Plant Cells
What are Cells?
• ROBERT HOOKE
– 1665 discovered tiny
compartments in
cork which he called
“cells”
History
• 1675- Malpighi, Italian physician, published an
account of the microscopic, internal structure
of plants
• 1838- Matthias Scheiden and Theodore
Schwann, “Cell Theory”
• 1846- von Mohl, termed the viscous liquid
which he found on boxlike cell plants and
animal cell as protoplasm
Cell Theory
Bodies of all plants and
animals are composed of
structural unit called “Cell”
Cells
Are the basic structural and functional unit
All living organisms are made up of cells
Physiological processes are encountered and
manifested at cellular level.
Prokaryote vs. Eukaryote
Prokaryote
• Cells without nucleus and
other membrane bound
organelles
Eukaryote
• Cells with nucleus and
membrane bound
organelles
• Chromosomes made up of
DNA only
• Chromosomes are made up
of DNA and protein
• Present in eubacteria and
archaebacteria
• Present in fungi, protists,
plants and animals
Prokaryote vs. Eukaryote
Prokaryote
Eukaryote
Plant Cells
Cell Wall
• Encloses and protects the cell components
• Plays a vital role in cell division and cell expansion
• Composed of overlapping cellulose, microfibril,
other polysaccharide and varying amount of
lignin
• Plasmodesmata- function in communication
between cells
- important in facilitating the flow
of water and mineral between
conducting cell
Cell Wall
• Middle lamella- region between the primary
walls of adjacent cell
- Composed of cementing
substance called “pectin”
• Other substance that may be present in the
cell wall are gums, resin, silica, calcium
carbonate, waxes and cutin and both
structural protein and enzyme
Plasma Membrane
• Semi-permiable membrane encloses the
cytoplasm within a cell
• Composed of variable amounts of fat type
molecules (lipids) and protein
• Has within it channels for the movement of
ions such as potassium (K+), calcium (Ca2+)
and Hydrogen (H+)
Cytoplasm
• Is a liquid, gel like substance and
contain several type of organelles
Vacuoles
• In a mature plant cell, one large vacuole
occupies most of the space within the cell
• Surrounded by a single layered membrane
• Functions in regulation of osmotic balance
and turgidity of the cell, and it stores
secondary metabolite
Nucleus
– Enclosed by a double membrane that has pores in
it to allow communication with the cytoplasm
– Within the nucleus are chromosome which
contain DNA needed to create proteins within the
cell
– Also present in the nucleus are one or more
nucleoli containing RNA
– The rest of the nucleus is filled by nucleoplasm
Organelles
• Plastids
- classified by the primary pigment the plant
contains
a. Chloroplast- plastid where photosynthesis takes
place
- in higher plants it is usually oval-shaped and
it is surrounded by a double membrane
- within it are sac like structure called
“thylakoid”
Organelles
- A stack of thylakoids is called granum, this is
where green chlorophyll pigments are located
- chlorophyll and proteins bound to the
thylakoid use light energy to make simple sugar
from carbon dioxide and water
b. Leukoplast- colorless plastid contain storage
product which includes protein bodies or starch
grain
Organelles
c. Chromoplast
- Plastids that are red, orange, yellow
depending on the pigment they contain
- As fruit color change, so do the plastid
structure, pigment type and content
Organelles
• Mitochondria
- Surrounded by a double membrane
- The inner of these two membrane has
infolding called “Cristae” , that protrude into
the cavity within
- Primary site of enzyme controlling respiration
Organelles
• Ribosome
- They contain ribosomal RNA and function in
protein synthesis
- Also found in cytoplasm and associated with
Endoplasmic reticulum in the cytoplasm
Organelles
• Ribosomes
- Contain ribosomal RNA and function in
protein synthesis
- Also found in cytoplasm and associated with
endoplasmic reticulum in the cytoplasm
Organelles
• Dictyosome/ Golgi Bodies
– These organelles appear appears as a flattened
sacs and associated vesicle
– Produce and secrete cell wall polysaccharide
precursor and complex carbohydrate substance
that are secreted out of root cap cell
Organelles
• Endoplasmic Reticulum
– System of membranous tubules and sac
– Primary function of the ER is to act as internal
transport system that allows molecules to move
form one part of the cell to another
a. Smooth Endoplasmic Reticulum
- Has no 80s ribosome
b. Rough Endoplasmic Reticulum
- Site of Protein synthesis studded with 80s ribosome
Organelle
• Microbodies
a. Lysosomes- spherical or sac like
- capable of digesting unwanted
molecules in the cell under acidic
condition
- function in resorption and
phagocytosis
Organelles
b. Peroxisome - similar appearance to
lysosome
- contain a variety of enzymes
- rid of toxic substances
hydrogen peroxide (a common
by product of cellular
metabolism)
Organelles
c. Glyoxysomes
- another type of microbody
- contain enzymes
Function:
- convert stored fats into sugar
Plant Cells
Crystals
Composition
• Calcium Oxalate (CaC2O4)
Types of Crystal
• Raphides- Needle like
• Rosette- star or rose like
• Prismatic- Prism or diamond
• Styloid- Knife like
• Calcium Carbonate (CaCO3)
• Cystolith- grape-like