Science Summary II Exam I Trimester
1. Biological Molecules
Biological Molecules are molecules that have carbon and some hydrogen atoms within their
skeleton. The basic unit of these is monomers. When two or more monomers join by
dehydration synthesis they form polymers, polymers may divide by hydrolysis.
Types of biological molecules:
A. Carbohydrates:
Basic Unit: Sugar
Types:
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Monosaccharides: Glucose, fructose, deoxyribose and ribose.
Disaccharides: Sucrose, Lactose and Maltose.
Polysaccharides: Starch, Quitin, Glycogen and Cellulose.
Characteristics:
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Main source of energy for many organisms.
Have a lot of –O and –OH groups.
In the cell they decompose to release energy, and bond to other monosaccharides.
Cellulose forms the Cell Wall of plants and Quitin in the mushrooms’.
B. Lipids:
Basic Unit: They don’t have.
Types:
-
Triglycerides: oils and fats Waxes: Beehive.
Phospholipids: Phosphatidylecholine.
Steroids: Cholesterol, testosterone and estrogen.
Characteristics:
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The contain only C, H and O
Phospholipids: water soluble “heads” and not soluble “tails”.
Phospholipids: Main components of cell membrane.
Fats: saturated: solid, unsaturated: liquid
Steroids: Four fusioned carbon rings.
C. Proteins:
Basic Unit: Amino Acid
Types:
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Peptides: keratin, hair, nails and claws.
Polypeptides: hemoglobin.
Enzymes: catalase
Characteristics:
 It has four structural levels
D. Nucleic Acids
Basic unit: Nucleotides
Types:
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Long chain nucleic acids: DNA and RNA
Single nucleotides: ATP (Carries energy), AMP (carries chemical signals in the
cell) NAD+ and FAD carry electrons.
Characteristics:
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DNA: Has the information necessary to build proteins
RNA: duplicates DNA.
The Cell:
The cell theory states three main aspects:
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Every single organism is composed of 1 or more cells
The smallest living organisms are composed of individual cells. Cells are functional
units of multi cellular organisms.
Every cell comes from a preexisting cell.
This theory was proposed by three scientists:
1. Rudolph Ludwig Virchow: “Ominis cellula e cellula” in other words, every cell
comes from another cell.
2. Theodor Shawnn: Discovered that the cell was the basic unit for animals, also
noticed cytoplasm structures.
3. Mathias Jacob Schliden: Discovered that the cell was the basic unit for plant
structures. Stated the importance of the nucleus.
The cells have three main attributes:
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They limit their seize (To exchange nutrients and wastes with the exterior)
They all have the same common characteristics.
They are divided into prokaryotic and eukaryotic
The biggest cell is the Ostrich egg.
Common Characteristics:
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Every cell has a cell membrane: contains the cell and regulates exiting and entering
of substances into the cell.
(Plasma Membrane)
- Every cell contains cytoplasm: the interior space
where organelles are kept. The liquid that resides in here is
called cytosol, and it is composed of water, salt and other
molecules.
- Every cell uses DNA as an inheritance information
map
- Every cell use RNA to duplicate DNA and create
proteins.
- Every cell obtains energy and nutrients from the
environment.
- Every cell uses building blocks to construct organic
molecules.
Two types of cells: Prokaryotic and Eukaryotic
(PROKAROTIC CELL)
The Eukaryotic Cell:

Some eukaryotic cells are supported by a cell wall (Plants, Fungi and some
Protists). This layer consists of three layers: Plasma membrane, secondary and
primary (The secondary only grows on old plants)

The cytoskeleton provides shape, support and movements (organelles and cells) and
cell division (they move chromosomes). It’s divided in microfilaments, intermediate
filaments and microtubes.

Cilia and Flagella emerge from the vassal body. Cilia are the “hairy” structures that
move parallel to the plasma membrane like a swimmer’s arm, flagella is much
bigger and moves the cell entirely. The both give movement to the cell and
movement to substances into the cell.

The nucleus is the most important part of the eukaryotic cell, it’s divided into:
nuclear envelop (allows selective exchange of materials), chromatin (contains DNA
for protein synthesis and the nucleolus (ribosome are found in here, is the “brain” of
the “brain”) * Ribosome: substances that create proteins from amino acids.

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Other characteristics:
Vacuoles store liquids.
Mitochondria extract energy form organic molecules.
Chloroplasts receive energy from the sun and transform it into chemical energy.
Plants used plastids for storage functions.
The main difference between plant cells and animal cells is that plants cells have:
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Cell walls
Chloroplasts
Plastids
Central vacuoles
Centriols
The Prokaryotic Cell:
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Very small
Specialized surface features.
Simple structures in the cytoplasm
Rigid cell wall
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They don’t have a defined nucleus and don’t have many other organelles
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The ones that have flagella can move.
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The common shapes are: helix, rod or sphere.

