Cells
Cell Theory
• Cells are the fundamental (smallest) units
of life.
• All organisms are composed of cells.
• All cells come from preexisting cells.
(Proved by Pasteur who disproved
spontaneous generation in 1859.)
• Spontaneous Generation
• Formulated in 1838 by Schwann and
Schleiden.
Surface area to volume ratio
• Cells have a large surface area to volume
ratio.
• The cell’s volume determines the rate of
chemical activities over time.
• The cell’s surface area determines the
amount of substances a cell can take in an
expel.
• Because cells need to transport substances
frequently, small size is essential.
• How do you increase cell SA without
increasing size?
SA
• Increase the folding to increase SA.
• The respiratory tract has the SA of a tennis
court due to folding…
• The intestines has the SA of a football
field….
• The excretory system has large SA for N
removal:
• Ammonia in fish
• Urea in humans and animals
• Uric acid in birds and reptiles
Surface Area of the lungs (alveoli)
Digestive Tract
Small Intestine averages 23 feet.
Villi and Microvilli on
the interior of the small
intestine
Key
Nutrient
absorption
Vein carrying blood
to hepatic portal
vessel
Microvilli
(brush border)
Blood
capillaries
Epithelial
cells
Muscle layers
Epithelial cells
Large
circular
folds
Villi
Lacteal
Villi
Intestinal wall
Lymph
vessel
Excretory Structures
Nitrogenous Waste filtering
Figure 4.2 Why Cells Are Small (Part 1)
Figure 4.2 Why Cells Are Small (Part 2)
Figure 4.1 The Scale of Life (Part 2)
Figure 4.1 The Scale of Life (Part 1)
Since cells are small we need ocular assistance…
Most cells are < 200 μm in size.
Minimum resolution of human eye is 200
μm.
Resolution is the distance apart that two
objects must be in order for the eye to view
them as distinct not a blur.
Microscopes improve resolution.
Figure 4.3 Looking at Cells (Part 1)
Figure 4.3 Looking at Cells (Part 2)
Figure 4.3 Looking at Cells (Part 3)
Types of Microscopes
• Light microscopes- glass lens and visible
light to form a magnified image of an
object. Magnifies about 1000x.
• Electron microscopes-uses electromagnets
to focus an electron beam. The beam is
then directed to a fluorescent
screen/photographic film to create a visible
image. Magnifies about 1,000,000x. Can
see subcellular.
Cell Similarities
• 1. All cells have a cell membrane.
(Phospholipid bilayer.)
• 2. All cells contain DNA.
Cell Membrane Structure
• 1. Phospholipids- are amphipathic. They
line up to form a barrier from the water that
is inside/outside the cell.
• Remember Phosphate heads are (-)
• Phosphates prevent hydration shells around
each phospholipid.
• 2. Proteins- are amphipathic.
• A. Integral run through c.m. Function:
structure and transport
• B. Peripheral- on one side of c.m. Function:
attachment of cytoskeleton and ECM
Cell Membrane
Amphipathic
Phospholipids
WATER
Hydrophilic
head
Hydrophobic
tail
WATER
Amphipathic
Proteins
Hydrophilic region
of protein
Phospholipid
bilayer
Hydrophobic region of protein
Cell Membrane
C.M. Proteins Cont.
The proteins of the cell membrane can have
several functions.
• Molecule transport (Helps move food, water,
or something across the membrane.)
• Act as enzymes (To control metabolic
processes.)
• Cell to cell communication and recognition
(So that cells can work together in tissues.)
• Signal Receptors (To catch hormones or other
molecules circulating in the blood.)
Membrane
Protein Functions
Signal
Enzymes
Receptor
ATP
Transport
Enzymatic activity
Signal transduction
Membrane
Protein
Functions
Glycoprotein
Cell-cell recognition
Intercellular joining
Attachment to the
cytoskeleton and extracellular matrix (ECM)
C.M. Cont.
