Cells
Cells
3 Major Parts of Cell
Plasma Membrane  controls passage of materials in/out of cell
Nuclear Region  Controls cell’s activities; contains DNA & RNA
Cytoplasm  Organelles and cytosol
Plasma Membrane
Nucleus
How Big is a Cell?
How Big is a Cell?
Not big (diameter = 0.000008in)
20,000 bacterial cells = 1 cm
Why Are Cells So Small?
High surface to Volume ratio!!
Greater the SURFACE, more stuff gets in and out of cell
Greater the VOLUME, less stuff gets in or out; cell starves or is
poisoned
Characteristics of Cells
Size
Size varies
Bacteria cell  small
Nerve cells large
Spinal Neuron-Over 3
feet long
Sperm Cell- 25 Micrometers
Internal Organization & Types of Cells
Each cell contains miniature organs called organelles
Each organelle performs specific functions for the cell
Eukaryotic Cells  Cells with a nucleus and outer cell membrane
which allows molecules to pass in and out
Prokaryotic Cells  Cells without a nucleus or other organelles
Organization of Cells
Tissue Groups of cells performing the same task
Exp. Nerve Tissue  transmits nerve impulses
Epithelial Tissue  protective outer layer
Organ  Groups of tissues performing the same task
Exp. Heart  Circulate blood through body
System  Group of organs working together
Exp. Circulatory System
Digestive system
Organism  Groups of systems working together
Plant & Animal Cell Organelles
•Cytoplasm All the area between the cell membrane and the nucleus and
contains all of the organelles within the cell
•Ribosomes  Make proteins from AA; found on ER or in cytosol
•Rough ER  Makes proteins and transports them to other parts of the cell via
vesicles (little packages)
•Smooth ER  transports proteins
•Golgi Apparatus  Found close to ER. Takes proteins from ER and modifies
them to make them work; then sends them on their way (mailroom of the cell)
•Mitochondrion  Powerhouse of the cell. Takes in food; Converts it to ATP,
which is broken down for energy. Some cells have more mitochondria than
others
•Cristae  folds in the inner membrane of mitochondria to increase surface
area
•Nucleus  Controls and coordinates cell’s activities. Contains chromatin
(DNA). DNA converted to RNA and stored in nucleolus. RNA sent out to cell
as a messenger
•Surrounded by nuclear envelope
•Nuclear pores allow RNA to leave nucleus
Plant & Animal Cell Organelles
•Cytoskeleton  Scaffolding that gives cell shape
•Microfilaments  Used for muscle contraction
•Microtubules  Thicker,move organelles
•Cilia and Flagella  Help some cells move around
•Lining of respiratory tract
•Lysosomes  Contain Digestive Enzymes; breaks down glucose; can
rupture and kill cell
•Nuclear Membrane Surrounds genetic material
•CentriolesSet of microtubules that move chromosomes during
mitosis
•Plasma Membrane  Selective Transport of molecules and
communication
Pictures of Cell Organelles
• You already have this information in
your notes!
• Do not write this down!
Cytoplasm
• All of the area between the cell
membrane and the nucleus
• Contains all of the organelles within the
cell.
Ribosomes
• Make proteins from
amino acids (AA);
• Found on ER or in
cytosol.
Rough Endoplasmic
Reticulum(ER)
• Makes proteins and
transports them to
other parts of the
cells via vesicles
(little packages).
Smooth Endoplasmic Reticulum
• Transports proteins
Golgi Apparatus
• Found close to ER.
• Takes proteins from
ER and modifies
them to make them
work; then sends
them on their way
(mailroom of the
cell).
Mitochondrion
• Powerhouse of the
cell.
• Takes in food
(glucose) and
converts it to ATP,
which is broken
down for energy
• Some cells have
more mitochondrion
than others.
Cristae
• Folds in the inner
membrane of the
mitochondria to
increase the surface
area
Nucleus
• Controls and
coordinates cell
activities. Contains
chromatin (DNA).
• DNA converted to
RNA and stored in
nucleolus. RNA
sent out to cell as a
messenger.
Nucleus
• Surrounded by
nuclear envelope.
• Nuclear pores allow
RNA to leave
nucleus.
Cytoskeleton
• Scaffolding that gives cell
shape.
– Microfilaments -used for
cell movement
– Microtubules -thicker,
used for support
Cilia and Flagella
• Help some cells
move around
• Some found in the
lining of respiratory
tract.
Lysosomes
• Contain digestive
enzymes
• Breaks down
glucose
• Can rupture and kill
cell.
Nuclear Membrane
• Surrounds genetic
material
Centrioles
• Set of microtubules
that move
chomosomes during
mitosis
Organelles only in Plant Cells
• Cell Wall
Protects Cell and
gives cell shape
• Vacuoles
Storage for food,
water, gives plant
cells shape
• Chloroplasts 
Found only in plant
cells. Used to trap
the sun’s energy
Structure of Plasma Membrane
•
•
•
•
Selectively Permeable  allows
some molecules in; keeps
others out
Phospholipid Bilayer Polar
heads on outside and inside of
cell; nonpolar tails on inside of
membrane
Polar = Hydrophilic = water
loving
Nonpolar = hydrophobic = water
hating
Why is there this arrangement of lipids?
Cytoplasm and outside of cell is watery
Molecules on the Plasma Membrane
• Carbohydrates  Act as receptors; molecules attach to cell; tell it
what to do
• Cholesterol  Gives membrane shape; rigidity
• Receptor Proteins  bind hormones & other substances coming in
from outside the cell
• Recognition Proteins  proteins on membrane that are used for
recognition by extra-cellular substances
• Adhesion Proteins  help cells of a certain type stick together to
form tissues
Protein Receptors
coming out of
plasma membrane
What gets in and out of the cell
membrane?
How do some substances pass through the
membrane while others stay out?
Materials moves across the membrane in two
ways
1. Passive Transport
2. Active Transport
Passive Transport
•
•
Diffusion  movement of molecules from high
to low concentration
Oxygen, CO2, fat soluble molecules, and water
pass through the membrane by diffusion
Active Transport
Active Transport  Using energy to transport large molecules into the
cell against their concentration gradients
1. Cell Membrane Pumps  carrier proteins pump ions against their
concentration gradient
2. Endocytosis  Engulfing of large particles or liquids by plasma
membrane
Cells take in cholesterol by endocytosis from bloodstream
Pinocytosis  Endocytosis of liquid
3. Exocytosis  vesicle contents expelled by cell
Proteins are transported by exocytosis
Exocytosis Animation
Endocytosis Animation
Osmosis
•
Osmosis  diffusion of water
Isotonic Solution Cells are at equilibrium; no
NET movement of water
Hypertonic solution  Cell is in a solution that
has lots of salts or other ions in it; water
rushes out of the cell and the cell shrinks
Hypotonic solution Cell is in a solution that has
little or no salts or other ions in it; water
rushes into the cell and the cell swells
Tonicity in Red Blood Cells