Transcript Chapter 4-Structure and function of Cell

Chapter 4: Structure and Function of the Cell
4-1 Introduction to the Cell
4-2 Parts of the Eukaryotic Cell
4-3 Multicellular Organization
4-1 Introduction to the Cell
I. Discovery of the Cell
• 1665, Robert HOOKE used a microscope to examine a thin slice of CORK
(1st CELLS TO BE OBSERVED WERE PLANT).
• 1673, Anton van Leeuwenhoek, Dutch microscope maker, was the first to
observe LIVING CELLS in a drop of pond water.
Critical Thinking
(1) The observations that LED to the formation of the CELL THEORY were
made within a 17-year time period by a COMMUNITY of biologists. WHY
do you suppose that MORE than one scientist was likely to make critical
observations (AND contributions) about cells within this time period?
(A) Cell Theory
• Using microscopy, THREE tenets have been proposed:
(1) ALL organisms are made of ONE or MORE cells.
(2) Cells are the SMALLEST living unit.
(3) Cells are BORN from DIVISION of PRE-EXISTING cells.
II. Cell Diversity (over 200 cell types in our body!)
• DIFFERENTIATION leads to DIVERSITY.
(A) Cell Size (we do not see huge cells, but why?)
• Cell GROWTH is limited in SIZE by SURFACE AREA and VOLUME.
(B) Cell Shape (form FOLLOWS function)
• Shape influences cell function, as do the INTERNAL parts of the cell.
(C) Internal Organization (organelles)
• A cell is NOT a simple ball of cytoplasm, it contains “parts of a machine.”
(1) Cell Membrane (a.k.a., LIPID BILAYER)
• COVERS cell and REGULATES what enters AND exits the cell.
(B) Nucleus
• Membrane-bound organelle, holds DNA, nucleolus, and directs protein
synthesis.
(C) Prokaryotes (i.e., bacteria, NO membrane-bound organelles)
• 1st cell type evolved, although LACK most organelles and do NOT possess
an organized nucleus.
(D) Eukaryote (average size: 10-50 micrometers, larger than bacteria)
• MORE evolved cell type, NUCLEUS and a variety of membrane-bound
organelles.
Critical Thinking
(2) What characteristics of EUKARYOTIC cells may bestow them a
greater CAPACITY for SPECIALIZATION than PROKARYOTIC cells?
4-2 Parts of the Eukaryotic Cell
I. Cell Membrane (LIPID BILAYER)
• Regulates what enters AND exits cell  PERMEABILITY.
(1) Selective Permeability
• Cell membrane  on SIZE and CHARGE of molecule.
(A) Membrane Lipids (2 TYPES)
• Phospholipids AND cholesterol add structure and durability.
(B) Membrane Proteins (2 TYPES)
• Are in charge of:
(1) Cell I.D.
(2) Transport of nutrients across membrane
(1) Peripheral Protein (I.D.)
• On INTERIOR and EXTERIOR of cell membrane.
(2) Integral Proteins (TRANSPORT)
• SPAN the lipid bilayer (cytosol connect to ECM).
(C) Fluid Mosaic Model of Cell Membrane
• Cell membrane is a DYNAMIC, moving structure and NOT fixed.
II. Organelles (“little organs”)
• Work TOGETHER for cell function and survival.
Critical Thinking
(3) A mature human RED BLOOD CELL contains NO nucleus NOR
mitochondria. It consists primarily of a MEMBRANE surrounding
HEMOGLOBIN, the protein molecule that carries oxygen. Suggest an
ADVANTAGE of the SIMPLE organization of human red blood cells.
(1) Cytoplasm (a.k.a., “cytosol”)
• Gelatinous FLUID (matrix)  salts, nutrients, and compounds.
(A) Mitochondria (contains its own DNA, MEMBRANE)
• POWERHOUSE of cell, convert NRG from CARBS into ATP.
(1) Cristae
• Inner folds INCREASE SURFACE AREA of mitochondrial membrane
(i.e., INCREASES ATP production).
(B) Ribosomes (“protein-workbench”)
• MOST numerous, (made of protein and RNA), can be FREE-FLOATING or
ATTACHED to ER in cell.
(C) Endoplasmic Reticulum (2 TYPES OF ER, smooth AND rough)
• A highway of FOLDS, moving AND sorting molecules used by the cell.
(1) Rough ER (ER with ribosomes)
• Found in cells that make LARGE amounts of protein.
(2) Smooth ER (ER without ribosomes)
• Used for STEROID synthesis, Ca monitoring, and metabolism of toxins.
(D) Golgi Apparatus (“post office”)
• Packages pre-assembled proteins into VESICLES for export by cell.
(E) Lysosomes (“suicide sacs”)
• Digests food compounds, old organelles (recycled), viruses, and bacteria.