• 3. Cholesterol- keeps c.m. flexibility. Also
prevents plant cell membranes from
freezing
Data Set (U1,D12)
Synthesis Question (U1,D12)
•
Question: All living cells have to have a cell membrane to remain living and intact. All cells
are mostly water inside the cell. Cells live mainly in a watery environment. Water is a polar
molecule. In four sentences or less, how does the presence of water on the inside and outside
of a cell contribute to the structure of cell membranes? (5 Points)
•
1pt. Discussion of negative phosphorus atoms, of phospholipids being attracted to water and
forming a barrier in the bi-layer.
1pt. Discussion of the bi-layer needed to prevent water from forming hydration shells
•
around the phospholipids.
1pt. Discussion of the fatty acid tails being protected sandwiched in-between the
Phosphorus barriers.
1pt. Correct use of scientific terms.
1pt. Answer has no more than three sentences. (Following Directions.)
Prokaryotic Cells
• “Kary” means kernel, in this case the
nucleus.
• Prokaryotes compose the Domains:
Archaea and Bacteria.
• Do not have membrane bound organelles.
• Thought to have been the “first cells”
Prokaryotes
• Can live in more diverse environments than
eukaryotes.
• Can sustain life on more diverse energy
sources than eukaryotes.
• Typically smaller than eukaryotes.
• Tend to aggregate in chains or clusters.
Prokaryote Composition
• 1. Plasma membrane regulating
incoming/outgoing substances.
• 2. Nucleiod- contains DNA, not a defined
region
• 3. Cytoplasm: (2 parts)
• Cytosol-consists mostly of water with ions and
water soluble molecules such as proteins
• Insoluble particles including ribosomes.
• Ribosomes are RNA and proteins.
Specialized Prokaryotic Features
• Some prokaryotes developed specialized
features. Why?
• 1. Cell Walls- located exterior to the cell
membrane. Dissimilar to plant cell walls
• Cell walls typically contain peptidoglycan an
amino sugar
• Sometimes have an outer membrane.
• Sometimes a capsule:= Slime layer made of
polysaccharides; prevents drying out and aids in
attachment to other cells (sickness)
Figure 4.4 A Prokaryotic Cell
Cell Walls, Internal Membranes, & Flagella and Pili
• Plasma membrane will fold in to form
specialized compartments for
photosynthesis, cell division, or catabolic
activities.
• Structures of Movement
• Flagella- made of protein flagellin, rotates like
an axel for movement.
• Pili- aka cilia, hairlike projections for
movement
Figure 4.5 Prokaryotic Flagella (A)
Figure 4.5 Prokaryotic Flagella (B)
• Cytoskeleton- helical structures just inside
the plasma membrane.
• Composed of proteins similar to actin. Actin
makes up cytoskeleton in eukaryotes.
• Cytoskeleton commonly found in rod shaped
bacteria.
Let’s Practice
• Cell Review
Eukaryotic Cells
• Eukaryotic cells ~10x bigger than
prokaryotes.
• Have membrane bound organelles.
• Organelle can be membrane bound or not.
• Organelles have a specific functions and
shapes.
• The role/function of an organelle is defined
by the chemical reactions that take place
Cell fractionation and microscopy
• Cell organelles first detected by light
microscopes.
• Cell fractionation-break down plasma
membrane, organelles separate based on
size/density.
• Biochemical analysis can then be done to
detect for certain macromolecules
• Many organelles identical in plants and
animals.
Figure 4.6 Cell Fractionation
Nucleus
• Typically the largest organelle in animal
cells.
• Site of DNA (chromatin vs. chromosome).
• Nucleolus- site of RNA and ribosome
synthesis.
Nuclear Structure
• Surrounded by a double membrane called
the nuclear envelope.
• ~3500 nuclear pores exist in the envelope
• The pores consist of over 100 different
proteins
• These proteins will aggregate in pore
complexes of 8 proteins.
• Small molecules can get into the pores,
larger molecules need a nuclear
localization signal. (chain of amino acids)
Figure 4.8 The Nucleus is Enclosed by a Double Membrane (Part 2)
Figure 4.8 The Nucleus is Enclosed by a Double Membrane (Part 1)
Ribosomes- NOT ORGANELLES
• Function: protein synthesis per nucleic acid
instructions
• Location:
• Attached to Endoplasmic reticulum-out of cell
proteins,
• free-floating in cytoplasm-in cell proteins
• inside mitochondria and chloroplasts.
