CELLS: THE LIVING UNITS

I. cell theory - all living things are made of cells

Use the following terms to label the indicated structures within this generalized animal cell.

A.	Centrioles	G.	Microtubules	M.	Peroxisome
B.	Chromatin	H.	Microvilli	N.	Plasma membrane
C.	Cytoplasm	I.	Mitochondria	O.	Ribosomes
D.	Golgi apparatus	J.	Nuclear envelope	P.	Rough endoplasmic reticulum (ER)
E.	Lysosome	K.	Nucleolus	Q.	Smooth endoplasmic reticulum (ER)
F.	Microfilaments	L.	Nucleus

Image from the American Society for Cell Biology

II. plasma membrane: _________________________________________

A. structure: _________________________________________, with proteins, and

cholesterol

B. _________________________________________
1. fluid: flows, self-healing
a. phospholipids
1) ______________________, polar phosphate head
2) ______________________, nonpolar lipid tail
b. cholesterol and glycolipids: stabilizes lipid membrane
2. mosaic: top and bottom of membrane may be different
a. integral proteins: imbedded in the membrane, structural
1)transmembrane proteins: form channels or carriers
  b. peripheral proteins: not embedded, functional
1) ______________________: biological cell markers, cell

recognition, ex) sperm and egg
2) enzymes, receptors, transport proteins, intercellular junction

C. interstitial fluid and extracellular fluid: bathes cells in fluid

D. ______________________: increase surface area for absorption

E. membrane junctions:
1. ______________________: impermeable, ex) digestive system
2. ______________________: “spot welds” anchoring, sew cells into a

functional group, ex) skin

3. ______________________: allow intercellular communication,

ex) heart

F. functions

1. membrane transport: interstitial fluid
a. ______________________: depends on kinetic energy of molecules

and/or pressure gradients
1) ______________________: moves molecules from greater to

lesser concentration, or concentration gradient, for fat soluble and

small, uncharged (nonpolar) molecules (e.g. oxygen & carbon

dioxide)
2) ______________________: movement of water across a

membrane, along a concentration gradient

a) osmolarity: total concentration of all solute particles in a

solution
           b) ______________________: "low salt", water goes in, ex) blood cells in distilled water

c) ______________________: "high salt", water goes out,

ex) in salt water

d) ______________________: same concentration on both

sides of a membrane
3) _________________________________, diffusion assisted by

specific carrier molecules
4) ______________________: solutions are forced through by a

pressure gradient or hydrostatic pressure (force of fluids), ex)

edema
b. ___________________________________: requires ATP
1) active transport: Na⁺-K⁺ pump, move against concentration

gradient
2) vesicular or bulk transport: plasma membrane surrounds and

moves large amounts enclosed in a vesicle
a) _____________________: materials go out
b) ______________________: materials move in
c) ______________________: cell eating, ex) white blood

cells, amoeboid motion
d) ______________________: “cell drinking” movement of

dissolved particles
3) membrane potential: voltage (charge separation) across a

membrane
a) resting membrane potential: determined by concentrations

of Na⁺ and K⁺
b) polarized: inside of membrane -, outside +

2. cell-environmental interactions
a. CAM: cell adhesion molecules: allow cells to stick together
b. membrane receptors: serve as binding sites, signaling, ex)

neurotransmitters, and hormones

III. ______________________: where most of the "work" of the cell takes place

A. cytosol: water, soluble proteins, salts, sugars, etc.

B. inclusions: chemical substances stored in the cytoplasm – granules

IV. ______________________: compartments that have a specific function for

the cell

A. ______________________: organelle that houses DNA

1. DNA carries the blueprints and instructions for everything that the cell will

make, everything it will do, & when it will do it.
a. direct control: protein synthesis, membranes, storage of secretory

products
b. indirect control: cell metabolism, synthesis of enzymes

2. double nuclear envelope: nuclear pores allow communication

with the ER
3. ______________________: darkly staining body w/in the nucleus. Assemble

ribosome subunits, ______________________ (rRNA will be released into the cytoplasm, where it will combine with a protein to become a ribosome – the workbenches on which proteins will be built. Proteins can either be structural or functional (enzymes))
4. Nucleoplasm – the granular fluid within the nucleus

5. ________________________________ – loose strands of DNA
6. histones and nucleosomes organize chromosomes, seen during cell division  

B. ______________________: "power plant", provide ATP through cellular respiration
1. ______________________: inner folds of the membrane (where respiration

takes place)
2. matrix: gel, stores Ca⁺²
3. has its own DNA, RNA and can self-replicate

