Cells. Cell: the smallest bit of matter that can be considered alive

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Jacklyn DeCady


Section 3.1

Cell: the smallest bit of matter that can be considered alive Robert Hooke: first observed and named the “cell” by looking at cork in 1665. (He named them cells because they looked like little rooms)

Antoni Van Leeuwenhoek later described cells that could move by viewing human blood and pond water with his own hand-made microscope. He also observed and described bacteria (animalcules).

He called them “wee beasties’”.

The early microscopes provided data to establish the Cell Theory. Development of the Cell Theory

1. Matthias Schleiden (1839) developed the theory that all pants are made by cells 2. Theodore Schwann (1839) proposed all animals are made of cells

3. Rudolf Virchow (1858) stated all cells arise only from pre existing cells

The Cell Theory states that…

1. All living things are composed of cells 2. All cells come from other cells

3. The basic unit of living things are cells (and they carry out life functions)

Cell Diversity: cells that different functions often have different shapes

● Nerve cells: have extensions that reach out in different directions ● Pollen grains have spikes to stick to insects


1. Plasma membrane (cell membrane): thin coats of lipids that forms the boundary of cell and environment

2. Cytoplasm: all material inside the cell except for the nucleus 3. Ribosomes: structures in cytoplasm where proteins are made 4. DNA: instructions to make proteins

Section 3.2

There are 2 basic types of cells…

1. Prokaryotic cells: the most common cell and the 1st to evolve but not organized nucleus. DNA is located in the cytoplasm in an area called a nucleoids. These are known as Prokaryotes

a. Bacteria

2. Eukaryotic cells: contains a nucleus and called eukaryotes a. Most are multicellular; some unicellular

b. Has a membrane (bound nucleus and a number of other organelle). i. Ex: protists (single celled organism)

ii. Plants and animals

Organelle: a small structure in the cytoplasm that performs a specific job

Both Prokaryotic and Eukaryotic cells… ● plasma membrane

● Chromosomes (DNA) ● Ribosomes


3 Domains ---> 6 Kingdoms

1. Archaea (Prokaryotic) --- Archaebacteria 2. Bacteria (Prokaryotic) --- Eubacteria

3. Eukaryota (eukaryotic) --- Plantae, Fungi, Animalia, Protista

Section 3.3

Viruses are invaders that sabotage our cells and are on the border of living and nonliving

Virus means poison.



● They do not respire or grow ● Only functions in a living cell

Viruses must reproduce inside a host cell, they CANNOT reproduce by themselves

Bacteriophages (phages): the viruses that infect bacteria

Viruses operate by:

a. Viral proteins bind to receptors on a host’s target cell b. Vital nucleic acid (DNA or RNA) enters the cell

c. It may remain dormant by integrating into a host chromosome

d. When activated, viral DNA/RNA triggers duplication, using. The host’s molecules and organelles

e. The host cell is destroyed, and newly replicated viruses are released to continue the infection

Viruses have two types of reproductive cycles:

Lytic cycle:

A. Viral particles are produced using particles parts of the host cell

B. The host cell lyes (dies) and viruses are released immediately to infect other cells

Lysogenic cycle (longer cycle):

A. Viral DNA is inserted into the host chromosome

B. Viral DNA is duplicated along with the host chromosome C. The inserted phage DNA is called a phophage

D. Most phophage genes are inactive

E. Environmental signals can cause a switch to the Lytic cycle at any time and the virus becomes active

Temperate Virus: capable of using the Lytic and lysogenic cycle


Emerging Viruses:

Emerging viruses cause human diseases Mutation: RNA viruses mutate rapidly

Contact between species: viruses from other animals spread to humans These viruses spread from isolated populations

Emerging viruses examples:


● Ebola virus ● West Nils ● Avian flu virus ● H1N1

Section 3.4

The plasma membrane: forms a barrier between the cell and its environment

● The plasma membrane (cell membrane) is a 2 layered

membrane that controls the movement of molecules into and out of the animal cell and gives support (with the help of cholesterol) It is located on the inside of the cell wall in plants

Semi permeability: only certain things are let are out of the cell

The Plasma membrane is a phospholipid bilayer ( made of fatty acids and alcohol) with a hydrophilic head and a hydrophobic tail

● Hydrophobic materials easily pass through the plasma

membrane because the hydrophobic tails are on the inside the membrane and hydrophobic materials easily pass by the

hydrophilic can't pass without help


Membrane proteins: protein molecules that are attached or associated with the membrane of a cell or an organelle

● There are 2 types of membrane proteins:

○ 1. Integral membrane proteins: embedded permanently into the membrane - they channel or transport molecules across the membrane

○ 2. Peripheral membrane proteins: a protein molecule that is temporarily attached or associated with the membrane of a cell or an organelle (most are hydrophilic)

Fluid Mosaic Model: integral proteins act as transport proteins and receptor protein. It says the proteins and lipids in the membrane move around so the plasma membrane acts as a fluid.

