CELLS
Structures and Functions
Basic Parts of All Cells
1. Plasma membrane – barrier between in and
outside of cell
2. Cytoplasm – region inside plasma membrane
•
Cytosol – includes molecules and small particles but
not organelles
3. Genetic material
4. Ribosomes
Organelles!
Eukaryotic Cell
Nucleus
The Nucleus
1. Most obvious structure (5μm)
2. Most eukaryotic cells contain a nucleus
3. Function:
•
•
Controls most functions of cell
Houses and protects genetic information
4. Structure:
•
•
•
Nuclear envelope – double membrane layer contains
genetic contents; porous – materials enter and exit
Nucleoplasm – jelly like fluid filling nucleus
Nucleolus – dense area where ribosomes are made
5. Processes:
• Cell Division

When cell is not dividing - DNA exists as
chromatin: long, thin structures
When cell is about to divide - DNA
condenses to form chromosomes:
structures made of DNA and protein
• Transcription – DNA converted to RNA in the
nucleus

Chromatin
Cell Division
Chromosome
Mitochondria
Mitochondria
1. Size: 1-10 μm long
2. Function:
• Transfer energy from organic molecules to
adenosine triphosphate (ATP) – powers most
cellular reactions
3. Structure: inner & outer membrane
• Outer – separates mitochondria from cytosol
• Inner – many folds (cristae) that capture and
store energy
• Mitochondrial DNA – have own DNA
• THEORY: mitochondria originated from
prokaryotic cells
4. Processes:
• Cellular respiration – enzymes in matrix aid
in formation of ATP by extracting energy
from food sources
Ribosomes
Ribosomes
1. small, spherical (< 25 nanometers)
2. Function:
• Build proteins
• Free ribosomes – make proteins used in cytosol
(Ex: enzyme)
• Bound ribosomes – make proteins used in
membranes, packaging, and elsewhere in body
3. Structure:
• Manufactured partly in nucleolus (protein &
RNA), completed in cytoplasm
• Have small and large subunit
Endoplasmic
Reticulum
Endoplasmic Reticulum (ER)
1.
2.
3.
System of cisternae - membranous tubes & sacs
Continuous with nuclear membrane
Function – moves molecules from one part of the cell to
another
4. Structure – Rough and Smooth
1. Rough ER – covered with ribosomes; involved in making
proteins
a. Secretory proteins – secreted in vesicles (Ex: digestive
enzymes)
b. Membrane proteins – inserted in membranes
2. Smooth ER – no ribosomes; builds lipids, produces steroid
hormones, detoxifies drugs and poisons
Golgi Apparatus
Golgi Apparatus
1.
2.
System of cisternae stacked up
Function:
a. Manufacturing, warehousing, sorting, shipping
b. Work with nearby vesicles coming from ER – vesicle contents
modified, given “address label (carbohydrate label),”
transported to other parts of cell
3. Structure:
a. Distinct polarity – membranes on opposite ends have different
thickness & molecular composition
b. Two poles:
1. Cis (same side) – receives materials from ER
2. Trans (opposing side) – vesicles bud off & are
transported/exported
Vesicles
1. Small, spherical shaped sacs
2. Function:
a. Migrate to and merge with cell membrane
b. Release contents outside of cell
3. Structure:
a. Single membrane
b. Different types (lysosomes, peroxisomes)
Lysosomes
1. Structure – bud from Golgi, contain digestive
enzymes – each vesicle is specific!
2. Function – Break down macromolecules
(proteins, carbohydrates, nucleic acids)
3. Processes:
1. Autophagy – Digestion of worn-out organelles
2. Autolysis – Digestion of damaged or extra cells
when time for cell to die
3. Phagocytosis – Cell eating
4. Receptor-mediated endocytosis
Vesicles
Peroxisomes
1. NOT produced in Golgi, contain different
enzymes, such as Catalase
2. Enzymes involved in reactions
3. Different types: Ex: Detoxify alcohol and other
drugs
4. Break down fatty acids
Vacuole
1. Membrane bound storage structures, contains
fluid
2. Types:
– Food – stores nutrients
– Contractile – contract, dispose of excess water
– Plant central vacuole much larger than animal
Vacuoles
Centriole
Centrioles
1. Animal cells ONLY!
2. Organize cell structure during division
3. 2 short cylinders of microtubules
Part of cytoskeleton
Cytoskeleton
• Provides shape and support
• 3 structural elements
– Microfilaments (Actin)- 2 strands intertwined; POLAR – can
be used in cell movement, muscle contraction, cell division
– Intermediate fibers – NONPOLAR - anchor nucleus and other
organelles in place, maintain shape
– Microtubules – hollow tubes made to maintain cell shape, hold
organelles in place, POLAR – used in movement of
chromosomes during division & organelles (like a railroad
track) via the use of kinesins
Plastidfound in plants
and algae.
Contain
pigments used
in
photosynthesis
Amyloplast- plant specific, no pigment.
Function: synthesis and storage of starch
Chromoplast– responsible for
carotene(orange), xanthophylls (yellow)
and red pigments.