Download Review Notes

The Cell Theory
PART A – BIOLOGY 11 – SUMMARY NOTES
A. All living things are composed of one or more cells.
B. Cells are the basic units of structure and function in an organism.
C. Cells come only from reproduction of existing cells.
All Living Things: are made up of one or more cells, reproduce, grow and develop, obtain and use energy.
*** Homeostasis is NOT the same as equilibrium!!! Homeostasis refers to an organism being in ideal
conditions which may not be true if equilibrium with surroundings is established. Eg. Your body temp
compared to room temp.
Cell Diversity
Not all cells are alike. Even cells within the same organism show enormous diversity in size, shape, and internal
organization. Your body contains at least 200 different cell types.
Cell size
MOST CELLS ARE SMALL FOR TWO REASONS:
a. CELLS ARE LIMITED IN SIZE BY THE RATIO BETWEEN THEIR OUTER SURFACE AREA AND
THEIR VOLUME. A small cell has more surface area than a large cell for a given volume of cytoplasm. This
is important because the nutrients, oxygen, and other materials a cell requires must enter through it surface.
As a cell grows larger at some point its surface area to volume ratio becomes too small to allow these
materials to enter the cell quickly enough to meet the cell's needs.
b. THE CELL'S NUCLEUS (THE BRAIN) CAN ONLY CONTROL A CERTAIN AMOUNT OF LIVING,
ACTIVE CYTOPLASM. Because information is sent to the cell from the nucleus via diffusion and this
process is not efficient or effective over long distances
Internal organization
1. Cells contain a variety of internal structures called ORGANELLES.
2. An organelle is a cell component that PERFORMS SPECIFIC FUNCTIONS for the cell.
THE CELL MEMBRANE
1. The cell membrane is a thin layer of LIPID (fat) and PROTEIN that separates the cell's content from the world
around it.
2. The cell membrane Functions like a GATE, Controlling what ENTERS and LEAVES the Cell. This
"SELECTIVELY PERMEABLE"
ORGANELLES
Organelles are structures that work like miniature organs. They carry out specific functions in the cell. All organelles
function in HOMEOSTASIS that means they maintain a constant internal environment.
• CYTOPLASM: Jelly-like substance between the cell membrane and the nucleus. It contains dissolved gases and
nutrients and holds organelles. When we talk about solute concentration inside a cell this is what we are talking
about.
• NUCLEUS: The nucleus is the control center (brain) of the cell. The nucleus contains DNA, the hereditary material
of cells and controls cellular activities. Genes are pieces of the DNA that code for specific proteins. Protein
synthesis is how the nucleus (DNA) controls the cell.
• ENDOPLASMIC RETICULUM (ER): The ER is a system of membranous tubules and sacs. The ER functions
primarily as an intracellular highway of membranes that connect the nucleus to the cell membrane, a path along
which molecules move from one part of the cell to another. The amount of ER inside a cell fluctuates, depending
on the cell's activity. Poisons, waste, and other toxic chemicals are made harmless. Can be ROUGH or SMOOTH.
A. ROUGH-ER is studded with RIBOSOMES and processes PROTEINS to be exported from the cell.
B. SMOOTH-ER is NOT covered with RIBOSOMES and processes LIPIDS (fats) and CARBOHYDRATES
(sugars).
• RIBOSOMES: Ribosomes are not surrounded by a membrane. They are the site of PROTEIN SYNTHESIS in a
cell. They are most numerous organelles in almost all cells. Some are free in the cytoplasm; others line the
membranes of ROUGH-ER.
• GOLGI APPARATUS: A system of membranes made of flattened sac like structures called cisternae. It works closely
with the ER to modify and package proteins for export by the cell.
• LYSOSOMES: Small spherical organelles or vesicles that are formed from pieces of the golgi apparatus that break
off. They enclose enzymes and. are the site of food digestion and worn out cell components. They can also cause
cell destruction. Lysosomes are common in the cells of animals, fungi, and protists, but rare in plant cells.
• MITOCHONDRIA: Rod-shaped organelles. Known as the "Powerhouse" of the cell because they produce the cell’s
energy by carrying out CELLULAR RESPIRATION C6H12O6 (sugar)+ O2 CO2 + H2O + ATP energy
Mitochondria are usually more numerous in cells that have a high energy requirement - your muscle cells contain
a large number of mitochondria.
• CILIA / FLAGELLA: Cilia and flagella are hair-like organelles that extend from the surface of the cell, where they
assist in movement. Cilia are short hair-like projections. Flagella are long whip-like projections. Cilia are often
numerous. Flagella are often singular.
• Unicellular organisms such as Paramecium and Euglena use cilia and flagella to move through water.
• Sperm use flagella to swim to the egg.
• In Humans, beating cilia line parts of the respiratory system, moving dust particles and bacteria away from the
lungs.
