Transcript Basic Principle in Plant Physiology

Nucleus
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The nucleus is the controller of
the cell.
It is surrounded by the nuclear
envelope which controls what
substances may exit/enter the
nucleus.
It contains DNA and the
nucleolus.
DNA is termed the “genetic
blueprint” and directs all
protein synthesis.
The nucleolus makes
ribosomes.
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Nucleus-Plant
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The nucleus is the controller of
the cell.
It is surrounded by the nuclear
envelope which controls what
substances may exit/enter the
nucleus.
It contains DNA and the
nucleolus.
DNA is termed the “genetic
blueprint” and directs all
protein synthesis.
The nucleolus makes
ribosomes.
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Ribosomes
• Free floating and fixed:
Endoplasmic
Reticulum
Cell
• Ribosomes are protein
factories. All protein
synthesis occurs within
the ribosome.
• They may be fixed
(attached to the
endoplasmic reticulum)
or free floating in the
cytoplasm
• They are composed of
rRNA and proteins.
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Ribosomes-Plant
• Free floating and fixed:
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Ribosomes are protein
factories. All protein synthesis
occurs within the ribosome.
They may be fixed (attached to
the endoplasmic reticulum) or
free floating in the cytoplasm
They are composed of rRNA
and proteins.
Endoplasmic
Reticulum
Cell
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Endoplasmic Reticulum
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The endoplasmic reticulum or
ER is a network of channels
which assist in the synthesis
and transport of cellular
products.
There are two types:
smooth ER which is involved
in the synthesis of lipid
products such as steroid
hormones.
Rough ER which has
ribsosomes attached to it & is
involved in protein synthesis.
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Endoplasmic Reticulum-Plant
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The endoplasmic reticulum or
ER is a network of channels
which assist in the synthesis
and transport of cellular
products.
There are two types:
smooth ER which is involved
in the synthesis of lipid
products such as steroid
hormones.
Rough ER which has
ribsosomes attached to it & is
involved in protein synthesis.
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Golgi Apparatus
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This organelle consists of
tubular channels which
function to assemble, and
check proteins coming from
the rough ER.
The golgi apparatus also
ensures that the completed
proteins go to the appropriate
area of the cell. (that proteins
for the cell membrane get to
the membrane, proteins
hormones exit the cell etc.)
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Golgi Apparatus-Plant
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This organelle consists of
tubular channels which
function to assemble, and
check proteins coming from
the rough ER.
The golgi apparatus also
ensures that the completed
proteins go to the appropriate
area of the cell. (that proteins
for the cell membrane get to
the membrane, proteins
hormones exit the cell etc.)
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Lysosomes
• Lysosomes contain
powerful digestive enzymes
which break apart anything
that gets inside it.
• They are important in
protection (splitting
bacteria) as well as, old
organelles.
• Lysosomes are able to
release the end products for
reuse in the cell.
• It is important that the
lysosome doesn’t rupture or
the enzymes would digest
the cell.
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Mitochondria
• Mitochondria are the
“powerhouses” of the cell.
• They are responsible for
carrying out aerobic cellular
respiration.
• This process forms ATP
from the food we eat and
requires oxygen.
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Mitochondria-Plant
• Mitochondria are the
“powerhouses” of the
cell.
• They are responsible
for carrying out aerobic
cellular respiration.
• This process forms
ATP from the food we
eat and requires
oxygen.
Back
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Cytoskeleton
• The cytoskeleton functions
as the “muscles and bones
“of the cell.
• It consists of:
• Microfilaments: which help
the cell to move (muscle
contraction)
• Intermediate Filaments:
which prevent the cell from
being pulled apart.
• Microtubules: function in
maintaining the cell shape.
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Central Vacuole
• Large organelle
• Consists of mostly water, plant pigments, and
toxins.
• Functions for storage of nutrients and
pigments, and retains waste products.
• The pigments which give a flower its color are
stored in the vacuole.
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Chloroplasts
• Contain green pigment
termed chlorophyll.
