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Structure and Function of The
CellReference:
Modern BiologyCHAPTER 4
Parts of the Eukaryotic Cell
Modern BiologyChapter 4 - Sect. 2
Pgs. 73 - 83
BIG IDEAS**There is a relationship between a cell’s
function and its structure (organelles)**All living organisms can be sorted into one of
two groups depending on the fundamental structure of their cells.
PROKARYOTE EUKARYOTE
A prokaryote is a single-celled organism,
composed of a prokaryotic cell - One
that lacks a membrane-bound nucleus,
mitochondria, or any other membrane-bound
organelles.Examples: bacteria,
cyanobacteria
A eukaryote is any organism that is
composed of eukaryotic cell(s) – One that contain
a nucleus and other structures enclosed within membranes.
Examples: yeast, paramecium, grass, humans,
pumpkins, apples, frogs, mushrooms, algae, dogs…
2 Basic Types of Cells
Prokaryotic vs. Eukaryotic
Similarities:Both are surrounded by
a:◦ Cell Membrane-surrounds the
cell and controls what passes into and out of the cell
Both contain:Cytoplasm-the area of the cell between the membrane and the nucleus, where the organelles are.DNA
• Prokaryote-has DNA in a region of the cell
• Eukaryote-has DNA in the nucleus
Differences:• Organelles: internal
structures that perform specific functions in the cell– Prokaryote-DO NOT
HAVE membrane - bound organelles
– Eukaryote-HAVE membrane -bound organelles
Summary:
Prokaryotic Cells Eukaryotic Cells
Nucleus NO YES
DNA Location Region of Cell In Nucleus
Cell Membrane Yes Yes
Cytoplasm Yes Yes
Membrane-bound Organelles
NO YES
Check for UnderstandingMake a Venn Diagram to show how prokaryotic and eukaryotic cells are
different and what they have in common.
Parts of Prokaryotic and Eukaryotic Cells
Parts of the Eukaryotic Cell
Just like your body is made up of many organs that work together, the tiny cells
in your body are made up of smaller units that work together.
These smaller units are called
organelles.
Organelles• Organelle- “Little Organ” - cell
part that performs a specific function for the cell– Most are surrounded by a membrane– Each helps to maintain life of the cell– They are specialized - *Organelles are
like the organs of your cells.
CELL OR PLASMA MEMBRANEStructure:Thin, flexible covering around the outside
of the cell.Phospholipid Bilayer:
• mainly made of lipids (fats) and proteins.
CELL OR PLASMA MEMBRANEFunction:• It holds the cell together• It protects the cell, keeping harmful
substances from entering the cell• It controls, or ‘selects’ the movement of
needed materials, such as nutrients, oxygen, and water into the cell and moves wastes out of the cell - “Selectively Permeable”
OTHER:
Often referred to the “fluid mosaic model”.• Phospholipids and proteins move laterally,
or side to side for short distances.
cell membrane animation
CYTOPLASMStructure:• the “gel-like material” between the nucleus and
cell membrane.• Cytosol- gelatin like aqueous fluid that surrounds the
organelles
Function:– Contains various organelles of the cell.
Other: Cytoplasm is the term for the cytosol plus the organelles suspended within the cytosol.
NUCLEUSStructure:• Surrounded by NUCLEAR MEMBRANE• Nuclear pores allow molecules in and out.• CONTAINS the CELL’S GENETIC MATERIAL
(DNA in the form of chromatin).Function:• Control center of the cellOther:• Contains NUCLEOLUS (dark spot) which is
the site of RIBOSOME production.
Nucleus and DNA• DNA is scrunched up as
chromosomes in DIVIDING CELLS.
• DNA is spread out as chromatin in NON-DIVIDING CELLS.
MITOCHONDRION (plural: MITOCHONDRIA)Structure:• Surround by double membrane.
– Outer membrane– Folded Inner membrane – cristae
where chemical reactions occur
FUNCTION:– Site of Cellular Respiration - Transfers energy
from sugar (organic compounds) to– Called the ”Powerhouse” of cell.
MITOCHONDRION (plural: MITOCHONDRIA)Other:• Contains its own DNA.• Endosymbiosis theory• More numerous in cells with high energy
requirements– Example: muscle cells
RIBOSOMESStructure:•Spherical shape•Made of RNA and proteinFUNCTION: • makes proteins for use in the cell (free) or for export
(bound).OTHER:• Can be free in the cytosol or bound to the
surface of Rough Endoplasmic Reticulum.
