College A&P exam #2

Resting membrane potential

produced by seperation of oppositely charged particles across plasma membrane in all cells

Voltage

Difference in electrical charge between two points is referred to as...

Membrane voltages range from....

-50 to -100 mV in different cells

K+ steps

1. Diffuses out of cell through K+ leakage channels down its concentration gradient
2. Then pulled back by more negative interior because of its electrical gradient

Membrane is more permeable to K+ than Na+

True

K+ is primary influence on RMP

True

RMP is maintained through action of the Na+-K pump

This continuously ejects 3Na+ out of cell and bring 2K back inside

Steady state is maintained by...

Rate of active pumping of Na+ out of cell equals the rate of Na+ diffusion into cell

Neuron and muscle cells "upset" this steady state RMP by...

Intentionally opening gated Na+ and K+ channels

Organelles

Metabolic machinery structures of cell; each with specialized function; either membranous or non membranous

Membranous examples:

Nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, peroxisomes, lysosomes

Nonmembranous examples:

Ribosomes, cytoskeleton, centrioles

Nucleus

Largest organelle; contains the genetic library of blueprints for synthesis of nearly all cellular proteins

Nucleus 3 main parts

Nuclear envelop, nucleolus, chromatin

Nuclear envelope

Double-membrane barrier that encloses the jelly-like fluid, the nucleoplasm

Nuclear pores

Allow substances to pass into and out of nucleus

Nucleolus

Dar staining spherical body within nucleus that is involved in ribosomal RNA synthesis

Chromatin

Genetic material, uncoiled DNA,

Chromosomes

Condensed chromatin

Mitochondria

Called the "power plant" of cells because they produce most of cells energy molecules via aerobic cellular respiration

Endoplasmic Reticulum

Consists of series of parallel, flattened membranous tubes that enclose fluid-filled interiors; continuous with nuclear membrane

2 types of endoplasmic reticulum

Rough ER and Smooth ER

Rough ER

External surface appears rough because it is stubbed with ribosomes; site of synthesis of proteins

Smooth ER

Functions in lipid synthesis, detoxification; lack ribosomes; network of looped tubules continuous with rough ER

Golgi apparatus

Stacked and flattened membranous sacs; modifies, concentrates, and packages proteins and lipids received from rough ER

Peroxisomes

Membranous sacs containing powerful detoxifying substances that neutralize toxins; play a role in breakdown and synthesis of fatty acids

Lysosomes

Spherical membranous bags containing digestive enzymes

Ribosomes

Non membranous organelles that are sit of protein synthesis; made up of protein and ribosomal RNA

free ribosomes

Free floating

Membrane-bound ribosomes

Attached to membrane of endoplasmic reticulum

Cytoskeleton

Extension network of micro tubules/microfilaments; act as cells "bones, ligaments, and muscle" by playing a role in movement of cell components

Centrioles

Pair of barrel-shaped organelles involved in cell division; help control cytoskeleton; form the basis of cilia and flagella

Cilia

Hair like, motile extensions on surfaces of certain cells; move substances across cell surfaces in one direction

Flagella

Longer extensions that propel the whole cell

Microvilli

Minute, finger like extensions of plasma membrane that project from surface of select cells; used to increase surface area for absorption

Cells make proteins by translating...

The genetic code into a protein

DNA controls life by controlling....

Protein synthesis

DNA replication

Prior to division, cell makes a copy of DNA; exact replica; occurs during interphase in preparation for mitosis/cytokinesis

Mitosis

Division of nucleus, which the duplicated DNA is distributed to new daughter cells

5 stages of mitosis

interphase, prophase, metaphase, anaphase, telophase

Cytokinesis

Cytoplasmic division and he creation fo two new cells

Protein synthesis

DNA is master blueprint that holds the code for this

Gene

Segment of DNA that holds the code for on polypeptide

Exons

Part of gene that actually codes from amino acids

Introns

Noncoding segments interspersed amongst exons

Role of RNA

"Go-between" molecules that links DNA to proteins; all is formed in nucleus

Messenger RNA

Single-stranded; code from DNA template strand is copied with complementary base paris; process if referred to as transcription

Ribosomal RNA

Structural component of ribosomes, organelle where protein synthesis occurs; helps translate message from MRNA into polypeptide

Transfer RNA

Carrier of amino acid; special areas that contain specific triplet code & allows each tRNA to carry a specific amino acid; process referred as translation

Anticodon of tRNA

Complementary base-pari with codon of mRNA

Transcription (easy def.)

