BY1101 Introduction to Molecular and Cellular Biology

1. BY1101 Introduction to Molecular and Cellular Biology Tutorial for module BY1101: Cells & organelles Joe Colgan (tcolgan@tcd.ie)

2. 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

3. 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?

4. BY1101 Introduction to Molecular and Cellular Biology Prokaryotic cell Which organisms have prokaryotic cells? Prokaryotes: Bacteria and Archaea Fimbriae/pili Chromosome Plasma membrane Cell wall Capsule Nucleoid Ribosome Flagella

5. BY1101 Introduction to Molecular and Cellular Biology Prokaryotic cell – organelles functions Name the organelles responsible for each of the following functions: Function Organelle Propels the cell Flagella Appendages that allow a bacterium to stick to a surface Frimbriae/pili Rigid structure that surrounds, supports, and protects the cell Cell wall Acts as a selective barrier, allowing passage of oxygen, nutrients, and wastes Plasma membrane Site of protein synthesis Ribosome Contains the genes that control the cell Nucleoid

6. BY1101 Introduction to Molecular and Cellular Biology Animal Eukaryotic cell Nuclear envelope Nucleolus Chromatin Flagellum Nucleus Smooth endoplasmic reticulum Plasma membrane Cytoskeleton Microfilaments Interm. filaments Microtubules Rough endoplasmic reticulum Ribosomes Microvilli Golgi apparatus Peroxisome Mitochondrion Centrioles Lysosome

7. BY1101 Introduction to Molecular and Cellular Biology Plant eukaryotic cell Nuclear envelope Nucleolus Chromatin Rough endoplasmic reticulum Nucleus Smooth endoplasmic reticulum Golgi apparatus Ribosomes Central vacuole Mitochondrion Microfilaments Interm. filaments Microtubules Peroxisome Plasma membrane Cytoskeleton Chloroplast Cell wall Plasmodesmata

8. BY1101 Introduction to Molecular and Cellular Biology Eukaryotic cell – organelles functions Name the cellular structures responsible for each of the following functions: Cell support and movement Synthesis of secretory proteins and membranes 3. Lipid synthesis, detoxification, and calcium storage Modifies, stores, and repackages products of the ER, mostly for secretion Protein synthesis 6. Support the cytoplasm 7. Carries out cellular respiration Selective barrier, allowing passage of oxygen, nutrients, and wastes Break down toxins in the cell-detoxify 10. Stores the cell's DNA and coordinates the cell's activities 11. Serves as tracks along which other organelles can move 12. Processes and packages proteins after their synthesis Cytoskeleton/Microfilaments Rough endoplasmic reticulum Smooth endoplasmic reticulum Golgi apparatus Ribosomes Cytoskeleton Mitochondrion Plasma membrane Peroxisome Nucleus Microtubules Golgi apparatus

9. BY1101 Introduction to Molecular and Cellular Biology PLANT Eukaryotic cell – organelles functions Name the 4 structures that are only present in plant eukaryotic cells? Chloroplast Central vacuole Cell wall Plasmodesmata Match the function to the correspondent structure: a. Connect the cytoplasmic fluid of one cell to neighbouring plant cells 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 Plasmodesmata Central vacuole Chloroplast Cell wall

10. BY1101 Introduction to Molecular and Cellular Biology ANIMAL Eukaryotic cell – organelles functions Name the 2 structuresthat are only present in animal eukaryotic cells? Centrioles Lysosome Match the function to the correspondent structure: a. Important in breaking down food and recycling b. Compression girders of the cytoskeleton Lysosome Centrioles

11. BY1101 Introduction to Molecular and Cellular Biology Tour of the cell

12. 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 2. Involved in the assembly of ribosomal subunits 3. Separates nucleus from the cytoplasm 4. DNA and proteins that make up the chromosomes Nuclear pores Nucleolus Nuclear envelope Chromatin

13. 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 inserted in membranes, packed into specialised organelles or exported (secreted) Proteins remain in the cytosol

14. BY1101 Introduction to Molecular and Cellular Biology Endoplasmic reticulum (ER) Function: Biosynthesis of a number of macromolecules What are the two sections? Rough ER Portion of ER studded with ribosomes Roles: Site of secretory proteins Membrane proteins Smooth ER Portion of the ER free of ribosomes Roles: Synthesis of lipids Drug detoxification Calcium storage Lumen Smooth ER Cisternae Rough ER Nucleus Ribosomes

15. 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

16. 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

17. BY1101 Introduction to Molecular and Cellular Biology Endomembrane RER Golgi apparatus 2. The transport vesicle moves through the cytoplasm to the Golgi apparatus 1. A secretory protein is synthesized inside the RER and migrates through it, and exits inside a vesicle

18. BY1101 Introduction to Molecular and Cellular Biology Endomembrane RER Golgi apparatus 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 3. The Golgi modifies the protein as it moves from cis face to trans face

19. BY1101 Introduction to Molecular and Cellular Biology What are the powerhouses of the cell?

20. BY1101 Introduction to Molecular and Cellular Biology Mitochondria Function: Conversion of oxygen and nutrients into adenosine triphosphate (ATP)

21. 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

22. BY1101 Introduction to Molecular and Cellular Biology Plasma membrane Function: Selective barrier, allowing passage of oxygen, nutrients, and wastes Extracellular matrix Carbohydrate Glycolipid Glycoprotein Phospholipids Cholesterol Cytoskeleton Extracellular matrix Protein

23. BY1101 Introduction to Molecular and Cellular Biology Selective permeability Hydrophobic interior of the bilayer Hydrophobic molecules (soluble in lipids) can move through Certain molecules, such as hydrophilic molecules or ions, move slowly through or cannot pass at all. How do they get through?

24. 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

25. BY1101 Introduction to Molecular and Cellular Biology Transport across the membrane What are the two types of transport Passive transport Active transport

26. 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

27. 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

28. BY1101 Introduction to Molecular and Cellular Biology Active transport Active transport – Requires ATP input Cells need to expel sodium and intake potassium Sodium ions bind to the transport protein. ATP transfers a phosphate group that changes the shape of the protein, the sodium ions are pushed across the membrane and released

29. 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.

30. BY1101 Introduction to Molecular and Cellular Biology 2 types of exocytosis Requires a sorting signal (clathrin coat) and an increase in intracellular calcium

31. BY1101 Introduction to Molecular and Cellular Biology 3 types of endocytosis – uptake material into cell “Cellular drinking” Dissolved in water Invagination Large particles Cell changes shape e.g. bacteria Small particles Receptor-ligand interaction e.g. Metabolism of cholesterol

32. BY1101 Introduction to Molecular and Cellular Biology Past paper questions Exam 2010

33. 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