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Parts of the Cell
Lecture PowerPoint
For CHAPTER 3
Cell Function and Structure
Stuff you need to be able to answer
1. prokaryotic and eukaryotic cells: similarities and differences?
2. Diffusion & osmosis: What’s moving, why, and where’s it going
3. How do antibiotics target bacteria,
4. Names and functions of eukaryotic organelles
1928, Alexander Fleming saw fungus can stop
bacteria from growing.
Wonder drug
Antibiotic (against life)
• chemical that can slow or stop the growth of bacterial
life forms (no harm to humans/animals)
• often naturally produced by living organisms
• For example, penicillin is produced by Penicillium
notatum (bread mold)
Later: how does antibiotic target bacterial cells (will discuss later)
Cells
All living things are made of cells
Eukaryotic cells Resist effects of antibiotics
Have organelles
(mini organs)
in membranes
Be able to identify/label these and know function
Cells
Only prokaryotic cells have
• Their DNA floating in cytoplasm
• No organelles
Only eukaryotic cells have
• A nucleus: organelle holding the DNA
• Many organelles
Many (most???) prokaryotes have cell wall
Cells
Prokaryotic cells: no organelles (especially, no nucleus)
Eukaryotic cells: membrane-bound organelles, including a nucleus
Cells
All cells (both Prokaryotic and eukaryotic) have
• A cell membrane of phospholipids and proteins (sometimes
called “plasma membrane”)
• Cytoplasm: gelatinous aqueous interior. (between nucleus
and plasma membrane)
• Ribosomes: made of RNA and protein, hooks amino acids
together to make a protein
• DNA as a molecule of heredity deoxyribonucleic acid
(be able to spell it)
Nucleus
• Holds most of cell’s
DNA
• Surrounded by the
nuclear envelope
• Double membrane
• Nucleolus - Where
we read DNA and
make RNA
Nucleolus
Dark spot in nucleus
Place where we read DNA and make RNA
Some of that RNA – the mRNA – is a
message with info to make protein
mRNA leaves nucleus through
Nuclear pore 
Endoplasmic Reticulum (ER)
• Network of
membrane-covered
“pipes”
• Proteins and lipids
synthesized here
• Rough ER - has ribosomes
• Smooth ER
Golgi Apparatus
• Stacked membranous discs (often drawn like stack of pancakes squished in the middle)
• Packages and transports proteins
• Cis face and Trans face
Making stuff: A shared job
Nucleus, ER, and Golgi apparatus work together
to produce and transport proteins
Lysosomes
“lyse” means “to break”
• Full of digestive enzymes
• Break down worn-out cell parts or molecules
• Recycle
Cytoskeleton (know all 3)
• Network of protein fibers
• Variety of functions, including cell support, cell movement,
and movement of structures within cells
• Three types of proteins
mitochondria
• Cells power plants
• Extract energy from
food
• Convert energy into a
useful form (ATP)
Glucose  ATP
(like coal  electricity)
Eukaryotic organelles
Chloroplasts
• Plant and algae cells
• Two membranes
• Internal system of
stacked membrane
discs
• Sites of
photosynthesis
– capture and
conversion of
sunlight energy into a
usable form
Central Vacuole
• Water enters
cell & fills
central
vacuoles
• Causes turgor
pressure
•
(more info in next ppt)
Remember: animal and plant cells
Mitochondria: animal and plant cells
Central vacuoles: mostly plant cells (uncommon in animal cells)
Chloroplasts: Plants not animals (unless stolen)
Both have
mitochondria
Origin of eukaryotic cells
Endosymbiosis theory
• Big prokaryotes take in little eukaryotes,
forming eukaryotic organelles
• Mitochondria and chloroplasts evidence
– Double membrane
– Own DNA
– Own ribosomes
– Own histone proteins
like prokaryote
Cell Wall
Cell wall = rigid structure around cell membrane
prokaryotes have walls of peptidoglycans
Many antibiotics attack prokaryote cell walls: more info towards end
Some eukaryotes also have a cell wall
plants = cellulose
fungi = chitin
protist: may or may not have wall
animal: no cell wall
The cell membrane
• Prevents many large molecules, like glucose,
and hydrophilic (charged) substances, like
sodium ions, from crossing
• Allows small uncharged substance to cross
– via diffusion (movement of solutes from high
concentration to low)
The cell membrane
• All cells surrounded by a cell membrane
– a phospholipid bilayer with embedded proteins that
forms the boundary of all cells
– Semipermeable
Hydrophillic head
Hydrophobic tail
The cell membrane
Semipermeable
• Structure is partly hydrophobic and hydrophilic
• In aqueous environment, phospholipids forms a bilayer
– Hydrophilic heads out toward water
– Hydrophobic tails in away from water
Antibiotics: attacking cell wall
Bacterial cell walls are rigid due to peptidoglycan
• a polymer made of sugars and amino acids
• allows bacteria to survive in watery environment
• Penicillin weakens cell wall
• Bacterial cells fills up with water and burst due to osmosis
“Water wants to dilute stuff” – lots more on this below
Some bacteria are resistant
Bacteria cells are either
• Gram-positive
—cell wall with layer of
peptidoglycan that retains
the Gram stain
• Gram-negative
— cell wall layer of
peptidoglycan surrounded by
lipid membrane that does
not retain the Gram stain
— prevents penicillin from
reaching the peptidoglycan
underneath
Another killing method
• Streptomycin: interferes with prokaryotic ribosomes
• Leaves eukaryotic ribosomes unaffected
Antibiotic target prokaryotic cells
Osmosis – “water wants dilute stuff” or “water follows salt”
– The diffusion of water across a semipermeable membrane
from an area of lower-solute concentration to an area of
higher-solute concentration
– Hypotonic vs. hypertonic vs. isotonic
Antibiotics target prokaryotic cells
• Antibiotics can cross prokaryotic cell membrane using
transport proteins
• Bacteria can resist antibiotics using transport proteins
as well
– Some bacteria can pump antibiotics out!!!
Summary
• Antibiotics are chemicals, originally produced by living organisms,
that selectively target and kill bacteria.
• All living organisms are made of cells, and new cells arise from
existing cells.
• Two types of cells, distinguished by their structure: prokaryotic and
eukaryotic.
• All cells are enclosed by a cell membrane, which controls the
passage of molecules between the exterior of the cell and the
cytoplasm.
• Substances cross cell membranes by simple or facilitated diffusion
or by active transport.
• Water crosses cell membranes by osmosis.
• All cells have ribosomes: complexes of RNA and proteins that
synthesize new proteins.
• Eukaryotic cells contain a number of specialized organelles.
Review and Concept
Questions
Concept Quiz
The main difference between active and
passive transport is
A.
Passive transport goes up a concentration gradient.
B.
Active transport goes down a concentration
gradient.
C.
Active transport requires energy.
D.
Passive transport requires energy.
Concept Quiz
__________ involves the ingestion of
specific molecules by the membrane
A. Endocytosis
B. Pinocytosis
C. Exocytosis
D. Receptor-mediated endocytosis
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