C. ______________________: enzymes detoxify alcohol, formaldehyde and free

radicals to peroxide and then to water, active in liver and kidney

D. ______________________: “workbenches” upon which proteins are made
1. free ribosomes: in cytoplasm
2. membrane bound ribosomes on rough endoplasmic reticulum

E. ________________________________: "production factory of the cell"

1. continuous with nuclear membrane, double-membraned, subdivides the

cytoplasm

2. ______________________: studded with ribosomes, make proteins
3. ______________________: makes phospholipids, cholesterol, steroid

hormones, glycerides, detoxification, glycogen synthesis, stores Ca⁺²

F. ______________________: “warehouse of the cell”

1. receives products from ER and then…

a. stores products for later use by cell

b. modify & activate product (ex. Proteins may be activated to become

enzymes)

c. packages products for shipping to other cell parts

2. Structure: saccules: stacks of flattened membranes outside ER

a. secretory vesicles or granules: sacs for transport

G. ______________________: vesicles filled with digestive enzymes,

remove wastes, bacteria, etc.
1. autolysis: self-digestion, seen in autoimmune diseases, ex) rheumatoid

arthritis
2. Tay-Sachs disease, lack lysosomes

H. ______________________: "cell skeleton", internal protein framework
1. microtubules: hollow tubes (tubulin), from centrosome
2. microfilaments: thin strands of contractile protein (actin)
3. intermediate filaments: tough, insoluble protein fibers, transport system
4. thick filaments: produce movement (myosin)
5. ______________________: cell center, microtubule-organizing center

(composed of 2 centrioles at right angles to each other)

a. centrioles (basal bodies) used in cell division and moving cilia and

flagella
b. cilia: work together to move substances over the surface of the cell
c. flagella: longer, move cells, (the only human cell example is sperm)

REVIEW OF CELLULAR ORGANELLES

Match the following organelles to the description of their function.

___ 1.	A selectively permeable phospholipid bilayer that encloses the cytoplasm of a cell.	A.	Chromatin
___ 2.	Microscopic cellular membrane protrusions that increase the surface area of cells, and are involved in a wide variety of functions, including absorption, secretion, cellular adhesion, and transduction.	B.	Microvilli
___ 3.	A membrane-enclosed organelle containing the genetic information (in the form DNA) of a cell. It is the “Command Center of the Cell,” responsible for growth and reproduction.	C.	Nuclear envelope
___ 4.	A darkly staining body within the nucleus of a cell during interphase. It plays an important role in ribosome manufacture and, by extension, protein synthesis.	D.	Nucleolus
___ 5.	Double membrane surrounding the cell nucleus; consists of outer and inner membranes perforated by nuclear pores.	E.	Nucleus
___ 6.	A complex of DNA, RNA and proteins within the cell nucleus that will condense to become visible chromosomes during mitosis.	F.	Plasma membrane

Match the following organelles to the description of their function.

___ 7.	Region of the endoplasmic reticulum that is not studded with ribosomes and is involved in lipid synthesis.	A.	Golgi apparatus
___ 8.	A system of membranous tubes and sacs containing ribosomes which function in the manufacture of membrane-bound proteins.	B.	Lysosomes
___ 9.	A protein synthesis 'machine,' made of ribosomal RNAs and proteins that translates the code on mRNA (messenger RNA) into proteins. “The Workbench Upon Which Proteins are Built”	C.	Peroxisome
___ 10.	A series of flattened, membrane-bound sacs involved in the storage, modification and secretion of proteins and lipids. This organelle packages proteins and carbohydrates into vesicles for export from the cell. This organelle is known as the “Warehouse of the Cell.”	D.	Ribosome
___ 11.	Organelles that contain powerful oxidase enzymes that use molecular oxygen to detoxify harmful or toxic substances, such as free radicals and peroxides. It also participates in the metabolism of fatty acids and other metabolites.	E.	Rough ER
___ 12.	Organelles that contain digestive enzymes. They digest excess or worn-out organelles, food particles, and engulfed viruses or bacteria. Some cell biologists call these “suicide bags” because they digest cells that are defective.	F.	Smooth ER

Match the following organelles to the description of their function.

