Cells

2.3 – Introduction to Biomolecules

The Levels of Organization

Organ Systems

Organism

Skin Cells and Stomach cells

How did cells get discovered??

1655 – was the first to identify cells, and he named them.

1674- because he made better lenses, Leeu observed cells in greater detail.

1655 – was the first to note that plants are made of cells.

1839 –concluded that all living things are made of cells.

1855 – proposed that all cells come from other cells.

• The Cell Theory has 3 principles:– All organisms are made of cells.

– The Cell theory has three principles.• All organisms are made of cells.• All existing cells are produced by other living cells

– The Cell theory has three principles.• All organisms are made of cells.• All existing cells are produced by other living cells.• The cell is the most basic unit of life.

All cells share certain characteristics.

• Cells tend to be microscopic.• All cells are enclosed

by a membrane.• All cells are filled with

cytoplasm.

Bacterium(colored SEM; magnification 8800x)

cell membrane

cytoplasm

There are two cell types:

EUKARYOTES vs PROKARYOTES•Eukaryotic cells have a nucleus.

•Prokaryotes do not have a nucleus.

nucleus

EUKARYOTES vs PROKARYOTES

•Eukaryotic cells have membrane bound organelles.

•Prokaryotes do not have membrane bound organelles.

nucleus

organelles

EUKARYOTES vs PROKARYOTES•Both Eukaryotic and Prokaryotic cells have cytoplasm and a cell membrane.

nucleus

organelles

cell membrane

cytoplasm

Living Things Come in All Sizes

• How does the size of a cell in a tadpole compare to a blue whale??– Most cells in a whale are similar in size to those in

tadpoles

• What makes a whale so Much larger than a tadpole?

– A whale has far more cells than a tadpole or the frog it Becomes.

Organelles

• All cells have a cell membrane– the cell membrane or plasma membrane, forms a

boundary between a cell and the outside environment.– Controls the passage of materials into and out of cell– Consists of a double layer of phospholipid molecules.

• Phospholipid- a phosphate group, 2 fatty acids, glycerol.

• Cell Wall ( ONLY IN PLANT CELLS!!!)– A rigid layer that gives protection, support, and shape to

the cell– Cell walls can adhere to one another to support an entire

organism• Example - much of the wood in a tree trunk consists of dead cells

whose cell walls continue to support the entire tree– Cell wall composition varies and is related to the needs of

each type of organism - tree vs algae– Even though it is tough, it still has channels to allow water

and other molecules to cross into and out of the cells survival.

• Cells have an internal structure.– Cytoskeleton is a network of proteins

(fibers/tubes) that is constantly changing to meet the needs of cells.

– The cytoskeleton has many functions.• supports and shapes cell• helps position and transport organelles• provides strength• assists in cell division• aids in cell movement

• Components of a Cytoskeleton: • 2 main types of fibers/tubes that make it up.

– Microtubules • long hollow tubes give cell its shape • act as tracks for movement of organelles • assist in cell division

– Microfilaments • smallest of the 2• tiny threads that enable cells to move & divide • play important role in muscle cells, allow muscle to

contract & relax

• Cytoplasm: – Clear, gelatinous fluid inside the cell

• Mostly made of cytosol

– Jelly-like material that consists mostly of water with proteins and carbohydrates

– Organelles are found within the cytoplasm

• Several organelles are involved in making and processing proteins.– Nucleus– Nuclear envelope– Nuclear pores– Nucleolus– Rough Endoplasmic Reticulum– Ribosomes– Golgi Apparatus– Vesicles

• Nucleus– Control center of the cell because it holds the

genetic information or DNA– DNA contains the genes that are instructions for

making proteins2 Major demands on DNA

1. DNA must be carefully protected2. DNA must be available for use at all times

Solution for these demands: * Nuclear envelope- a double membrane that surrounds and protects DNA, with tiny nuclear pores that allow certain large molecules in and out.

• Nucleolus– Tiny dense region within nucleus– Essential for making ribosomes

• Endoplasmic Reticulum – A large part of most eukaryotic cells is filled by the

ER. – Interconnected network of thin folded

membranes– Numerous processes, including the production of

proteins and lipids, occur on both the surface and inside the ER

– 2 types of ER: • Rough Endoplasmic Reticulum• Smooth Endoplasmic Reticulum

• Rough ER – its surface is dotted with ribosomes– Proteins are being made on ribosome and the

rough ER can modify the protein by adding sugar chains to it which can help it fold into a shape.

• Ribosomes – Tiny organelles that link amino

acids together to form proteins.– Both the site of protein synthesis

and actively participates in the process.

– Ribosomes themselves are made up of proteins and RNA.

