ch 3 - cell level of organization part 2

8/10/2019 Ch 3 - Cell Level of Organization Part 2

1/68

The Genetic Code1. A triplet code comprised of three nucleotide

bases in a sequence.

2. How many triplet codes?

20 common amino acids in a protein4 diff. bases on DNA A,T,C, & G

| | | |4 diff. bases on RNA U,A,G, & C

4 things put together in combinations of 3 =

43= 64

Therefore - 64 different DNA triplet codes or RNA

codons


2/68

The 64 triplet codes

60 code for amino acids

4 act as "stop" and "start " codes

Degenerate Code- more than onetriplet code for some amino acids

e.g.,


3/68


4/68

The 64 triplet codes

60 code for amino acids

4 act as "stop" and "start codes

Degenerate Code- more than onetriplet code for some amino acids

e.g.,

All code for the

amino acid glycine

GGG

GGU

GGC

GGA


5/68

Codons

Table 32

Coding

strand

Nonsense

strand


6/68

Nucleus Controls Cell

Structure and FunctionDirect controlthrough synthesis of:

structural proteins

secretions (environmental response)

Indirect controlover metabolism through

enzymes


7/68

KEY CONCEPTGenes:

are functional units of DNA

contain instructions for 1 or more proteins

Protein synthesis requires:

several enzymes

ribosomes RNA

Mutation is a change in the nucleotide sequence of a gene:

can change gene function

Causes: exposure to chemicals

exposure to radiation

mistakes during DNA replication


8/68

How do th ings get in ou t of cells?Overcoming the Cell Barrier

The cell membrane is a barrier, but and nutrients

must get in products and wastes must get outPermeability determines what moves in & out of a cell

impermeable

freely permeableselectively permeable

Cell membrane is selectively permeable -

allows some materials to move freely butrestricts other materials

Selective permeability restricts materials based on

size, electrical charge, molecular shape, lipid

solubility


9/68

TransportTransportthrough a cell membrane can be:

active(requiring energy and ATP)

passive(no energy required)

3 Categories of Transport

Diffusion(passive)Carrier-mediated transport (passive or active)

Vesicular transport(active)

SolutionsAll molecules are constantly in motionMolecules in solution move randomly

Random motion causes mixing


10/68

Table 33

The 7 methods of transport


11/68


12/68

Factors Affecting Diffusion Rates

Distancethe particle has to move

Moleculesize:

smaller is faster

Temperature: more heat, faster motion

Gradient size:

the difference between high and low

concentration

Electrical forces:

opposites attract, like charges repel


13/68

Diffusion and the Cell MembraneDiffusion can be simpleor channel-mediated

Simple (1) - Materials

which diffuse through

cell membrane:

lipid-soluble

compounds (alcohols,

fatty acids, and

steroids) dissolved gases

(oxygen and carbon

dioxide)


14/68

Channel-Mediated (2) - Materials which pass

through transmembrane proteins(channels):

are water soluble compounds

are ions

factors - passage depends on size, charge,

interaction with the channel

O i (3)


15/68

Osmosis (3)

Figure 316

Osmosisis the diffusion of water across the cell membrane

More solute molecules, lower concentration ofwater molecules

Membrane must be freely permeableto water,

selectively permeableto solutes


16/68

Osmosis Water MovementWater molecules diffuse across membrane

toward solution with more solutes

Volume increases on the side with more solutes

Osmotic PressureIs the forceof a concentration gradient of waterEquals the force (hydrostatic pressure) needed

to block osmosis

TonicityThe osmotic effect of a solute on a cell:

2 fluids may have equal osmolarity, but different

tonicity


17/68

IsotonicSolutions

A solution that does not cause osmotic flow of

water in or out of a cell

iso= same, tonos= tension

H t i S l ti


18/68

HypotonicSolutions

hypo= below

Has lesssolutesGainswater through osmosis

A cellin a hypotonicsolution:

gainswater

ruptures (hemolysisof redblood cells)

H t i S l ti


19/68

HypertonicSolutions

Hyper = above

Has moresolutesLosseswater through osmosis

A cellin a hypertonicsolution:

losewater

shrivels (crenation ofred blood cells)

KEY CONCEPT


20/68

KEY CONCEPTConcentration gradients tend to even out

In the absence of membrane, diffusioneliminates concentration gradients

When different solute concentrations exist on

either side of a selectively permeablemembrane, osmosis moves water through the

membrane to equalize the concentration

gradients


21/68

What are special transpo rt mechanism s?

