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Anatomy & Physiology Ch. 3 (cellular structure)


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3 main parts of a cell
plasma membrane
plasma membrane consists of:
lipid bilayer
cytoplasm consists of:
nucleus contains
function of lipid bilayer
the framework of the plasma membrane
types of lipid molecules in the lipid bilayer
phospholipids - 75%
cholestrol - 20%
glycolipids - 5%
structure and function of phospholipids
non-polar tail/ hydrophobic
polar head/ hydropilic
function of cholestrol
firms up cell channels - supports membrane structure
function of glycolipids
sugary coating (glycocalyx)
acts like a molecular signature (cell identity marker)
to enable MHC (major histocompatability)
function of plasma membrane
flexible, sturdy barrier that surrounds and contains the cytoplasm of the cell
fluid mosaic model
descriptive term for the structure of the plasma membrane - constantly in motion; consisting of a variety of small parts
2 types of membrane proteins
integral (transmembrane)
integral membrane proteins
amphipahtic (phobic & philic)
extends through the lipid bilayers (transmembrane)
peripheral membrane proteins
either on the inner or outer membrane (hydrophilic)
functions of plasma membrane proteins
1) ion channel
2) transporter
3) receptor
4) enzyme
5) linkers
6) cell identity marker
ion channel
integral protein
that forms a water filled pore
integral protein
tube shaped -
binds to a specific substance
then changes shape to move & eject the substance across memebrane
receptor proteins
integral protein
recognizes annd binds to specific ligand molecules
integral or peripheral protein
catalyzes reactions
integral or peripheral protein
aids in structural stability by
connecting to filaments inside or outside the membrane
cell identity markers
that identifies "foreigners"
MHC (major histocompatability) is one important class
a chemical substance that binds to a specific receptor
(basic description)
55% of total cell volume
75-90% of that volume is Hâ‚‚O and dissolved and suspended components
components in cytosol Hâ‚‚O
dissolved & suspended components:
ions, glucose, amino acids, proteins, lipids, ATP & waste
aggregations of organic molecules
such as: droplets containing triglycerides
glucogen granules
cytosol function
site of many chemical reactions required for cell's existence
[ie. catalyzes glycolysis:
10 chemical reactions that produce 2 molecules of ATP from one molecule of glucose]
network of 3 types of protein filaments that extend through the cytosol:
intermediate filaments
composed of protein actin
thinnest element of cytoskeleton
prevalent at the periphery
has 2 functions
2 functions of microfilaments
1] generate movement:
muscle contraction
cell division
cell locomotion
2] mechanical support for basic strength and shape of cell by anchoring the cytoskeleton to integral plasma membrane proteins

2b] also support microvilli as a core of parrallel filaments
intermediate filaments
composed of several different proteins
found in parts of cells subject to mechanical stress
2 functions of intermediate filaments
1] help stabilize the position of organelles
2] helps attach cells to one another
composed of protein tubulin
long, unbranched hollow tubes
begin in the centrosome and grow outward
3 functions of microtubules
1] help determine cell shape
2] function in the movement of chromosomes (chromatid pairs) during cell division
3] function in the movement of secretory vesicles and specialized cell projections such as cilia and flagella
located near the nucleus
consists of two centrioles
surrounded by pericentriolar material
nine clusters of three microtubules each (triplets)-
arranged in a cylindrical structure
two of these compose the basis of a centrosome
pericentriolar material
surrounds the centrioles
contains hundred of ring shaped complexes compose of the protein tubulin
center for growth of the mitotic spindle
short, hairlike motile projections that extend from the surface of the cell
composed of 10 fused doublets of microtubules anchored to a basal body just below the surface of the plasma membrane
facilitate steady movement of fluid along cell's surface
similar in structure to cilia but are typically much longer
they usually move an entire cell
only human flagella= sperm
site of protein synthesis
high content of one type of ribonucleic acid - ribosomal RNA (mRNA)
also contains 50+ proteins
their structure is of 2 subunits - large subunit & small subunit
lg. & sm. subunits are made separately,
then come together in the cytoplasm
attached ribosomes
attached to the outer surface of the nucleus and rough ER they synthesize
organelle proteins
membrane proteins
secretory proteins
"free" unattached ribosomes
synthesize protein used in the cytosol
ribosomes within mitochondria
synthesize mitochondrial proteins
Endoplasmic reticulum