___ 13.	A microscopic network of actin filaments and microtubules in the cytoplasm that functions as the cell’s "scaffolding" or "skeleton." It gives the cell its shape and provides for internal movements and sometimes external movements.	A.	Centriole
___ 14.	Also known as actin filaments, these are the thinnest filaments of the cytoskeleton. They are usually involved in cell motility or changes in cell shape.	B.	Centrosome
___ 15.	Components of the cytoskeleton composed of hollow cylindrical rods, formed of a protein called tubulin. They help cells to maintain their shape; they also occur in cilia, flagella and the centrioles, and form the spindle during nuclear division.	C.	Cytoskeleton
___ 16.	One of a pair of small, barrel-shaped microtubule structures involved in the formation of the spindle during mitosis.	D.	Mitochondria
___ 17.	The area of the cell containing paired centrioles. The centrosome will be replicated during the G2 period of interphase. The centrosomes move to opposite poles of the cell during prophase, stretching the spindle fibers between them. Recall that it is the spindle fibers that move the chromosomes during mitosis.	E.	Microfilaments
___ 18.	An organelle found in the cytoplasm of eukaryotic cells that is responsible for the conversion of food to usable energy in the form of ATP through a process called cellular respiration. The inner membrane is folded into pleats called cristae, which increases the surface area upon which cellular respiration takes place. This organelle contains genetic material separate from the nucleus called mitochondrial DNA (mDNA). This organelle is known as the “Power House of the Cell.”	F.	Microtubules

V. cell growth and reproduction

Human Cell Mitosis

A cell’s life begins when a parent cell divides into 2 daughter cells, continues as the cell grows and matures, and ends when the cell divides. This is known as the cell cycle.

Cell specialization (differentiation) is dependent on what type of proteins are made by that cell,

INTERPHASE

When cells are not actively dividing, they are in interphase. A cell may spend up to 95% of its life in interphase. At this time, the DNA is in a loose, soupy form known as chromatin. The chromatin contains a person’s chromosomes. Chromosomes are long strands of DNA where genes (instructions for specific traits and proteins) are encoded. Interphase can be divided into three periods; the G₁ Period, S Period, and G₂ Period.

1. During the G₁ (Gap 1) Period the cell rapidly increases in size to adult cell size.

a) Cells make proteins, centrioles begin to replicate at the end of this phase

2. The G₀ (Gap 0) Period occurs in cells that permanently stop growing – neurons, skeletal, and cardiac muscles
3. During the S (Synthesis) Period, DNA replication takes place.
4. During the G₂ (Gap 2) Period, mitochondria and other cellular organelles replicate. Duplication enzymes and proteins are produced. Also, the chromosomes begin to coil and condense.

Human cell in Interphase

Please label the following: A. Centriole B. Centrosome C. Chromatin D. Nuclear envelope E. Nucleolus F. Nucleus

DNA Replication

DNA replication is semiconservative. An enzyme (DNA Helicase) unzips the double helix molecule, DNA. Each strand then acts as a template for the synthesis of a new and complimentary strand. This results in the formation of 2 identical strands of DNA (sister chromatids, connected at their centromere.

Humans have 23 homologous pairs of chromosomes.

Parts of a replicated chromosome include…

1. Sister chromatids – the identical strands of DNA
2. Centromere – structure that holds the sister chromatids together
3. Kinetochore – structures that develop on the sides of a centromere during late prophase. The spindle fibers attach at this point of the chromosome.

Please label the following: A. Centromere B. Kinetochore C. Spindle fibers D. Sister chromatids

MITOSIS

Mitosis refers to division of the nucleus, normally accompanied by the

division of the rest of the cell called cytokinesis.

· Mitosis is divided into four phases; prophase, metaphase, anaphase, and telophase.

· Mitosis results in the production of identical daughter cells.

· We use mitosis when we are growing and repairing tissues.

Controls of cell division:

1) Surface/volume ratio

2) Contact inhibition: cells usually stop dividing when they fill the space & touch

PROPHASE

During prophase, the following events take place:

1. The centrosomes replicate and then migrate to opposite poles of the nucleus. Spindle fibers stretch out between them as they move, forming a football-shaped spindle between the centrosomes.
2. Microtubules radiate outward from the centrosomes to form asters. The asters will push the poles of the cell away from each other during late anaphase and telophase.
3. The nuclear chromatin condenses into visible chromosomes.
4. The nucleolus gradually disappears.
5. The nuclear membrane completely fragments.
6. Some spindle fibers grow from the poles to the center of the cell and attach to the chromsomes at the kinetochores.

Human cell in prophase

Please label the following: A. Aster B. Centromere C. Centrosome D. Chromosome E. Sister Chromatids F. Spindle

METAPHASE

During metaphase, the following events take place:

1. The spindle fibers pull the chromosomes to the center of the cell.

2. The chromosomes are lined up along an invisible circular plate, perpendicular to the axis of the spindle, called the equator.

Human cell in metaphase

Please label the following: A. Equator B. Poles

ANAPHASE

During anaphase, the following events take place:

1. The centrosomes begin reeling in their spindle fibers.
2. The centromeres break, allowing the sister chromatids to separate and be dragged toward opposite poles.
3. The sister chromatids, once separated, are known as daughter chromosomes.
4. The aster bodies begin pushing the poles of the cell further apart.

