A&P Chapter 3: Flashcards
cell theory
- a cell the structural and functional unit of life
- structures and functions are complementary
- continuity of life has celluar basis
substance that acts as glue to hold cells together
extracellular matrix
acts as an active barrier separating intracellular fluid (ICF) from extracellular fluid (ECF)
plasma membrane
structure of plasme membrane
- consists of membrane lipis that form a flexible bilayer
- surface sugars form glycalyx
- membrane structures help to hold cells together through cell junctions
Lipid bilayer is made up of:
- 75% phospholipid which consists of two parts; phosphate heads are hydrophilic (water lovers), and fatty acid tails are hydrophibic (water haters)
- 5% glycolipids
- 20% cholesterol
Two types of membrane proteins:
- Integral proteins
- Peripheral proteins
Intergral proteins
- firmly inserted into membrane
- most are transmembrane proteins
- have hydrophilic and hydrophobic region which hydrophilic interacts with water and hydrophobic interacts with lipis tails
- function transport proteins, enzymes, or receptors
Peripheral proteins
- loosely attached to intergral proteins
- include filaments on intracellular aurface used for plasma membrane for support
- functions as enzymes, motor proteins (for shape change), and cell-to-cell connections
Membrance proteins performing many tasks:
a.) transport:
b.) receptors:
c.) enzymatic activity:
d.) cell-to cell regonition:
e.) attatchment to the cytoskelrton and extracellular matrix (ECM)
f.) cell-to-cell joining
cell junctions
- some cells are “free” (not bound to any other cells)
- most cells are bound together to form tissues and organs
The three ways cells can be bound to each other:
1.) tight junctons
2.) desmosomes
3.) gap junctions
- intergral proteins on adjacent cells fuse to form an imperable junction that encircles whole cell
- prevent fluids and mose molecules from moving betwen cells
tight junction
rivet-like cell jucntion formed when linker proteins (cadherins) of neighboring cell interlock like the teeth of a zipper
desmosomes
transmembrane proteins (connexons) form tunnels that all small molecules to pas from cell to cell
gap junctions
Structure of Plasme Membrane
the plasme membrane is selectively permeable allowing certain molecules to cross
Two essential ways substancs cross plasme membranes
1.) Passive transport: no energy is required
2.) Active transport: energy (ATP) is required
Three types of passive transport
1.) simple diffusion
2.) facilitated diffusion
3.) osmosis
very small molecules that can pass through membrane or membrane channel
- ex: oxygen, fatty acid, carbon dioxide
simple diffusion
larger or non-lipid souble or polar molecules can cross membrane but inly with assistance of carrier molecules
facilitated diffusion
is special name for movement of solvent (usuallu water), not molecules
osmosis
- channels with aqueous-filled cores are formed by transmembrane proteins
- two types: leackage channels (always open), and gated channels (controlled by chemical or electrical signals
channel-mediated facilitated diffusion
measure the concentration of the total number of solute particles in solvent
osmolarity
outward pressure exerted on cell side of membrane caused by increase in volume of cell due to osmosis
hydrostatic pressure
inward pressure due to tendency if water to be “pulled into a cell with higher osmolarities
osmostic pressure
has same osmolarity as inside cell, so volume remains unchanged
isotonic solution
has higher osmolarity than inside cell, so water flows out of cell, resulting in cell shrinking
hypertonic solution
has lower osmolarity than inside cell, so water flows into cell, resulting in cell swelling
hypotonic solution
two major active membrane transport processes:
1.) active transport
2.) vesicular transport
transport one substance into cell while transporting a different substance out of cell
antiporters
transport two different substances in the same direction
symporters
required energy comes directly from ATP hydrolysis
primary active transport
required energy is obtained indirectly from ionic gradients created by primary active transport
secondary active transport
involves transport of large particles, macromolecules, and fluids across membrane in membranous sacs called vesicles
vesicular transport
transport into cell
endocytosis
transport out of cell
excytosis
type of endocytosis that is referred to as “cell eating”
phagocytosis
