BY1101 Introduction to Molecular and Cellular Biology
Tutorial for module BY1101:
Cells & organelles
Joe Colgan (tcolgan@tcd.ie)
BY1101 Introduction to Molecular and Cellular Biology
Tutorial objectives
• Define and describe major cell groups
• Examine organelles and their functions
• Examine mechanisms of transport in and out
of the cell
BY1101 Introduction to Molecular and Cellular Biology
What is a cell?
Basic structural or functional unit of an organism
Prokaryotic cell
Eukaryotic cell
(Plant)
Eukaryotic cell
(Animal)
Which cell is which and why?
BY1101 Introduction to Molecular and Cellular Biology
Prokaryotic cell
Which organisms have prokaryotic cells?
Prokaryotes: Bacteria and Archaea
Chromosome
Fimbriae/pili
Plasma membrane
Cell wall
Nucleoid
Capsule
Ribosome
Flagella
BY1101 Introduction to Molecular and Cellular Biology
Prokaryotic cell – organelles functions
Name the organelles responsible for each of the following functions:
Function
Propels the cell
Appendages that allow a
bacterium to stick to a surface
Rigid structure that surrounds,
supports, and protects the cell
Acts as a selective barrier,
allowing passage of oxygen,
nutrients, and wastes
Site of protein synthesis
Contains the genes that
control the cell
Organelle
Flagella
Frimbriae/pili
Cell wall
Plasma
membrane
Ribosome
Nucleoid
BY1101 Introduction to Molecular and Cellular Biology
Flagellum
Nuclear envelope
Nucleolus
Chromatin
Nucleus
Animal Eukaryotic cell
Smooth endoplasmic
reticulum
Plasma membrane
Cytoskeleton
Microfilaments
Interm. filaments
Microtubules
Rough endoplasmic
reticulum
Ribosomes
Microvilli
Golgi apparatus
Peroxisome
Mitochondrion
Centrioles
Lysosome
BY1101 Introduction to Molecular and Cellular Biology
Plant eukaryotic cell
Nucleus
Nuclear envelope
Nucleolus
Chromatin
Rough endoplasmic
reticulum
Smooth endoplasmic
reticulum
Golgi apparatus
Ribosomes
Central vacuole
Mitochondrion
Microfilaments
Interm. filaments
Microtubules
Peroxisome
Plasma membrane
Cell wall
Cytoskeleton
Plasmodesmata
Chloroplast
BY1101 Introduction to Molecular and Cellular Biology
Eukaryotic cell – organelles functions
Name the cellular structures responsible for each of the following functions:
Cytoskeleton/Microfilaments
1. Cell support and movement
Rough endoplasmic reticulum
2. Synthesis of secretory proteins and membranes
3. Lipid synthesis, detoxification, and calcium storage
Smooth endoplasmic reticulum
4. Modifies, stores, and repackages products of the ER, mostly for secretion Golgi apparatus
5. Protein synthesis
6. Support the cytoplasm
7. Carries out cellular respiration
Ribosomes
Cytoskeleton
Mitochondrion
8. Selective barrier, allowing passage of oxygen, nutrients, and wastes Plasma membrane
9. Break down toxins in the cell-detoxify
Peroxisome
10. Stores the cell's DNA and coordinates the cell's activities
Nucleus
11. Serves as tracks along which other organelles can move
Microtubules
12. Processes and packages proteins after their synthesis
Golgi apparatus
BY1101 Introduction to Molecular and Cellular Biology
PLANT Eukaryotic cell – organelles functions
Name the 4 structures that are only present in plant eukaryotic cells?
Central vacuole
Chloroplast
Cell wall
Plasmodesmata
Match the function to the correspondent structure:
a. Connect the cytoplasmic fluid of one cell to neighbouring plant cells Plasmodesmata
b. Storage, waste disposal, protection and growth
c. Carries out photosynthesis / where chlorophyll traps solar energy
d. Maintain cell shape and protects from mechanical stress
Central vacuole
Chloroplast
Cell wall
BY1101 Introduction to Molecular and Cellular Biology
ANIMAL Eukaryotic cell – organelles functions
Name the 2 structures that are only present in animal eukaryotic cells?
Centrioles
Lysosome
Match the function to the correspondent structure:
a. Important in breaking down food and recycling
Lysosome
b. Compression girders of the cytoskeleton
Centrioles
BY1101 Introduction to Molecular and Cellular Biology
Tour of the cell
BY1101 Introduction to Molecular and Cellular Biology
Nucleus
Function: The “brains” of the cell. The nucleus directs cell activities and contains genetic
material called chromosomes made of DNA. Storage, replication and
transcription of DNA.
Match the function to the correspondent structure:
1. Allows ribosomal subunits and mRNA transcribed off genes in the DNA to leave the
nucleus, enter the cytoplasm, and participate in protein synthesis
Nuclear pores
2. Involved in the assembly of ribosomal subunits
3. Separates nucleus from the cytoplasm
4. DNA and proteins that make up the chromosomes
Nucleolus
Nuclear envelope
Chromatin
BY1101 Introduction to Molecular and Cellular Biology
Ribosomes
What is the function of the ribosomes?