PLANT CELLS have three additional structures not found in animals cells.
• CELL WALL: Cell walls of plants contain CELLULOSE - a complex carbohydrate. A cell wall DOES NOT
REPLACE the cell membrane; cells with walls also have a cell membrane. Plant cells are covered by a rigid cell
wall that lies outside the cell membrane. The rigidity of cell walls helps SUPPORT and PROTECT the plant.
• VACUOLES: A large membrane-bound sac that takes up a large amount of space in most Plant Cells. It serves as a
STORAGE AREA, and may contain stored proteins, ions, waste, or other cell products. Vacuoles of some plants
contain poison that discourages animals from eating the plant's leaves.
• CHLOROPLASTS: A type of PLASTID that converts sunlight into food for the cell (solar energy into chemical
energy) through PHOTOSYNTHESIS solar energy + H2O + CO2 C6H12O6 (sugar) + O2
CELLULAR ORGANIZATION
1. The presence or absence of a nucleus is important for classifying cells.
• organisms whose cell contain a nucleus and other membrane-bound organelles are called EUKARYOTES.
• organisms whose cells never contain a nucleus and other membrane-bound organelles are called
PROKARYOTES.
2. Unicellular organisms such as bacteria and their relatives are PROKARYOTES. – Kingdom Monera
3. All other organisms are EUKARYOTES – Kingdom Protista, Animalia, Fungi, Plantae
5. In Eukaryotic cells, most organelles are surrounded by a membrane. (Eukaryotic cells generally have three main
components: a cell membrane, a nucleus, and other organelles.)
6. Prokaryotic cells have NO MEMBRANE-BOUND organelles.
*** Prokaryotic cells are very diverse and can still perform most of the functions that occur within organelles of
Eukaryotic cells. The time line (not on test) illustrated this.
7. ENDOSYMBION HYPOTHESIS – prokaryotic cells engulfed and formed symbiotic relationship with other
prokaryotes over time leading to the first organelles and thus eukaryotic cells.
Biochemical Processes
METABOLISM is all of a living organism's chemical processes. The organism's metabolism can be classified into two
parts: the synthesis of organic molecules (anabolism) and their breakdown (catabolism).
*** THERE ARE TWO STEPS TO AN ORGANISM ACQUIRING CELL ENERGY 1: GET AN ENERGY
MOLECULE 2: BREAK IT DOWN TO RELEASE ITS ATP ENERGY***
1: Get an energy Molecule – Autotroph (chemosynthesis or photosynthesis)
-- Heterotroph (consumer or decomposer)
2: Release the ATP nrg – Anaerobic No O2(Fermentation, denitrification, methanogen)
-- Aerobic with O2(cellular respiration)
PHOTOSYNTHESIS and RESPIRATION are complementary biochemical processes in the living world. But they
are not the opposite to one another!!!
PHOTOSYNTHESIS uses the energy of sunlight to produce sugars and other organic molecules. These molecules in
turn serve as food for other organisms. Many of these organisms carry out RESPIRATION, a process that uses O2 to
form CO2 from the same carbon atoms that had been taken up as CO2 and converted into sugars by photosynthesis.
The FIRST CELLS on the earth are thought to have been capable of neither photosynthesis nor respiration.
However, photosynthesis must have preceded respiration on the earth, since there is strong evidence that billions of
years of photosynthesis were required before enough O2 had been released to create an atmosphere rich in oxygen.
(The earth's atmosphere now contains 20% O2.)
PHOTOSYNTHESIS
1. Photosynthesis is the process that provides glucose (energy molecules) for almost all lifeforms.
2. Photosynthesis occurs in the chloroplasts of plant cells and algae and in the cell membranes of certain bacteria.
3.
4. The energy stored in the carbohydrates can be used later to produce ATP during CELLULAR RESPIRATION.
CELLULAR RESPIRATION
1. Respiration is the opposite of photosynthesis but it produces Energy!
2. By breaking down organic molecules into simpler molecules, CELLS RELEASE ENERGY.
3. The main energy of cells - ATP (Adenosine triphosphate) – is released during cellular respiration.
5.
5. Note that CO2 is a WASTE PRODUCT that diffuses out of the cells.
CELL TRANSPORT
Solutes are molecules in a solvent (usually water) and because one is in the other, their concentrations are
opposite one another ie. More solute concentration means less solution concentration.
Diffusion is the movement of solutes as a result of KMT. It does not require a cell or a membrane, just a
concentration gradient and solutes always go from high to low down the concentration gradient until they
reach an equilibrium (not to be confused with homeostasis). Osmosis describes the movement of the solvent
(water) and since its concentration gradient is opposite that of the solute it has a net movement in the opposite
direction. However it is important to know that the reason for this is still KMT and that the water is still moving
down ITS concentration gradient from where the water is higher to where the water is lower.
