Cell Theory

Robert Hooke

• English Botanist.

• Examined cork slices from oak tree bark.

• Coined the term “cellulae” in 1665.

Anton van Leeuwenhoek

• First to observe bacteria, protozoa, nematodes,

and rotifers.

• Developed powerful single-lens microscopes.

Robert Brown

• Scottish Botanist.

• Discovered the nucleus of a cell.

Matthias Schleiden

• German Botanist.

• Found that all parts of plants are made of cells

(1838).

Theodor Schwann

• German Physiologist.

• Defined the cell as the basic unit of animal

structure (1839).

Rudolf Virchow

• German Pathologist.

• Proved that cells come from pre-existing cells.

Lynn Margulis

• American Biologist.

• Proposed the Endosymbiotic Theory (1970).

• Mitochondria and chloroplasts originated as free-

living bacteria engulfed by early eukaryotic cells

organelle

is a biological structure that

performs a distinctive function inside a cell.

Cell Wall

• Protecting the cell against physical damage

and invading pathogens.

• Controls and regulates the direction of cell

growth.

• Provides strength, structural support and

maintains the shape of the cell.

• Functions as a storage unit by storing

carbohydrates in plants.

 Cell Membrane / Plasma Membrane

• Present in all organisms.

• Controls both solute and solvent entry and

exit between the cell and the environment.

• A semi-permeable or selectively permeable in

nature.

• Providing support and maintaining the shape

of the cell.

• Helps in regulating cell growth through the

balance of endocytosis and exocytosis.

• Plays an important role in cell signaling and

communication.

Nucleus

• Considered as the central unit of a cell.

• Regulates almost all forms of cellular

activities like metabolism and division.

• A eukaryotic cell organelle containing the

genetic material.

Nuclear Envelope

encloses the genetic material inside the nucleus.

 Nuclear Pores

serve as a passage for

molecules in and out of the nucleus

Nucleolus

the site where ribosomes are

created

Nucleoplasm

liquid component of the nucleus.

Rough Endoplasmic Reticulum

• A part of the cell’s internal system that helps

in making and modifying proteins.

• Mainly focuses on modifying, folding, and

altering proteins, especially extracellular

proteins.

• Helps the cell deal with damaged proteins

and can trigger cell death.

• Has ribosomes attached to it, which makes it

look rough under a microscope.

Smooth Endoplasmic Reticulum

• It is not studded with ribosomes,

• Mainly makes and sometimes breaks down

fats (lipids).

• In liver cells, it helps turn stored

glycogen into glucose (sugar).

• It also helps make steroid hormones in

certain glands, like the adrenal glands

Golgi Apparatus/ Golgi Complex

• Receives proteins from the ER, processes

them, and sorts them for delivery to different

locations in the cell.

• Also makes certain lipids, like glycolipids and

sphingomyelin.

• In plant cells, it helps build complex

carbohydrates for the cell wall.

• Key for handling various materials that need

to be moved around or outside the cell.

Vesicle

• Small sacs that store and move substances

within a cell or between cells.

• Enclosed by a membrane like the cell’s

plasma membrane.

• Can merge with the cell membrane to release

contents outside the cell.

Vacuole

• Present in the cytoplasm and filled with a

watery fluid containing various substances

• Stores food or other nutrients required by a

cell to survive.

• Stores waste products and prevents the

entire cell from contamination.

• Occupies more than 80% of the volume of the

plant cell.

turgor pressure

It provides shape to the cell and helps it to withstand

extreme conditions.

Lysosome

• Structures containing chemicals that can

break down materials in the cell.

• Contains the powerful enzymes called

lysozyme, which can defend a cell from

invading pathogens.

• Break down damaged or worn-out cell parts.

• The "suicide bag" of the cell as they can

trigger cell death (apoptosis) when necessary.

Peroxisome

• Sacs with enzymes that digest harmful

substances.

• Breaks down complex molecules into smaller

ones.

• The liver has many ___ to help

break down alcohol in the body

• Involved in the breakdown of long-chain fatty

acids and the synthesis of specific

phospholipids that are essential for the

structure of cell membranes.

 Ribosome / Ribosomal Unit

• A complex molecular machine that produces

proteins from amino acids during protein

synthesis.

• Found in both prokaryotic and eukaryotic

cells.

• A complex of RNA and protein composed of

two subunits – smaller and larger.

• It can be free-floating in the Cytoplasm or

attached to the Rough Endoplasmic

Reticulum

Mitochondria

Mitochondria

• Generate most of the chemical energy needed

to power the cell's biochemical reactions.

• Have their own DNA and are generally

inherited only from the mother.

• Generate large quantities of energy in the

form of adenosine triphosphate (ATP).

• Site of Cellular Respiration.

Chloroplast

• They are the food producers of plants.

• Site of Photosynthesis

• Green-colored plastids of green-colored

pigments within the plant cell and are called

chlorophyll.

Centrosome

• a small dense region of

cytoplasm that serves as the main

microtubule-organizing center (MTOC).

• is where microtubules are

organized and assembled.

Cilia And Flagella

• Locomotory projections in cells that allow

movement.

• For single cells, the movement of __ and

___ results in swimming.

Cilia

are little hairs with a much shorter

length.

Flagella

looks like a whip or a tail.

Cytoskeleton

• Provides sturdy structural and mechanical

support to the cell.

• Helps in organizing cellular contents and

directing the cell movement.

PROKARYOTIC CELLS

• Classified into two domains, Archaea and

Bacteria.

• The first organisms to exist.

• Simpler and Smaller than eukaryotic cells.

• Lack membrane-bound organelles.

• Unicellular organisms.

EUKARYOTIC CELLS

• Includes Plants, Animals, Fungi, and Protists.

• Evolutionary descendants of the prokaryotic

cells.

• Complex and larger than the prokaryotic

cells.

• Can be easily distinguished by a nucleus that

contains the DNA organized into

chromosomes.

Cytosol

the fluid component of cells.

Cytoplasm

refers to the cytosol plus all cellular components.

RIBOSOMES

Present in both Prokaryotic and Eukaryotic Cells

centriole

• The main function is to help

with cell division in animal cells.

capsule

if firm and compact. May

protect the cell from the environment.

slime

if loose and unstructured. Aids

in surface adhesion.

Peptidoglycan

the primary component of

the prokaryotic cell wall.

 thick peptidoglycan

Gram-positive bacteria

thin peptidoglycan

Gram-negative

bacteria.

plasmodesmata

for communication, channels that connect neighboring cells, allowing transport of substances