Unit 2 quiz 3 - Leaves/chlorophyll

Membranes of chloroplast

Inner (smooth)

Outer (smooth)

Thylakoid

Site of light dependent photosynthesis

Grana

Stack of thylakoids

Lamellae

Unstacked thylakoids between grana

Stroma

Semi-liquid material inside the chloroplast

Lumen

water filled things inside the thylakoids

Where does photosynthesis take place

Inside the stroma and thylakoid membrane

Unique qualities of chloroplasts

Has own DNA and ribosomes

Replicate by binary fission

Overall equation for photosynthesis

6CO2 + 12H2O + light energy → C6H12O6 + 6O2 + 6H2O

Cuticle

Waxy outer layer of leaf

Protects from dessiccation, chemical and physical agents and uv radiation

Epidermis

Under cuticle, allows light to reach mesophyll

Spongy Mesophyll

Palisade Mesophyll

Parenchyma

Ground tissue (mesophyll layers in leaves)

Vascular tissue

Xylem (transport water and nutrients from root to leaf)

Phloem (transports photosynthate around plant)

3 types of plant tissue

• dermal (lower and upper epidermis)

• Ground tissue (parenchyma/mesophyll)

• Vascular tissue (xylem and phloem)

Guard cells

Swell to create stomata to regulate the amount of CO2 entering and O2 leaving the leaf.

Guard cells are turgid

Stomata is open

Guard cells are flaccid

stomata is closed

Factors influencing stomata’s opening (generally)

Light -open

Dark - close

High CO2 inside leaf - close

Low CO2 inside leaf - open

Drought stress - close

Purpose of stomata

Regulate O2 and CO2 concentration in plant

Transpiration

Transpiration and purposes

Loss of water through stomata

• creates a pull that helps move water and minerals up the plant

• Creates a cooling effect by water evaporating off the plant

Which is more important to a plant: having CO2 or having H2O

H2O - hence why stomata will close during a drought

Abscisic acid

Phytohormone that overrides other signals and closes stomata during droughts

How do stomata open

Blue slight activates potassium pumps that move K+ into the cells

Creates a concentration gradient for water to enter cell by osmosis

Guard cells swell (become turgid). Thin outer wall and thick inner wall cause bean shape which opens stomata

Photoreceptor + example

where light reactions take place eg chlorophyll

Chlorophyll

Traps light energy and converts it into chemical energy

Absorbs blue-violet and red photons

Reflects green photons

Photosystems

Groups of chlorophyll found in thylakoid membrane

2 types of chlorophyll + structural differences

Chlorophyll a - CH3 in side chain

Chlorophyll b - CHO in side chain

Side chain (top right)

Chlorophyll a

Transfers energy of light to carbon fixation reactions of photosynthesis

Chlorophyll b

Accessory pigment,

Absorbs photons that chlorophyll a absorbs poorly, transfers energy to chlorophyll a

Carotenoid

Absorbs energy in blue-violet range

Reflects yellow-red range

Energy absorber more than photosynthetic

• absorbs photons that could damage chlorophyll

• Enzymes split molecule into 2 identical halves to produce vitamin A

Xanophylls

Accessory pigment that reflects yellow pigment

Anthocyanins

Reflect red, violet and blue photons

Found in cell vacuoles

What causes colon change in leaves during fall

Plants stop producing and disassemble chlorophyll

Anthocyanin is produced which causes the yellow, red and brown colours of the leaves

Where are accessory pigments found

Spread out in the thylakoid membrane

Placement of stomata in monocots vs dicots

Monocots would have stomata on either side of the leaf (grow straight up)

Dicots would have stomata on underside of leaf

They are avoiding direct sunlight

Spongy vs palisade mesophyll

Palisade - tall and stacked, does most photosynthesis, arranged to expose chloroplasts to maximum sun

Spongy - cubical, loosely packed, air pockets for rapid gas exchange

Photosynthesis in shady vs sunny areas

Shady - thinner, broad leaves. As many chloroplasts in spongy mesophyll as palisade mesophyll. Lower rates of respiration, photosynthesize more

Sunny - thicker leaves, more chloroplasts in palisade mesophyll than in spongy mesophyll, Higher rate of respiration