Chapter 6 - A tour of the Cell

Microscope

An optical scope used to visualize microscopically small objects

2 main types of Microscopes used (Light Microscopes)

Uses visible light to magnify small objects

2 main types of Microscopes used (Electron Microscopes)

Uses electrons for a higher magnification of even smaller objects

Scanning Electron Microscope (SEM)

Visualizes external cell surfaces

Transmission electron microscope (TEM)

Visualizes internal cell structures

Prokaryotic and Eukaryotic are

broadest and most distinct groupings of all life

Prokaryotic Cells

Do not have a nucleus (Includes both Bacteria and Archaea)

Eukaryotic Cells

Do have a nucleus and other membrane-bound organelles

Bacteria

The most abundant and diverse organism on Earth

Bacterial DNA

circular in shape and found in a region called the nucleoid

Bacteria

have a small (70s) ribosomes and divide by binary fusion

Eukaryotic Cell

Membrane-organelles, Has a nucleus, located inside the nucleus, Large (80s) ribosomes and divide by mitosis and cytokinesis

Both Eukaryotic and Prokaryotic have

Cell membrane

Contain the major biomolecules (Proteins, Carbohydrates, Lipids and nucleic acids)

Eukaryotic Characteristics

Has a nucleus

Larger

More complex

Unicellular or multi-cellular

Linear DNA

Has membrane-bound organelles

Cell division: Mitosis and Cytokinesis

Larger 80S ribosomes

Prokaryotic Cells

No nucleus

Smaller

Less complex

Only uni-cellular

Circular DNA

No membrane-bound organelles

Cell division: Binary Fission

Small 70S Ribosomes

Ribosomes are also referred to as

Non-membranous organelles

Ribosomes

Molecular “Machines” that build proteins in all living things

Translation

The process conducted by ribosomes that builds proteins

Ribosomes can either be

“Free” (Floating in cytoplasm) or attached to another organelle (rough ER)

Endomembrane System

A group of membrane-bound organelles inside a eukaryotic cell

Endomembrane System

Includes many organelles that are interconnected by vesicles (little membrane bubbles)

Endomembrane system

Has multiple functions including protein section and cellular digestion

Protein section consists of

Nuclear Envelope (Nucleus)

Endoplasmic Reticulum

Golgi Apparatus

Transport Vesicles

Cellular digestion consists of

Lysosomes and peroxisomes

Vacuoles

Secretion

A process by which a substance is released into the environment

Protein secretion starts

Nucleus, which stores DNA for making proteins

Nucleus

A rounded structure that contains and protects most of a eukaryotic cells DNA

Nuclear Envelope

the double membrane that surrounds the nucleus and acts as its barrier

Nuclear pores

Tiny “Holes” in the nuclear envelope that allow entry/ exit into and out of the nucleus

Nucleolus

A small dense structure inside the nucleus where ribosomes are assembled

Endoplasmic Reticulum (ER)

Membranous structures continuous with the nuclear envelope with multiple functions

ER lumen

The internal space/compartment of the ER

Rough ER (rER)

Closer to nucleus with a rough, ribosome-coated surface

-Newly built proteins fold and are modified in the rER lumen

Smooth ER (SER)

Further from nucleus with a smooth, ribosome-Free surface

Synthesis lipids and detoxifies drugs/poisons

Molecules synthesized in the ER

Transported by vesicles to the golgi apparatus

Golgi Apparatus

Stack of flat, membranous sacs (cisternae) that function as a “processing center”

Golgi Apparatus

Receive vesicles, modify vesicle contents and repackages contents into vesicles for export

Receiving end of the Golgi= “Cis” end

Shipping end of the Golgi=”Trans” End

Some vesicles shipped from Golgi apparatus can fuse with the cell membrane for secretion

Lysosomes

Acidic vesicles of digestive enzymes that breakdown and recycle food, debris, bacteria, etc

Lysosomes

Primarily found only in animal cells and originate at the golgi apparatus

Peroxisomes

Vesicles of enzymes that breakdown toxic compounds

Peroxisomes

Found in all eukaryotic cells and originate at the rough endoplasmic reticulum (rER)

Central Vacuole

Large membrane-enclosed vesicle in plant cells that degrade and recycle molecules

Central Vacuole

Other functions include filling up with water to exert turgor pressure against cell membrane

Mitochondria (Powerhouse of the cell)

Organelles that synthesize lots of energy for the cell

Adenosine Triphosphate (ATP)

High energy molecules used to “Power” Cellular reactions

Cellular respiration

Mitochondrial process that breaks down food sources like sugars and lipids to make ATP

Mitochondria Structure

Mitochondria vary in shape and have their own ribosomes and DNA that is independent of the nuclear DNA

Mitochondria have 2 membranes

Outer membrane and folded inner-membrane (cristae=folds)

Inter-membrane space

Region in-between the two membranes

Matrix

Region within the inner membrane containing enzymes, ribosomes, and mitochondrial DNA

Chloroplasts

Green organelles that function as the site of photosynthesis in many plant cells

Photosynthesis

Process that uses energy from sunlight to synthesize sugars (glucose)

Chloroplasts

Have 2 membranes (outer and inner) but unlike mitochondria neither have folds/ cristae

Thylakoids

Interconnected pancake-shaped sacs within the chloroplast

Grana

Stacks of thylakoids

Stroma

Innermost region of the chloroplast containing enzymes, ribosomes, and chloroplast DNA

Endosymbiotic Theory

Mitochondria and chloroplasts were once independently living bacteria

Cytoskeleton

Network of elongated proteins in the cytoplasm with multiple functions

Cytoskeleton

Functions include providing cell-shape, structure, movement, transportation and biosignaling

3 major components of the cytoskeleton: Microfilaments

Smallest in size and usually made of thin rods of repeating actin proteins

major components of the cytoskeleton: Intermediate Filaments

Intermediate in size and made of variable proteins

3 major components of the cytoskeleton: Microtubules

Largest in size and forming tubes made of repeating tubulin proteins

Microtubules are a major structural component

Cilia and flagella which provide cell movement

Cilia

Multiple short “Hair-like” Structures that move like “oars” to move objects or provide cell movement

Flagella

Longer “Tail-like” structures that move like a “whip” to provide cell movement

Neighboring cells of eukaryotic organisms are able

directly interact with one another at cell junction

4 types of cell junctions: Tight

Membrane protein link cells creating a leak-proof barrier

4 types of cell junctions: Anchoring (Desmosomes)

Intermediate filament that anchor neighboring cells together

Gap

Protein channels that connect the cytoplasms of two animal cells

Plasmodesmata

Gaps in the cell walls that connect the cytoplasms of two plant cells