Name __________________________________ Test Date___Oct 1st ______

CELL STRUCTURE AND FUNCTION

I. DISCOVERY OF CELLS A. History of Microscopes The invention and development of the microscope in the 1600’s enabled scientists to discover and study cells - basic unit of structure and function in in all living things

1. Anton von Leeuwenhoek – was the first to try stacking several lenses_ together to view tiny objects. He looked at pond water_ through his lenses and became known as the first scientist to describe living cells as seen through a microscope.

2. Robert Hooke - In 1665, he used a _microscope_ to examine thin slices of cork and then described what he saw and called them _cells__. He chose the name “cells” because the chambers he saw reminded him of the rooms in a monastery which were called cells.

B. Cell Theory Nearly a century after Hooke’s findings, several other scientists discoveries led

to the formation of the _cell theory_.1. Matthias Schleiden (botanist) & Theodor Schwann (zoologist) –

together they reached the conclusion that _all living things__; from oak trees to violets, and from worms to tigers; were composed of cells _.

2. Rudolf Virchow – elaborated on Schleiden & Schwann’s proposal and added “omnia cellula e cellula” : all cells come from cells _

These discoveries, confirmed by other biologists, are summarized in the cell theory, a fundamental concept in Biology….. The cell theory states that:

a. All organisms are ____composed of cells______ b. Cells are the smallest working units of life. c. All cells come from ____pre-existing cells________

II. TYPES OF CELLS Living organisms are made of either _prokaryotic__ or _eukaryotic_cells – the two major kinds of cells which can be distinguished by _structural organization__

A. Types of Prokaryotic Cells – (All Uni-Celled) 1. Eubacteria – have shapes such as cocci (round), bacilli (rod), spirilla (spiral); ex. include E.coli,Streptococcus. Have a cell wall made of _ __ peptidoglycan __.

2. Archaebacteria – “ancient” bacteria; live in extreme environments (salty, hot, acidic); ex. methanogens. Have a cell wall made of _other polysaccharides_.

B. Types of Eukaryotic Cells – (Uni or Multi-celled) 1. Protista – ex. Amoeba, Euglena, Paramecium 2. Fungi - ex. Penicillium, yeasts, molds, mushrooms. Have a cell wall made of ___chitin___.

3. Plants – ex. Mosses, ferns, flowering plants. Have a cell wall made of __cellulose__. 4. Animals – ex. Sponges, worms, snails, insects, mammals. No _cell wall_.

III. CELL BOUNDARIES A. Cell Wall Cell Walls are the outer most boundary in _bacteria_, _plants_, and _fungi_. They are not found in __animal cells_____. The primary function of the cell wall is to _provide support and structure__.

B. Cell Membrane Every cell is surrounded by the cell membrane. Its function is to maintain homeostasis__ in the cell by separating and protecting the cell from its environment. It also regulates exchange with the environment. The cell membrane is also called the __plasma membrane_. It is _selectively permeable _ which means that it allows some substances to pass through; acts a barrier to others.

IV. INSIDE A EUKARYOTIC CELL Within the cell membrane, the cell is composed of the nucleus with its corresponding structures, the _nucleolus_ and _nuclear envelope__.

The cytoplasm includes all the rest of the material inside the cell membrane. The cytoplasm includes two components: Cytosol – a semi-gelatinous substance that contains dissolved nutrients and wastes Organelles – means “little organs”. Each has a specific role in the overall function of the cell.

StructureProkaryoticEukaryotic or Both?

Plant, Animal

or Both

General Characteristics and Functions

Nucleus Eukaryotic Both

Control center of the cell. Contains genes that control cell activities. Contains most of the cell's DNA, which is stored as chromatin (DNA wrapped in protein).

Nucleolus Eukaryotic Both

Small, dense region in the nucleus. Involved in the synthesis of ribosomes which are important in protein synthesis. "Little nucleus"

Nuclear Envelope Eukaryotic Both

Double membrane, each consisting of a phospholipid bilayer. Perforated by nuclear pores which allow RNA molecules to leave the nucleus.

Ribosomes Both Both

Constructed in the nucleolus, these tiny, non-membrane bound organelles are located in prokaryotic and eukaryotic cells. These organelles function in protein synthesis, and can be either free (suspended in the cytosol), or bound (attached to rough ER). Free ribosomes aid in the production of proteins that will stay in the cell, and bound ribosomes aid in the production of proteins that will be transported out of the cell.

Rough Endoplasmic Reticulum

Eukaryotic Both

Extensive network continuous with the nuclear envelope. Appear "rough" due to the presence of ribosomes all along the membrane. Function of the rough ER is to modify and transport proteins. Most of these proteins are packaged into vesicles (pieces of the membrane that act as a protective sac) and shuttled to the Golgi Apparatus.

