Hooke
1600s
-first to observe cells thru microscope-looking at plants
Schleiden & Schwann
1830s
-came up with idea that all living things are made up of cells
Virchow
1850s
- cells only arise from other cells
ex. mitosis
plasma membrane
separates the intracellular fluid from the extracellular fluid
cytoplasm
cellular material between the plasma membrane and the nucleus. Site where most cellular activities are accomplished. Made of 3 major elements:
- cytosol
- organelles
- inclusions
nucleus
control center of the cells, contains genetic info
diffusion
- passive process
- where molecules or ions move from an area of higher concentration to area of lower concentration
- they move “down” the concentration gradient
membrane potential
voltage across the membrane - its electrical potential energy from the separation pf oppositely charged particles.
-typically ranges from -50 to -100 mV (millivolts)
gene
segments of DNA that code for one polypeptide chain (protein)
exon
amino acids specifying sequences
intron
non-coding sequences
-junk DNA
cell differentiation
development of specific features in the cells
- allows embryo stem cells to develop into all cell types.
- differentiation is probably dependent on different chemical signals that channel them into specific developmental pathways.
apoptosis
programmed cell death
codon
3 base mRNA for each three sequence DNA sequence
anti-codon
a 3 base sequence complimentary to the mRNA coding fro the amno acid carried by tRNA
integral membrane protein
firmly inserted into the bilayer, many go all the way through
-used for enzymes, used for transport (either as channels or carriers) or as receptors for hormones
peripheral membrane protein
loosely attached to integral protein, could be in intra or etxra positions
tight junction
protein molecules are fused together to form an impermeable junction, connection between cells
ex. cells lining digestive tract
desmosomes
- binding body
- anchoring junctions, act to distribute tension to reduce risk of tearing
ex. skin cells need to stretch, heart beats-changes shape
gap junction
cell-cell communication -spaces for small molecules to go between cells
ex. ions, simple sugars
- in heart
cell adhesion molecules
involved in embryonic development, wound repair, and immunity
-type of glycocalyx molecule
contact signaling
cells actually physically touch one another, they recognize each other
-important- in development and driving immunity
chemical signaling
- ligands -signalling chemicals that bind to specific membrane receptors
- ex. neurotransmitters, hormones
glycocalyx
-glyco-proteins with sugar groups and occur in the cells surface, used in cell, cell recognition
mitochondria
power plants of the cell
- job is to harvest chemical energy in food, use this energy to create ATP
- mito. is usually clustered where the action is.
- busy cells (kidney & liver) have more mitochondria
- 2 membranes: smooth outermembrane and a folded inner membrane
ribosomes
made of proteins and RNAs
-site of protein synthesis
rough endoplasmic reticulum
contains ribosomes that manufacture proteins secreted from cells.
- makes components for membranes
smooth endoplasmic reticulum
enzymes catalyzing many reactions- NO role in protein synthesis:
1- lipid metabolism, cholesterol synthesis
2-synthesis of steroid-based hormones(sex horm.
)
3- absorb, synthesize & transport fats
4- detox certain drugs, pesticides and carcinogens
5- breakdown the stored glycogen to form free glucose (liver cells)
Golgi apparatus
- postal distribution center-traffic director for cellular proteins
- consists of stacked & flattened membraneous sacs, shaped like hollow dinner plates
- GA receives transport vesicles from thh Rough ER, modifies them(ex.adding phosphate), sorts them out the other side
lysosomes
contain digestive enzymes, its their job to break things down:
a) digesting particles, taken in by endocytosis(bacteria, toxins)
b) breakdown organelles that are worn out
c) perform metabolic functions(ex. glycogen breakdown/release)
d) breakdown nonuseful tissues(ex. uterine lining-period)
e) beak down bone to release calcium ions into the blood
cytoskeleton-microtubules
large hollow tubes, determine cell shape and distribution of organelles
-motor proteins-powered by ATP, transport organelles along microtubules
cytoskeleton-microfilaments
thin, made of actin, strengthen the cell surface, involved in cellular movement
ex. in muscle cell contraction
cytoskeleton-intermediate fibers
tough, insoluble proteins with high tensile strength
-attach to desmosomes and act as guide wires to resist pulling forces exerted on the cell
cellular extension- flagella
long projections formed by centrioles; propel entire cell.
Ex.cell
cellular extension-cilia
whiplike motile cellular extensions occurring in great numbers on some cell surfaces.
