Transcript Cells

Chapter 4: Cell
Organization
 Pgs 74-105
Student Objectives
 Summarize the relationship among cell
organization, cell size and maintaining
homeostasis.
 Discuss microscopy used to study cells
 Compare and contrast general
characteristics of prokaryotic and
eukaryotic cells
Student Objectives
 Distinguish among the different
organelles of a cell.
 Describe the structure and function
of the cytoskeleton.
 Compare and contrast cilia and
flagella.
Cell Theory
 Cells are the basic units of organization
and function. (No isolated part of the
cell is capable of survival)
 Cells come from other existing cells
 All living things are made up of cells.
(They are the building blocks of
complex organisms)
Cells
Three main parts:
Plasma membrane (cell membrane) selectively permeable
Cytoplasm: Fluid and organelles outside
of the nucleus. (cytosol-fluid)
Nucleus - Control center of the cell.
Eukaryotic cells
Cell Size
 Cells are microscopic
 Measured in micrometers (µm)
 Cells organelles are measured in
nanometers (nm) - 1/1000 of a micrometer
 Cell size limited by its surface area to
volume ratio
*Some cells can be seen without a
microscope. (Eggs) human egg cell is 130
µm.
Cell Beginnings
First studied and documentated in 1665
by Robert Hooke.
He examined ‘cork’ cells. (dead
wood)
Anton van Leeuwenhoek - later looked at
cells at up to 200 times mag.
Microscopes
Allowed scientists to see microscopic
things.
 Light Microscope.
Simple - 1 lens
Compound - 2 lens (ocular and
objective)
Magnify from 40 to 1000
Bright field or dark field microscopy
Microscopes
Electron Microscopes (EM)
Began in 1950’s
Can magnify up to 250,000 times
Transmission electron Microscope (TEM)
-Specimen is embedded in plastic and
cut into thin sections
Scanning Electron Microscope (SEM)
-Electrons strike the surface of the
specimen.
Electron Microscope
Cell Parts
 Nucleus
 Large organelle (5 µm) usually near the
center of the cell. ‘Control Center’ Contains chromosomes
 Nuclear membrane contains the
nucleoplasm.
 Material is transported between
nucleoplasm and cytoplasm through nuclear
pores.
Cytoplasmic Organelles
 Endoplasmic reticulum (ER) - complex
compartments of the cell. Contain
enzymes ‘catalysts’
 Two Types
 Smooth ER - no ribosomes - site of lipid
metabolism
 Rough ER - ribosomes - site of protein
synthesis
Cytoplasmic Organelles
 Ribosomes
 Site of protein synthesis. Works
closely with ER and RNA
Cytoplasmic Organelles
 Golgi Complex
 Similar to ER except the stacks of
flattened membranous sacs are not
continuous
 Processes proteins and complex
sugars
Cytoplasmic Organelles
 Lysosomes
 Small sacs of digestive enzymes.
Slightly acidic
 Break down worn out organelles,
digest bacteria or other debris
Cytoplasmic Organelles
 Peroxisomes
 Contain enzymes that catalyze the
split of hydrogen peroxide H202 which
is toxic to the cell.
Cytoplasmic Organelles
 Vacuoles
 Found mainly in plant cells, does the same
job as lysosomes.
 As the vacuole grows with the addition of
water the size of the cell grows.
 May be up to 90% of a plant cell volume.
 Some vacuoles are specialized
 Food vacuoles - digest foods
 Contractile vacuoles - remove excess water
Cytoplasmic Organelles
 Mitochondria - ‘powerhouse’
 Site of aerobic respiration conversion of chemical energy to ATP
 Most numerous in cells requiring high
energy
Cytoplasmic Organelles
 Chloroplasts - similar to
mitochondria
 Found only in algae and plants cells
 Convert light energy into chemical
energy
 Contains chlorophyll, the green
pigment that traps light
(photosynthesis).
Cytoskeleton
 Give the cell its shape
 Dense network of protein fibers
 Microtubules - thickest filaments of
the cytoskeleton (25 nm)
 Microfilaments - flexible solid fibers
(7 nm)
Centrosome
 Cell division center
 Contains two centrioles (found in
animal cells but not plants)
 Centrioles move to the ‘poles’
Spindle Fibers
 Serve as a framework and
attachment for chromosomes for
the seperation to the opposite
‘poles’
Cell Coverings
 Glycocalyx (cell coat)
 Formed by carbohydrates, proteins
and lipids on the plasma membrane.
 Form adhesives for neighboring cells
and help in cell signaling
 Plant cells have Cell Walls - made of
cellulose
Cilia and Flagella
 Made up of microtubes, aid in
movement of the cell
 Flagella are long compared to the
cell (200 µm)
 Cilia are short (2-10 µm), usually
many