Smooth Endoplasmic Reticulum

Eukaryotic Both

Similar to rough ER in structure, except that it lacks ribosomes. Smooth ER functions in the synthesis of lipids (steroids), breaks down glycogen, and detoxifies drugs, and poisons. Smooth ER (esp. in muscle and liver cells) also stores Ca+ ions that are used for muscle contraction.

Golgi Apparatus Eukaryotic Both

Flattened, round sacs with the appearance of pita bread. Golgi is sometimes called the "UPS man" because it functions in modifying, storing, and re-routing the products of the ER. Golgi is packed with enzymes that aid in modifying the products before they are shipped out by way of a transport vesicle into the cytosol.

Lysosome Eukaryotic Animal??

Membrane bound bag of hydrolytic enzymes that help to digest macromolecules, as well as recycle used cell components. Lysosomes are made from parts of the ER (enzymes) and Golgi apparatus (phospholipid membrane). Also used as a defense against bacteria and viruses.

Vacuole Eukaryotic Both

Sacs that may be used as storage for ions , molecules, water, or wastes. Plants have a very large central vacuole for maximum water storage.

Mitochondria Eukaryotic Both

Double membrane structure that has its own proteins embedded in phospholipid bilayers, as well as its own DNA. This DNA programs a small portion of the mitochondria's protein synthesis; however, a majority of their proteins are synthesized according to the directions from nuclear DNA. Has inner folds called cristae. Uses glucose to manufacture energy in the form of ATP .

Chloroplasts Eukaryotic Plant

Found in plant cells. Bound by a double membrane that helps partition its contents from the cytosol. Contain the green pigment chlorophyll which is used to harvest energy from the sun to produce glucose (photosynthesis). Also contains its own DNA. The three functional compartments of the chloroplast are the intermembrane space, the thylakoid, and the stroma.

Centrioles Eukaryotic Animal

Found only in animal cells. Made up of bundles of microtubules that play a role in cell division. Centrioles help to organize the assembly of the spindle fibers for cell division. This organelle is part of the cytoskeleton.

Cytoskeleton Eukaryotic Both

Network of fibers throughout the cytoplasm that forms a framework for support/movement. Enables the cell to maintain or change shape and anchors the organelles. Provide motility for some cells in the form of cilia or flagella. There are three types of fibers that make up the cytoskeleton: microtubules (thickest), microfilaments (thinnest), and intermediate filaments (intermediate).

V. VIRUSES (pg 478-483) Viruses are not considered alive because they do not exhibit any of the

characteristics of life; rather, they are thought to be the bridge between the non-living and living. Because of this, they are not included in a kingdom and should not be referred to as an organism. The correct term for describing a virus is a particle. A viral particle is simply genetic information enclosed in a protein coat. A virus lacks enzymes for metabolism and ribosomes for making proteins. It requires a host cell to reproduce.

A. Structure of Viruses 1. Genetic Material – The genome of a virus may be either DNA or RNA, but never both. Viral genes carry information for reproduction only – a virus carries out no other activities.

2. Protein Coat – The DNA or RNA is surrounded by a protein coat called a capsid. The shape of the virus is important in the infection process. Some viruses are enclosed by a protective protein envelope.

Viruses are classified by shape, type of genetic info (DNA or RNA), enveloped or no envelope (outer lipid membrane), and type of cell it infects.

II. Viral Replication B. Viral Cycles There are three initial steps that are common to all viral infections:

Virus attaches to the cell membrane of the host cell Virus penetrates, or fuses with, the host cell’s cell membrane Virus releases its genetic information (DNA or RNA) into the host cell

Once inside the host cell, there are two ways that a virus can take over and use the host to reproduce. These two mechanisms are:

1. Lytic infection – Upon release of genetic material into host cell, virus destroys host cell DNA, and then reprograms the host cell to copy viral genes and make viral proteins (transcription and translation), using all the enzymes, raw materials, and energy from the host cell. After this

capsid DNA

tail sheath

tail fiber

capsid proteins

RNA

surface proteins envelope

RNAcapsid

replication, the new viral genes and proteins are assembled & the new virus mature. Finally, the new viruses lyse the host cell and are released to attack other cells. This viral cycle is virulent and symptomatic, because it results in death of the host cell. 2. Lysogenic infection – In a lysogenic infection, also known as viral latency, viral genome becomes incorporated into the host cell’s chromosomes. This incorporated viral DNA is known as a prophage. This prophage does not interfere with the host cell’s normal activities. Every time the host cell replicates, the virus is replicated as well. This virus is asymptomatic and can remain latent (inactive) in the host cell for many generations. At some point, a lysogenic infection can switch to a lytic infection and become symptomatic. Example of lysogenic infections include HIV, Herpes, Chicken pox.