EUKARYOTIC CELL
ORGANELLES AND
STRUCTURES
Cytoplasm:
• The cytoplasm is the cellular region
between the nuclear membrane and the
plasma membrane; It consists of a fluid
called cytosol (which contains dissolved
solutes, stores nutrients, secretory products
and pigment granules) and organelles-the
metabolic machinery of the cytoplasm and
the cell. Function: Provides moisture and
nutrition.
Nucleus:
• Function: It is the control center of the cell;
responsible for transmitting genetic
information and providing the instructions
for protein synthesis.
• The nucleus contains chromatin-granular,
threadlike material composed of DNA and
histone proteins both of which make up
genes. When a cell is ready to divide,
chromatin coils, condenses, and becomes
chromosomes.
Nuclear Envelope
• The Nuclear envelope is a double-membrane
structure surrounding the nucleus. It is pierced by
the pores and the outer membrane is continuous
with the cytoplasmic endoplasmic reticulum.
• It functions to separate the nucleoplasm from the
cytoplasm and regulates passage of substances to
and from the nucleus.
• The Nucleolus is a dense, spherical (nonmembrane
bound) body made of ribosomal RNA and
proteins: functions in making ribosomes. A single
nucleus has one or more nucleoli.
Ribosomes:
• Ribosomes are non-membranous organelles.
Function: to make proteins; ribosomes are
free in the cytoplasm or bound to rough ER
(endoplasmic reticulum). Proteins to be
used within the cytosol are produced by the
free - floating ribosomes; proteins to be
inserted into membranes or exported from
the cell are made by the ribosomes attached
to the rough ER.
Endoplasmic reticulum:
• It is a network of canals extending from the
plasma membrane to the nucleus. Function:
to transport proteins out of the cells. Two
types: Rough ER-has ribosomes attached to
it, and functions to attach polysaccharide
groups to proteins as they are made by the
ribosomes to be exported from the cell;
Smooth ER-has no ribosomes attached; and
functions to make lipids and hormones
(steroids) to be exported from the cell, or
sometimes used by that cell.
Golgi apparatus:
• Is a group of flattened sacs arranged like a
stack of bowls; functions to modify and
package proteins and lipids into vesiclessmall, spherically shaped sacs that bud from
the outside surface of the Golgi body. After
modifications are done, these are shipped
outside the cell.
vesicles-membrane bodies with many functionsusually storage or transportation
• Lysosomes: vesicles from a Golgi apparatus that
contains digestive enzymes. Function to break
down food, cellular debris, and foreign invaders
such as bacteria. Not present in plant cells.
• Peroxisomes: sacs in the cytoplasm that contain
powerful oxidase enzymes. Function:to use
molecular oxygen to detoxify harmful substances
by changing it to water. Common in liver and
kidney cells; also in photosynthesizing plant cells.
Mitochondria:
• look like kidney beans or linked sausages;
these are the powerhouse of the cell;
function as sites of aerobic respirationwhere energy in the form of ATP is
obtained from carbohydrates.
• Most numerous in cells having a high
energy requirement(muscle cells, or liver
cells). Each contains an inner membrane
and outer membrane. The inner membrane
has many long folds called cristae-these
enlarge the surface area of the inner
membrane, allowing more space for
chemical reactions to occur during times of
great energy production. The outer
membrane serves as a boundary between
the mitochondrion and the cytosol.
• ****Mitochondria also have their own
DNA-this is unique. New mitochondria can
only arise when existing ones grow and
divide. Theory is mitochondria developed
from prokaryotic cells that lived inside
eukaryotic cells-?????
• Cell Fibers-microtubules, intermediate
filaments, and microfilaments-all function
in making the shape of or in coordinating
the movements of the cytoskeleton-internal
scaffolding of the cell within the cytoplasm.
• Flagella-long, hair-like structure-whips for
movement (are the tails on sperm)
• Cilia-hundreds of tiny, hair-like structureswhip for movement (in mucosa areasbronchial tubes, nasal passages, etc)
• Microvilli-fingerlike extensions of the
plasma membrane used to increase surface
area. (intestines-absorb food).
• Centrioles-two dots that form near nucleus
during cell division-will make a
microtubule spindle in animal cells during
mitosis (located in centrosomes-areas
containing centrioles)
In Plants:
• Chloroplasts-carry out photosynthesis
• Plastids – store nutrients and pigment
molecules
• Cell walls-made of cellulose or chitinprovide support for cell. (found in plants,
fungi, protists, bacteria).
• (Large)Vacuole -membrane bodies usually
used for storage