The Eukaryotic Cell
Cells are Dynamic
Essential cell activities:
Exhibit selective permeability (only let certain things in and certain things out)
Interpret and use information in DNA (30% of your DNA is a virus)
Virus ▯Dead DNA, they don’t reproduce without a host
RNA can be an enzyme; can reproduce
Separate chemical reactions from one another
Discovery of Cells
1660, The Netherlands – microscopes (magnify small things)
▯same time eye glasses was developed
Robert Hooke coined the term “Cells”
worked with Boyle, and Isaac Newton
looked at cork from a tree, cut the cork thinly, and looked at it under the
microscope ▯reminded him of a monastery which was called cells
Father of Microscopy – 1670’s – Anton van Leeuwenhoek
made many microscopes and looked at everything
he used his microscopes for his cloths because he was a merchant, for thread
First to see bacteria and sperm cells (animalcules)
1838 Schleiden (plants) and Schwann
All organisms composed of one or more cells.
The cell is the structural unit of life.
Cells can only arise by division from a preexisting cell.
Two types of cell:
1. Prokaryotes (no real nucleus)
“Pro” = before “karyotes” = nucleus
▯no membrane bound nucleus
▯ o membranebound anything
▯Archaea (different type of bacteria that live in weird environments)
“Eu” = true “karyotes” = nucleus
▯Compartmentalized Groups of Prokaryotes
There are 1000 microns (micrometer) in 1 mm.
Most eukaryotic cells are between 10 and 100 (micrometers).
Most animal and plant cells are 30 microns.
Most prokaryotic cells are 25 microns.
Endomembrane System – movement of vesicles
largest organelle in the cell.
every cell in the body has a nucleus or previously had one.
purpose ▯oxygenate tissue
Genetic info = Chromatin
Chromatin = DNA + Proteins
has two membranes
has nuclear pores because things need to go out and go in
in nucleus in cytoplasm
DNA ▯ RNA ▯
mRNA, tRNA, rRNA
Nuclear Lamina (mesh like membrane)
holds the nucleus and the shape together
rRNA is being made, combines with proteins and makes ribosomes
codes for nothing, mRNA codes and tRNA deciphers the code.
large (50 proteins) and small subunits
rRNA and protein
protein synthesis is their only function
Where are they found?
found free in cytosol
attached to membranes (endoplasmic reticulum and nucleus) mitochondria and Chloroplasts (smaller ribosomes)
Rough Endoplasmic Reticulum
~Rough because ribosomes are attached
Proteins to be exported out of cell
Proteins to be incorporated into membranes
Proteins to be imported into other organelles.
Smooth Endoplasmic Reticulum
Two main functions:
hydrophobic (don’t like water) and hydrophilic (like water)
referred to as the Golgi Complex
named after Camilio Golgi
every cell at least have one
adjacent to the ER but not connected
each stack (cisternae) are not to connected to each other
▯formed from ER vesicles
▯cis, medial and tans cisternae (polarity)
manufacturing/modifying (add sugars)
Cisternal Maturation Model
Golgi cisternae move in a cis to trans direction
Vesicles bud off the ER.
Fuse together to form the cis
The “medial” cisternae of the Golgi Complex are primarily formed from maturation of
the cis cisternae.
comes from the Golgi
are not secreted
stomach of the cell
has 50 hydrolytic enzymes (using water break apart) – acidic pH 5 (enzymes only
work in this condition)*has a 100 more hydrogens than pH 7 Intracellular digestion
1. Phagocytosis (“Cell eating”)
2. Autophagy (“Self eating”)
The Eukaryotic Cell
Mitochondria (Mitochondrion) Major Role E ▯ nergy Conversion (i.e. ATP Synthesis)
ROLE IN THE CELL IS TO MAKE ATP
95% of your ATP came from mitochondria
2 membranes – outer and inner membranes
Majority of the membranes are not continuous
Inner membrane (goes backwards and forwards) ▯Cristae
▯a lot of the proteins involved in making ATP synthesis are on that membrane=
increase the surface area
Inter membrane space = space between outer and inner membrane
Inside the inner membrane is the matrix
▯ ellylike material, jam pack full of proteins
▯ as ribosomes and DNA
Free ribosomes, membranebound ribosomes and mitochondrial ribosomes are
Mitochondrial DNA found in the mitochondria is circular in shape.
Mitochondria used to be a bacteria
All Maternal M ▯ itochondria is from the mother, not the father.
occurred 2.5 billion years ago
forms a skeleton around the cell, it is not made out of bone, but made out of
Microfilaments ▯smallest sized
▯can fall apart quickly and readily
Microtubules ▯biggest sized
▯can fall apart quickly and readily
Intermediate filaments m ▯ edium sized
▯more stable and rigid ( don’t disassemble)
Movement and motility (Microfilaments and microtubules)
Made of protein actin ▯small protein
▯can assemble this rodlike structure
▯40% of protein inside a cell is actin
Can be found it all over the cell, where the cell moves, find it in the stress fibres Works with the protein myosin
1. Change cell shape (intimately involved in the movement of the cell)
2. Move organelles (organelles are attached to the myosin motor)
3. Cell division (cytokinesis) ▯splitting into two daughter cells
4. Muscle contraction (actin forms a track in the sarcomere)
composed of two proteins ▯alpha and beta tubule = form heterodimer
13 Protofilaments will line up together and make a tube = microtubule
▯All functions are perform on the outside of the microtubule
They are polar structures because they start going from negative to positive
Always radiating from the center.
