Introduction

Biological membrane

• Phospholipid bilayer that contains protein

• allows the uptake of certain substances

• Has various transporter proteins consuming metabolic energy for selective transport

• regulates the fluxes of ions and metabolites

• described as a fluid-mosaic model

components of a fluid-mosaic model

1. phospholipid bilayer

2. integral proteins

3. peripheral proteins

4. anchored proteins

Integral Proteins

embedded in the bilayer and span the entire width of the bilayer to serves as ion channels

Peripheral Proteins

bound to the surface of the membrane surface by noncovalent bonds, and can be dissociated from the membrane with a high salt solution.

peripheral proteins are involved in interactions between the plasma membrane and components of the cytoskeleton such as ,…..

Microtubules and actin microfilaments

Anchored Proteins

bound to the membrane surface via lipid molecules (covalently)

Plastids are derived from

Proplastids

Proplastids

an organelle found in the meristematic region of the plant that is colorless and small ,and is still underdeveloped. ( when developed they turn to specialized plastids)

Chloroplasts

Plastids with chlorophyll and are involved in photosynthesis

Chromoplasts

involved in producing and storing pigments ( carotene, xanthophylls. etc) and are found in fruits, flowers and roots

Leucoplast

lacks pigments and involved mainly for storing food

types of leucoplast

1. Amyloplast (stores starch)

2. Elaioplast (stores fat)

3. proteinoplast (stores protein)

Mitrochondria

plastids that have their own DNA and ribosomes

Semiautonomous organelles

Organelles that contain their own DNA and protein-synthesizing machinery, however they depend on the nucleus for the majority of their protein

Example of semiautonomous organelles

mitochondria and chloroplasts

DNA of semiautonomous organelles

circular chromosomes that are localized in a specific region (nucleoids)

Cell division in plants are limited to ——— post embryonic growth and development

the meristems

meristems are divided into

1. Shoot Apical Meristem (SAM)

2. Root Apical Meristem (RAM)

3. Lateral Meristem

Shoot Apical Meristem (SAM)

Growth lengthwise upward

Root Apical Meristem (RAM)

Growth lengthwise downwards

Lateral Meristem

Growth in diameter

Cytoskeleton

a three-dimensional network of filamentous protein

Cytoskeletons function

1. Spatial organization for the organelles

2. Scaffolding for the movement of organelles

3. Fundamental role in meiosis, cytokinesis, wall deposition

4. Maintenance of cell shape, and cell differentiation

types of cytoskeletal elements

1. Microtubules

2. Microfilaments

3. Intermediate filaments

Microtubules

a hollow cylinder that are composed of polymer of the protein tubulin

Protofilaments

a single microtubule consists of hundreds of thousands of tubulin monomers arranged in 13 columns

Microfilaments

solid, and composed of a special form of the protein found in muscle (G-actin). consisting of two chains of polymerized actin subunits that intertwine in a helical fashion

Intermediate filaments

a diverse group of tough, helically wound fibrous elements that function in the structural support of membranes ,and are composed of linear polypeptide monomers of various types.

Plasmodesmata

tubular extensions of the plasma membrane that traverse the cell wall and connect the cytoplasm of the adjacent cells

the cytoplasm form a continuum referred to as the symplast because ?

most plant cells are interconnected by the plasmodesmata

Symplastic transport

Intercellular transport of solutes through plasmodesmata

Plasmodesmata Function

regulating macromolecular traffic from cell-to-cell

the complex internal structure of plasmodesmata

contains a narrow tubule of ER called desmotubule

Desmotubule

is a continuous with the ER of the adjacent cells

Plant Cell

Microtubules

Microfilaments

Desmotubule

Plasmodesmata