The plasma membrane may contain extensions of: 1. Cilia: short hairlike structures

a. Cells that sweep mucus out of our lungs have cilia 2. Flagella: long whip like tails

a. Animal sperm are flagellated

3. Both are made of microtubules that bend

Cytoskeleton is made of microtubules that bend and make up the framework of the cell

1. Cilia and flagella are actually the extension of the plasma membrane

Section 3.6


The cytoplasm (everything inside of the plasma membrane {the cytosol and organelles}) makes up ⅔ of the cells weight. The cytoplasm includes the watery, gel like material called the cytosol. Functions:

1. Suspend organelles

2. Push against the plasma membrane to keep the cell’s surface 3. Provide a site for biochemical reactions to take place

Function of the cytoskeleton:

1. Helps maintain the cell shape

2. Help material move around in the cell 3. Helps with cell division

Cytoskeleton: made of protein fibers, gives the cell its structure

Microtubules: hollow cylinder made of protein called Tubulin that helps a cell keep its shape. They are important in mitosis

Microfilaments: actin and myosin fibers are involved in cell movement

Intermediate Fibers: reinforce cell shape and gives the cell strength. It's made of keratin (found in skin and hair)

Section 3.7 Nucleus

Nucleus: controls the cell's activity and is the largest membrane bound organelle found in eukaryotic cells that contains most of the cell’s

genetic info


● Inside the chromatin is the nucleolus, an organelle which helps to assemble ribosomes

The nucleus regulates gene expression

● Gene expression: process where info in a gene is decoded to produce a protein molecule or RNA molecule

Nuclear envelope: a 2 layer membrane whose outside contains ribosomes and attaches to the endoplasmic reticulum

● Contains nuclear pores: controls materials in and out of the nucleus

Ribosomes: (looks like dots) made in the nucleolus and does not contain a membrane. They are exported to the cytoplasm and they contain rRNA (ribosomal RNA) which helps to assemble proteins from amino acids and takes place in the cytoplasm

Section 3.8

Ribosomes and Mitochondria

Cells that must synthesize large amounts of protein have a large number of ribosomes

Some ribosomes are free; and others are bound

● Free ribosomes are suspended into the cytoplasm ● Bound ribosomes are attached to the ER

There are 2 subunits that make up a ribosome

● Ribozymes: a type of enzyme made of RNA that helps catalyze reactions such as Translation

● Translation: process where amino acids are assembled into proteins


Mitochrondria: the powerhouse of he cell and is enclosed by a double membrane

This is where energy is made in the cell through a process called cellular respiration

● Cellular Respiration: the conversion of chemical energy in foods to chemical energy of ATP - the energy source for cellular work

○ ATP: cell’s energy source; mostly made in the mitochondria but some is made in the cytosol

● Mitochondria have their own DNA, in humans, mitochondrial like DNA is the same as our mothers. The egg provides the

organelles and DNA (sperm only provides DNA) It has 2 phospholipid layers

1. Outer layer separates it in the cytosol 2. Inner layer contains cristae

a. Folds that increase its surface area so it can produce more ATP

b. Matrix: fluid filled is made

Mitochrondria have their own DNA and can reproduce asexually. (It is for this reason they descended from prokaryotes)

Endosymbiosis Hypothesis: the belief that mitochrondria and chloroplast were formally small prokaryotes that were engulfed by another larger cells and began living in the larger cell

The symbiosis (mutual gain) benefited both cell types. Both organelles provide the cell with ATP and received protection from the cell


Other cell organelles

Endoplasmic Reticulum: a network of phospholipid membrane that forms hollow tubes, flattened spaces, and flattened sheets


The two jobs of the ER are:

a. Transports molecules around the cell like a highway

b. Synthesis: helps make lipids and assembles proteins (Rough ER contains ribosomes)

