Chapter 3

The Cellular Level of Organization

3 main parts of cell fig 3.1 _______________- forms cell’s flexible

outer surface, barrier, regulates flow, role in communication

____________- all cellular contents between plasma membrane & nucleus

– 2 compartments- cytosol & organelles ___________- large organelle housing

DNA, contains chromosomes that contain genes

Cell Membrane fig 3.2

__________________- permit passage of certain substances but restricts passage of others.

Fluid mosaic- ever moving phospholipids, mosaic of many different proteins

Cholesterol also present See cell membrane handout

Membrane _____________ and their different functions

Cytoplasm = cytosol & organelles _______________- fluid portion of cytoplasm

– 55% of total cell volume– 75-90% water

• Ions, glucose, a.a., f.a., proteins, lipids, ATP, waste; and sometimes: lipid droplets, glycogen

– Site of chemical rxns• glycolysis• protein synthesis

_________- specialized structures for specific function in cell growth, maintenance & repro– Each have own enzymes– # and type vary from cell type to cell type– Cooperate to maintain homeostasis

Nucleus

____________________ structure called nuclear envelope encapsulates

Nuclear pores–larger molec selectively pass Controls cellular structures Directs cellular activities Produces ribosomal subunits in __________ ________________ - single piece of DNA

– ____________- segments of DNA control cellular structure and direct cellular activities

Nucleolus

Spherical body inside nucleus Cluster of_____, ______, & _________ _____________ & ___________ of

rRNA and protein into ribosomal subunits

Muscle and liver have many cells

Endoplasmic Reticulum

2 types– ________ ER - synthesizes glycoproteins

& phospholipids organelles, inserted in p.m. or secreted during exocytosis

– ________ ER – synthesizes f.a. & steroids• inactivates or detoxifies drugs & harmful

substances• remove P from glucose-6-phosphate• stores and releases Ca 2+ to trigger muscle

contraction

Mitochondria

____________ thru rxns of cellular respiration

Each cell: _____ to __________________ Muscles, liver, kidney have large # Inner membrane folds = cristae

– large surface area for celluar respiration rxns to take place

Can self replicate Matrix contains ribosomes

Ribosome

Site of ____________________ rRNA and protein 2 subunits made in nucleolus & come

together in cytoplasm Can be:

– ______ to ER – synthesize proteins p.m.– __________ – syn proteins used in cytosol– __________________

Golgi bodies

Modifies, sorts, packages & transports proteins received from rough ER

Forms __________________ that exocytose processed proteins to ECF

Form membrane vesicles that carry new molecules to ____________________

Form transport vesicles carrying molecules to _______________________– lysosomes

Lysosome

Digests substances that enter cell via endocytosis and transport final products into cytosol

__________ – digestion of worn out organelles

__________ – digestion of entire cell Carry out extracellular digestion

Centrioles

Pericentriolar material contains tubulins that build ___________________ in non-dividing cells

Form the mitotic spindles during _______________

Secretory vesicles

Take proteins to the plasma membrane & _______________ them to the ECF– Pancreatic cells release insulin

Form at the exit face of the __________ _____________

Cytoskeleton

Serves as __________ that helps to determine a cell’s shape & to organize the cellular contents

_______________________ of:– organelles within cell– chromosomes during cell division– wholes cells

• phagocytes

Cilia and flagella

___________ – “eyelashes,” short, hairlike projections– Composed of 20 microtubules in p.m.– Move like coordinated oars– Fluid flow along cell’s surface

________ – whip, similar to cilia, longer– Move entire cell

DNA= DeoxyriboNucleic Acid

_______________ consisting – One of 4 nitrogenous bases

• Adenine, cytosine, guanine, or thymine

– Deoxyribose– Phosphate group

Genetic code _________________ helix

– Hydrogen bonds between bases (Figure 3.29)

Fig. 03.32

DNA (2)

Purines pair with pyrimidines– A -- 2 H bonds T– C --- 3 H bonds G

Sugar and phosphate create the backbone ________________ codes for inherited

differences among humans Atleast half is “junk” DNA Estimate 35,000-45,000 genes in our DNA

Genes

Hereditary units __________________ at a definite position

on a particular chromosome– Humans- 23 homologous pairs of chromosomes

Codes for specific RNA ___________= alternate form of a single

gene that controls the same inherited trait• Example: gene for body hair can have different alleles:

such as coarse hair or fine hair ___________= total genetic information

carried in cell or organism

DNA Replication fig 3.29

Helix uncoils, strands separate Each strand of DNA is able to pair with its

______________ base Chemical bonds form between neighboring

nucleotides (& H bonds form between bases) Original DNA is now 2 identical strands, one

goes to each of 2 daughter cells DNA ______________: catalyzes the

addition of the nucleotide to the 3’ end During _____________ of interphase

DNA RNA protein

________________= process in which gene’s DNA is used to direct synthesis of specific protein– _____________- base triplets of DNA are

template for creating COMPLEMENTARY strand of RNA

– ________________- RNA to protein

______= complementary sequence of 3 RNA nucleotides, codes for specific amino acid

Genetic code

Set of rules relating the base triplet sequence of DNA to the __________________________of RNA and the amino acids code for in the polypeptide sequence