Central Zone = microtubule organizing center
Microtubules act as railway tracks for motility within the cell
1. Kinesin – move towards the outside of cell “+” end directed movement
2. Dynein – move towards the inside of cell ““ end directed movement
The centrosome is the microtubuleorganizing center of the cell.
Centrioles are made out of 3 microtubules.
Microtubules form cilia and flagella.
Humans have cilia, but men have flagella.
The difference between cilia, flagella and sperm is the length.
We line our trachea with cilia.
Internal Structure is called the Axoneme. (“9+2” pattern)
▯9 doublet microtubules
▯two single microtubules in the centre
Cilia and Flagella attach to the cell at the Basal body (“9+0” pattern)
▯none in the centre
Motor molecule dynein allows cilia and flagella to move.
the flagella (different than bacterial flagella – they rotate)
Flagella has a rigid structure
when they walk along, they bend
causes whip like motion
Intermediate in size
Stabilize cell structure (main function)
very strong, resist tension
no motility, no motor molecules
variety of different proteins ▯Keratin (hard keratin makes up hair) (soft keratin are on top of cells)
The Extracellular Matrix is found on the OUTSIDE of the cell.
how it connects with tissue
Mainly composed of glycoproteins (proteins attached to long sugar chains)
o Collagen is the most abundant protein
▯found on the outside of the cells
▯an example of a glycoprotein(glycol – sugar, protein – amino acids) (more
protein, less sugar)
▯with age, collagen breaks down ▯causes wrinkles
▯can be used to get rid of scars
o Proteoglycans majority of them have large amount of sugar and less
▯connected on the inside of the cell, even if it is in the outside
Coordinate cell behaviour
Cells are connected to other cells via Junctions
▯made out of three proteins
▯fuse two membranes of different cells together
▯connected to keratin
▯connect one cell with another
▯ reates flexibility between tissues
▯Fastens cells together
▯ llows cells to communicate between tissues
▯ llows communication through a junction
▯ mall hole between cells so tiny signaling molecules can move between the two
1. Carbohydrates (i.e. Sugars)
2. Lipids (i.e. Fats)
4. Nucleic Acids
Cell structures are made of macromolecules. Monomer #1 + Monomer #2
built like lego, usually the same molecule
almost always one of the monomer has a hydrogen attached to it and the other
monomer has a hydroxyl group attached to it, these groups interact and release
Many macromolecules are formed via condensation reactions (AKA Dehydration
these reactions need a biological catalyst to occur
▯Condensation reactions are catalyzed by enzymes
These biological catalysts lower the Activation energy
When enzymes and biological catalysts are done their job, they do it over and
Opposite = hydrolysis reaction
▯also needs enzymes and give off energy
▯activation energy is also lowered
Hydrolytic enzymes ▯acidic pH
Carbohydrates (end in –ose)
all contain Carbon, Hydrogen and Oxygen
molar ratio of 1:2:1 (CH2O)n
▯n = number of carbons
e.g. C2H4O2 or C6H12O6
Monosaccharides are the monomer for carbohydrates
Glucose is an example (C6H12O6)
Two monosaccharides linked = disaccharide (2 sugars)
Maltose is an example, which is found in plants
▯Glucose + Glucose = Maltose (a disaccharide)
Glucose (monosaccharide) + Fructose (monosaccharide) = Sucrose (disaccharide)
Sucrose is also found in plants (sugar beets, sugar cane)
Fructose is twice as sweet as Glucose
Glucose + Galactose = Lactose (milk sugar)
Lactose Intolerant ▯can’t produce lactase Polysaccharides = hundreds or thousands of monosaccharides linked together.
used to STORE carbohydrates
Glycogen is an example
▯stored in the liver and brain loves glycogen
Another example is Starch
▯two types Amylose (wind up) and Amylopectin (branches)
▯Plants store starch
▯Amylopectin can be digested slower than Amylose
Cellulose is another example.
Starch and Cellulose are both long chains of glucose.
Starch: 14 linkage of alpha monomers
Cellulose: 14 linkage of beta monomers
▯ sed as structural sugar in plants, not as storage sugar
ALL OF THESE ARE HYDROPHOBIC
Water is a polar molecule, that forms lattice like structures.
Ice cubes are less dense than water.
Polar molecules like water.
Transpiration – movement of water in a tree
Hydrocarbon chains are NOT charged
Therefore they are nonpolar or hydrophobic.
A hydrocarbon chain with a carboxyl group on end is called a fatty acid.
Storage Fats = 3 fatty acids + 1 glycerol
Triglycerol – storage fats
keeps warm & insulates organs
This is how lipids are stored in cells
Adipose cells store lipids (keeps storage energy for us for long periods of time)
Saturated vs. Unsaturated Fats
Refers to whether there are double bonds in the hydrocarbon chain or not.