• Composed of two different subunits:
• rRNA- ribosomal RNA
• Protein molecules (>50 different ones)
Endomembrane System
• Made up of Endoplasmic Reticulum and
Golgi Bodies/Apparatus
• Vesicles serve as transporters of substances
between the endomembrane structure and
within the cell.
Endoplasmic Reticulum
• Location: extends from the outer membrane
of the nuclear envelope.
• Two Types: RER,SER
• Because of its many folds it has a surface
area greater than the cell membrane
• The interior of the ER is called the lumen
• Tubes are called cisternae
Rough Endoplasmic Reticulum
• It is called rough because ribosomes are
temporarily attached .
• Site of protein synthesis
• Proteins undergo folding within the RER
• Proteins can then be shipped to
incorporated endomembranes (GB), other
organelles, or extracellular locations.
Smooth Endoplasmic Reticulum
• No ribosomes attached
• Function:
•
•
•
•
•
Modification of some proteins from RER
Hydrolysis of glycogen
Synthesis of lipids, phospholipids, and steroids
Detoxifies blood
Stores calcium
What does this mean?
• Cells that synthesize a lot of proteins have a
lot of ER.
• e.g. Gland cells that secrete enzymes and WBC
• Cells that modify molecules that enter the
body (food) have a lot of ER
• e.g. liver cells have lots of SER
Figure 4.10 Endoplasmic Reticulum
Figure 4.11 The Golgi Apparatus (Part 1)
Golgi Bodies/Apparatus
• Flattened membranous sacs called
cisternae, think stacks of pancakes
• Functions:
• further modifies proteins by attaching sugars to
them so they can leave through the c.m.
(glycoproteins)
• Concentrates, packages, and sorts proteins to
be shipped extracellular
• Makes cellulose/starch for plant cell walls
Medial Region
Lysosome
• Originate from the Golgi bodies
• Contain digestive enzymes to hydrolyze all
4 macromolecule types
(enzymes=lysozymes)
• When molecules enter through
phagocytosis: called the phagosome
(vesicle/vacuole with macromolecule)
• Phagosome attaches to primary lysosome
forming a secondary lysosome where
digestion takes place
Figure 4.12 Lysosomes Isolate Digestive Enzymes from the Cytoplasm (Part 1)
Small particles diffuse
through cytoplasm
Figure 4.12 Lysosomes Isolate Digestive Enzymes from the Cytoplasm (Part 2)
Phagocytosis & Pinocytosis
Lysosomes and Autophagy
• Autophagy- organelles are ingested,
hydrolyzed, and released into the cytoplasm
for reuse.
• Plant cells do not have lysosomes, but their
central vacuole contains digestive enzymes.
.
1 µm
Nucleus
Lysosome
Lysosome contains
active hydrolytic
enzymes
Plasma
membrane
Food vacuole
fuses with
lysosome
Hydrolytic
enzymes digest
food particles
Digestive
enzymes
Lysosome
Digestion
Food vacuole
Phagocytosis: lysosome digesting food
Mitochondria and Chloroplasts
• Prior to the mitochondria and chloroplasts,
breakdown of fuel molecules begins in the
cytosol.
• Both organelles transform energy from one
form to another
• Chloroplasts take light energy and convert
it into chemical energy.
• Mitochondria take molecules such as
glucose and convert it into a usable form of
energy
Mitochondria and Cellular Respiration
• Mitochondria make ATP (adenosine
triphosphate) through cellular respiration.
• Cells that require the most energy have the
most mitochondria per volume. (Liver cells
have ~1000/cell.)
• Mitochondria can reproduce by binary
fission
• Contains its own DNA, ribosomes, and
enzymes
• Thought to have been purple bacteria.
Figure 4.13 A Mitochondrion Converts Energy from Fuel Molecules into ATP
Outer Membranelittle resistance to
flow of materials.
Inner Membranefolded (cristae):
greater surface area
than O.M.
