Download Cell Structure

Cell Structure
a. cell membrane
- boundary
b. cytoplasm (=cytosol)
cell is basic unit of all life; structural and functional
c. nucleus
d. organelles and
internal structures
if its alive, must contain at least a single cell
the function of an organism is the summation of
functions of its individual cells
– includes everything except
cell membrane
-genetic material
- highly organized, specialized
structures
1. Cell Membrane
in human body
single fertilized egg ! 75–100 trillion cells (adult)
defines boundary
highly ordered
[>10x’s more bacterial cells in body]
There are about 200 different kinds of cells in the
human body with a variety of sizes and shapes
!consists mainly of phospholipids & proteins
phospholipids tend to arrange themselves into
double layered films
human cells range in size from:
eg. sperm cells are some of the smallest human cells
eg. human eggs & fat cells are some of the largest, barely visible
to naked eye
eg. some nerve cells are 3 ft long (humans)
proteins “float” randomly in this bilayer creating a
“fluid mosaic” (1972 Singer & Nicholson)
some of these protein functions:
while there is a great diversity in size and shape
receptors (ie. docking sites) for specific
substances
junctions between cells
carriers: move specific solutes across membrane
enzymes: energy transforming enzymes
!less diversity in function
in most:
the cell membrane is selectively permeable
Structure
some things enter freely, some things cannot
cross or cross only with “help”
Basic Components of Cell:
Microscopy , Cells, Tissues: Cell Structure – Animals/Humans; Ziser Lecture Notes, 2010.5
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densely packed chromosome region within
nucleus
2. Cytoplasm (=Cytosol)
contains mostly water, ions, organic molecules etc
site of RNA synthesis
variety of enzymes eg. glycolysis
5. Mitochondria:
3. Nucleus
largest of internal cell structures
Microscopy , Cells, Tissues: Cell Structure – Animals/Humans; Ziser Lecture Notes, 2010.5
power plants of cells:
contain enzymes for respiration and ATP synthesis
(except in plants)
produces most of cells ATP (=energy)
number varies: one to many
cells thrive in O2
in humans
most cells have one nucleus
RBC’s have none
a few cells are multinucleate (2-50 nuclei)
!use oxygen gas in energy releasing reactions
the oxygen dependent energy releasing
reactions = aerobic respiration occur
in mitochondria
eg. liver, skeletal muscle cells and certain osteoblasts
and ‘thromboblasts’
contains genetic material:
replication and reproduction
daily metabolism
typical cell has dozens to 100,000’s
!number related to cells activity
eg: muscle cells
(?) 100,000’s/cell
liver cells
1000’s/cell
sperm cells
~25/cell
genetic material
=chromosomes
100’s times length of cell
humans ~3’ of DNA/cell
= DNA with chromatin
6. Ribosomes
protein factories (translation)
workbenches for protein synthesis
4. Nucleolus
Microscopy , Cells, Tissues: Cell Structure – Animals/Humans; Ziser Lecture Notes, 2010.5
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Microscopy , Cells, Tissues: Cell Structure – Animals/Humans; Ziser Lecture Notes, 2010.5
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smooth ER
up to 1000’s per cell
most common in lipid synthesizing cells
># ribosomes = > amount of protein synthesis
eg. liver cells
adrenal cortex (steroid hormones)
testes – steroid hormone synthesis
7. Endoplasmic Reticulum
(= “little network within the cytoplasm”)
8. Golgi Bodies (=Golgi Apparatus)
a single highly branched membranous tube, with
sacs and flattened channels = cisternae
stack of membranes (flattened sacs)
two types:
most cells contain both types
functions in “packing & shipping”
(in different proportions)
encloses chemicals in vesicles and takes them
to the cell membrane for secretion
Rough ER:
lots of ribosomes attached to surface
usually 1 to several 100 golgi bodies in a cell;
but may be up to 25,000/cell
protein synthesis and transport
!highest in secretory cells
especially in protein exporting cells
9. Lysosomes
eg. liver and pancreas
membrane bound package of digestive enzymes
Smooth ER:
several 100/cell
no ribosomes
“digestive system” of cell:
lipid metabolism
contains at least 50 different enzymes
transports lipids throughout cell
!capable of breaking almost every kind of large
organic molecule
most cells have only a small amt of
Microscopy , Cells, Tissues: Cell Structure – Animals/Humans; Ziser Lecture Notes, 2010.5
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Microscopy , Cells, Tissues: Cell Structure – Animals/Humans; Ziser Lecture Notes, 2010.5
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! esp in liver and kidney cells
a. destroys unwanted materials, cellular
debris, worn out organelles
11. Cytoskeleton
microfilaments and microtubules
eg. mitochondria
b. also used by WBC’s and neuroglia cells to
destroy invading pathogens
some are contractile
responsible for the overall shape & rigidity of each
kind of cell
c. gets rid of worn out cells = suicide bags
Functions in:
= apoptosis (programmed cell death)
cell movement
phagocytosis
holds organelles in place
helps move things around in the cell
plays a role in cell division and growth
eg. during development, removes “webs” from
between fingers and toes
eg. restores original size of uterus after delivery
12. Centrioles
at full term weighs ~30 oz (900g)
shrinks to 2 oz (60 g) within 5 or 6 weeks
after delivery
(Centrosome)
each cell has a pair – at right angles to each other
10. Peroxisomes
functions in cell division
! helps to form spindle
resemble lysosomes but with a different set of
enzymes
! contains oxidases
Structures found on the Surface of Cells
13. microvilli
removes poisons from cells = detox
extensions of cell membrane that greatly
increase its surface area
eg. free radicals
eg. alcohol and other drugs
for absorption (intestine) or reabsorption (kidney)
several 100 per cell
1000’s/cell in intestine
Microscopy , Cells, Tissues: Cell Structure – Animals/Humans; Ziser Lecture Notes, 2010.5
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Microscopy , Cells, Tissues: Cell Structure – Animals/Humans; Ziser Lecture Notes, 2010.5
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eg. intercalated discs in cardiac muscle cells
! give cells 15 – 40 times more surface area
15. Cilia
14. Membrane Junctions
formed by various proteins associated with the cell
membrane
allows cells to attach to each other in different
ways:
cilia are hairlike processes found in most body cells
some are able to move
beat in waves moving mucus or egg cells
along tubes
eg. tight junctions
mainly in respiratory tract and uterine tubes
16. Flagella
form impermeable junction encircling cells
! makes it difficult for materials to pass
BETWEEN CELLS, must got through cells to
cross membrane
similar to cilia but much longer and only 1/cell
flagella found only in sperm cells
eg: keep digestive enzymes in intestine
from leaking into blood
17. Membrane Receptors
eg. prevents intestinal bacteria from invading
tissues
some of the proteins embedded in the cell
membrane allow cells to “recognize” and bind
various chemicals to trigger some kind of
response
eg. desmosomes
act as “guy wires” throughout sheet of cells
! “activates” cell to do something
!prevents stretched sheets of cells from tearing
also important in cell-to-cell identity sd surface
markers
eg. skin, neck of uterus, heart muscle
eg. gap junctions
pores that allows direct passage of small molecules and
ions between joined cells
Microscopy , Cells, Tissues: Cell Structure – Animals/Humans; Ziser Lecture Notes, 2010.5
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!defense against foreign cells & tissues
Microscopy , Cells, Tissues: Cell Structure – Animals/Humans; Ziser Lecture Notes, 2010.5
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