Cell Theory and Plant Cell Structure

All life forms are made up of cells (Schleiden & Schwann) ○ Can exist on its own

The cell is the basic unit of life (Schleiden & Schwann) ○ Simplest form of life

Cells come from pre-existing cells (Virchow) ○ Evolves through reproduction (cycle)

What are the three basic tenets of the cell theory?

Hans and Zacharias Janssen

Who first invented the compound microscope in 1595.?

Robert Hooke

Who coined the term “cell” after observing a cork under the microscope in 1665?

Antonie van Leeuwenhoek

Who made his own microscope in 1668 and is known as the Father of Microscopy and Microbiology?

Theodore Schwann & Matthais Schleiden

Who found that animals were composed of cells?

Rudolf Virchow

Who concluded that cells can only come from preexisting cells in 1855?

Prokaryotic Cells

Single-celled organisms without nuclei and membrane-bound organelles.

examples: bacteria and archaea

Eukaryotic Cells

Multicellular organisms with organized compartments, membrane-bound organelles, and membrane-bound nucleus. Possess a cytoskeleton for support and to maintain cellular structure

examples: Protists, fungi, plants, and animals

Endosymbiotic Hypothesis

This hypothesis claims that eukaryotes arose from a symbiotic relationship between various prokaryotes

Cell Structure

All cells share genetic material and plasma membrane.

Cell Membrane

Phospholipid bilayer acting as a selective barrier.

Ribosomes

Cellular structures for protein synthesis.

Cellulosic Cell Wall

Provides structure and support in plant cells.

Surrounds growing cells, meristematic cells, and cells in succulent tissues

Primary Cell Wall

First layer surrounding growing plant cells; produced after mitosis

Secondary Cell Wall

Inner layer, thickens plant cells for sturdiness; pushes the primary cell outward

More common in MORE STURDY parts of the plant (wood, cork)

has 3 layers

Middle Lamella

Cements primary walls of adjacent plant cells.

Plasmodesma

Cytoplasmic thread allowing communication between plant cells.

Lipid Rafts

Specialized membrane domains for cellular functions.

made up of Lipid bilayer, cholesterols, and sphingolipids

Fluid Mosaic Model

Describes heterogeneous nature of cell membranes.

Soluble Fiber

Dissolves in water, lowers cholesterol levels.

Insoluble Fiber

Speeds digestion, reduces colon cancer risk.

Cytoplasm

Semifluid matrix containing organelles and cytosol.'

gel-like fluid inside the cell. It is the medium for chemical reaction

Plastids

Organelles involved in storage and pigment synthesis.

Chloroplasts

Site of photosynthesis, contains chlorophyll and DNA.

Genetic material (in a nucleoid or nucleus)

Cytoplasm (semifluid matrix)

Plasma membrane (phospholipid bilayer)

Ribosome (protein synthesis)

What are the common cell structures among all cells?

Prokaryotic

What kind of cell is this?

From the prokaryotic cell, it may have swallowed another prokaryotic cell. This prokaryotic cell now becomes part of the mother prokaryotic cell.

If the mother prokaryotic cell swallowed an organism with chlorophyll pigments that can undergo photosynthesis

As it accumulates, these parts have evolved into specialized parts within the mother cell.

Aerobic bacterium now has become a mitochondria

Bacterium with chlorophyll now has become the chloroplastid

The nuclear material inside now has developed its own membrane around it

There developed subunits or organelles with specific functions within the cell. It now has become more complicated and in turn, into a EUKARYOTIC CELL

Describe the endosymbiotic hypothesis

Mitochondria; chloroplasts

In the endosymbiotic hypothesis,

Heterotrophic bacteria became_______

Cyanobacteria became_________

The mitochondria and chloroplasts

1. Similar to bacteria in both size and structure

2. Bounded by a double membrane (outer membrane is the engulfing vesicle, the inner from the prokaryote)

3. Each contain a circular DNA and divide by splitting

4. Have their own ribosomes and produce some proteins, like prokaryotes

Pieces of evidence for the endosymbiotic hypothesis

Centriole and the lysosome are present in only animal cells, not plant cells

What are unique to animal cells?

Cell walls, chloroplastids, large central vacuole

What structures found in plant cells but not in animal cells?

lysosomes

Break down materials

Central vacuole

What is the equivalent of lysosomes in plant cells?

Cellulose, hemicellulose (alkali-soluble portion of the cell wall), pectin (water soluble), and glycoprotein

What are cell walls (primary wall) composed of?

lignin

An aromatic polymer that rigidifies secondary cell walls

pectin

Cementing substance made up of calcium and magnesium pectates

Pectin

Primary wall

Secondary wall (S1)

Secondary wall (S2)

Secondary wall (S3)

Describe the sequence from the outside to the inside of the cell wall

The roughness of the older cell wall

What makes the cementing substance stick together?

It loses its stability

What happens if the hemicellulose, lignin, proteins etc are dissolved in the secondary wall?

An extra cellular layer between two cells that keep them together

What is mid lamella/middle lamella?

30-35%

All higher plants except the grass family have walls of ______ pectin

10%

How much pectin does the grass family contain?

Fiber

__________ is an undigestible complex carbohydrate found in plants

Describe soluble fibers

Describe insoluble fibers

Thin areas on the secondary cell walls of plants. They look like depressions on the walls. Also, they aid in the transport of minerals and water between the cells

What are pits?

External

Cytoplasm is __________ to the endomembrane system

Eukaryotic cells are full of membrane-enclosed compartments

Separates incompatible chemical and physical conditions

Proteins can be both synthesized and hydrolyzed within a single cell

What is compartmentalization?

cytosol

It is found in the cytoplasm, where the cytosol acts as the liquid portion composed of water, enzymes, precursors, and intermediate by-products where all the organelles are suspended in

Stroma

What are the chloroplast constituents?

Proplastids

Specialized for dividing to form new plastid and are usually found in meristematic cells

Etioplasts

These plastids develpo in the absence of light. This does not need photosynthesis

Amyoplasts

These are specialized for storage that contain a large amount of starch. It also does not contain chlorophyll

Chromoplasts

Contains red, orange, or yellow carotenoid pigments that are water-insoluble

Elaioplasts

Contains oil droplets and usually found in fruits or seeds

proteinoplast

Plastids that contain proteins

Proplast

Etioplast

Amyloplast

What are the different leucoplasts (colorless)?

Non-raft lipids: portions with lipid and proteins

Raft: clustering of specific lipids and proteins that move along the surface

Non-raft vs raft lipids

No, because lipids with those proteins change positions around the cell membrane

Are lipid rafts stable?

Glycolipids

Carbohydrates attached to the phospholipid bilayer are called

Glycoproteins

Carbohydrates attached to membrane proteins are called