Saturated = no double bonds, solid at room temperature
Butter is an example
Most animal fats are saturated
Unsaturated = double bonds present liquid at room temperature (because there’s a double bond that causes a kink in
one of the tails)
When there is more than one more kink it is called polyunsaturated
Can be either cis or trans
▯cis isomer : The two Xs are on the same side (will form a bend)
▯trans isomer : The two Xs are on opposite ends. (No bends)
Plants and fish
Hydrogenated vegetable oil don’t eat/use
Phospholipids = Glycerol + 2 Fatty Acids + phosphate and another small molecule
found in membranes
Amphipathic ▯molecule that has both hydrophobic and hydrophilic sections
Steroids (also Amphipathic)
4 rings and has groups linked to it
Cholesterol is stored in the membrane.
Cholesterol is the precursor for the sex hormones.
Polymers of amino acids linked end to end in a specific sequence.
Movement, Storage, Structural, Enzymes, Antibodies, Hormones, Receptors, and
All made of a monomer called Amino Acid
▯Amino group (acidic) and a carboxyl group
▯20 different R groups
Nonpolar side chains – hydrophobic
Polar side chains – hydrophilic
Electrically side chains hydrophilic
Glycine is the smallest amino acid, has H attached to it.
Polar side chains ▯Hydrophilic
o Acidic (negatively charged)
o Basic (positively charged)
Amino acid #1 + Amino Acid #2 (removes water) = Peptide covalent bond
the next amino acid is added to the carboxyl group
There are four levels of protein structure
Primary Structure = order of the amino acids
Secondary Structure = Hydrogen bonds between atoms of the polypeptide
▯Alpha Helix – reminiscent of a slinky
▯Beta Pleated Sheet – Beta strand, shown as a flat arrow pointed toward the
carboxyl end. They make Hydrogen bonds between the sheets.
Tertiary Structure = 3D shape Due to interactions between side chains (i.e. R
groups) ▯van der Waals forces (hydrophobic likes hydrophobic)
▯Ionic bond (there’s a charge)
Hydrophilic vs. Hydrophobic Amino Acids
Majority of the hydrophilic are on the outside and majority of the hydrophobic are in the
Omega 3 is a lipid macromolecule.
Membranes and their Structures and Function
1. Composition (physical structure and biological activity)
2. Selective Permeability (passive and active transport)
Lipids (phospholipids and cholesterol)
Phospholipids = Glycerol + 2 Fatty acids + phosphate + another small molecule
Phosphate ions with stable covalent bonds
Lipids = amphipathic (molecule that is polar and nonpolar)
will form spontaneously in water
one layer + one layer = bilayer
Unsaturated hydrocarbon tails = increased fluidity
Saturated hydrocarbon tails = decreased fluidity
Cholesterol also affects membrane fluidity (also amphiphatic)
has 4 ringlike structures that are embedded in the membrane
less rigid at low temperatures
high temperatures = holds the membrane together
Phospholipids move side to side rapidly but almost never flip flop.
Flippase is the enzyme that moves phospholipids from one leaflet to the other leaflet.
Proteins are another important component of membranes.
can either be integral (can either attach to one or both leaflets) or peripheral (attached to
the membrane but not attached to the leaflets). Integral proteins penetrate into the hydrophobic region of the bilayer.
Out of the 20 amino acids, these are the most hydrophobic amino acids (stable).
Structure of the most transmembrane proteins (i.e. integral proteins)
When they are made in the membrane they are asymmetric. This orientation must be
maintained all the time.
Peripheral proteins – not embedded, but are on surface of the membrane.
Can be found on the outside or in the inside and are loosely attached
Membrane Carbohydrates (always found on the outside of the cell)
Covalently attached to glycoproteins (longer and bigger, found on the outside) and
glycolipids (smaller and also covalently attached, found only on the outside).
Fluid Mosaic (something embedded in something else) Model
– fluid bilayers
integral and peripheral
Biological membranes are barriers to solute movement.
Selective Permeability (how does the cell transport “stuff” in?)
1. Passive (no energy required)
molecules move “down” their gradient only (i.e. [high] ▯[low])
a.) Simple Diffusion [high] ▯[low]
Only molecules that are soluble in lipid
CO2 or O2
No ATP needed
No proteins involved
All ions are impermeable to membranes
Aquaporin (an example of a channel protein)
There are proteins in biological membranes that allow water to go through.
b.) Facilitated Diffusion
Channel Transport Protein [high] ▯[low]
~ will only allow certain molecules to go through Carrier Transport Protein [high] ▯[low]
~ works by changing the shape of the protein (conformational change)
Facilitated Diffusion is Passive (no energy involved), Specific (for the molecule that is
going to be transported) and Saturable (can only work in a certain rate).
2. Active (requires energy – ATP)
molecules usually move “up” (i.e. [low] ▯[high])
Transport may be against concentration gradient
Transport proteins involved
Can be primary or secondary
Primary Active Transport (ATP is directly involved)
ATP participates directly in the transport mechanism