Controls flow of
substances
Embedded with
proteins to synthesize
ATP
Matrix- contains
enzymes, DNA, and
ribosomes
Chloroplast
•
•
•
•
•
Type of Plastid (plastid-pigment container)
Located in plants and algae
Have DNA, ribosomes, enzymes
Reproduce by binary fission
Thought to have been blue green algae
Chloroplasts
Lynn Margulis
Endosymbiotic Hypothesis
Peroxisomes
• Membrane bound organelles that contain
toxic peroxides.
• Peroxides are unavoidable by-products of
chemical reactions, that can be safely
broken down within the peroxisome.
Vacuoles
• Membrane bound organelle filled with an
aqueous solution and many solutes.
• Function:
• Central-Storage
• Food vacuoles- in simple eukaryotes, used in
lieu of digestive system. Intake of food cause a
vacuole which fuses with a lysosome, and
chemical energy is released in to the cell.
• Contractile vacuoles- typically in protists;
helps with movement as a result of filling with
water because of osmotic pressure differences.
Figure 4.18 Vacuoles in Plant Cells Are Usually Large
Contractile Vacuole
Removes excess water in aquatic
single celled organisms
Cytoskeleton
• Not a membrane-bound organelle.
• Function:
•
•
•
•
Supports and maintains cell shape
Provides for some cellular movement
Positions organelles with in the cells
Some fibers can act as tracks that motor
proteins can move organelles intracellularly
• Interacts with extracellular structures to anchor
the cell in place.
• Types: microfilaments, intermediate filaments,
and microtubules
Microfilaments-smallest cytoskeleton
• Can exist alone, in bundles, or networks
• Made up of actin (protein). These PULL.
• Microfilaments responsible for:
• Cytoplasmic streaming- movement of
cytoplasm
• Pinching/Mitotic Movement- formation of
daughter cells
• Pseudopodia- “False feet” for movement
Intermediate filaments-medium
cytoskeleton
• Fibrous proteins of the keratin family.
• Function: stabilize cell structure.
Microtubules-largest cytoskeleton
• Function: move organelles or cell.
• Composed of the protein microtubulin.
• Examples:
• Cilia and flagella
• Centrosomes/Centrioles
• Spindle Fibers
Cell Walls
• Plant cell= cellulose
• Fungus= chitin
• Bacteria= peptidoglycan
Anticipatory Set 9-8-11
Organic
Compound
Monomer
Example
Amino acid
Fat, oil, wax
carbohydrate
Function
Synthesis Questions U1,D16
• Question: The one part of evolution tries to show
unity and diversity exists among all organisms on
earth. All living organisms on Earth are either
composed of Prokaryotic cells or Eukaryotic cells.
In no more than four sentences, justify unity by
stating one cellular structure all organisms have in
common and for diversity state two structures
that all eukaryotic cells possess that Prokaryotic
cells do not possess. For each structure state the
structures function within the cell. (5 Points)
•
•
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1pt. (Half point for one of the following: DNA, ribosomes, cell membrane, cytoplasm)
(Half point for structures purpose: information, making proteins, Holding cell
together, space to work)
1pt. Structure 1 with correct function from following list
RER – make proteins
SER – lipids and carb metabolism, detoxification
Mitochondria – Making energy
Chloroplast – Sugar production
Golgi Apparatus – protein modification
Vesicles – Storage
Lysosomes – Digestion
Cytoskeleton – support
Cell Wall or ECM - protection
1pt. Structure 2 with correct function
1pt. Correct use of scientific terms.
1pt. Answer has no more than three sentences. (Following Directions.)
Figure 4.20 The Cytoskeleton (Part 1)
Extracellular Matrix
• Area outside of animal cells
• Composed of fibrous proteins like collagen
and proteoglycans/glycoproteins (proteins
+ sugar).
• The extracellular matrix is specific to the
tissue type, and is made of proteins and
fluids the cells secrete.
Function of Extracellular Matrix
• Holds cells together in tissues
• Contributes to physical properties of
cartilage, skin, and other tissues.
• Helps filter materials passing between
tissues.
• Helps orient cell movements during
embryonic development and tissue repair.