Function: Main sites of protein synthesis
Appear in two cytoplasmic locales (i.e. Locations)
Free ribosomes
Suspended in the cytosol
Bound ribosomes
Bound to nuclear envelope
or endoplasmic reticulum
Proteins remain in the
cytosol
Proteins inserted in
membranes, packed into
specialised organelles or
exported (secreted)
BY1101 Introduction to Molecular and Cellular Biology
Endoplasmic reticulum (ER)
Function: Biosynthesis of a number of macromolecules
What are the two sections?
Smooth ER
Portion of the ER free of ribosomes
Roles:
Synthesis of lipids
Drug detoxification
Calcium storage
Smooth ER Cisternae Lumen
Rough ER
Portion of ER studded with ribosomes
Roles:
Site of secretory proteins
Membrane proteins
Rough ER
Nucleus
Ribosomes
BY1101 Introduction to Molecular and Cellular Biology
Golgi apparatus
What is the function of the golgi apparatus?
Function: Processes and packages proteins after their synthesis
BY1101 Introduction to Molecular and Cellular Biology
Lysosome
What is the function of the lysosome?
Function: Degradation of host and foreign macromolecules into
individual monomers
BY1101 Introduction to Molecular and Cellular Biology
Endomembrane
RER
Golgi
apparatus
1. A secretory protein is synthesized
inside the RER and migrates through
it, and exits inside a vesicle
2. The transport vesicle moves
through the cytoplasm to the Golgi
apparatus
BY1101 Introduction to Molecular and Cellular Biology
Endomembrane
RER
Golgi
apparatus
3. The Golgi modifies the protein as
it moves from cis face to trans face
4. The protein is dispatched from the
Golgi in a transport vesicle that then
fuses with the plasma membrane,
releasing the protein to the outside
of the cell
BY1101 Introduction to Molecular and Cellular Biology
What are the powerhouses of the cell?
BY1101 Introduction to Molecular and Cellular Biology
Mitochondria
Function: Conversion of oxygen and nutrients into adenosine triphosphate (ATP)
BY1101 Introduction to Molecular and Cellular Biology
Chloroplast
•Chloroplast contains thylakoid vesicles
•Thylakoid vesicles are stacked together to
form structures known as grana
• Thylakoids contain chlorophyll and are the
site of photosynthesis
• Soluble matter (stroma) fixes carbon dioxide
BY1101 Introduction to Molecular and Cellular Biology
Plasma membrane
Function: Selective barrier, allowing passage of oxygen, nutrients, and wastes
Extracellular matrix
Carbohydrate
Glycoprotein
Glycolipid
Phospholipids
Cholesterol
Cytoskeleton
Extracellular matrix
Protein
BY1101 Introduction to Molecular and Cellular Biology
Selective permeability
1. Hydrophobic interior of the bilayer
2. Hydrophobic molecules (soluble in
lipids) can move through
3. Certain molecules, such as hydrophilic
molecules or ions, move slowly through
or cannot pass at all.
How do they get through?
BY1101 Introduction to Molecular and Cellular Biology
Transport proteins
Specific membrane transport proteins in the plasma membrane form a
channel through which water molecules of a specific solute can pass
BY1101 Introduction to Molecular and Cellular Biology
Transport across the membrane
What are the two types of transport
Passive transport
Active transport
BY1101 Introduction to Molecular and Cellular Biology
Diffusion
What is diffusion?
Tendency for particles of any kind to move from where they are more
concentrated to less concentrated
Molecules are also said to move along their concentration gradient.
What is the concentration gradient?
A region along which the density of a chemical substance increases or decreases
BY1101 Introduction to Molecular and Cellular Biology
Facilitated diffusion
What is facilitated diffusion?
Spontaneous passage of molecules and ions, bound to specific transport proteins,
across a biological membrane down their concentration gradients
BY1101 Introduction to Molecular and Cellular Biology
Active transport
Active transport – Requires ATP input
1. Cells need to expel sodium and intake
potassium
2. Sodium ions bind to the transport protein.
3. ATP transfers a phosphate group that
changes the shape of the protein, the
sodium ions are pushed across the
membrane and released
BY1101 Introduction to Molecular and Cellular Biology
Active transport
4. Potassium ions now bind to the protein
and the phosphate group is released.
5. The release of the phosphate group
causes the protein to revert to its original
shape, releasing the potassium ions into
the cell. The process can be repeated.
BY1101 Introduction to Molecular and Cellular Biology
2 types of exocytosis
Requires a sorting signal (clathrin coat) and
an increase in intracellular calcium
BY1101 Introduction to Molecular and Cellular Biology
3 types of endocytosis – uptake material into cell
Large particles
Cell changes shape
e.g. bacteria
“Cellular drinking”
Dissolved in water
Invagination
Small particles
Receptor-ligand interaction
e.g. Metabolism of cholesterol
BY1101 Introduction to Molecular and Cellular Biology
Past paper questions
Exam 2010
BY1101 Introduction to Molecular and Cellular Biology
Questions
(tcolgan@tcd.ie)
Further reading:
Campbell
Chapter 6: Tour of the cell
Chapter 7: Membrane structure and function