2 types of ER:

1. Smooth ER: lacks attached ribosomes and is important in

synthesis of lipids, calcium ion storage, and drug detox (found in plant cells but has a different job)

2. Rough ER ribosomes lines the outer surface of membrane and make proteins that are transported out through transport vesicles that are in made in the ________ _______

a. Also helps make more of itself

Golgi Apparatus: made of 5-8 cistern are that modifies, sorts,and

packages different substances. Like the post office, the Golgi A. works the ER by acting as a received from the ER

● It packages the product and releases vesicles that transport materials throughout the cell and to the plasma membrane Vesicle: small circular container with at least one lipid bilayer, that helps to transport materials to the plasma membrane and _______ ___ _____


1. Transport Vesicle: move molecules throughout the cell

2. Lysosomes: a sac containing digestive enzymes. The digestive enzymes are contained in the sac to keep the enzymes safely away from the rest of the cell. Formed by the Golgi Apparatus

a. They break down harmful cell products, waste material and cellular debris and remove them from the cell

b. They digest invading organisms

c. They break down cells that are ready to die in a process called autolysis

3. Peroxisomes: vesicles that use oxygen to break down toxic substances in the cell. Peroxisomes self replicate by growing bigger and then dividing. They are common in liver and kidneys cells that break down harmful substances.

a. Peroxisomes are named for the hydrogen peroxide that is produced when they break down organic compounds

Vacuoles: membrane bound organelles that have secretory, excretory and storage function. Plant cells have very large vacuoles that store water. Vacuoles are larger than vesicles.

Types of Vacuoles:

● The central vacuoles in plants that store water

● Pigment vacuoles in plants to provide color to flowers

● Contractile vacuoles in some protists to expel water from the cell Centrioles: rod like structures made of 9 groups of 3 short

microtubules made of tumbling

1. 2 perpendicular centrioles make up a centrosome


Section 3.10

Plant Cell structures

Most organelles are common to both animal and plant cells. Plant cells have 3 organelles that animal cells don't have:

A. Cell wall

B. Large central Vacuole

C. Plastids like Chloroplast (plastids contain pigment or food) Plants make their own food during photosynthesis. They take in carbon dioxide, and water and converts them into sugars

Cell Wall: the rigid outside of a plant cell made of cellulose and other polysaccharides (aka fiber)

● It protects and provides skeletal support that helps the plant upright against gravity

Plasmodesmata are pores in the cell wall that let water and nutrient enter and exit and allows communication with neighboring cells Central Vacuole: takes up more than a third of the cell’s volume

A. Tonoplast: membrane that surrounds the central vacuole B. Keeps the pressure against the cell wall

C. Stores pigment that colors flowers

Liquid in a plant cell is called cell sap - differs from cytosol, and contains water, enzymes, ions, salts as well as toxic substance removed from the cytosol. These toxins protect the plant from being eaten


A. Chloroplast: the organelle of photosynthesis. Has a double membrane. The fluid inside the chloroplast is the stroma a and contains DNA and ribosomes. Within the stroma are thylakoids (they have flattened disk shape) and is the site of

photosynthesis. The thylakoids are arranged in sacs called grana B. Chromoplasts: make and store pigments that give petals and

fruit their orange and yellow colors

C. Leucoplasts do contain pigments and are located in roots and non- photosynthetic tissue of plants. Some are the site of bulk storage of starch, lipid, or protein. Others make molecules such as fatty acids and many amino acids

Section 3.11

Organization of Cells

Single celled organisms are able to carry out the processes of life without the help from other cells. Single celled prokaryotes and eukaryotes show order in the way their cells are arranged. Some single celled organisms can group together and can form a biofilm.

● Biofilm: a large grouping of many bacteria that sticks to a surface and makes a protective coating over itself. There is a division of labor where each group does a job

● Biofilm so are not considered multicellular organisms and re instead called colonial organisms. The difference between a multicellular organism and a colonial organisms is that individual organisms form a colony and, if separated, survive on their own, while cells from a multicellular organism cannot


● The colonial theory proposes that this cooperation led to the development of a multicellular organism

○ Multicellular organisms: organisms that are made up of more than one type of cell and have specialized cells that are grouped together to carry out specialized functions. ○ Cells of a multicellular organism would not survive as

independent cells

The body of a multicellular organism exhibits organization at several levels:




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