• Role in chemical signaling.
Figure 5.1 The Fluid Mosaic Model
Figure 3.20 Phospholipids (A)
Repeat Fig 3.20A here
Cell Membrane
• All biological membranes consist of lipids,
carbohydrates, and proteins.
• The cell membrane is sometimes referred to
as the fluid mosaic model.
• This is because it prevents a lot of hydrophillic
substances from rapidly entering, and embeds a
lot of floating proteins.
Figure 5.2 A Phospholipid Bilayer Separates Two Aqueous Regions
Cell Membrane Content
• Phospholipids can vary with respect to fatty
acid chain length, degree of unsaturation
(presence of double bonds), and phosphate
groups present.
• 25% of lipid content can be cholesterol.
• Most cholesterol in membranes is not
detrimental to your health; maintains
membrane integrity.
Cell Membrane Fluidity
• Fluidity is affected by:
• Lipid composition
• Temperature
• When temp. decreases, membrane fluidity
decreases. Therefore cellular function
decreases.
• Plants and animals that hibernate may change
their lipid content (sat. to unsat. F.A. tails to
achieve shorter tails) to survive.
• Fluidity=Function No Fluidity=No Function
Membrane Proteins
• All membranes have proteins.
• Two Types of Membrane Proteins:
• Integral- hydrophobic and hydrophillic regions,
located within the membrane. Include
transmembrane proteins.
• Peripheral- only have hydrophillic regions,
interact with other hydrophillic regions of other
proteins or heads of phospholipids.
Transmembrane Proteins
• Transmembrane proteins
are a type of integral
protein. Extend out on
both sides of the
membrane.
• R groups from amino acids
determine
hydrophobic/hydrophillic
location.
• Integral proteins are only
on one surface of the cell
membrane. (Inside or
outside)
Carbohydrates in Cell Membranes
• Located on the outer surface of cell
membranes.
• Serve as a recognition site for other cells
and molecules.
• Sometimes carbohydrates fuse with lipids
and proteins:
• Glycoproteins
= carbohydratecovalent bond protein
• Glycolipid
= carbohydrate covalent bond lipid
Cell Recognition
• Cell recognition- one cell specifically binds
to another cell of a certain type.
• An example would be sperm and egg fusing.
• Homotypic binding- same glycoprotein sticks
out of both cells, and the exposed similar
carbohydrates bind cells together. eg. tissues
• Heterotypic binding- different glycoproteins
stick out from cells, but they have an affinity
for one another so they bind together. eg.
fertilization
Cell Adhesion
• Cell Adhesion- the connection between two
cells is strengthened.
• Cell Junction- result of cell adhesion; 3 types.
1. Tight Junctions
• Link epithelial cells
which line organs and
inside of mouth.
• Function of T.J.
prevent substances
from moving
between cells, and
dictate the function of
each region of the
cell.
• Like a quilted pattern
• (Controls membrane
proteins)
2. Desmosomes
• Connect adjacent cell membranes like a
spot weld. Allow substances to move
everywhere but the connection.
• Desmosome attached to intermediate
filaments inside each cell
3. Gap Junctions
• Function in communication between cells.
(Desmosomes and tight junction have
mechanical functions.)
• Connexons are the channel proteins that
span between cells and allow for molecules
and ions to pass through
Figure 5.1 The Fluid Mosaic Model
Theory of Endosymbiosis
1. Prokaryotes first absorbed food through environment.
2. Then Photosynthesis evolved.
3. Larger cells engulfed smaller cells, but smaller cells
were not digested.
4. The smaller cell divided along with the bigger cell.
5. The big cell provides protection, the little cell
provides energy.
6. 1980s, Margulis suggests endosymbiosis of
chloroplast and mitochondria because they have their
own circular DNA, ribosomes, and same size as
prokaryotes.
Endosymbiosis
• Theory is strengthened by:
• Prokaryotes and eukaryotes share:
• Nucleic acids as genetic material
• Same 20 amino acids in protein structure
• D sugars and L amino acids
2011 Released Essay Prokaryote vs.
Eukaryote
• Scoring Guide