type of endocytosis that is referred to as “cell drinking” or fluid-phase endocytosis
pinocytosis
involves endocytosis and trancytosis of specific molecules
receptor-mediated endocytosis
gel-like solution made up of water and soluble molecules such as proteins, salts, sugars, etc
cytosol
insoluble molecules; vary with cell type
inclusions
metabolic machinery structures of cell; each with specialized function; either membranous or nonmembranous
organelles
- produces most ATP
- contains ribosomes and enzymes
mitochondria
make protein
ribosomes
free floating; site of synthesis of soluble proteins that function in cytosol or other organelles
free ribosomes
attached to membrane of endoplasmic reticulum (ER)
membrane-bound ribosomes
- produces proteins
- External surface appears rough because it is studded with attached ribosomes
rough er
- fats, detoxides
- Network of looped tubules continuous with rough ER
smooth er
- Stacked and flattened membranous cistern sacs
- Modifies, concentrates, and packages proteins and lipids received from rough ER
golgi apparatus
Membranous sacs containing powerful detoxifying substances that neutralize toxins
peroxisomes
toxic, highly reactive molecules that are natural by-products of cellular metabolism; can cause havoc to cell if not detoxified
free radicals
breakdown sugar and release calcium
lysosomes
Elaborate network of rods that run throughout cytosol
cytoskeleton
- Thinnest of all cytoskeletal elements
- Semi-flexible strands of protein actin
- Each cell has a unique arrangement of strands, although share common terminal web
microfilaments
- Size is in between microfilaments and microtubules
- Tough, insoluble, ropelike protein fibers
- help cell resist pulling forces
intermediate filaments
- Largest of cytoskeletal elements; consist of hollow tubes composed of protein subunits called tubulins, which are constantly being assembled and disassembled
- Most radiate from centrosome area of cell
microtubules
complexes that function in motility
motor proteins
aid in the movement of the cell or of materials across the surface of the cell
cilia and flagella
are fingerlike projections that extend from the surface of the cell to increase surface area
microvilli
are whiplike, motile extensions on surfaces of certain cells (such as respiratory cells)
cilia
are longer extensions that propel the whole cell (example: tail of sperm)
flagella
allow substances to pass into and out of nucleus
nuclear pores
Cell grows and carries on its usual activities
interphase
Cell divides into two
cell division (mitotic phase)
interphase broken into three subphases
- G1 (gap 1): vigorous growth and metabolism
- S (synthetic): DNA replication occurs
- G2 (gap 2): preparation for division
attaches to primer and begins adding nucleotides to form new strand
DNA polymerase
of cell cycle is phase in which division occurs; consists of 2 distinct events:
m (mitotic) phase
is crucial, so cells divide when necessary, but do not divide unnecessarily
control of cell division
is the division of nucleus, in which the duplicated DNA is distributed to new daughter cells
mitosis (M phase)
Chromatin condenses, forming visible chromosomes
early prophase
Nuclear envelope breaks up
late prophase
Centromeres of chromosomes are precisely aligned at cell’s equator
metaphase
Chromosomes are pulled toward their respective poles by motor proteins of kinetochores
anaphase
- Begins when chromosome movement stops
- New nuclear membranes form around each chromatin mass
telaphase
Begins during late anaphase and continues through mitosis
cytokinesis
- Single stranded
- Code from DNA template strand is copied with complementary base pairs, resulting in a strand of mRNA
- Process is referred to as transcription
messenger RNA (mRNA)
- Structural component of ribosomes, the organelle where protein synthesis occurs
- Along with tRNA, helps to translate message from mRNA into polypeptide
ribosomal RNA (rRNA)
- Carrier of amino acid
- process is referred to as translation
tranfer RNA (tRNA)
DNA information coded in mRNA
transcription
mRNA decoded to assemble polypeptides
translation
RNA polymerase separates DNA strands
initiation
RNA polymerase adds complementary nucleotides to growing mRNA matching sequence of based on DNA template strand
elongation
Transcription stops when RNA polymerase reaches special termination signal code
termination
transcription is broken down into three parts:
initiation, elongation, and termination
