Cell Structure
DO NOW: Read over
todays lab!
Prokaryotes
● Simplest and smallest of cells
● First cells (before) and the only organisms on earth 3.5
billion years ago.
● Cannot carry out as many specialized functions due to
size.
Characteristics of a
Prokaryotes
● Lack a nucleus.
● No internal structures that divide the cell into compartments
= free to move
● Genetic material is a single circular molecule of DNA.
● Cell wall is made of polysaccharides connected by short
chains of amino acids.
● Some are surrounded by a capsule (helps cling).
● Many of flagella that enable movement.
● Like a propeller
Eukaryotic Cells
● Evolved about 2.5 billion years ago
● CONTAINS a Nucleus
● Is composed of organelles that carry out specific activities
in the cell.
● Has a cytoskeleton that provides interior framework of an
animal cell.
● Composed of protein fibers
● Some Eukaryotic cells have cilia.
● Hair-like structures used for movement
The Cell Membrane
● Selective permeability – determines what can enter and
leave the cell (like a bouncer)
● Composed of phospholipids
● Made of a phosphate group and 2 fatty acids
● Has a polar head (attracted to water)
● 2 non-polar tails (repelled by water)
Hydrophilic = water loving (polar)
Hydrophobic = Does not like water (non polar)
Cytoskeleton
●A network of fibers throughout the cell’s cytoplasm that
helps the cell maintain its shape and gives support to
the cell.
●Like our own skeleton!
Cytoplasm
●A clear jelly-like fluid that fills the inside of the cell and
surrounds all the internal structures.
CELL ORGANELLES
● Nucleus
● Endoplasmic reticulum
● Vesicle
● Golgi apparatus
● Lysosome
● Mitochondrion
● Chloroplast
● Central vacuole
All have specific
functions!
The Nucleus
Controls the functions of the cell
● Surrounded by a double membrane called the nuclear
envelope
● The nuclear envelope has nuclear pores, to let substances
made in the nucleus out (such as ribosomes)
● Contains the genetic information of the cell in DNA.
● DNA strands are called chromosomes (46)
Nucleolus
● Found in the nucleus
● Forms around specific chromosomal regions.
● Transcribes ribosomal RNA (rRNA) and combine with
proteins to form incomplete ribosomes.
Challenge Question
●Where do you find the DNA or a
eukaryotic cell?
●If prokaryotes do not have a
nucleus, where is their DNA?
Ribosomes
● Locations where proteins are made.
● A ribosome is made of dozens of proteins and RNA
● Some are suspended from the cytosol to help build
new organelles.
Endoplasmic Reticulum - ER
● An extensive system of internal membranes that move
proteins and other substances through the cell.
● Rough ER = Section with attached ribosome
● Looks rough through a microscope
● Helps transport proteins made in the attached ribosomes
● A vesicle pinches off with a completed protein
ER
●Smooth ER = Section that lacks ribosomes
●Looks smooth through a microscope
●Makes lipids and breaks down toxic substances
Challenge Questions
●What do the free ribosomes do?
(don’t think too hard)
●What does the rough ER do?
●What does the smooth ER do?
Golgi Apparatus
● Golgi Apparatus = A set of flattened membrane-bound sacs
that serve as a packaging and distribution center.
● Enzymes inside modify those proteins.
● The modified proteins are put in new vesicles and sent
throughout the cell.
● New vesicles are called lysosomes. They are small
spherical organelles that contains the cell's digestive
enzymes.
Processing of Proteins
1. Proteins are made by ribosomes on the rough ER.
2. Vesicles carry proteins from the rough ER to the Golgi
apparatus.
3. Proteins are modified in the Golgi apparatus and enter
new vesicles.
4. Some vesicles release their proteins outside the cell.
5. Other vesicles remain in the cell and become
lysosomes.
CW
● Write a story explaining your travels through protein
processing. Pretend you are actually in the cell.
● Explain what you are seeing and where you are traveling
to and from.
● Include at least 2 paragraphs (8 complete sentences)
Mitochondria
● Harvests energy to make…. ATP!
● Also contain DNA and ribosomes. DNA is similar to the
circular DNA found in prokaryotic cells.
● Cells that have a high energy requirement, such as muscle
cells, may have thousands of mitochondria.
● Outer membrane is smooth
● Inner membrane is folded = MAX SURFACE AREA
Unique Features of Plant Cells
● Cell Wall - composed of proteins and carbohydrates
● Supports the cell and maintains its shape
● Central Vacuole – large membrane bound sac that takes up
most of the plant cell’s volume.
● Stores water, along with ions, nutrients, and waste.
● Makes cell rigid when full
● Chloroplasts – Uses light energy to make carbohydrates
from CO2 and water.
● Helps power activities of the plant cells
● Contains their own DNA