Module 3: Plant Cell

CELLS

s  smallest living unit

s  discovery was made in 1665 by Robert Hooke, used a primitive microscope to examine thin slices of cork found in stoppered wine bottles

s  Eukaryotic Cell : cells with nuclei (“eu” – well or good, “karyon” – nucleus)

s  Prokaryotic Cell : cells without nuclei (“pro” – before, “karyon” – nucleus)

CELL THEORY

s  all biological organism are composed of cells

s  cells are the unit of life

s  all life comes from preexisting life

DEVELOPERS OF CELL THEORY:

Matthias Schleiden

s  1838

s  stated all plants composed of cells

s  observed a smaller body within the nucleus that he called “nucleolus”

Theodor Schwann

s  1839

s  stated all animals also composed of cells – thus claimed all living things is composed of cells

Rudolf Virchow

s  1858

s  all cells come from pre-existing cells

CYTOLOGY

s  Robert Hooke – Father of Cytology

s  the study of the structure and the function of cells.

s  The two primary kinds of cells are:

1.        Prokaryotic

2.        Eukaryotic – true nucleus

PLANT CELL

s  basic building block of plant life and they carry out all the functions necessary for survival.

s  they are eukaryotic cells, which have a true nucleus along with specialized structures called organelles that carry out different functions.

CELL WALL

s  outermost part of the plant cell

s  it is composed of cellulose (main component) and other substance like lignin, suberin and cutin.

s  Cellulose is a structural carbohydrate and considered a complex sugar because it is used in both protection and structure.

s  Contains a sub-organelle called "plasmodesmata"

CYTOPLASM

s  “Cell Jello”

s  it is present within the cell membrane of all cell types and contains all organelles and cell parts.

s  cytoplasm is responsible for giving a cell its shape and most chemical. processes take place here.

CYTOSKELETON “Framework”

s  involved in the movement within the cell.

Functions: maintains cell shape and help in internal movement and motility

·        MICROTUBULES - made up of protein tubulin

·        MICROFILAMENTS - made from G-actin protein

MICROTUBULES

s  these are large tubular structures composed of the protein tubulin.

s  move chromosomes during cell division. (spindle fibers)

s  part of the structure of cilia & flagella

MICROBODIES

s  small, spherical organelles with specialized enzymes & are bound by single membrane.

·        Peroxisome

·        Glyoxisome

·        Lysosomes

LYSOSOME

s  it is an organelles that contain digestive enzymes.

s  only in ANIMAL cells

PEROXISOME

s  it is a membrane-bound packets of oxidative enzyme

s  Contain enzymes needed by plants to survive during hot conditions, process is called PHOTORESPIRATION

GLYOXISOME

s  it converts the fatty acids to sugar as fuel for respiration

s  eg. seed germination

CYTOPLASMIC STRUCTURES

ENDOPLASMIC RETICULUM

s  system of membrane-bound channels visible only under the electron microscope

s  transport of material within the cell

s  connected with the outer membrane of the nucleus

s  modification of proteins

Smooth Endoplasmic Reticulum

§  ribosomes aren’t attached.

§  Lipid + phospholipid are synthesized

§  Function: Synthesis, storage, or secretion of lipids

Rough Endoplasmic Reticulum

§  ribosomes are attached.

§  Synthesis of protein

§  Function: Synthesis, storage, or secretion of proteins.

RIBOSOMES

s  these are dense granules present in the cytoplasm involved in protein synthesis.

s  it may be free or attached to the endoplasmic reticulum.

MITOCHONDRIA

s  double layered organelle of the plant cell.

CRISTAE - inside folds

s  its main function is to perform cellular respiration and to regulate cellular metabolism.

s  "powerhouse of the cell”

ATP- Adenosine Triphosphate

PLASTIDS

s  they occur in a variety of shapes and sizes (with the chloroplast)

s  for higher plants, the chloroplast resemble 2 frisbees glued together. Higher plants have more chloroplast.

s  Grana found within the chloroplast formed from membranes like a stack of coins

s  Thylakoids stacks of 2-100 found in each granum; it contains green chlorophyll pigments; where the 1^st steps of photosynthesis happen.

s  Rounded, oval, or irregularly shaped protoplasmic bodies which are three main types:

A.        Chloroplast (proplastid)

·        Green plastids

B.        Leucoplast

·        Colorless plastids

·        Some are involved in the storage of starch (amyloplast)

·        If oil (elaioplast)

·        If air storage of proteins (aleuroplast)

Example: Tubers / Roots 7 Stems of plants

C.       Chromoplast

·        Plastids with red and yellow pigments called Carotenoids

GOLGI BODIES “dictyosomes”

s  composed of circular, flattened vesicles of cisternae aligned in stacks.

s  "Packaging of proteins" areas, transport of substances to and from the cell.

s  named after Camilo Golgi (discoverer, 1898)

CELL MEMBRANE / PLASMA MEMBRANE

s  also calles as “plasmalemma”

s  selectively permeable which regulates the entrance and exit of substances in a cell.

s  its basic function is to protect the cell from its surroundings.

