Download What is a cell?, List two difference between prokaryotic and

What is a cell?, List two difference between prokaryotic and eukaryotic cells. Name five organelles from
memory.
Structures in Cells
-Each cell starts out as a fully functional living thing.
-To sustain life, each cell must create and maintain substances and structures that then perform the essential task for
the functioning of the cell.
All living cells must:
-Obtain food and energy.
-Convert energy from an external source into a form the cell can use.
-Construct and maintain the molecules that make up cell structures.
-Carry out chemical reactions.
-Eliminate wastes.
-Reproduce.
-Keep records of how to build structures.
While there is an almost endless variety of cells in the world, there are two main categories used to classify
them.
1) Prokaryotic cells, a.k.a. Prokaryotes
2) Eukaryotic cells a.k.a. Eukaryotes
1) Prokaryotes
-The smallest living cells.
-Relatively simple internal structures.
-All bacteria are prokaryotes. Eg: Escherichia coli (fig 1.10 pg 23)
-“pro” means before, and “karyon” means nucleus, so prokaryotes do not contain a nucleus.
-Their DNA is concentrated in an area called a nucleoid.
-They are the most abundant cells on earth.
-They can survive in diverse and extreme habitats. Eg: salt laden waters of the Dead Sea and the hot sulphur
springs of Old Faithful.
-They lack most organelles.
2) Eukaryotes
-“Eu” mean true, and they do contain a nucleus. The nucleus in an enclosed region that separates the DNA
from the rest of the cell contents.
-Eukaryotes contain specialized structures called organelles to perform specific functions within the cell.
-The organelles divided the cell interior into specialized compartments where different chemical reactions are
constantly taking place. The compartments allow the reactions to occur without interfering with each other.
You need to be able to identify cell organelles in a diagram or picture, and describe the function of each organelle.
Specific cell structure and their functions.
There are so many kinds of cells, they require specific structures to perform needed tasks. Eg: blood, nerve,
bone cells, skin, sperm, eggs, mail, plant, mold etc.
A) Protoplasm
-General term for all the living material in a cell.
B) Cell Membrane
-Layer that separates the cell interior from the outside world.
-Controls the movement of material into and out of the cell.
C) Cytoplasm
-Gel-like in consistency, mostly made of water.
-Creates the chemical environment so other organelles can work.
D) Nucleus
-About 5µm in diameter, it is the largest organelle.
-Stores the cell’s genetic information. That information determines the cell’s structure and function.
-Unless the cell is preparing to divide, the DNA strands are uncoiled and called chromatin.
-The nucleus is contained within the nuclear membrane.
E) Nucleolus
-A specialized area of chromatin within the nucleus. The nucleolus produces the chemical used to construct
the ribosomes.
F) Ribosomes
-Tiny organelles that make proteins.
-Every cell contains thousands.
-Assembled in the nucleus.
-Some float freely in the cytoplasm (free ribosomes) and are used to make proteins.
-Some ribosomes are attached to the endoplasmic reticulum (ER). These ribosomes make proteins that are
processed by the ER and are sent to the golgi apparatus.
G) Endoplasmic Reticulum (ER)
-Numerous folded membranes with huge surface areas where chemical reactions can take place.
-Rough ER are covered with ribosomes. Some strong enzymes and proteins that would damage the cell are
made in the ER. Eg: insulin
-Smooth ER is not covered in ribosomes. They usually process lipids (fats). Eg. testosterone.
-Sections of ER can pinch off to make vesicles or pouches to transport molecules to the cell membrane or
golgi apparatus.
H) Golgi Apparatus
-Stack of membrane covered sacs (like a stack of pancakes).
-Completes the processing of chemicals from the ER and makes them fully functional.
-The golgi then separate the chemicals, bind them in vesicles for transport to the appropriate cell location.
-It takes about 12 minutes for a protein to be fully formed from ribosome in rough ER to finished form in the
golgi.
I) Vesicle
-Small membrane bound transport sac.
J) Mitochondria
-Powerhouse of the cell where macromolecules of energy are broken down into a usable form of energy
(called ATP).
-The inner folds (cristae), provide the surface area for these chemical reactions.
-They ave their own DNA and duplicate themselves by dividing down the middle to produce two daughter
cells, just like prokaryotes.
