Cells!

The Cell Theory

• All Living Things are composed of cells• Cells are the basic units of structure and

function in living things• New cells are produced form existing cells

Basic Cell Structures

• All cells have:– Cell membrane• Cytoplasm: within the cell membrane, but not in the

nucleus

• Some cells have:– Cell wall– Nucleus

Biologists divide cells into two categories: Eukaryotes and

Prokaryotes

Prokaryotes

• Generally smaller and simpler• Have cell membranes and cytoplasm• DO NOT CONTAIN NUCLEI• All bacteria are prokaryotes– Escherichia coli: lives in your intestines– Staphylococcus aureus: can cause skin infections

• http://alabama.scout.com/story/454296-prothro-update

Eukaryotes

• “Eu” – true• “karyon” – nucleus• Also have– A cell membrane– Cytoplasm• Organelles

Cell Walls

• Provides support and protection for the cell• Lies outside of the cell membrane• Found in– Plants– Algae– Fungi– Nearly all prokaryotes

*ANIMALS CELL DO NOT HAVE CELL WALLS

Nucleus

• THE NUCLEUS CONTROLS MOST CELL PROCESSES AND CONTAINS THE HEREDITARY INFORMATION OF DNA

• Robert Brown – botanist• Chromatin• Chromosomes

• http://www.nature.com/scitable/topicpage/dna-packaging-nucleosomes-and-chromatin-310#

• Use this article to define– Nucleosome– Histone– Chromatin– Chromosomes– Chromatosomes

Chromatin

• Granular material visible within the nucleus• Consists of DNA bound to protein• Spread throughout the nucleus

Chromosomes

• When a cell divides, chromatin condenses to form chromosomes

• Chromosomes: Distinct, threadlike structures containing the genetic information that is passed from one generation of cells to the next

Nucleolus

• Most nuclei contain a small, dense region known as the nucleolus

• Assembly of ribosomes begins here

Nuclear Envelope

• Double membrane layer• Contains nuclear pores – allow material to

move into and out of the nucleus• Nucleus sends a steady stream of RNA and

other information-carrying molecules to the rest of the cell through the nuclear pores

Central Dogma of Molecular Biology

Cytoskeleton

Cytoskeleton

• The cytoskeleton is a network of protein filaments that helps the cell to maintain its shape

• The cytoskeleton is also involved in many forms of cell movement

• The cytoskeleton is made up of a number of important structures:– Microtubules– Microfilaments– (p 176)

Microtubules

• Hollow tubes of protein about 25 nanometers in diameter

• Maintain cell shape and can serve as “tracks” along which organelles are moved

• Important in cell division – help separate chromosomes

• Form a pair of centrioles (animal cells)• Can sometimes form cilia and flagella

Network of Microtubules connecting cellular organelles

Important in cell division – help separate chromosomes

Form a pair of centrioles (animal cells)

Microtubules can sometimes form cilia and flagella to help the cell move through liquid

Microfilaments

• Long, thin fibers that function in the movement and support of the cell

• 7 nm in diameter• Tough flexible framework - support

Organelles in the Cytoplasm

• Ribosomes• Endoplasmic Reticulum• Golgi Apparatus• Lysosomes• Vacuoles• Chloroplasts• Mitochondria

Organelles = “tiny organs”

Ribosomes

• Making proteins• Proteins are assembled ON ribosomes– Where are ribosomes assembled?

• Ribosomes: small particles made of RNA and protein

• Produce proteins by following coded instructions that come from the nucleus– This coded instruction is called mRNA

Endoplasmic Reticulum

• An internal system of membranes• Only in eukaryotes• The endoplasmic reticulum is the organelle in

which components of the cell membrane are assembled and some proteins are modified

• Rough ER• Smooth ER

Rough Endoplasmic Reticulum

• Involved in the synthesis of proteins• “Rough” due to the ribosomes on the surface• Newly made proteins move directly from

these ribosomes into the rough er, where they are chemically modified

Smooth ER

• No ribosomes on surface• It is an extension of the Rough ER• Contains many enzymes that performed

specialized tasks – Ex: Synthesis of lipids

Rough & Smooth ER

Golgi Apparatus

• Proteins produced by the rough endoplasmic reticulum move into a stack of membranes called the Golgi Apparatus

• Enzymes in the Golgi apparatus attach carbohydrates and lipids to proteins

• From the Golgi apparatus, proteins are sent to their final destination

Golgi Apparatus

• Cis face: receiving side• Trans face: shipping side

Lysosomes

• Small organelles filled with enzymes• Breaks down lipids, carbohydrates, and

proteins from food into particles that can be used by the rest of the cell

• Also break down “old” organelles– Remove debris

1. Digestion2. Organelle degradation

Vacuoles

• Store water, salts, proteins, and carbohydrates• Saclike structures• Found in single-celled organisms and animals• Vesicles: smaller vacuoles involved in

transporting substances• Useful in plants– Pressure in these central vacuoles makes it

possible for plants to support heavy structures such as leaves and flowers

Chloroplasts

• Found in plants and some other organisms– Not found in animal and fungal cells

• Chloroplasts use the energy from sunlight to make energy-rich food molecules in a process known as photosynthesis

• Bound by two envelope membranes and contain large stacks of photosynthetic membranes

• Green pigment chlorophyll is located in the photosynthetic membranes - thylakoid

Mitochondria

• Mitochondria use energy from food to make high-energy compounds that the cell can use to power growth, development, and movement

• Found in almost all eukaryotic cells– Including plant and algae cells

• Enclosed by an outer and an inner membrane– Inner membrane is folded

Organelles that contain their own DNA

• Chloroplasts• Mitochondria

• This DNA contains information that is essential for the normal function of these specific organelles

Mitochondrial DNA

• All of a mitochondria come from the cytoplasm of the ovum, or egg cell

• So, genes in the mitochondria are specifically genes from your mother

• http://ghr.nlm.nih.gov/mitochondrial-dna/show/Genes

Endosymbiotic Theory