of Photosynthesis

1. Light Reaction1. H2O enters through the roots and CO2 enters

through the stomata.

2. Sunlight reacts with chlorophyll to make ATP

2. Dark Reaction /

Calvin Cycle1. Stomata close to

conserve water

2. Carbohydrates

and oxygen are

formed

Steps of Photosynthesis

Steps of Photosynthesis

What Affects Photosynthesis?

• Light intensity: as light increases, so does the

rate of photosynthesis

• Carbon Dioxide: as CO2 increases, so does

the rate of photosynthesis

What Affects Photosynthesis?

• Temperature: Rate of photosynthesis decreases

if the temperature gets too low OR too high

Formula Comparison

Photosynthesis & Aerobic

Cellular Respiration Comparison