– After ribosomes are made in the nucleolus, they pass through the nuclear pores into the cytoplasm where they can attach to the rough ER or just float.

– 2 types of ribosomes: • Attached ( on ER)• Free ( floats in cytoplasm)

• Golgi Apparatus – Closely layered stacks of membrane-enclosed

spaces that process, sort, and deliver proteins.– Its membranes contain enzymes that make

additional changes to proteins– Packages proteins and stored for later use– Transports proteins to other organelles– Transports proteins to membrane where they are

secreted outside the cell.

• Vesicles– Small membrane-bound sacs that divide some materials

from the rest of the cytoplasm– Transport these materials from place to place within the

cell– Generally short-lived and are formed and recycled as

needed.• **after proteins have been made, part of the ER pinches off to

form a vesicle surround it.• **the protein can then be safely transported to the golgi

apparatus. • ** After being modified in Golgi, Vesicles form ( pinch off) to take proteins out of cell.

Overview of Protein Synthesis:

• Ribosomes are made in nucleolus

•Ribosomes leave through the Nuclear pores on the nuclear membrane

•Some attach to ER, while others remain free floating

•Ribosomes begin attaching Amino Acids together to form proteins

•Proteins enter into Rough ER to be modified and folded (shaped) into structures

Overview of Protein Synthesis: •Vesicles form from Rough ER and carry proteins to Golgi apparatus

•There proteins are packaged, sorted and/ or stored in Golgi

•Once the proteins are ready to leave, vesicles form to transport proteins throughout the cell and to other cells.

• Other organelles have various functions– Smooth Endoplasmic Reticulum– Mitochondria– Lysosomes – Centriole – Vacuole – Chloroplasts

• Other type of ER: • Smooth ER – its surface does not contain

ribosomes– Makes lipids– Breaks down drugs and alcohol (liver cells)– Calcium storage (muscle cells)

• Mitochondria (powerhouse)– Supplies energy to the cell– chemical reactions take place within the inner

folds and convert molecules from the food you eat into usable energy

– Unlike most organelles, mitochondria have their own ribosomes and DNA. This suggests that they were originally free-living prokaryotes that were taken in.

– Found in cells that are very active (muscle cells)

• Lysosomes (garbage disposal)– Membrane-bound organelle that contain enzymes

to break down worn-out cell parts and debris.– They also defend a cell from invading bacteria and

viruses– They are numerous in animal cells and their

presence is still questioned by scientists in plant cells.

• Centriole – Are cylinder-shaped organelles made of short

microtubules arranged in a circle.– Located in a small region in the cytoplasm called

the centrosome that produces these microtubules.– Both Plant and Animal cells have a centrosome

region, but only Animal cells form centrioles.– Help divide DNA during cell division– Help form cilia (little hairs)

and flagella (whip/tail) for cells.

• Vacuole– A fluid-filled sac used for storage of materials

needed by a cell.– These materials include water, food molecules,

inorganic ions and enzymes– Most animal cells contain small vacuoles– All plant cells have a large central vacuole that

strengthens the cell and helps to support the entire plant.

• When a plant wilts, its leaves shrivel because there is not enough water in the vacuole to support its normal structure

• A plants vacuole may also contain substance that are toxic to harm predators, waste products, and pigments that give color to cells – such as those in the petals of flowers.

Milkweed

• Chloroplasts– Organelles that carry out photosynthesis– Like mitochondria, they have their own ribosomes

and DNA so scientist believe they too were taken in by larger cells

– ONLY IN PLANT CELLS!!!

Centriole

Centrosome

Golgi Appratus

Vesicle

Small Vacuole

NucleolusNuclear Pores

Nucleus Lysosome Cytoskeleton

Rough ER

Cytoplasm

Mitochondria

Smooth ER

Cell Membrane

Ribosome (attached)

Centrosome

Golgi Appratus

VacuoleCell Wall

Nucleolus

Nucleus

Nuclear Pores

Vesicle

Cytoskeleton

Rough ER

Ribosomes

Cell Membrane

Smooth ER

Mitochondria

Chloroplast

Prokaryotes Eukaryotes

Cell membraneRibosomesGenetic MaterialCytoplasm

NucleusERGolgi apparatusVesiclesLysosomes (animal)

VacuolesMitochondriaCytoskeletonChloroplast (plant)

Venn Diagrams

No Nucleus

Genetic material not in nucleus

No membrane bound organelles

Animal Cells Plant Cells

Lysosomescentrioles

Cell membraneRibosomesNucleusNucleolusERVesicleGolgi apparatusVacuolesMitochondriaCytoskeletonCytoplasmcentrosome

Venn Diagrams

Cell WallChloroplasts