Anatomy & Physiology Ch. 3 (cellular structure)
Terms
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- 3 main parts of a cell
-
plasma membrane
cytoplasm
nucleus - plasma membrane consists of:
-
lipid bilayer
proteins - cytoplasm consists of:
-
cytosol
organelles - nucleus contains
-
chromatin
nucleolus - 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
-
amphipathic
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)
peripheral - 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 - transporter
-
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 - enzyme
-
integral or peripheral protein
catalyzes reactions - linkers
-
integral or peripheral protein
aids in structural stability by
connecting to filaments inside or outside the membrane - cell identity markers
-
glycolipid
that identifies "foreigners"
MHC (major histocompatability) is one important class - ligand
- a chemical substance that binds to a specific receptor
-
Cytosol
(basic description) -
ICF
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] - cytoskeleton
-
network of 3 types of protein filaments that extend through the cytosol:
microfilaments
intermediate filaments
microtubules - microfilaments
-
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 - microtubules
-
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 - centrosome
-
located near the nucleus
consists of two centrioles
surrounded by pericentriolar material - centrioles
-
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 - cilia
-
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 - flagellum
-
similar in structure to cilia but are typically much longer
they usually move an entire cell
only human flagella= sperm - ribosomes
-
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 -
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) - peroxisomes
-
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 - proteasomes
-
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 - mitochondria
-
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 - nucleus
-
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
chromatin
nucleolus - nuclear envelope
-
double membrane that separates the nucleus from the cytoplasm
both layers are lipid bilayers
opening called nuclear pores extend through the envelope - nucleoli
-
produces ribosomes
disperse and disappear during cell division
reorganize once new cell is formed - chromatin
-
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 - chromatid
-
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
- intron
-
does not code for parts of protein
(introverted) - exon
-
codes for parts of protein
(expressive)