When bacteria infect organisms, the do it by direct contact. This is possible thanks
to the hot tissue (capsules, slime layers and pili) these are made of polysaccharides.
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They only have one chromosome composed of a long DNA fiber, located in the
nucleoid region. They also have plasmids, located in the cytoplasm, that are DNA
rings.
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Some photosynthetic bacteria have membranes with light capturing proteins and
enzymes that catalyze synthesis of high energetic molecules.
CELL ORGANELLS
A.
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The Cell Wall (found in plants, mushrooms and some protists)
The give support and protection to the cells.
Made of polysaccharides: Quitin and Cellulose.
The primary level is the exterior part, the secondary the middle and the tertiary is
the plasma membrane. They are bonded with a substance called intermediate
lamella.
B.

Cytoskeleton
Protect fiber net inside the cell.
Made of proteins called: microtubules, intermediate filaments and microfilaments.
They give the cell: shape, movement (sperm cells), organelle movement.
Cell division: microtubes separate chromosomes, and help centrioles move.
Organelle movement: Endocytosis: when large particles are engulfed by the plasma
membrane and pull the vesicles into the cell. Exocytosis: vesicles are pulled off the
ER or Golgi apparatus.
C. Cilia and Flagella
- Extensions of the plasma membrane come from the basal bodies. Basal bodies
come from centrioles.
- The use ATP to generate motion.
- They move the cell or create liquid currents around the cell.
- Cilia rows resemble to the arm of the swimmer.
- Flagella move in wave-like motion.
D. Nucleus:
- It’s the main part of eukaryotic cells.
- It is divided into: nuclear envelop, chromatin and nucleolus.
a. Nuclear envelop: consists of a double membrane that has pores that transport
organic and inorganic molecules in and out of the nucleus.
- The nucleus has DNA either in chromosomes (composed of genes, have the code of
proteins) or in chromatin (direct DNA’s reactions with RNA to create proteins).
b. Nucleolus: ribosome are synthesized here, ribosome synthesizes amino acids to
make proteins.
E.
a.
b.
1.
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Membrane systems:
Plasma membrane and other organelles’ membranes.
Nucleus, ER, Golgi apparatus, lysosomes, vesicles and vacuoles.
Plasma membrane: isolates the cell and regulates entering and exciting of
substances into the cell.
The vesicles are transport capsules that carry substances through the cell.
The Endoplasmic Reticulum (ER):
The smooth ER
No ribosome
Has enzymes that eliminate toxicity
Manufactures lipids, like hormones
Synthesis lipids
Stores calcium.
2.
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The rough ER
Produces proteins
For example Insulin
Produces also all the components for new membranes.
c.
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The Golgi apparatus:
It gets proteins form de ER and classifies them.
Modifies certain molecules (FE: proteins into glycoproteins)
They add carbohydrates to proteins.
Packs materials into vesicles and export them
What is the destination of substances produced in the membrane systems?
1. The proteins are expelled by the RER, and then they travel through the Golgi
apparatus and then exported by the plasma membrane by Exocytosis.
2. The digestive proteins that are produces by the RER travel through the Golgi
apparatus and are packed like lysosomes (mix the proteins with food vacuoles and
digest the food into basic nutrients) to be used by the cell itself.
3. Proteins and lipids that are produced in the ER flow through the Golgi apparatus
and enlarge the plasma membrane and the organelle membranes.
d. Vacuoles: Cellular membrane “bags” that contain certain fluids.
- To drain water (contractile vacuoles)
- In plants: they store water, nutrients, they participate in the hydric equilibrium in
the cell, and they provide trugor or trugent in the cytoplasm to keep the cell rigid.
e.
f.
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Mitochondria: rounded, oval or tubular organelle.
Their interior membrane is called cristae.
The intermembrane compartment is held between membranes.
The matrix is found within the interior membrane folds.
(the endosymbiotic hypothesis states that mitochondria evolved form bacteria)
They extract energy form food molecules.
Energy is stored as ATP.
These processes are called anaerobic and aerobic reactions.
Chloroplasts: specialized organelle surrounded by double membrane.
The outer membrane and the outer membrane (stroma)
The membrane empty and interconnected sacks (granum) are located in the stroma.
They are called thylacoides.
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The thylacoides contain chlorophyll and other light capturing pigments that capture
sun light and synthesize sugar from H2O and CO2. (Photosynthesis)
g. Plastids: found only in plants and photosynthetic protists.
- Surrounded by a double membrane
- They store starch, (produced from the synthesis of sugars produced in
Photosynthesis)
- They store molecules from the pigments that give fruits their color.
GOOD LUCK EVERYBODY!