A&p Lecture 4:

Front 1

Nucleus

Back 1

- Usually the largest membranous organelle
- The cell's control center
-- Contains all the info to create 100,000+ proteins
found in human body
- Most cells have 1 Nucleus

Definition:
- Nucleoplasm containing nucleotides, enzymes, nucleoproteins, and chromatin
- Surrounded by a double membrane (nuclear envelope)

Front 2

Functions of Nucleus:

Back 2

1. Control of Metabolism
2. Storage and Processing of Genetic Information
3. Control of Protein Synthesis

Front 3

Single Nucleus Exceptions:

Back 3

1. Skeletal Muscle Cells
- Multiple Nuclei

2. Mature Red Blood Cells
- Zero Nuclei

Front 4

The Nucleus is Surrounded By:

Back 4

1. Nuclear Envelope

2. Nuclear Pores

Front 5

Nuclear Evnvelope

Back 5

Double membrane around the nucleus

Two layers are separated by a perinuclear space

Front 6

Nuclear Pores

Back 6

- Cover 10% of the membrane
- The passages that allow ions, RNA, very small molecules
to enter or leave the nucleus

- Allows chemical communication between the nucleus
and the cytoplasm
- Contains regulatory proteins that control the transport
of proteins/RNA into or out of nucleus

Front 7

Contents of the Cell Nucleus:

Back 7

1. DNA
2. Nucleoplasm
3. Nuclear Matrix
4. Nucleoli (Nucleolus)
5. Nucleosomes

Front 8

DNA

Back 8

*Deoxyribonucleic Acid

- All information to build and run organisms
-- Contains instructions for every protein in the body
- Composed of deoxyribonucleic acid subunits
(nucleotides)

Front 9

Nucleoplasm

Back 9

The fluid contents of the nucleus

Contains:
1. ions
2. enzymes
3. nucleotides
4. some RNA
5. Nuclear Matrix

Front 10

Nuclear Matrix

Back 10

A network of fine filaments that provide structural support
-- Support filaments
-- May be involved in the regulation of genetic activity

Front 11

Nucleoli (Nucleolus)

Back 11

1. Composed of RNA, enzymes, and histones
-- (DNA wraps itself around histones to cause DNA to
condense)

2. Related to Protein Production
-- Produces rRNA and ribosomal subunits
-- The site of rRNA synthesis and assembly of
ribosomal subunits

3. Prominent in cells that produce lots of muscle cells
-- Ex: Liver, Nerve, and Muscle Cells

(most cells contain several of these dark-staining areas)

Front 12

Nucleosomes

Back 12

DNA coiled around histones
-- Helps organize and pack DNA away to help condense
DNA and regulate which parts of DNA will or will not
be expressed

In cells that are NOT dividing:
-- Nucleosomes are loosely coiled --> chromatin

In cells that ARE dividing:
-- Coiling tightens --> distinct chromosomes

Front 13

DNA Coiling

Back 13

The degree of coiling can determine the level of compactness

1. Chromatin
2. Chomosomes

Front 14

Chromatin

Back 14

- Unwound DNA

- Loosely coiled DNA (in un-dividing cell)
- Fine filaments, makes the nucleus appear grainy

Front 15

Chromosome

Back 15

- Tightly coiled DNA (in dividing cells)
-- Form distinct structures

- Visible under light microscope

Front 16

DNA Coiling Process:

Back 16

DNA Wraps Around Histone --> Nucleosome --> Loose Coils --> Supercoiled --> Condensed Chromosome

Front 17

Genetic Code

Back 17

The chemical language of DNA instructions
-- Sequence of Nitrogenous Bases (Adenine, Thymine,
Cytosine, Guanine)
-- Triplet Code

Front 18

Triplet Code

Back 18

sequence of 3 nitrogenous bases that code for an amino acid

Front 19

Gene

Back 19

Functional Unit of Heredity
-- Codes for the production of a polypeptide or sequence
or RNA

-- The DNA containing instructions for one protein
-- Sequence of triplet codes that dictate the sequence of amino acids in a protein

Front 20

The Role of Genes in Protein Synthesis:

Back 20

1. The Nucleus Contains Chromosomes

2. Chromosomes Contain DNA

3. DNA Stores Genetic Information for Proteins

4. Proteins Determine Cell Structure and Function

5. To produce proteins, the portion of DNA containing the
gene for that protein must unwind, exposing the
nucleotide sequence for RNA production

*Form determines function of cell

Front 21

Gene Activation

Back 21

Requires uncoiling of DNA
-- Disruption of hydrogen bonds between babes of the
two DNA strands
-- Removal of the histone

