Download Cells, Transport, Mitosis, Protein Synthesis

Chapter 3 Notes
Cells and Tissues
4 main elements of a cell: C, O, H, N
– Traces of others, but are still important
60% of cell is water
Interstitial fluid – dilute salt water solution
that bathes cells
– Exchange btw blood and cells takes
place here
Parts
of
the
cell
3 main regions
– Nucleus – nucle = kernel
Control center
Contains DNA
If nucleus is lost – cell will die
Shape conforms to cell
Nuclear envelope (membrane)
– Double membrane – space
btw is fluid filled
– Nuclear pores – openings that penetrate both layers
– Nucleoplasm
Nucleoli
– site of ribosome assembly
Chromatin
– DNA
– Usually threadlike
– During division it condenses = chromosomes
– Plasma membrane
Phospholipids bilayer
– Heads – hydrophilic
– Tails – hydrophobic – keeps the membrane impermeable
to most water soluble molecules
Cholesterol – found throughout
– stabilizes
Proteins – specialized functions
– Receptors – cell exterior
– Binding sites
– Transport
Protein channels –
opening through membrane
Carriers – bind to & carry material in/out
– Glycoproteins – have sugars attached
Determine blood type
Microvilli – projections to
increase absorbtion
– small intestines
Membrane junctions
– Tight junctions –
leakproof
Prevent material
from passing btw
cells
ex. Small
intestines –
digestive
enzymes are kept
from blood stream
– Desmosomes –
anchoring
Connects cells
to each other
– Gap junctions –
allow direct
communication
Connexons –
hollow
cylinders –
connect cells
– Cytoplasm – 3 major elements
Cytosol – suspension fluid
Inclusions – store nutrients
– Ex. Lipid droplets, pigments
Organelles – “little organs”
– Mitochondria
Double membrane
Outer – smooth
Inner has protrusions (cristae)
Convert chemical energy from food into ATP
Large #s in liver and muscle cells
– Ribosomes
Ribosomal RNA
Site of protein synthesis
– Endoplasmic Reticulum
Network of channels
Rough ER – covered w/
ribosomes
Proteins pass through and
complete their formation
Are then sent to other areas in
transport vesicles
Numerous in pancreas cells –
export protein products
Smooth ER
Lipid metablolism
Detox of
drugs/pesticides
Numerous in liver cells
–Golgi Apparatus
Modifies and packages proteins
Secretory vesicles – release protein
from cell
Forms lysosomes – transport vesicle
w/ digestive enzymes
– Lysosomes – “breakdown
bodies”
Contain digestive
enzymes
Wornout/nonusable
cell structures, foreign
substances
Numerous in white
blood cells
– Peroxisomes – “peroxide
bodies”
Oxidase enzymes
Detox
harmful/poisonous
material
Liver, kidney
Convert free radicals
(scramble protein and
nucleic acid structures)
into H2O2
– Cytoskeleton
Structure, support,
transportation
Intermediate
filaments – form
desmosomes and
internal guy wires
Microfilaments –
actin, myosin
Cell motility
Change cell shape
Microtubules
Determine cell
shape
Roll in cell division
– Centrioles –
paired
Made of
microtubules
Form mitotic
spindles
May multiply
and form
cilia/flagella
Cell Diversity
Connect body parts
– Fibroblasts, erythrocytes
Covers and lines body organs
– Epithelial cells
Move organs and body parts
– Skeletal muscle and smooth muscle cells
Store nutrients
– Fat cells
Fight disease
– Macrophage
Gathers info and controls body function
– Nerve cells
Reproduction
– Oocyte – largest cell in body
– Sperm
Membrane Transport
– Solution – homogenous mixture of 2 or more
components
– Solvent – dissolving medium – water
– Solutes – particles found in water
– Intracellular fluid – nucleoplasm and cytosol
Contains gases, nutrients, salts
– Interstitial fluid – exterior of cells
Nutrients, hormones, neurotransmitters, salts,
waste products
– Plasma membrane – has selective
permeability
Passive transport – no energy input from cell
– Diffusion – particles move down their concentration
gradient
Simple diffusion – must be small enough to pass through
pores or dissolve in the fatty portion of the membrane (lipid
soluble)
– Osmosis – diffusion of water – passes through
aquaporins
– Facilitated diffusion
For large particles or lipid insoluble
Uses protein channels or protein carriers
– Allows continual movement of oxygen and glucose
into cell and carbon dioxide out
– Filtration – water/solutes pushed through by
hydrostatic pressure
Caused by blood
Used by kidneys
Active transport – uses energy
– Solute pumping
Uses solute (protein) pumps
Allow movement against concentration gradient
Amino acids
Sodium-potassium pump – nerve cells
– Bulk transport
Exocytosis – out
– Hormone secretion
– Packaged by golgi apparatus
Endocytosis – in
– Surround w/ pseudopods
– Phagocytosis – cell eating – white blood cells
– Pinocytosis – cell drinking
Cell absorption
– Receptor-mediated – specific targets
Cell Division
Cell Life Cycle
– Interphase – cell growth – aka metabolic
phase – longest
DNA replication
–DNA helix uncoils and separates into 2
chains
–Each strand is a template
– Cell division - Mitosis
Prophase
– Chromosomes appear – made up of 2
strands (chromatids) connected by a
centromere
– Centrioles begin to move to poles forming
mitotic spindles
– Nuclear envelope and nucleoli disappear
Metaphase
– Chromosomes line up in center along
spindles
Anaphase
– Centromeres split
– Chromatids move toward poles
Telephase
– Chromosomes uncoil
– Nuclear envelope and nucleoli reappear
– Takes about 2 hours
Cytokinesis – division of cytoplasm
– Usually begins during anaphase
– Cleavage furrow – squeezes cell in two
– Doesn’t always occur in liver – results in
binucleate or multinucleate cells
Protein Synthesis
DNA – blueprint for protein synthesis
Gene – DNA segment that carries instructions
for building protein
Each sequence of 3 bases (triplet) codes for
an amino acid
– AAA – phenylalanine; CCT – glycine
Btw 300 – 3000 base pairs in a single gene
RNA
– Transfer RNA – takes amino acids to ribosomes
– Messenger RNA – takes instructions from nucleus
to ribosomes
– Ribosomal RNA – forms ribosomes
2 phases
– Transcription – in
nucleus
Transfer of info from
DNA to mRNA
Codons – 3 base
sequence of mRNA
DNA
–AAT-CGT-TCG
mRNA codons
–UUA-GCA-AGC
– Translation – in cytoplasm
mRNA attaches to
ribosome
tRNA transfers amino
acids to ribosome
ribosome moves
mRNA to next codon
enzymes bind amino
acids
–have anticodon to
match up correct
amino acids