Carrier-Mediated Transport

Carrier-mediated transport of ions and organicsubstrates: facilitated diffusion& active

transport

Characteristics of Carrier-Mediated TransportSpecificity: 1 transport protein, 1 set of

substrates

Saturation limits: rate depends on transportproteins, not substrate

Regulation: cofactors such as hormones

C t t


22/68

Cotransport2 substances move in the same direction at the

same time

Countertransport1 substance moves in while another moves out

F ilit t d Diff i (4)


23/68

Facilitated Diffusion (4)Passive and carrier mediated

Figure 318

Carrier proteinstransport molecules too large tofit through channel proteins (glucose, aminoacids):

molecule binds to receptor siteon carrier protein

protein changes shape, molecules pass through

receptor site is specific to certain molecules


24/68

Active Transport (5)Active transport proteins:

move substrates against

concentration gradient

require energy, such as ATP

ion pumpsmove ions (Na+,

K+, Ca+, Mg2+)

exchange pump

countertransports 2 ions at

the same time

Sodium-Potassium Exchange Pump - Active transport,

carrier mediated:

sodium ions (Na+) out, potassium ions (K+) in

1 ATP moves 3 Na+


25/68

Secondary Active Transport (5)

Sodium Potassium Pump

Figure 320

Na+concentration gradient drives glucose

transport

ATP energy pumps Na+back out


26/68

Transport Vesicles

Also calledbulk transport

Vesicles:

Endocytosis (6)(endo= into)

active transport using ATP:

receptor-mediated

pinocytosis

phagocytosis

exocytosis(7) (exo= out of)


27/68

Receptor-Mediated Endocytosis

Figure 321

Receptors (glycoproteins) bind target molecules

(ligands)Coated vesicle (endosome) carries ligands and

receptors into the cell

Exocytosisisthe reverse

of

endocytosis

Pi t i


28/68

Figure 322a

PinocytosisPinocytosis(celldrinking)

Endosomes drinkextracellular fluid

PhagocytosisPhagocytosis(cell eating)

pseudopodia(psuedo= false,

podia= feet)

engulf large objects in

phagosomes

How do cel ls reproduce?


29/68

Cell Life Cycle

Figure 33

How do cel ls reproduce?

Most of a cells life is spent in a nondividing

state (interphase)

Body (somatic) cells divide in 3 stages:

DNA replicationduplicates genetic material exactly

Mitosisdivides genetic material equally

Cytokinesisdivides cytoplasm and organelles into 2

daughter cells

Interphase


30/68

InterphaseThe nondividing period: G-zero phase

specialized cell functionsonly

G1phasecell growth,organelle duplication,protein synthesis

S phaseDNAreplicationand histonesynthesis

G2phasefinishes

protein synthesis andcentriole replication

DNA R li ti


31/68

DNA Replication

Figure 324

DNA strands unwind

DNA polymeraseattaches complementarynucleotides


32/68

Somatic Cell Nuclear Division

Two important processes tomaintain constant number of

chromosomes.