K) Lysosomes
-Vesicle filled with digestive enzymes to break down worn-out cell components or other materials such as
invading bacteria.
-The remaining chemicals will be recycled by the cell to build new components.
-Only found in animal, not in plant cells.
L) Cytoskeleton (3 parts)
i) Actin Filament
-Dense web of protein cables under the cell membrane. Major component of muscle fibers.
ii) Intermediate Filaments
-Protein cables that anchor organelles into regions of the cell.
iii) Microtubules
-Rod-like, hollow protein tubes that act like tracks other organelles can move along.
-Give the cell shape, like tent poles.
-Can be taken apart and used to form the spindles for cell division.
-Structural component of cilia and flagella.
M) Cilia
-Singular= cilium
-Hairlike structures that extend from the cell membrane and beat in a co-ordinated rhythm to produce
movement. (Pg 14, fig 1:9 letter C, paramecium)
N) Flagella
-Singular = flagellum
-Long projections that produce undulating, whip-like motion. Eg: Sperm.
O) Vacuole
-Fluid filled sac for the temporary storage of food, water or waste.
-Plant cells usually contain several small and once large central one.
Plant cells require some extra cell structures. Most plant cells tend to have a geometrical shape such as a rectangle.
P) Cell Wall
-Made mainly of cellulose and provides strength and rigidity to the cell. Eg. Grass can stand up.
-Helps prevent the plant cell from bursting if it absorbs too much water.
Q) Plastids.
-Double membraned sacs that may be:
i) Chloroplasts
-Contain green pigment (chlorophyll) that traps solar energy and through photosynthesis produces
food. Photosynthesis occurs on the folded membrane (pg 33, fig 1.21)
ii) Chromoplasts
-Contain various pigments also useful for photosynthesis.
-Gives colour to flower petals.
iii) Leucoplasts
-Have no colour and serve to store starch.
With the compound microscope we can see the cell membrane, cell wall, nucleus, nucleolus and large vacuoles.
Most Prokaryotes have a cell wall, and their organelles lack membranes. They do contain many ribosomes. They
often contain flagella and use them as propellers.
Assignment: Pg 34 #1-2, 4-8, 10, 12
What is the purpose of the cell membrane?
The Cell Membrane
It looks like a thin, dark dividing line, but it must be more. Cells, like humans and cities are not closed systems.
Things enter and exit cells all the time.
The activities of a living cell depend on the membrane to:
1) Transport raw materials into the cell.
2) Transport manufactured products and wastes out of the cell.
3) Prevent the entry of unwanted matter into the cell.
4) Prevent the escape of matter needed for cellular fruitions.
The cell membrane is composed of phospholipid molecules. Phospholipids have two fatty acids bonded to a
glycerol “backbone”. This created a “head” and two fatty acid “tails”. (Pg 51 Fig 2.22)
The electrical charge over the molecule isn’t even. The polar head of the phospholipid is attracted to polar
water molecules. That is, the head is soluble (able to dissolve) in water. The tails are insoluble (not attracted to
water), but are compatible with other lipids (fats).
Why is this important?
When phospholipids are spread in a film on water, a curious thing happens. The attractions and repulsions of
the heads and tails cause them to form a cage-like spherical layer. (Pg 51, fig 2.23).
-The water attracting heads face in and out of the sphere.
-The non-polar tails face each other.
-This phospholipid bilayer forms the basis of the cell membrane.
Biochemists and electron microscopists have found various components scattered throughout the membrane,
much like raisins in raisin bread. Many of these molecules are proteins and they can drift around the bilayer. This
supports the idea that the phospholipid bilayer has a fluid consistency. Therefore, the cell membrane is often called
the fluid-mosaic membrane model.
Some of these molecules include:
-Cholesterols found in animal cell membranes. These keep the membrane fluid at lower temperatures.
They also prevent some other molecules from passing through.
-Protein and carbohydrate arrangements in the cell membrane the allow the cell to be “recognized” by
other cells. (Pg 52, fig 2.24)
In multicellular organisms, the cells are bathed in a thin layer of extracellular fluid, which is made of water,
mineral and some cell wastes that have been discarded.
The cell membrane is selectively permeable, it allows some molecules to pass through and prevents others
from doing so. In so doing, the cell can maintain homeostasis, a relatively stable environment despite changes.
