( 1 ) The Plant Cell Wall and the Chloroplast

This is about the plant cell and the chloroplast.

Plant Cell Wall

This is a cellulose-based covering outside the cell membrane.

Plant Cell Wall

It provides additional covering and protection to the cell.

Maintenance of cell shape; creation of cell to cell interface; and intercellular communication.

The function of a plant cell wall includes:

1. Provides support and limited plasticity

2. Prevent the loss of water

3. Protection from insects and pathogens

4. Filter

5. Prevent overexpansion caused by too much water

6. Keep the shape of the plant

7. Allow plants to grow to great heights

Functions of Plant Cell Wall

The primary and secondary cell walls and a middle lamella

What are the three layers of a plant cell wall?

Primary Cell Wall

• Usually elastic with loosely arranged fibrils containing about 20% proteins.

• Composed of cellulose in the form of microfibrils.

Secondary Cell Wall

• This cell wall of plant is the thicker and stronger layer.

• Composed of three sublayers: S1, S2 and S3 (differ in cellulose composition and orientation of microfibrils).

• S2 has low microfibril angle while S1 and S3 have higher microfibril angles.

Middle Lamella

• First to be formed during the synthesis.

• The outer layer of the cell wall acts as the cement that binds two adjacent cell walls.

• Rich in pectin.

Xylan (Secondary)
Xyloglucan (Primary)

This hemicellulose is found in the secondary cell wall while this is found in primary cell wall.

Pectin

This is maybe present from the secondary cell wall and no structural proteins are known.

Plasmodesmata

These are holes that allow for nutrients to enter the cell as well as waste to exit the cell.

Pectin

It helps to strengthen the plant and give it the ability to resist compression.

Cellulose

A structural carbohydrate and is considered a complex sugar used in both protection and structure.

Microfibril

A fine fibril or fiber like strand consisting of glycoproteins and cellulose.

Lignin

A very hard and has considerable strength.

• A durable, waterproof polymer that serves as a "backbone" for plants, providing structure and support.

Xylan

A type of hemicellulose, a polysaccharide consisting mainly of xylose residues.

Chloroplast

It is an organelle responsible for the process of photosynthesis.

• Converts solar energy to chemical energy.

• Site of photosynthesis.

• Absorbs light and use water and CO2 to produce food for the plant.

Chloroplast

They are biconvex or planoconvex in shape among higher plants and are abundant in the mesophyll layer of plant leaves.

• They vary in shape among different plant species.

Spiral and star shaped

In algae, chloroplast may appear ______ (Spyrogyra sp.) or ____ shaped (Zygnema sp.)

Plastids

Chloroplast is a member of a group called?

Ernst Haeckel

Who first discovered the plastids?

Andreas Franz Wilhelm Schimper

Who defined the plastids discovered by Ernst Haeckel?

Plastids

These are membrane-bound organelles considered endosymbiotic cyanobacteria, they manufacture pigments that determine the color of the plant cell such as green in the case of chloroplast.

Endosymbiosis

The incorporation into the plant cell is described by an evolutionary event called?

Outer Membrane

The membrane that is semi-porous covers the chloroplast- this allows the small molecules to diffuse easily.

• Acts as a barrier, providing a selective permeability that allows the entry and exit of molecules.

Inner Membrane

This membrane regulates the passage of materials into the chloroplast, also responsible for manufacturing the lipids and carotenoids.

• Regulates the transport of materials into and out of the chloroplast and houses many transport proteins.

Intermembrane Space

This space of about 10 – 20 nanometers is present between the outer and inner membranes.

• The space between the inner and outer membranes, playing a role in the transport of substances.

Stroma

It is a fluid-filled space within the chloroplast that surrounds the stacks of thylakoid termed as grana.

Stroma

The fluid-filled space within the inner membrane that contains enzymes, DNA, and ribosomes. It is the site of the Calvin cycle, where carbon fixation occurs.

Thylakoid System

This system is suspended in the stroma and individual thylakoids contain chlorophyll – these membrane-bound compartments are stacked collectively as grana.

Grana

Stacks of thylakoids that increase the surface area for light absorption and enhance the efficiency of photosynthesis.

Thylakoid

Membrane-bound structures stacked into granum; contain chlorophyll and are the site of the light-dependent reactions of photosynthesis. They capture light energy and convert it into chemical energy.

Lumen

It is the space in the thylakoid.

Chlorophyll

The green pigment located in the thylakoid membranes that absorbs light energy, primarily from the blue and red wavelengths, and plays a crucial role in converting light energy into chemical energy.

Lamella

Membrane structures that connect grana, facilitating the transfer of energy and materials between thylakoids.

Ribosomes

Present in the stroma, they synthesize some of the proteins needed for the chloroplast's function.

Chloroplast DNA (cpDNA)

Circular DNA located in the stroma, encoding some of the proteins necessary for chloroplast function and allowing for some level of autonomy from the nuclear DNA.