• Function in
photosynthesis
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The importance of water to living
organisms
Metabolic role of water:
• 1. Hydrolysis
• 2. Medium for chemical reactions
• 3. Diffusion and osmosis
• 4. Photosynthetic substrate/raw material
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Water as a solvent:
It readily dissolves many substances & therefore is used for
• 1. Transport
• 2. Removal of wastes
• 3. Secretions
Water as a lubricant:
• 1. Mucus
• 2. Synovial fluid
• 3. Pleural fluid
• 4. Pericardial fluid
• 5. Perivisceral fluid
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Supporting role of water:
because of its incompressiveness, support is possible
• 1. Hydrostatic skeleton
• 2. Turgor pressure
• 3. Humours of the eye
• 4. Amniotic fluid
• 5. Erection of the penis
• 6. Medium in which to live
Miscellaneous functions of water:
• 1. Temperature control
• 2. Medium for dispersal
• 3. Hearing and balance
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Protoplasm , colloid, diffusion and imbibitions
Oxygen atom
1050
Hydrogen atom
Hydrogen atom
0.1539 nm
22.1.1 Structure of the water molecule
• normal water molecule: 1H216O
• isotopes:
• heavy water - 2H216O may be harmful to living
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organisms
Colloids
• Cytoplasm is a colloid, made up largely of protein
molecules dispersed in water.
• It is hydrophillic, i.e. attracts water molecules
around them and prevent them to aggregate into
large particles and settle out.
• Imbibition is the process by which water is
absorbed by hydrophilic colloids inside seeds at
the beginning of germination.
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Water Relations of A Plant Cell
Water potential of a system is the difference
in chemical potential of water in a system and
that of pure water at the same temperature
and pressure.
The water potential of pure water at standard
temperature and pressure is “0”.
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 Osmotic potential is the component of water
potential that is due to the presence of solutes.
 Pressure potential is the component of water
potential that is due to the hydrostatic pressure.
 Incipient plasmolysis is the point at which the
protoplast of the cell just lost contact with the cell
wall.
 Plasmolysis is a condition of the cell when the
protoplast shrinks away from the cell wall due to
osmosis.
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Molecular Movement
• Diffusion - movement of a substance from
an area of higher concentration and/or
pressure towards and area of lower
concentration and/or pressure
• Osmosis - the diffusion of water across a
semipermeable membrane
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• Click here to see the water relations movies
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Potentials
• Osmotic Potential - the effect of dissolved
solutes on water potential
• Pressure Potential - the effect of pressure on
water potential
Positive pressure potential is called
turgor pressure
Negative pressure potential is called
tension
Water Potential = osmotic potential + pressure potential
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Plasmolysis
• the shrinkage of protoplasts away from cell
walls caused by loss of water by osmosis
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Imbibitions
• movement of water into plant tissues due to
water being attracted to polar substances,
e.g. cellulose and starch
• first step in germination
• can produce tremendous pressures
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Plant Enzymes
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Characteristics of Enzymes
• Most are globular proteins that act as biological
catalysts
• Holoenzymes consist of an apoenzyme (protein)
and a cofactor (usually an ion) or coenzyme
• Enzymes are chemically specific
• Frequently named for the type of reaction they
catalyze
• Enzyme names usually end in -ase
• Lower activation energy
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Characteristics of Enzymes
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Mechanism of Enzyme Action
• Enzyme binds
substrate(s) at
active site
• Product is
formed at a
lower activation
energy
• Product is
released
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Cofactors
• provide “chemical teeth” for enzymes
• sometimes referred to as coenzymes
• enzymes: proteins with catalytic activity
– simple enzymes: large protein (polypeptide) that catalyzes
a reaction. The enzyme gets all the “tools” (chemical
teeth) it needs from the amino acids. However, there are
only 20 different amino acids
– conjugated enzymes : apoenzyme + cofactor =
holoenzyme
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EXAMPLE: Proteases: enzymes that cleave
peptide bonds
Enzymes perform catalytic reactions such as hydrolysis; the
side chains of amino acids participate in the reactions
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example of a simple enzyme
Usually electronrich
side chains are
involved
in the catalysis
Aliphatic chains
are normally
involved in
hydrophobic
interactions
A serine protease enzyme such as chymotrypsin
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HYDROLYTIC CATALYSIS
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Example of a conjugated enzyme
Zinc protease such
as ACE
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