Draw the phospholipid bilayer and explain why it forms.
What is meant by “passive transport”?
Homework: read Osmosis pg 56-57
Transport Mechanisms
Transport mechanisms across the cell membrane may be:
A. Passive
B. Active
C. Bulk (create vesicles)
A. Passive Transport (3 parts)
1. Diffusion
-The passive movement of small molecules through the cell membrane.
-Diffusion involves the movement of molecules from an area of high concentration to an area of low
concentration.
-Small, uncharged molecules can diffuse through the cell membrane quite easily. eg: O2 and CO2.
-Atoms and molecules of substances are constantly moving in a random pattern (Brownian motion). They
collide and bounce off in all directions. Because it requires no additional energy from the cell, it is called
passive.
-Diffusion always happens across a concentration gradient. One area has a high concentration and its
molecules move to an area of low concentration.
eg: perfume throughout a room.
-Diffusion explains how some molecules move back and forth across the cell membrane.
2. Osmosis
-Some membranes only allow certain materials to pass through. The membrane is said to be selective or semipermeable.
-When a liquid, usually water is passing through a selective, or semi-permeable membrane, the processes
called osmosis.
-It requires no energy, so like diffusion it is passive.
-It follows the concentration gradient of solvent or water molecules (from high to low concentration).
-It continues until the concentration is the same on both sides of the membrane, i.e. until equilibrium is
reached.
Show eggs
In the eggs
-Osmosis is occurring with water molecules.
-In the water and egg jar, the water is moving into the egg across the membrane in an attempt to equalize the
concentration on both sides of the membrane. Consequently, the egg swells. The egg molecules are too large
to diffuse out.
-In the corn syrup and egg jar, the water is moving out of the egg and into the jar it an attempt to equalize the
concentration on both sides of the membrane. Consequently, the egg shrinks.
There are 3 terms used to describe the solute concentration of a solution. The terms are used to refer to the solution
the cell is bathed in.
i) Hypertonic
-The solute concentration is greater outside the cell. ie, the water concentration inside the cell is greater that
outside the cell.
-Water will move across the membrane and out of the cell.
ii) Hypotonic
-The solute concentration is lower in the solution than inside the cell. ie, the water concentration outside the
cell is greater than inside the cell.
-Water will move across the membrane and into the cell.
iii) Isotonic
-The solute concentration is the same on both sides of the cell membrane. ie, the water concentration inside
the cell is equal to the water concentration outside the cell.
-Osmosis continues with water moving into the cell at the same rate as water moving out of the cell. No
observable change in cell size is noted.
The cell membrane can not prevent the movement of water because it is permeable to water. A cell can only
remain healthy for a long time in an isotonic solution.
See page 55 to see the three conditions and how plant and animal cell differ when exposed to them.
In both osmosis and diffusion, the only energy involved is natural molecular Brownian motion. The cell is not
expending any of its own energy.
Your cells are bathed in tissue fluid. They are in a liquid environment. Materials the cells need such as
oxygen diffuse from the blood vessels into the tissue fluid and then across the membrane into the cells. Waste
products in the cells diffuse out of the cells and into the tissue fluid and back into the blood vessels.
Draw a cell in a hypotonic solution. Use arrows to show the movement of water into or out of the cell.
Compare and contrast carrier proteins and channel proteins (give 2 similarities and 2 differences).
Continuing passive transport mechanisms.
3. Facilitated Diffusion
-Oxygen, carbon dioxide and water can be moved easily with passive transport. However, some molecules are
too large, or have too much electrical charge to pass through the lipid bilayer (eg, carbohydrates).
-The larger or charged molecules are moved with the help of specialized transport proteins in the cell
membrane.
-The structure of the transport proteins makes them very selective. A particular transport protein will only
recognize and transport one type of dissolved molecule based on its shape, size and electric charge.
-These molecules are still moving with the concentration gradient (from high to low concentration), so this is
called facilitated diffusion.
There are two types of transport proteins.
a) Carrier proteins.
-Accepts only non-charged particles eg: glucose.
-Allows particles to move in or out of the cell.( Fig 2.27 pg 57)
-Changes shape (rocking motion) to transport the molecule.
b) Channel proteins
-Accepts charged particles that are opposite in charge to themselves. ie, a negatively charged channel
protein can accept a positively charged molecule and vice versa.