The copying of DNA into RNA controlled by:
-- Promoter
-- Terminator

Front 22

Promoter

Back 22

The region of DNA that regulates gene transcription
-- the control segment

Front 23

Terminator

Back 23

Stop signal

Front 24

Transcription

Back 24

Copies instructions in DNA into mRNA; the synthesis of RNA from a DNA template
-- Occurs in the nucleus

RNA polymerase produces messenger RNA (mRNA)

Front 25

mRNA

Back 25

carries the information needed to synthesize proteins
-- carries it outside of the nucleus

Front 26

RNA polymerase

Back 26

An enzyme that binds to the promoter of the gene
-- 1st step of transcription

Produces messenger RNA (mRNA)

Front 27

Translation

Back 27

ribosome reads the genetic code from mRNA
-- Occurs in the cytoplasm
-- Assembles amino acids into polypeptide chain

Front 28

Protein Processing

Back 28

occurs in the rough ER and Golgi Apparatus to produce proteins

Front 29

Differentiation

Back 29

Since all somatic cells have the same DNA:
1. All cells carry complete DNA instructions for all body
functions
2. Cells specialize or Differentiate
-- To form tissues (liver cells, fat cells, and neurons)
-- By turning OFF all genes not needed by that cell
3. Differentiation depends on which genes are active and
which are inactive

**All body cells, except sex cells, contain the same 46 chromosomes.

Front 30

Steps of Transcription:

Back 30

A gene is transcribes into mRNA in 3 steps:

1. Gene Activation
2. DNA to mRNA
3. RNA Processing

Front 31

Step 1: Gene Activation

Back 31

1. DNA uncoils and the histones are removed

2. "Start" (promoters) and Stop codes on DNA mark the
location of the gene (codes for a polypeptide or RNA
strand)

Front 32

Step 2: DNA to mRNA

Back 32

The enzyme RNA polymerase Transcribes DNA:
1. RNA polymerase binds to the promoter (start)
sequence
2. Reads DNA Code for gene
3. The enzyme attaches nucleotides that compliment
the DNA strand to form a strand of mRNA
4. RNA uses the same nitrogenous bases as DNA
except "thymine" is replaced with "uracil"

Front 33

Step 3: RNA processing

Back 33

At "stop" signal, mRNA detaches from DNA molecule
1. Code is edited (RNA processing)
-- Unnecessary codes (introns) are removed
-- RNA sequence that codes for the protein (Exons)
are spliced together
2. Triplet of three nucleotides (codon) on the mRNA
strand represents one amino acid

Front 34

Codon

Back 34

triplet of three nucleotides on the mRNA strand
-- represents 1 amino acid

interacts with tRNA and tells it specifically which amino acid to bring

Front 35

Introns

Back 35

nonsense regions; unnecessary codes

they are removed

Front 36

Exons

Back 36

remaining coding sequences

sliced together

the RNA sequence that codes for the protein

Front 37

Translation

Back 37

*occurs in cytoplasm

mRNA codon --> amino acid

mRNA moves:
1. From the nucleus through a nuclear pore
2. To a ribosome in the cytoplasm
3. mRNA binds to ribosomal subunits
4. tRNA delivers amino acids to mRNA

Front 38

Steps of Translation

Back 38

1. tRNA anticodon binds to mRNA codon
-- 1 mRNA codon translates to 1 amino acid

2. Enzymes join amino acids with peptide bonds
-- Polypeptide chain has specific sequence of amino
acids

3. At the stop codon, components (ribosome subunits
and mRNA) separate and translation ends

*Just because protein synthesis is complete, doesn't mean protein is complete (can still be modified further)

Front 39

Levels of Control of Cell Structure and Function by the Nucleus:

Back 39

1. Direct Control

2. Indirect Control

Front 40

Direct Control

Back 40

Control through the synthesis of:
1. Structural proteins
-- Cytoskeletal components, membrane proteins
(including receptors)
2. Secretions (in response to the environment)

Front 41

Indirect Control

Back 41

Control over metabolism
-- Regulation of enzyme synthesis

Ex: Increase rate of glycolysis by increasing the number
of enzymes used in glycolysis in cytoplasm

Front 42

Cell Life Cycle

Back 42

1. Most of a cell's life is spent in a non-dividing state (interphase)

2. Somatic Cell Division (3 stages)

Front 43

Somatic Cell Division

Back 43

1. DNA Replication
-- duplicates genetic material exactly

2. Mitosis (nuclear division)
-- divides genetic material equally
* Mitosis occurs in somatic cells; Meiosis occurs to
produce sex cells with 1/2 the genetic information

