Homework 1: Organelle Composition and Function
membrane: The plasma membrane serves as a barrier between the interior of the
cell and the exterior environment. It is made up of half lipids and half
The nucleus is the main part of the eukaryotic cell that organizes genetic
material, replicates DNA, and processes pre-mRNA. It contains chromatin, RNAs,
and nuclear proteins. The nucleus is the overall brain of the cell, and
controls what happens in the cell.
The nucleolus is the site where rRNA genes are transcribed and ribosomal
subunits are assembled. It is the largest structure within the nucleus.
A chromosome contains a linear molecule of DNA. The DNA is tightly packed into
RNA, also called ribonucleic acid, is a polymer made up of covalently linked
ribonucleotide monomers. It takes what the DNA has stored for information and
carries out the instructions. There are three roles of RNA including,
messenger, transfer, and ribosomal. Unlike DNA it is a single stranded
DNA, also called deoxyribonucleic acid, is the regulatory region of the
chromosomes. It stores hereditary information in the cell and is what allows
the information to go to offspring. It stores information for protein synthesis.
The ribosome is composed of RNA and proteins that control protein synthesis. Within
the ribosome the small ribosomal subunit reads RNA and the large subunit forms
polypeptide chains by joining amino acids.
endoplasmic reticulum: Part of the endoplasmic reticulum that does not have
ribosomes. It is involved in lipid metabolism and the synthesis of
phospholipids and cholesterol.
endoplasmic reticulum: Part of the endoplasmic reticulum that is covered in ribosomes
on the outer surface. It is involved in protein processing.
apparatus: The Golgi apparatus is the factory where proteins received from the
endoplasmic reticulum are processed and sorted for transport to lysosomes, the
plasma membrane, or secretion. The Golgi has flattened membrane-enclosed sacs
and associated vesicles.
Lysosomes are membrane-enclosed organelles containing enzymes that can break
down biological polymers including nucleic acids, proteins, carbohydrates, and
lipids. They serve as the digestive system of the cell by degrading material
from outside the cell and digesting unimportant parts of the internal cell.
Peroxisomes are membrane-enclosed organelles that have enzymes that are
involved with metabolic reactions including energy metabolism. They are similar
to lysosomes, but they are assembled from proteins that are synthesized on free
ribosomes into complete polypeptide chains that are imported into peroxisomes.
During endocytosis the material being internalized is surrounded by plasma
membrane which forms inside the cell as a vesicle. Vesicles are the carrying
mechanism in the cell.
The mitochondria provide energy for the cell by breaking down carbohydrates and
fatty acids and converting it to ATP. It is surrounded by a double-membrane
system which results in folds in the inner membrane. It involves proteins.
Microfilaments are thin, flexible fibers containing actin. They are abundant
beneath the plasma membrane where they provide structure and allow movement for
Microtubules are involved in cell movement, the intracellular transport of
organelles, and separation of chromosomes during mitosis. They are rigid hollow
rods composed of polymerized tubulin.
filament: Intermediate filaments are part of the cytoskeleton that plays a
structural role by giving mechanical strength to the cells. They are composed
of different proteins including keratin, vimentin, desmin, nestin, and lamins.
The cytoplasm is the part of the cell excluding the nucleus which includes the
cytosol and the cell organelles. It is about 80% water and is usually colorless.
It is what allows transport of different nutrient in the cell.
The centriole is the cylinder structure with nine triplets of microtubules in
the centrosomes of cells. They occur in pairs and are involved in the
development of spindle fibers in cell division.