-It has a tunnel shape that allows the particle to pass through.
Since no energy is required and materials move along the concentration gradient, diffusion, osmosis and
facilitated diffusion are all forms of passive transport.
B. Active Transport
-Cells often need to transport materials across the concentration gradient. For example, removing toxic waste from a
cell. We want it completely removed from the intracellular environment, not in a state of equilibrium.
-This requires the cell to expend energy to transport substances from an area of lower concentration to an area of
higher concentration (against the concentration gradient).
-How much energy is expended depends on how “steep” the concentration gradient is (like biking up steeper slopes
on a bike).
-Your kidneys use 90% of their energy on active transport as they filter your blood.
Active Transport Examples
a) Your kidneys take glucose and amino acids out of urine to put it back into your blood.
b) Root cells pump nutrients from the soil.
c) Fish gill cells pump out sodium ions in salt water.
d) Your stomach lining cells pump acid into the stomach.
Different transport proteins are used to make a variety of active transport pumps. They are similar to the ones used
in facilitated diffusion, but these are working against the concentration gradients. This requires energy. The energy
used by cells is a molecules called ATP (adenosine triphosphate).
Fig 2.31 pg 60 shows the protein pumps of a sodium-potassium pump.
-The cells creates an artificial concentration gradient to push other molecules it needs into the cell.
-Now that the sodium ions are outside the cells, they are like a group of skiers at the top of a hill, the sodium ions
have nowhere to go but down (into the cell).
-The cell pushed them up the ski lift and it uses that energy to have them bring something with them as they re-enter
the cell.
-The sodium ions use the stored energy to re-enter the cell through another carrier protein and take a molecule such as
glucose or an amino acid with them. No new energy is required for the return trip.
-Sodium potassium pumps are always at work in your body. Even when you are resting, they are consuming 1/3 of
the cells’ energy.
Homework. Pg 61 #1, 3-18
Why do cells expend the energy required to operate sodium potassium pumps.
Third transport mechanism
C. Bulk Transport
There are macro molecules that the cell must take in or expel that are too large for either active or passive
transport. The cell membrane will then fold in on itself to create a membrane enclosed sac- a vesicle. With these
vesicles, cells are able to take in and expel larger molecules.
Endocytosis
When a cell folds in, trapping and enclosing a small amount of matter form the extracellular fluid. There are
two forms:
1) Pinocytosis
-Cell “drinking”.
-A vesicle is created for the intake of small droplets of extracellular fluid and the dissolved substances or very
small particles it may contain.
-Common in most cells types.
2) Phagocytosis
-Cell”eating”.
-A vesicle is created for the intake of large particles. Eg: a bacteria.
-Only occurs in specialized cells like amoeba and macrophages (the bacteria eating cells of your immune
system)
Exocytosis
-The reverse of endocytosis.
-A vesicle from inside the cell fuses to the interior of the cell membrane (restoring what was taken in during a
previous endocytosis).
-The contents of the vesicle are then extreted into the extracellular fluid.
-Very important to pancreas cells producing excreting insulin and other specialized cells.
Draw a cell undergoing phagocytosis.
Write the complete reaction for
photosynthesis
Explain how photosynthesis and cellular
respiration are complimentary processes.
Energy and Cells for Life
Photosynthesis
-All living organisms need energy to grow and carry out their required life processes.
-Some organisms can trap energy directly from the sun and make organic compounds. These are called autotrophs
(self-feeding). They make food through a process called photosynthesis.
-In Greek, photo means “light”, syn means “together” and sis means “putting”.
-Photosynthesis actually involves over 100 different chemical relations. We will look at a summary of these.
-In green plants, chloroplasts are the location of photosynthesis. These are found mostly, but not exclusively in the
leaves.
-Chloroplasts are small. 40 lined up next to each other are less than 1mm long. They can perform thousands of
reactions in a second.
-Photosynthesis combines carbon dioxide and water in the presence of sunlight, and chlorophyll to produce
carbohydrates (usually glucose, a sugar). In other words, light energy is converted into stored chemical energy in the
bonds of carbohydrate molecules.
light energy and chlorophyll
6CO2 + 6H2O
----------->
C6H12O6 + 6O2
carbon dioxide
water
glucose
oxygen
-Organisms that can’t make their own food, but must instead consume other organisms (plant or animal) are called
heterotrophs.