*** Homeostasis does NOT mean equilibrium. Often equilibrium is not ideal for the cells.
TYPES OF CELL TRANSPORT:
 Passive – osmosis and diffusion through the phospholipid bilayer of the membrane
 Facilitated – movement of solutes down the concentration gradient without using cell energy but with
the help of transport proteins
 Active transport – movement of large “things” that can not get in passive or facilitated, or movement of
solutes AGAINST their concentration gradient. Requires ATP energy of the cell.
o Protein Pumps – move solutes against the gradient to maintain homeostasis
o Endo (in)and Exocytosis (out) and involved pinching off of sections of the membrane to form
vesicles (phago (large) and pinocytosis(small))
Study Your Notes and Make sure you Prepare for the Long Answer Questions for BOTH units
Look at the mark allocations
UNIT 2 - THE ROLE OF DNA = template for DNA replication & protein synthesis.
 DNA contains the GENETIC CODE in sequences of chemicals called NUCLEOTIDES. = Monomers or the
DNA polymer
o Each nucleotide contains a phosphate group, deoxyribose sugar and Nitrogen Base
o There are 4 different nucleotide bases Adenine and Guanine (Purines with two rings) and Cytosine and
Thymine (Pyrimidines with one ring)
o Base pairing occurs through weak Hydrogen bonds between base pairs A-T and C-G (purine to pyrimidine)
and forms the ladder connections down the center of the two Antiparallel strands of DNA
o The DNA strands are connected via strong Phosphodiester Bonds that form the Sugar Phosphate backbone of
each of the antiparallel strands. This is important to keep the DNA sequence protected.
 Each portion of the nucleotide sequence in DNA is responsible for one particular protein. =Gene
o All ENZYMES are proteins and enzymes control such reactions
o Proteins can also build structures, etc. so cell control is the result of making the protein required.
o Often more than one gene and therefor more than one protein results in a given trait.
DNA REPLICATION: As part of the cells life cycle every cell replicates its entire DNA sequence (all the chromosomes).
It does this during Interphase of the cell cycle.
 In Interphase the cell makes more organelles, grows, does its cell job, replicates its DNA and proofreads the
replications. Chromosomes contain thousands of genes each. Different organisms have different numbers of
chromosomes but essentially they are wound-up condensed DNA.
 Chromosomes at the start of Interphase contain only one copy of the DNA but by the end of interphase, they
contain two connected copies (the X) This should not be confused with the Homologous Pair you have of each
chromosome.
 Homologous Pairs of Chromosomes – if you are a diploid cell then you have 2N chromosomes. This means that
you have two chromosomes #1’s, two chromosome #2’s etc… one from the mother cell and one from the father
cell. This “Set” of chromosomes will contain the same genes but possible different alleles (versions) of those
genes.
o In humans your somatic cells contain 46 chromomes (23 from mom, 23 from dad = 23 homologous
pairs and these are diploid cells. Your sex cells (egg or sperm) contain only 23 chromosomes and are
haploid.
PROTEIN SYNTHESIS: Genes code for proteins and proteins (polymer) are chains of amino acids (monomer)
 Step 1 = transcriptions – in nucleus – mRNA complimentary strand of the gene is transcribed (U-A)(C-G)

Step 2 = translation - at the ribosome – codons (3 base pairs) on the mRNA are complimentary paired the
corresponding anti-codons of tRNA that have specific amino-acids attached to them (Codon Chart)
TYPES OF REPRODUCTION
• In ASEXUAL REPRODUCTION, an individual can reproduce without the involvement of another individual of
that species. It is not, however, limited to single cell organisms. Faster and less energy but less diversity
• SEXUAL REPRODUCTION, however, requires the involvement of two individuals of a species, typically one of
each sex.. More diversity but also more energy.
TYPES OF CELL DIVISION - Reproduction: Mitosis vs Meiosis - Before division can occur, the information which
is stored in chromosomes must be DUPLICATED (DNA replication in Interphase) and then SEPARATED
(Mitosis or Mieosis) cleanly between cells.



MUTATIONS or “mistakes” can occur during the replication process or cell division when pieces of the
chromosome breaks off , reattaches or is lost altogether.
Single-celled organisms REPRODUCE by MITOSIS. Multicellular organisms GROW by way of MITOSIS.
MEIOSIS and SEXUAL REPRODUCTION increases genetic variability and chances of survival. MEIOSIS
occurs only in germ cells, which are set aside for the formation of specialized sex cells called GAMETES (i.e.
sperm and egg).
MITOSIS = chromosomes line up along center line and chromatids (identical copies attached in a chromosome)
are separated so that each new cell gets a copy off all of the DNA (all chromosomes) 2N-2N or 1N-1N
MEIOSIS = homologous pairs of chromosomes are separated in the first division (reduce 2N-1N) and then in a
second division chromosomes line up along center line and chromatids are separated.