[plasmic=cytoplasm; reticulum=network]
network of membranes that extend from the nuclear envelope throughout the cytoplasm
>50% of membranous surfaces within most cell's cytoplasm
2 kinds - rough ER
smooth ER
Rough endoplasmic reticulum
continuous with the nuclear envelope
folded into a series of flattened sacs
proteins synthesized by attached ribosomes
enter rough ER spaces for processing and sorting
Smooth endoplasmic reticulum
extends from the rough ER to form a network of membrane tubules
does not have ribosomes on it's surfaces
contains unique enzymes and synthesizes fatty acids & steroids
functionally more diverse than rough ER
enzymes help detoxify potentially harmful substances
helps "free" certain glucose to enter the bloodstream
ions trigger muscle contractions
Golgi complex
1st step in the protein transport process
3-20 cisternae:
convex entry or cisface cisterna
concave exit or transface cisterna
medial cisterna
each type of cisterna has different enzymes to modify, sort & package proteins for transport
Golgi complex
processing & packaging of proteins
1] transport vesicles from rough ER fuse to cisface & release proteins into the lumen (space)

2] proteins move into the medial cisternae & are processed

3] after processing, proteins leave the transface in:
secretory vesicles for exocytosis
membrane vesicles for incorporation into the plasma membrane
transport vesicles for other intracellular destinations, such as lysosomes

[lyso=dissolving; somes=bodies]
membrane enclosed vesicles that form from the Golgi complex
contains powerful digestive enzymes
interior has acidic Ph5 for optimum enzyme function
lysosome function
digest substances that enter via endocytosis and
transport final products of digestion into cytosol
carry out autophagy
carry out autolysis
carry out extracellular digestion (sperm head)
similar to lysosomes but smaller
contain several oxidases which oxidize and detoxify
abundant in the liver

also contains catalase which decomposes hydrogen peroxide a
byproduct of oxidation
tiny, barrel-shaped structures

continuously destroy unneeded, damaged, or faulty proteins
with myriad proteases
which chop up proteins into small peptides
so they can be broken down into amino acids and recycled
self-replicating, containing it's own DNA
this "powerhouse" of the cell generates ATP through aerobic cellular respiration
consists of : outer mitochondrial membrane,
small fluid-filled space then
the inner mitochondrial membrane which contains
a series of folds called cristae [increases surface area for chemical reactions]
enclosed by the inner mitochondrial membrane is the matrix
mitochondrial genes are inherited only from your mother
spherical or oval shaped structure
prominent feature of most cells
contains most of the cell's genes
control cellular structure
directs cellular activity
nuclear envelope
nuclear envelope
double membrane that separates the nucleus from the cytoplasm
both layers are lipid bilayers
opening called nuclear pores extend through the envelope
produces ribosomes
disperse and disappear during cell division
reorganize once new cell is formed
complex of DNA, proteins and some RNA
beads-on-a-string structure
each nucleosome "bead" has a core of eight proteins called
histones with double-stranded DNA wrapped around twice
holding the nucleososmes together is linker DNA
replicated DNA forms a pair of chromatids
during cell division a pair of chromatids constitutes a chromosome
gene expression
gene's DNA is expressed as a template for the synthesis of a specific protein
genetic code
the set of rules that relate the base triplet sequence of DNA to the corresponding codons of RNA
base triplet
sets of three nucleotides where genetic information is stored
does not code for parts of protein
codes for parts of protein

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