Human cell in anaphase

Please label the following: A. Daughter chromosomes

TELOPHASE

During telophase, the following events take place:

1. The daughter chromosomes reach opposite poles.
2. The spindle begins to break down.
3. The chromosomes begin to uncoil and become chromatin once again.
4. Nuclear envelopes form around the two newly formed nuclei.
5. Nucleoli reform

CYTOKINESIS

Cytokinesis is the process whereby the cytoplasm of a single eukaryotic cell is divided to form two daughter cells. This process results in a cleavage furrow appearing. The cleavage furrow contracts, “cutting” the parent cell into two, identical daughter cells.

Human cell in telophase

Please label the following: A. Cleavage furrow

Mitosis Review

Looking at the pictures below and to the right, please identify which phase of mitosis each cell is in

____ Interphase ____ Prophase ____ Metaphase ____ Anaphase ____ Telophase

Mitosis Review

Below are descriptions of some of the events that occur during mitosis. Please indicate which phase the events take place by recording…

I for interphase	M for metaphase	T for telophase
P for prophase	A for anaphase

____ Daughter chromosomes are dragged toward opposite poles of the cell.

____ The spindle fibers drag the chromosomes to align at the cell’s equator.

____ This phase occurs immediately before cytokinesis.

____ A cell may spend up to 95% of its life in during this phase.

____ The aster bodies begin pushing the poles of the cell away from each other.

____ Spindle fibers attach to the chromosomes via their kinetochores.

____ The cleavage furrow develops.

____ The chromosomes’ centromeres break.

____ DNA replication takes place.

____ The chromatin will condense into chromosomes that are visible.

____ The daughter chromosomes reach opposite poles of the cell.

____ The spindle forms.

VI. The Central Dogma of Molecular Biology – the flow of information from DNA to RNA to proteins

A. ______________________________________ – the process of duplicating double-stranded DNA, prior to mitosis

1. DNA is composed of a double strand of nucleotides in the form of a double helix.

2. The nucleotides include nitrogen containing bases: A, G, C, and T

B. ______________________________________ – the process of copying the information encoded on DNA into RNA.

1. RNA is a single-stranded molecule, containing the bases A, G, C, and U

2. A set of 3 nucleotides on mRNA = a codon.

3. Codons encode for 20 specific amino acids (aa)

C. ______________________________________ – the process of interpreting the information carried by messenger RNA (mRNA) in order to synthesize the encoded protein.

1. Proteins are long chains of amino acids (aa). The sequence of the aa is determined by the codons on mRNA.

2. The aa are joined together by peptide bonds. (proteins, therefore, are also known as polypeptides)

3. Proteins may be structural (and form membranes, etc.) or may mediate cellular activities (e.g. enzymes)

D. Gene Expression

1. A ______________________________________ is a segment of the DNA chromosome that contains the instructions to build a protein.

2. Transcription begins when RNA polymerase recognizes and binds to the promoter on the DNA molecule that identifies the location of the gene.

i. Elongation phase – when the RNA polymerase is synthesizing a complimentary mRNA strand from the gene on the chromosome

ii. Transcription terminator – the point on the chromosome where the gene ends and RNA polymerase falls of the DNA, releasing the mRNA

3. Translation begins when a ______________________________________ joins the mRNA and begins the process of translation from the “Start” codon (AUG). The ribosome reads the mRNA one codon at a time, bonding the appropriate amino acids together as it goes.

i. ______________________________________ – the ribosome joins the mRNA

ii. ______________________________________ – the ribosome reads the mRNA, adding the encoded amino acids as it goes

iii. ______________________________________ – When the ribosome reaches a “Stop” codon (UGA, UAA, or UAG), there are no amino acids that match & translation ends.

1. The protein is freed

2. The ribosome falls off the mRNA

E. Regulating the Expression of Genes

1. Protein synthesis is generally controlled by regulating the synthesis of mRNA molecules.

2. mRNA is a short-lived molecule because RNases degrade it within minutes.

F. ______________________________________ – permanent alterations in DNA

G. ______________________________________ – a disease caused by an uncontrolled division of abnormal cells in a part of the boy.

1. carcinogens: cause DNA mutations, ex) radiation, viruses, chemicals, etc.

2. ______________________________________ cancer – a local tumor, encapsulated, growing slowly

3. ______________________________________ cancer - nonencapsulated, rapid growth, undifferentiated

i. metastasis: spread, consume large amount of nutrients, cause wasting away

ii. oncogenes: cancer-causing genes in rapidly spreading cancers

iii. anti-oncogenes: promote normal division, when removed allow rapid division