Download CELLS: Structures and Functions

CELLS: Structures and
Functions
vacuole
 It is a fluid-filled organelle that stores
enzymes and metabolic waste.
 Plant cell vacuoles can be large, centrally
located & filled with water or other liquids.
tonoplast – the membrane
enclosing a vacuole in a
plant cell
plant
cell
tonoplasts
A large plant cell vacuole,
filled with water, produces
turgor pressure & gives
the cell some support.
PLASTIDS
• Plant cells have organelles surrounded by two
membranes and contain DNA.
• Some store starch or fats, while others contain
pigments that absorb visible light.
• Example:
chloroplast
ribosome
• An organelle that organizes the synthesis of
proteins. Ribosomes are numerous in the cell.
• They are attached to the endoplasmic
reticulum, or found unattached in the
cytoplasm.
chloroplast (plant cells only)
It stores sun’s energy in energy-rich
food molecules (chemical energy in
organic compounds) through
photosynthesis. (It is referred to as a
plastid – It’s where carbohydrates are
made)
Plant cells with many chloroplasts
cytoplasm
• The area of the cell between the cell
membrane & the nucleus. The cytoplasm
contains organelles and cytosol.
• Cytosol is a gelatin-like aqueous solution of
dissolved salts, minerals, and organic
compounds.
nucleolus
This is the organelle in which ribosomes are
synthesized and partially assembled before
they pass out of the nucleus
mitochondrion
It is the location of cellular respiration.
It transfers energy from food (organic
compounds) to make high energy
molecules (ATP) for cell use.
nucleus
The nucleus controls most cell
processes and contains stored
hereditary information in DNA; & site of
RNA synthesis.
chromatin
• It appears as granular material visible
in the nucleus.
• It is composed of fine DNA strands and
protein which condenses into
chromosomes for cell division.
• It is part of the cytomembrane system.
• It forms an intracellular highway to transport
molecules throughout the cell.
• It chemically modifies proteins to prepare
them for export, and assembles cell
membrane components.
ALSO: Endoplasmic reticulum synthesizes
steroids, regulates calcium levels in muscle
cells, breaks down toxic substances in liver
cells.
RER – rough endoplasmic reticulum (has
attached ribosomes)
SER – smooth endoplasmic reticulum (has no
ribosomes)
lysosomes
• Lysosomes are the cell’s garbage disposal
system.
• They breakdown the products of ingested
materials.
• They contains enzymes to digest molecules,
old organelles, and foreign substances, such as
bacteria & viruses (rare in plant cells).
microtubules & microfilaments
They provide support, and movement of
organelles in the cell. Major parts of
the cell’s “cytoskeleton.” (Help
maintain cell shape)
Cytoskeleton filaments
microtubules
• Microtubules maintain cell shape & serve
as tracks along which organelles are
moved.
• They separate chromosomes, form
centrioles, and form cilia & flagella.
• Microtubule “9+ 2 ” arrangement in
flagella and cilia = 9 pairs of microtubules
in a circle with 2 single in center.
Microtubule Origination Centers
• There are areas within the cell that can rapidly
form microtubules. These origination centers
occur throughout the cell.
• Centrosomes are microtubule origination centers
that produce the centrioles, as well as the
spindle apparatus for cell division.
Centrioles have 9 + 0 arrangement with none
in center.
Centrioles play a role in animal cell division.
centrioles
centrioles
Cilia & Flagella
microfilaments
• Microfilaments aid cell movement & muscle
cells contraction. They are narrower than
microtubules & form extensive networks in
some cells.
• They also provide a tough, flexible
framework that supports the cell.
(Motor Proteins – force organelles to move along
the microfilaments and microtubles.)
Golgi apparatus
• It processes and packages substances
produced by the cell so they can be exported
from the cell.
• It is part of the “cytomembrane system” &
forms vesicles that eventually fuse with the
plasma membrane.
• It forms
lysosomes.
cytomembrane system
• It consists of ribosomes, endoplasmic reticulum,
vesicles, Golgi apparatus, and the cell membrane.
• It is responsible for moving proteins from their point
of synthesis to the cell exterior.
• 1) Ribosomes, attached to the E.R. makes proteins.
• 2) The proteins are modified in the E.R.
• 3) Vesicles (little sacs) carrying the proteins move from
the E.R. to the Golgi apparatus, & fuse with it.
• 4) The proteins are modified inside the Golgi.
• 5) Vesicles carrying the proteins move from the Golgi to
the cell membrane, and fuse with it.
• 6) The proteins exit the cell in a process called
exocytosis.
Cell Wall (plant cells only)
 It supports and protects a plant cell.
 It is composed of long chains of cellulose.
 Pores in the cell wall allow ions and
molecules to enter & leave cell
Animal cells do not have chloroplasts,
or cell walls. They do have centrioles,
which plant cells lack.
cell membrane
 It controls movement of materials into and out
of the cell (contributes to homeostasis of the
cell).
 It is composed of a phospholipid bilayer,
proteins, carbohydrates & cholesterol.
• The phospholipids are arranged with their
hydrophobic (nonpolar) tails facing each other.
• The hydrophilic (polar) heads are arranged
toward the water in the cytoplasm, or on the
outside of the cell.
phospholipid
Phospholipids in a bilayer
Fluid-Mosaic Model
 The cell membrane consists of a continuous, fluid,
double layer of phospholipids.
 Proteins either are embedded in the bilayer or
associated with either the cytoplasmic (inside the cell) or
extracellular face (toward the outside of the cell).
 Carbohydrates are
linked to the
proteins
(glycoproteins)
lipids (glycolipids)
only on the
extracellular side.
or
Cholesterol, in varying amounts
depending on the cell type, lies within the
membrane serving to stabilize it.
It prevents the fatty acid tails from sticking
together.