Transcription (DNA RNA)

_____________________ catalyzes transcription of RNA– Must be instructed where to start & end along

DNA strand• Promoter- special nucleotide sequence near beginning of

gene• Terminator- sequence specifies end of gene

– Only one of 2 DNA strands can be the template– RNA polymerase attaches at _______________

Fig. 03.28

RNA, 3 types

_________ =mRNA- directs protein synthesis _____________= rRNA- joins w/ ribosomal

protein to make ribosomes _______= tRNA- binds a.a. to hold it in place

on ribosome while incorporated into protein.– One end carries amino acid, other end- triplet of

nucleotides = anticodon -complementary to mRNA codon

mRNA is a modified product

Not all of the gene actually codes for parts of the protein!

_________- DO NOT code for part of protein __________ - coding region After transcription:

– 1st product = pre-mRNA from which intron will be removed by small nuclear ribonucleoproteins (snRNPs)

– NOW, the coding mRNA goes out to cytoplasm

Translation (RNA protein)

Nucleotide sequence of mRNA specifies the amino acid sequence of a protein

___________ in cytoplasm is where translation occurs

Translation always starts at start codon = _________, which codes for the amino acid methionine

Cell cycle fig 3.28

Orderly sequence, _________ cell duplicates its contents and divides into 2 cells

Humans - 23 pairs of chromosomes– _________________- belong to same pair– One from mother, one from father– Gene pair at identical sites on the 2 homologs

Chromosomes are duplicated in order to pass on genes

Cell cycle has _________________: interphase & mitotic

Interphase

Phase when __________________ ______________ additional organelles

and cytosolic components State of high ____________________

– Cell does most growing during this phase G1, S, and G2

– G = gap, S = synthesis

G1 Phase of interphase

Between mitosis and S phase Metabolically active ________________

organelles & cytosolic components Duration of cell cycle varies for different types

of cells– Embryonic & cancer cells have very short G1

____________- cells that remain in G1 for a very long time, perhaps never destined to divide again– Ex) most nerve cells

S phase of interphase

Between G1 and G2

_____________________– 2 daughter cells have genetically identical

material Once entered into S phase cell is

committed to divide

G2 phase of interphase

Between S and mitosis _________________ of cell Enzymes & proteins made in

_______________ for cell division _________________ replication is

complete– Involved in mitosis- poles to which

chromosomes are drawn towards

Mitotic phase fig 3.30

Mitotic phase- nuclear division (mitosis) and cytoplasmic division (cytokinesis)

____________ daughter cells are created & are identical to the somatic parent cell

2 sets of chromosomes (from S) are sent into 2 separate nuclei

________________ of mitosis:– Prophase– Metaphase– Anaphase– Telophase

Metaphase

Centromeres of chromatid pairs ____________ at metaphase plate– Microtubules of mitotic spindle align the

centromeres

Anaphase

_____________________– Chromatid 2 chromosomes

Individual chromosomes __________________ towards opposite poles– Pulled by mitotic spindles

Telophase

________________ and ___________ reappear– Chromosomes uncondense & become threadlike,

diffuse chromatin form

____________________ disappear Contractile ring forms __________________

around center of cell– Plasma membrane pulled progressively inward to

form 2 daughter cells = __________________

Meiosis fig 3.31-32

“lessing condition of” Reproductive cell division that occurs in

________________ Produces ______________

– Chromosome # reduced in 1/2– Single set of 23 chromosomes (NOT

homologous pairs)• Homolog- belong to the same pair

Meiosis (2)

__________ (1n) cells = cell has the single set of not homologous chromosomes. – Sperm and egg are haploid cells, all other body

(somatic) cells are diploid

Somatic cells are ______________= 2n Fertilization then restores the diploid number

of chromosomes from 2 haploid cells (one egg, one sperm)

Cellular diversity/cell specialization

Human body ≈ 100 trillion cells ≈ 200 cell types Vary in:

– ______________________– ______________________– ______________________

Cell differentiation (2)

Not all cells look or perform the same function

_____________ - process of specific regulation of gene expression

In general, differentiation is the result of highly programmed pattern of gene activation and gene repression

Gene expression is controlled at __________– Switches to turn on and off transcription

Surface area-to-volume ratio

Greater for small animals than large surface of integument for water or solute exchange is also greater for smaller animals– Smaller animals dehydrate or hydrate more

quickly– Larger animals have lesser oxygen requirements– Heat gain and loss differs – Gas exchange – Absorption of nutrients– Filtration