Unified Cell Theory

Unified Cell Theory

C

B

Prokaryotes

• since cells lack a nucleus, cytoplasm simply means everything found inside the plasma membrane

Eukaryotes

• since cells have a nucleus, the cytoplasma is everything between the plasma membrane and nuclear envelope

• DNA is located in nucleoid
• Cell organelle that houses DNA and directs synthesis of ribosomes and proteins is found in nucleus

A

Matthias Schleiden & Theodor Schwann proposed the Unified Cell Theory:

• All living things composed of ≥≥≥one or more cells
• The cell is the most basic unit of life
• new cells arise from existing cells

Microscopes are used for study:

Light microscopes study living cells

• Electron microscopes have higher magnification and resolution, but sample preparation kills the specimen

A

Prokaryotes

• DNA is found in nucleoid, not nucleus

B

2) CYTOPLASM

• The matrix inside cells. Provides structure to cell; medium in which organelles are found.
• A major component is a gel-like crytosol which is a water-based solution that contains ions, small molecules, and macromolecules.

3) DNA

Eukaryotes

• DNA is found in nucleus, not nucleoid
• The nucleus contins the cell's DNA in the form of chromatin and directs the synthesis of ribosomes and proteins
• It is surrounded by a double-membrane punctuated by pores and
• connects to the endomembrane system
• the Endodmembrane system:
• the endophplasmic reticulum (ER)is a series of interconnected tubules which modify proteins and synthesize lipids; and rough and smooth ER have specialized functions
• the Golgi apparatus is rsponsible for sorting, tagging, packaging, and distribution of lipids and proteins

C

B

A

All cells share 4 features:

1) Plasma membrane

2) Cytoplasm

3) DNA

4) Ribosomes

• The cellular structures responsible for protein synthesis
• Free ribosomes appear as either clusters or single tiny dots floating freely in the cytoplasm
• May be attanched to plasma membrane or ER
• found in practically every cell, although smaller in prokaryotic cells

• Seperates cell from external environment, controls passage if organic molecules, ions, water, oxygen, and waste into and out of the cell
• All cells have a phospholipid bilayer plasma membrane which holds it all together

C

There are 2 types of cells:

Prokaryotic Cells, and

Eukaryotic Cells (which include plant and animal cells)

4) RIBOSOMES

1) PLASMA MEMBRANE

A

• Cell size is limited because volume increases much more quickly than does cell surface area
• Prokaryotes: Size is limited to allow ions and organic material to enter and spread throughout them quickly
• Eukaryotes: Have structural adaptations to allow cellular transport

B

found in Prokaryotes, but smaller

Cells

B

found in Prokaryotes

C

found in Eukaryotes

C

found in Eukaryotes

PROKARYOTIC CELLS

• A simple, single-celled (unicellular) organism that lacks a nucleus, or any other membrane-bound organelle
• Examples include Bacteria and Archaea
• bacteria have a cell wall made of peptidoglycan and many have a polysaccharide capsule
• some prokaryots have flagella (long, hair-like structures that extend from the plasma membrane and are used to move an entire cell), pili, or fimbriae

EUKARYOTIC CELLS

• A cell that has a membrane-bound nucleus and other membrane-bound compartments or sacs, called organelled, which have specifialized functions
• typically larger than prokaryotic cells
• may be single-celled organisms or may be part of a multicellular organism
• Shared Characteristics:
• nucleus surrounded by envelope with nuclear pores
• mitochondria-often called the "powerhouses" or "energy factories" of a cell because they make adenosine triphosphate (ATP), the cell's main energy-carrying molecule
• a cytoskeleton containing the structureal and motility components
• flagella (long, hair-like structures that extend from the plasma membrane)and cilia (when present, they are many in number and extend along the entire surface of the plasma membrane), organelles associated with cell motility
• chromosomes
• mitosis, a process of nucear division
• sex, a process of genetic recombination
• cell walls in all major lineages

Plant Cell Specific Organelles: the cell wall is a rigid covering; found in plants; chloroplaasts functon in photosynthesis andcan be found in photoautotrophic eukarytopic cells such as plants and algea.

Animal Cell Specific Organelles: lysosomes are the cell's "garbage dispisal"; cells can also communicate with each other by direct contact, referred to as intercellular junctions-a tight junction is a watertight seal between 2 adjacent animal cells, desmosomes act like spot welds between adjacent epitheelial cells, and gap junctions in animal cells are like plasmodesmata in plant cells.