3. Cytokinesis
-- Divides cytoplasm and organelles into two daughter
cells

Front 44

Interphase

Back 44

The non-dividing period

4 Phases:
1. G-zero Phase (G0)
2. G1 Phase
3. S Phase
4. G2 Phase

*most of the cell's life is in interphase, not mitosis

Front 45

G-zero Phase (G0)

Back 45

specialized cell functions only

most cells will NOT be in G0

Ex: skeletal muscle cells, neurons; usually stay in this
stage and do NOT divide

*stem cells don't go to G0 (if they do, they can't divide or
replace lost cells)

Front 46

G1 Phase

Back 46

cell growth, organelle duplication, protein synthesis

Front 47

S Phase

Back 47

DNA replication and histone synthesis

Front 48

G2 Phase

Back 48

finishes protein synthesis and centriole replication

Front 49

Mitosis

Back 49

Divides duplicated DNA into 2 sets of chromosomes (exact copies)
-- DNA coils tightly into chromatids
-- Chromatids connect at a centromere

4 Stages of Mitosis

Compared to the rest of the phases of the cell cycle, mitosis is relatively short

Front 50

Stages of Mitosis:

Back 50

1. Prophase
2. Metaphase
3. Anaphase
4. Telophase

Front 51

Prophase

Back 51

1. Nucleoli disappear
2. centriole pairs more to cell poles
3. Microtubules (spindle fibers) extend between centriole
pairs
4. Nuclear envelope disappears
5. Spindle fibers attach to kinetochore (located on
chromatids)

Front 52

Metaphase

Back 52

Chromosomes align in central metaphase plate

Centrioles at each pole

Front 53

Anaphase

Back 53

Microtubules pull chromosomes apart

Daughter chromosomes group near centrioles

Front 54

Telophase

Back 54

(basically the opposite of prophase)

1. Nuclear membranes re-form
2. Chromosomes un-coil
3. Nucleoli reappear
4. Cell has 2 complete nuclei

Front 55

Cytokinesis

Back 55

Division of the cytoplasm

Starts in late anaphase and continues throughout telophase

1. Cleavage furrow forms around the metaphase plate
2. Membrane closes, producing daugther cells

Front 56

Cleavage Furrow

Back 56

Microfilaments cause cleavage furrow to form and eventually leads to cells pinching off --> 2 daughter cells

Involves microfilaments and the motor protein, myosin

Front 57

Mitotic Rate

Back 57

The rate of cell division

Slower mitotic rate = longer life expectancy

Front 58

Energy Use during Cell Division

Back 58

Cell division requires large amounts of energy (ATP)
-- Because cells have to synthesize all of these elements
(proteins, etc.)

Front 59

Cells That Rarely Divide

Back 59

1. Muscle Cells
2. Neurons

-- They are usually stuck in G0

Front 60

Exposed Skin Cells

Back 60

Skin and Digestive Tract

Live only days or hours
-- Replenished by stem cells

Front 61

Stem Cells

Back 61

Can protect DNA with an enzyme that lengthens DNA to keep it from being too short

Front 62

Shortening DNA Strands

Back 62

--> aging

DNA replication can't copy every DNA strand (ends can't be copied)
-- Every copy makes the DNA strand shorter and shorter
-- Eventually Cell Dies

*Cells that undergo a lot of mitosis live shorter than cells than don't

Front 63

Steps of Cancer Development

Back 63

1. Abnormal Cell
2. Primary Tumor
3. Metastasis
4. Secondary Tumor

Front 64

Abnormal Cell

Back 64

*1st Step of Cancer Development

Cell growth and division not under normal control processes

Front 65

Primary Tumor

Back 65

*2nd Step of Cancer Development

the tumor of origin

Front 66

Metastasis

Back 66

*3rd Step of Cancer Development

Dispersion of malignant cells to different tissues/organs

Front 67

Secondary Tumor

Back 67

*4th Step of Cancer Development

Tumor formed in a tissue
-- (The origin of the cancer cells is from the primary
tumor)

Front 68

Tumor

Back 68

*Neoplasm

Enlarged mass of cells caused by abnormal cell growth and division

Two Types

Front 69

Types of Tumors

Back 69

1. Benign Tumor

2. Malignant Tumor

Front 70

Benign Tumor

Back 70

Contained within epithelium or a connective tissue capsule

Not life threatening unless it's large

Front 71

Malignant Tumor

Back 71

Spreads into surround tissues (invasion)
-- May travel to distant tissues and organs (metastasis) to
form secondary tumors