Lecture 6 CSF Intro to the Cell 2024 PDF

Lecture 6: Cell Structure & Function - Introduction We have ~ 37 trillion cells – thats ~13,000 reactions per cell per second! https://youtu.be/gFuEo2ccTPA Questions? before/after lectures, Piazza, email [email protected] or call by 106-111d My 107 wish list for all of you, have you: familiarise...

Lecture 6: Cell Structure & Function - Introduction We have ~ 37 trillion cells – thats ~13,000 reactions per cell per second! https://youtu.be/gFuEo2ccTPA Questions? before/after lectures, Piazza, email [email protected] or call by 106-111d My 107 wish list for all of you, have you: familiarised yourself with our canvas pages and resources? checked when 107 assessments are due, including the test? kept up to date with lectures for Cells & Tissues? developed a study approach for yourself? completed the Cells & Tissues Lecture quiz? DUE WEDNESDAY completed the Lab health and safety quiz (prelab 1) accessed Peerwise? Problems with any of this? – please just ask me (or ask on Piazza) https://canvas.auckland.ac.nz/courses/103366/pages/need-some-study-advice Lecture 6: Cell Structure & Function - Introduction Lecture 6: Cell Structure & function – Introduction Lecture 7: Harvesting Chemical Energy Lecture 8: How Cells Communicate Lecture 9: From Gene to Protein Lecture 10: Cell Division Lecture 11: Mutations and Cancer Todays learning Objectives: Lecture 12: Tutorial At the end of todays lecture, you should be able to describe: 1. the three main parts of the cell: the plasma membrane, nucleus and cytoplasm. 2. the structure and function of the plasma membrane, and the functions of membrane proteins. 3. the structure and function of the cell’s major organelle systems. 4. the structure and function of DNA, including the nucleosome, chromatin and chromosomes. 5. the structure and function of the cytoskeletal system. What is examinable for this topic? Examinable content for the CSF section is from all sources: CSF lecture slides lecture guide what is said in lectures –ie. in the provided recording (not the textbook readings – but please use them, if you need clarification) CSF questions will be a mixture of types. Be guided by the lecture objectives CSF questions may also include questions including details from C&T and Special Topics section slides. Linking knowledge across topics is important! Cell Theory 1. All living organisms are composed of one or more cells 2. The cell is the basic unit of structure and organisation 3. All cells arise only from pre-existing cells Universal similarities between cells: 1. DNA as the heritable material, RNA as a messenger and proteins as the workers 2. Major cellular organelles - functions and arrangements within the cell 3. ATP as an energy source The Central Dogma DNA RNA PROTEIN Prokaryote cell versus eukaryote cell Both have: Plasma membrane, cytosol, DNA, RNA, protein and ribosomes Eukaryotic cells have membrane-bound organelles and are much larger Prokaryote cells lack a membrane-bound nucleus Q: what are we? Campbell Biology 11th Fig 1.4 Objective One Cytoplasm The cytoplasm is everything inside the plasma membrane including the organelles, but not including the nucleus The fluid portion of the cytoplasm is the cytosol: - water plus dissolved and suspended substances (eg. ions, ATP, proteins, lipids) Major organelles include: Nucleus Endoplasmic Reticulum (smooth and rough) Golgi apparatus Lysosomes Mitochondria Ribosomes the endomembrane system (along with plasma membrane, they work together to package, label and ship molecules) Objectives 1&3 Cellular Organelles homework Q: can you draw a generalised cell? Remember, cells don’t actually look like this! The cell Objective Two Plasma membrane The plasma membrane is a selectively permeable barrier controlling the passage of substances in and out of the cell A human keratinocyte (HaCaT) showing the plasma membrane, mitochondria and nucleus double layer of phospholipids with embedded proteins Physical barrier separating the inside / outside of cell Much of our body is hydrophilic or “water loving” Fats are hydrophobic (“water hating”) Fats in cell membrane provide a barrier to water Campbells 10th 7.2 and the image gallery at https://tools.thermofisher.com Objective Two What is a phospholipid? Hydrophobic region hydrophilic polar heads (phosphate) hydrophobic lipid tails (fatty acids) arranged as a double layer around cytoplasm, tail to tail this is enough detail for now, you will learn more in Module 5 Q: what is this? Objective Two