ENDOPLASMIC RETICULUM (ER)Structure:• Internal network of membranous folded sacs
and tunnels throughout the cytoplasm. (found around the nucleus)
Function:• Intracellular highway that transports
molecules throughout the cellOther:
– Rough ER: ribosomes attached– Smooth ER: no ribosomes attached.
ENDOPLASMIC RETICULUM (ER)ROUGH ER vs. SMOOTH ER
– FUNCTION: ROUGH ER: transporter of proteins to be used inside and outside the cell.
– FUNCTION: SMOOTH ER: involved in the production and storage of lipids (steroids) and key enzymes and ions (Calcium) needed for chemical reactions inside the cell.
GOLGI APPARATUS (BODY)STRUCTURE:• Looks like a stack of flattened sacs.FUNCITON: • Processes, packs and secretes
substances from ER for transport out of cell (vesicles)
Other: Works closely with ER
LYSOSOMEStructure:• Sac – like vesicle• containing digestive enzymes.
FUNCTION:• Digests: food particles, disease-causing
bacteria and viruses, and worn out or broken cell parts.
Other:• Plays a role in apoptosis “programmed cell
death”. Cell suicide for the good of the organism.
CYTOSKELETON (NO MEMBRANE)
STRUCTURE:• Network of long protein strands• All of the microfilaments and microtubules
combine to form the cytoskeleton of the cell.
• FUNCTION:– Help maintain cell size and shape (support). – Aid in movement of cellular materials.
Two Components of the of Cytoskeleton
Microfilaments Microtubules
Structure long, thin, stringy proteins
thick, strong spirals of thousands of subunits
Function Cell support, movement, muscle contractions
Cell support, cell division (movement of chromosomes)
Examples actin Spindle fibers, cilia, flagella
CILIA & FLAGELLA• Made of microtubulesCILIA: short and hair-like• FUNCTION: aid in movement and
protection; move fluid AROUND cells.FLAGELLA: long and whip-like• FUNCTION: aid in movement, protection,
and feeding; move cells through fluid
Organelles – Eukaryotic Animal Cell
Nucleus
Ribosomes
Cytoplasm
Vacuole
Mitochondria
Endoplasmic Reticulum
Cell Membrane
Golgi Body
Lysosomes
1 2
36
5 8
7 9
4
PLANT CELLS(the other Eukaryote!)
Animal cells and plant cells have some similar & different cell
parts.
CELL WALLStructure:• Rigid barrier found OUTSIDE
the cell membrane.• Made of Cellulose - makes plant cells sturdy.
** FYI – Almost all bacteria have cell walls made of sugar and proteins instead of cellulose.
Function:• Provides structure, protection and support.Other:• FOUND ONLY IN PLANT CELLS & BACTERIA
Organelles Found in Plant Cells
VACUOLEStructure:•Fluid-filled sacs
Function:• Storage space for: waste products &
toxins, nutrients, and water.Other:• Huge in plant cells (90% cell)
– small & numerous in animal cells (often called lysosomes)
– NOT in found in prokaryotic cells.
PLASTIDS Structure:• Surrounded by double membrane.• MOST FAMILIAR = CHLOROPLAST!
– Flattened membrane sacs called thylakoids Contain CHLOROPHYLL where photosynthesis happens.
– Gives plants their green color (some other pigments are responsible for the colors of fruits and flowers)
– FOUND ONLY IN PLANT CELLS, and some photosynthetic bacteria.
Function:• Store starch or fats• Contain pigments, absorb light
Plant Cells
Nucleus
Golgi Body
Endoplasmic Reticulum
Ribosomes
Cell Wall
Vacuole Mitochondria
Cytoplasm Cell MembraneChloroplasts
1 2
3 4
5 6
7 8 9 10
Parts of ProkaryotesBacteria are the most
common prokaryotic cell
–Prokaryotic cells do not contain membrane-bound organelles. –They do not have a nucleus, but do contain a single loop of DNA.–Like all eukaryotic cells, bacteria do have a cell membrane which contains the gel-like cytoplasm of the cell.–Prokaryotes do have a cell wall.
Eukaryotes vs. Prokaryotes
Summary:Prokaryotic Cells Eukaryotic Cells
Nucleus NO YES
DNA Location Region of Cell In Nucleus
Cell Membrane Yes Yes
Cytoplasm Yes Yes
Membrane-bound Organelles
No Yes