Duplication of chromosomes

Distribution of duplicated

chromosomes into two daughter cells


33/68

1

2 3

4

5

6 7 8

9

10

11

12

13

14

15 16

17

18

19 20 21 22

Y

X

X Y

The Human

Karyotype


34/68

4646

462N or Diploid Numberin Humans

Mother Cell

Daughter Cells

Importance of Mitosis


35/68

Importance of Mitosis (cont.)

a. Cellular replacement

b. Tissue Repair

c. Development

d. Tumor growth


36/68

Cell cycle prior to mitosis:

Interphase: nondividing state but cell is

metabolically active.

nucleus clearly visibleone or more nucleoli-nucleolar organizer

regions of chromosomes.

chromosomes long and thincentriole (animal cells only) located along

margin of nucleus

Replication of DNA and duplication


37/68

Replication of DNA and duplication

of chromosomes occurs in the cell

cycle.

Centromere

Chromatids


38/68

Prophase:

prepares the cell for divisionchromosomes shorten and thicken

centriole divides into two entities

which migrate down sides of

nuclear envelope, spindle fibers

stretch between centrioles


39/68

Prophase: The cell is prepared for

nuclear division

- Nuclear envelope has disappeared

- Spindle has formed

- Chromosomes short and thick

M t h fi l ti f


40/68

Metaphase: final preparation for

nuclear division

chromosomes line up on equatorial plateof division

centromeres of chromosomes attached

by kinetocores (protein) to spindle fibers,microtubules made up of tubulin

A i l h


41/68

A single chromosomeattached to spindle fibers

A h h


42/68

Anaphase: chromosome

halves migrate to poles

centromeres dividechromosome halves migrate to opposite

poles of cell

chromosomes migrate by sliding ofmicrotubules


43/68

Telophase:

reverse of activities of prophasechromosomes reach poles of

cell

spindle fibers degradednuclear membrane reassembled

chromosomes elongate

nucleoli reassembled

Cytokinesis - division of the cell


44/68

Cytokinesis - division of the cell

Cytokinesis occurs by constriction of actin

fibers forming a belt around cell in animalcells

Plant cells form a cell plate from nuclear

membrane and then cellulose is added tothe plate.


45/68

Animal cell - cytokinesis occurs by

constriction of actin fibers


46/68

Typical Timing of Mitosis


47/68


48/68


49/68


50/68


51/68


52/68


53/68


54/68


55/68


56/68


57/68


58/68


59/68


60/68


61/68

Wh t l t l l d i i i ?


62/68

What regu lates cel l d iv is ion?

Mitotic Rateand EnergyRate of cell division:

slower mitotic rate means longer cell life

cell division requires energy (ATP)

Long Life, Short LifeMuscle cells, neurons rarely divide

Exposed cells (skin and digestive tract)live only days or hours

Chemicals Controlling Cell Division


63/68

g

Table 34

Regulating Cell Life


64/68

Regulating Cell LifeNormally, cell division balances cell loss

Factors Increase Cell DivisionIncreases cell division: internal factors (Maturation Promoting Factor)

extracellular chemical factors (growth factors)

Factors Decrease Cell DivisionDecreases cell division:

repressor genes(faulty repressors cause cancers)

worn out telomeres(terminal DNA segments)

Cancer


65/68

Ca ce

Figure 326

Cancer illness that disrupts cellular controls and

Oncogenes: mutated genes that cause cancer

produces malignant cells

Cancer Stages - develops in steps:

abnormal cell

primary tumor

metastasis

secondary tumor

Cell Division and Tumors


66/68

Cell Division and TumorsTumor(neoplasm):

enlarged mass of cells

abnormal cell growth and division

Benign TumorsBenign tumor:

contained

not life threatening

Malignant TumorsMalignant tumor: spread into surrounding tissues (invasion)

start new tumors (metastasis)


67/68

KEY CONCEPT

Mutations disrupt normal controls over cell

growth and division

Cancers often begin where stem cells are

dividing rapidly

More chromosome copies mean greater

chance of error

What makes cells different?


68/68

Cell Diversity

All cells carry complete DNA instructions for allbody functionsCells specialize or differentiate:

to form tissues (liver cells, fat cells, and neurons)

by turning offall genes not needed by that cellAll body cells, except sex cells, contain the

same 46 chromosomes

Differentiation depends on which genes areactive and which are inactive

ch 3 - cell level of organization part 2

Documents