Aerobic Cellular Respiration
-The energy trapped in plant carbohydrates (starches and sugars) has to be released in animal cells before those cells
can use it to function.
-This process occurs in the mitochondria of the cells and is called cellular respiration.
-ALL organisms use cellular respiration to extract energy from organic molecules. (Autotrophs use it too) MOST
organisms use aerobic cellular respiration. This means the process requires oxygen. (Some organisms use anaerobic
respiration).
-Aerobic cellular respiration occurs in the mitochondria. Here, carbohydrates are broken down (metabolized) and
combined with oxygen in a series of chemical reactions to release energy is a form that is useful to the cell.
mitochondria
C6H12O6 + 6O2
--------->
6CO2 + 6H2O + ATP
glucose
oxygen
carbon dioxide
water
energy
ATP/ -Adenosine triphosphate
-38 ATP are produced from one glucose molecule in bacterial cells, and 36 ATP molecules are formed in cells with
mitochondria. 2 ATP are lost to intermediate energy carrier molecules in the eukaryotic cells.
-ATP acts as an energy carrier (like a battery) that stores the released energy from carbohydrates and carries it where
it is needed in the cell to do work. eg: active transport, produce proteins, contract a muscle...
-ATP has a phosphate-to-phosphate bond that is relatively easy to break, but when it is broken, that chemical bond
releases enough energy to drive essential cell reactions.
-After the phosphate group breaks off, the ATP molecule becomes ADP (adenosine diphosphate) and is again
available to accept a phosphate group as part of cellular respiration.
-In an average adult at rest, the cycle of ATP to ADP and back to ATP occurs so often that an estimated 40kg of ATP
are processed every day.
-This process continues over and over in every cell as long as molecules of food and oxygen are available.
Note: When no oxygen is present, anaerobic respiration can occur, but only 2 ATP are formed for each
glucose molecule.
Photosynthesis and cellular respiration are complimentary processes. The reactants of one are the products of
the other. Photosynthesis stores energy and cellular respiration releases it. Together, these processes drive the carbon
cycle. Carbon, the basic element of most living things enters living systems through photosynthesis during the
production of carbohydrates. Some of that carbon returns to the atmosphere through cellular respiration in the form
of CO2. (See pg 87, fig 3.18)
Global Implications
The earth is a closed system: little or no matter comes in from the outside. The processes of photosynthesis
and aerobic cellular respiration have great importance to our world:
1. To Sustain Life
Nutrients are moved through a series of cycles, the carbon cycle being one. Photosynthesis and respiration are
two halves of the living components of the carbon cycle.
i) On Land
Photosynthesis takes carbon from CO2 and forms organic molecules (carbs), for use in life processes and
respiration breaks them down releasing energy and returning CO2 to the atmosphere once again.
ii) In the Ocean
CO2 dissolves in oceanic water to form carbonic acid which breaks down to form bicarbonate ions (HCO3-).
These ions are the source of carbon for all aquatic plants’ photosynthesis.
2. In Industry
Photosynthesis is the biological basis for primary industries worldwide.
A) Agriculture and B) Forestry
Both of these involve the harvesting of plants and plant material for food, construction, paper, fabrics,
cosmetics, medicines, and personal care products.
C) Fisheries
Depend on aquatic autotrophs as the basis of the aquatic food chain to feed the species they wish to catch.
(Herring, turbot, lobster...)
D) Mining
The mining of fossil fuels has its beginning when the petroleum and coal of today were the ocean floors and
ancient forests millions of years ago. Petrochemicals are the source of fuels (95%), plastics, cosmetics, detergents,
drugs, and synthetic fibers like nylon, polyester and synthetic rubber.
3. On the Environment
The carbon cycle is different today than it was in the past.
-1850, 28 ppm or 0.028% of the atmosphere by volume was CO2.
-Today, it is 35ppm, or 0.035%.
The increase in CO2 levels is an important factor in climate change and it is due to:
-Society’s dependance on fossil fuels as an energy source.
-The removal and burning of vast stands of trees that otherwise would absorb CO2 during photosynthesis and store it.
See bio fact pg 87.