DNA information coded into mRNA

Translation (easy def.)

.mRNA decoded to assemble protein

Transcription (in depth)

Process of transferring code help in DNA gene base sequence to complementary base sequence of mRNA

Transcription factors

Loosening histones from DNA in area to be transcribed so DNA segment can be exposed; mediating binding of RNA polymerase, enzyme that synthesizes mRNA, to promoter region

Promoter

Binding to special sequence of gene to be transcribed

3 phases of transcription broken down

Initiation, elongation, termination

Initiation

RNA polymerase separate DNA strands

Elongation

RNA polymerase adds complementary nucleotides to growing mRNA matching sequence of based on DNA template strand

Termination

Transcription stops when RNA polymerase reaches special termination signal code

Processing of mRNA

Newly formed mRNA is then edited and processed before translation can begin

Pre-mRNA

Before processing

Introns

Removed by special proteins called splices ones leaving exon coding regions

Translation (in depth)

Step of protein synthesis where the language of nucleic acids is translated into the language of proteins

Process in translation involves

MRNA, genetic code, tRNA and ribosomes, translating events, sometimes rough ER

Codon

Each 3-base sequence on DNA is represented by a complementary three-base sequence on mRNA

Redundancy

Helps protect against transcription errors

tRNA

Bonds a specific amino acid at one end

aminoacyl tRNA

Amino acid is loaded onto tRNA, molecule is now called...

Anticodon

Triplet code that determines which amino acid will be bound at stem

Ribosomes coordinates

Coupling of mRNA and tRNA

Aminoacyl site

incoming Aminoacyl-tRNA.

peptidyl site

tRNA linked to growing polypeptide chain

Exit site

outgoing tRNA

Initiation

Small ribosomal subunit binds to a special initiator tRNA and then to the mRNA to be decoded

Start codon

Ribosome scans mRNA looking for first methionine codon, which is referred to as...

Elongation 3 steps

codon recognition, peptide bond formation, translocation

Codon recognition

tRNA binds complementary codon in A site of ribosome

Peptide Bond Formation

Ribosomal enzymes transfer and attach growing polypeptide chain from tRNA in P site over to amino acid of tRNA in A site

Translocation

Ribosome shifts down three bases of mRNA, displacing tRNAs by one position

Termination

When 1 of 3 stop codons on mRNA enters A site, translation ends; protein release factor binds to stop codons, causes water added to chai instead of another tRNA; causes release of polypeptide chain as well as separation of ribosome subunits and degradation of mRNA; final polypeptide product will be further processed by other cell structures into functional 3-D protein

True

DNA triplets are coded to mRNA codons

True

MRNA codons are based on-paired with tRNA anticodons

Tissues

Groups of similar cells, which work together toward a specific functions

Four basic tissue types

epithelial, connective, muscle, nervous

Epithelial tissue

is a sheet of cells that covers a body surface or cavities

Covering and lining epithelial

On external and internal surfaces

Glandular epithelia

secretory tissue in glands

epithelial tissue (main functions)

Protection, absorption, filtration, exercer Tino, secretion, and sensory reception

Polarity

Cells have polarity (top and bottom)

Apical surface

upper free side, is exposed to surface or cavity

Basal surface

Lower attached, faces inwards toward body

Basal lamina

Adhesive sheet that holds basal surface of epithelial cells to underlying cells

Specialized contacts

Bind adjacent epithelial cells together

Connective tissue support

Epithelial sheets are supported by this

Reticular lamina

Deep to basal lamina; consists of network of collagen fibers

Basement membrane

Made up of basal and reticular lamina; reinforces epithelial sheet; resists stretching and tearing

Avascular, but innervated

Must be nourished by diffusion from underlying connective tissues; supplied with nerve fibers

Regeneration

Stimulated by loss of apical-basal polarity and broken lateral contacts; some cells are exposed to friction, some to hostile substances, resulting in damage; epithelial cells have high .... Capacities

Simple epithelia

single layer of cells

Stratified epithelia

Two or more layers thick and involved in protection