(holds an important membrane).
(F) Cytoskeleton (made of microtubules and microfilaments)
• FRAMEWORK for SUPPORT as well as MOVEMENT of the cell.
(1) Microfilaments (microtubules)
• Threads of PROTEIN used in contraction of CYTOSKELETON.
(2) Actin & Spindle Fibers
• Larger SPINDLE FIBERS used with CELL DIVISION (i.e., mitosis).
(G) Cilia and Flagella (assist in MOVEMENT)
• HAIR-LIKE structures EXTEND OUT of cell membrane.
III. Nucleus (membrane bound)
• Protects DNA and nucleolus of cell.
(1) Nuclear Envelope and Nuclear Pores
• Regulates substances entering AND leaving the nucleus.
(2) Chromatin and Chromosomes (inside nucleus of a cell)
• Fine strands of DNA and protein; AND densely packed chromatin .
(3) Nucleolous (inside nucleus)
• Makes RIBOSOMES AND transports them to CYTOSOL.
IV. Plant Cells
• AUTOTROPHIC cells have 3 additional structures:
(1) Cell Walls
(2) Vacuoles
(3) Plastids
Critical Thinking
(4) PLANT cells possess cell walls, HOWEVER animal cells do NOT. What
do you suppose the evolutionary trade-off for this phenomenon might be?
(A) Cell Wall (made of CELLULOSE, indigestible polysaccharide)
• RIGID covering, lined with PORES, deals with TURGOR PRESSURE.
Critical Thinking
(5) LIVESTOCK in the western United States often DIE after consuming a
locoweed species, such as Astragalus toanus. The CHEMICAL that the
plant contains is ALSO poisonous to other plants. HOW might the
locoweed plant species prevent self-poisoning?
(B) Vacuoles (poisonous plants)
• Fluid-filled bubbles safely STORE enzymes, water, & metabolic products.
(C) Plastids (e.g., chloroplasts)
• MEMBRANE-bound (own DNA)  storage of starch, fats, and pigments.
(1) Chloroplast (double lipid bilayer)
• Converts SOLAR NRG into CHEMICAL energy (i.e., SUGARS).
(2) Thykaloid (in a stack, called a “GRANUM”))
• FLATTENED SACS within EACH chloroplast  increases surface area.
4-3 Multicellular Organization
I. Tissues, Organs, and Organ Systems
Organ Systems Make up the Organism
Organs
Make up an Organ System
Tissues make up
Organs
Similar cells make up tissues
Critical Thinking
(6) The COILS of a radiator provide a LARGE SURFACE AREA from which
HEAT is radiated into a room. Which CELL ORGANELLES have a structure
SIMILAR to that of a radiator? How might the design of the STRUCTURE
RELATE to ITS function?
II. Evolution of Multicellular Organization
• Prokaryote led to Eukaryote (Endosymbiotic Theory), due to competition
for limited resources.
NOTE: The First Eukaryotes (Heterotrophic and Autotrophic)
• Lynn Margulis (1960s)—Evidence suggests that between 1.5-2.0 b.y.a.,
TWO types of small aerobic PROKARYOTE entered and began to live and
reproduce INSIDE larger, anaerobic prokaryotes.
Endosymbiosis
• Theory of a MUTUALISM between large anaerobic prokaryotes and two
types of aerobic prokaryotes…
(a) The FIRST invading aerobe evolved to become a mitochondrion.
(b) The SECOND invading aerobe evolved to become a chloroplast.
• This theory is backed up by BOTH of these organelles having their OWN
DNA as well as replicating on their own.
(A) Colonial Organization
• A group of GENETICALLY IDENTICAL cells live together in a
CONNECTED GROUP (i.e., colonial organism).
Ex: Volvox spheres contain between 500-60,000 cells.
• Photosynthetic, Locomotion, and Reproductive individuals
Mr. Fungus is ready to
greet our friend the alga
Friend alga cell is prepared to
greet Mr. Fungus.
The Lichen is created between the fungus and the alga.
Extra Slides AND Answers for Critical Thinking Questions
(1) Once good quality microscopes became available, a number of scientists
could use them to examine cells.
(2) The presence of organelles and more membranes in eukaryotic cells
makes possible a greater specialization of function.
(3) A red blood cell is specialized to perform one main function. Without a
nucleus or mitochondria, it can carry more hemoglobin and therefore, more
oxygen.
(4) Cell walls may add strength and stability to plants, but they make them
immotile. All but a few animals require motility to obtain the nutrients
they need to survive.
(5) The poisonous chemical is stored in a vacuole, isolating it from the rest
of the cell.
(6) The endoplasmic reticulum, the cristae of mitochondria, and the inner
folds of chloroplasts have large surface areas similar to those of radiator
coils. Such structures provide more area for biochemical reactions.