PLASMODESMA

s  holes all over the cell wall which allows the nutrients to enter the cell and also allows the waste to exit the cell.

s  tiny strands of cytoplasm thread that connects and extends between cell openings

s  Chemical communication

STRUCTURES OF NUCLEUS

NUCLEUS

s  structure that stores DNA and acts as a cell's command center.

s  it is surrounded by the nuclear envelope and is filled with nucleoplasm.

s  the nuclear envelope contains nuclear pore which allow molecules with the appropriate nuclear import and export signals in and out of the nucleus.

s  CONTROL CENTER OF THE CELL

NUCLEAR ENVELOPE

s  the membrane that surrounds the nucleus

s  a semi-permeable membrane that regulates the passage of substance into and out of the nucleus

s  acts like the “cell membrane” of the nucleus

NUCLEUSPASM

s  or Nuclear sap

s  the fluid portion of the nucleus

CHROMATIN

s  darkly staining material suspended within the nucleoplasm

s  portion of the chromosome visible only when the cell is dividing.

CHROMOSOMES

s  condensed chromatin strands

s  contains the "genes" that determines the hereditary characteristics of the cell.

s  controls the activity of the cell.

NUCLEOLUS

s  its primary function is to assemble ribosomes, is the largest structure in the cell nucleus.

s  the nucleolus organizes regions of chromosomes which harbour the genes for pre-rRNA, are the foundation for the nucleolus.

INCLUSION BODIES

VACUOLE - vacuus (empty)

s  filled with aqueous solutions containing various dissolved substances

s  bound by VACUOLAR MEMBRANES (tonoplast) similar function with plasma membrane

Functions:

·        Useful for maintaining cell structure and water balance

·        Used for the storage of waste and food

CELL SAP

s  fluid portion of the vacuole

s  slightly acidic, vacuole also contains sugar, organic acids, and soluble proteins

Rhoeo Discolor

- bangka-bangkaan

Monocot: dumbbell

Dicot: kidney-shaped

STOMATA - are dotted tiny opening or pore that is used for gas exchange. They are mostly found on the under-surface of plant leaves (or sometimes upper) which allows entry of CO₂ and the diffusion of 0_2.

GUARD CELLS - controls water loss when the guard cells inflate or deflate, by opening or closing of pores

Chlorophyll - chloroplast: The green color of the upper surface is due to the chloroplasts and chlorophyll that is present in the mesophyll cells near the upper epidermis.

Anthocyanin- vacuole: The cells of the lower epidermis of Rhoeo discolor contain this pigment that is dissolved in the cytoplasm.

Enumerate the Plant Cell Structures:

·        CELL WALL

·        CYTOPLASM

·        MICROTUBULES

·        MICROBODIES (LYSOSOMES / PEROXISOME / GLYOXISOME)

Enumerate the Cytoplasmic Structures

·        ER

·        RIBOSOMES

·        GOLGI BODIES

·        PLASTIDS

·        CELL MEMBRANE

·        PLASMODESMA

Enumerate the Structures of Nucleus

·        NUCLEAR ENVELOPE

·        NUCLEAR SAP

·        CHROMATIN

·        CHROMOSOMES

·        NUCLEOLUS

GROWTH AND DIVISION OF THE CELL

CELL DIVISION

s  Cell division is the process in which one cell, called the parent cell, divides to form two new cells, referred to as daughter cells.

s  Cell division is simpler in prokaryotes than eukaryotes because prokaryotic cells themselves are simpler.

s  Prokaryotic cells have a single circular chromosome, no nucleus, and few other organelles.

s  Eukaryotic cells, in contrast, have multiple chromosomes contained within a nucleus.

CELL CYCLE

s  An orderly series of events where cells divide

s  2 divisions:

1.        INTERPHASE

Ø  a period in which chromosomes are NOT visible with light microscope

Ø  living cells are NOT dividing

3 INTERVALS:

              I.               G1 - (growth or gap one) lengthy period after the nucleus divides; RNA are ribosomes are produced & cell increase in size

           II.               S- synthesis - DNA replication takes place

         III.               G2- (growth or gap two) mitochondria & other organelles divide; microtubules are produced; coiling & condensation of chromosomes begin

2.        MITOSIS

Ø  where one cell divides into two and each of the two cells to produce two more daughter cells.

Ø  Location: MERISTEM (found in roots and stem tips)

Ø  CYTOKINESIS- normally comes with mitosis; division of the remainder of the cell

Ø  The daughter cells have the exact number of chromosomes as the parent cell

MITOSIS

Ø  Prophase -nuclear envelope breakdown, chromosome condensation, spindle formation.

Ø  Metaphase -chromosomes are lined up precisely on the metaphase plate, or middle of the cell.

Ø  Anaphase - spindle pulls sister chromatids apart.

Ø  Telophase - chromatids begin to decondense and become chromatin. Spindle disappears.

Ø  Cytokinesis

-        divide cell and organelles. Actin ring, or cleavage furrow splits cell.

-        the division of the cytoplasm to form two new cells, overlaps with the final stages of mitosis.

-        cell plate forms down the middle of the cell, splitting it into two daughter cells separated by a new wall.

MEIOSIS

s  type of cell division in sexually reproducing organisms that reduces the number of chromosomes in gametes

THE STAGES OF MEIOSIS I AND II