Ex. respiratory tract-pseudostrat ciliated columnar
cellular extension-microvilli
tiny finger-like extensions of the plasma membrane projecting from a free cell surface. Ex. intestine, kidney - increased surface area for absorption
which mature body cell not have a nucleus
red blood cell- needs more room to carry O2
function of nuclear envelope
- double membrane barrier separated by a fluid-filled space
1. the outer surface is studded with ribosomes and the inner membrane is lined by nuclear lamina, which help maintain the shape of the nucleus
2. nuclear pores(holes that form protein transport channels)
3. encloses a jell-like fluid called the nucleoplasm(liquid part of nucleus)
nucleoli
found in nucleus, not bound by membranes
- these are the sites where ribosomal subunits are assembled
chromatin
- made up of 30% DNA, %60 histone proteins and ~ 10% RNA chains
- nucleosomes-fund. units of chromatin, 8 histone P. connected by DNA
- histone-pack DNA molecules into compact form, gene regulation
- chromatin is usually not visible in the cell, but when it condenses to form chromosomes before cell division it is dense enough to be seen
3 tyoes of RNA
- Ribosomal RNA-rRNA
- Messenger RNA-mRNA
- Transfer RNA-tRNA
ribosomal RNA
- constituent of ribosome
- exists within ribosomes of cytoplasm and assists in protein synthesis
transfer RNA
short chain RNA molecules that transfer amino acids to the ribosome
messenger RNA
long nucleotide strands that reflect the exact nucleotide sequences of the genetically active DNA and carry the message of the latter.
cytokinesis
division of cytoplasm, formed when cleavage furrow pinches apart
active vs. passive transport
substances can cross the plasma membrane either passively(always occurs via diffusion) without any energy input, or actively, with help of ATP.
diffusion
where molecules or ions move from an area of higher concentration to an area of lower concentration - down their concentration gradient
simple diffusion
nonpolar and lipid soluble substances diffuse directly through lipid layer
facilitated diffusion
glucose, amino acids & ions- go straight across or with help of carrier proteins -passive trans
osmosis
diffusion of a solvent, often water, through a selectively permeable membrane, something liquidy, particles can go through
- water passes through aquaporins
- water is moving- moves from areas of higher water lower solute to areas of lower water & higher solute, until equilibrium occurs
tonicity
ability of cell to change its shape by altering internal water volume
isotonic
concentration of particles is the same inside & out
-no net movement
hypertonic
more solutes outside, water will leave the cell-cells shrivels- crenates
hypotonic
more solutes on the inside than outside - water will move into the cell; cell will eventually burst-lyse
primary active transport
-requires carrier proteins that combine with the substance to be transported, but requires energy because it is pumping molecules against their concentration gradient.
Ex. CA2+, Na+,
secondary active transport
when an ion is actively pumped across a membrane, it will leak back through with help of a carrier protein, this can drag or Cotransport other things with it
Symport
both substances move in same direction
Ex. sugars, amino acids, ions
antiport
substances move in opposite directions - “wave to eachother”
ex. regulation pf pH by driving out H+ ions
vesicular transport
- energized by ATP (or GTP) -active transport
- fluid-containing large particle, macromolecules are transported across cellular membranes inside membraneous sacs called “vesicles”
- processes that eject substances, from cell interior into extracellular fluid are called “exocytosis”
types of vesicular transport
exocytosis, endocytosis, transcytosis, substance trafficking
exocytosis
transport out of cell
ex. secretion of neurotransmitters, hormones, mucus, ejection of cell wastes
endocytosis
transport into the cell
ex. WBC, macrophages, dissolved solutes, some hormones, cholesterol, iron and most macromolecules
transcytosis
movement into, across, then out of cell
substance(vesicular) trafficking
transport from one area of the cell to another area
types of endocytosis
- phagocytosis
- pinocytosis
- receptor-mediated endocytosis/transcytosis
phagocytosis
cellular eating
e. WBC engulfs a bacteria
Pinocytosis
cellular drinking, allows sampling of extracellular fluid
ex. cells in intestine use this to absorb nutrients
Receptor-mediated endocytosis and transcytosis
very selective receptors in the membrane bind only to certain substances
ex. hormones, enzymes but also flu, diphtheria, and Cholera(trick cells into taking them in)
helicase
- in DNA replication
- helicase enzyme unwinds the DNA double helix to form a replication fork
nucleotide
each nucleotide strand serves as a template to build new strand
DNA polymerase
after RNA primers initiate DNA synthesis:
the enzyme polymerase assembles in short segments free base pairs to their matching complimentary bases open on the DNA replication fork.
DNA ligase
DNA ligase then splices together the short segments assembled by DNA polymerase
-glues segments
RNA polymerase, mRNA & nucleotides, terminal signal
-used in transcription(protein synthesis)
-RNA polymerase pulls apart the strands of DNA double helix so that transcription can begin at promoter(DNA sequence start point).
- RNA polymerase creates a new mRNA strand by adding a free RNA nucleotides to the DNA strand as it unwinds the double helix- only a little DNA unwound at a time
-the polymerase reaches a termination signal, transcription finished and new mRNA strand drops off
-finally, mRNA has to edited before it can move on
Spliceosomes come in and remove introns(junk DNA), then splice together remaining exons
codons
for each three sequence DNA triplet, there are three base mRNA called codon
Ribosome role in translation
- mRNA hooks up with ribosome when it leaves the nucleus
- ribosome also contains rRNA
translation
language of nucleic acids(base pairs), translated into language of proteins