Plasma Membrane proteins Membrane proteins mediate movement of hydrophilic substances Are often amphipathic, meaning they have both hydrophilic and hydrophobic regions Integral proteins: embedded (partially or fully) into the membrane eg. Transmembrane proteins are integral membrane proteins that fully span the entire membrane, contacting both extracellular and cytoplasmic areas Peripheral membrane proteins: associated with the membrane, but not actually embedded in it allow cell-cell identification and facilitate intercellular communication Objective Two What do the plasma membrane proteins do? For example, channels, transporters, may be general or selective, gated or not Carry out chemical reaction, may or may not be a part of a team of enzymes More in CP section and relevant for ET:N External signaling molecule causing communication of information to the inside of the cell More in lecture 9 Campbell Biology 11th Global Fig 8.7 Objective Two More jobs for plasma membrane proteins Use of glycoproteins (carbohydrate + protein) as molecular signatures of the extracellular side of the cell For example, gap junctions or tight junctions. Remember GAGs? Lecture 3 C&T Proteoglycans (GAGS + protein) are a type of glycoprotein This is the basis of “tissue typing” For example, fibronectin mediates contact between cell surface integrins and ECM (eg. collagen). can facilitate movement Campbell Biology 10th Global Fig 8.7 Objective Two Membranes are not static… the membrane is a mosaic of molecules bobbing in a fluid bilayer of phospholipids Pearson BioFlix movie (Tour of an animal cell) –within CANVAS for this module Look at how the membrane moves (14-36sec) cell specific and dynamic repertoire of membranebound proteins present as required W. Carter [CC0], via Wikimedia Commons Objectives 3&4 Nucleus The largest distinct structure inside the cell Enclosed by double lipid bilayer called nuclear envelope, continuous with rough ER Entry and exit through nuclear pores Nucleolus: rRNA production, assembly of small and large subunits of ribosomes Functions: to house/protect DNA make RNA and assemble ribosomes pores regulate movement of substances (eg protein and mRNA) in and out molecule segregation to allow temporal and spatial control of cell function Campbell, Fig 6.9 Objective Four In the nucleus: Deoxyribonucleic Acid (DNA) Q: The DNA in one cell stretches out to ~ 2 metres, how does it fit? DNA wrapped 2x around group of 8 histones, to form nucleosomes -collectively known as chromatin As the cell prepares for cell division, chromatin condenses to form chromatin fibers then condenses further into loops and then stacks as chromosomes. More in lecture 10 Most of the time, our DNA is present as chromatin and chromatin fibers Chromosome – comprises many genes Gene - a DNA segment that contributes to phenotype/function Objective Three Ribosomes two subunits, small and large made of ribosomal RNA (rRNA) in complex with many proteins rRNA made in nucleolus Subunits assemble in the nucleolus leave through nuclear pores Function: protein production (translation), found in two places within the cell: More in Lecture 9 free in the cytoplasm - making proteins to be used in cytosol (non-endomembrane destinations) OR attached to the RER - making non-cytosolic proteins/endomembrane Campbells, 11th edition, Fig 6.10 Objective Three Endoplasmic Reticulum The ER is an extensive network of tubes and tubules, stretching out from the nuclear membrane two types: Rough ER and Smooth ER Campbells 10th edition, Fig 6.11 Objective Three Rough Endoplasmic Reticulum nuclear envelope continuous with nuclear envelope dotted with attached ribosomes Rough ER Smooth ER ribosomes Major function is production of: Secreted proteins Membrane proteins Organelle proteins proteins enter lumen within the rough ER for folding Rough ER membrane surrounds the protein to form transport vesicles destined for the Golgi More in lecture 9 Objective Three Smooth Endoplasmic Reticulum nuclear envelope Extends from the rough ER Rough ER Lacks ribosomes : doesn’t make proteins Smooth ER Major function is as a housing unit for proteins and enzymes Synthesizes lipids, including steroids and phospholipids Storage of cell-specific proteins, not all cells make all proteins ribosomes Functions of Smooth ER vary greatly from cell to cell – very cell/tissue-type specific Examples: Liver: houses enzymes for detoxification and for glucose release Muscle: calcium ions (refer ET:M) Objective Three Golgi apparatus – receiving and modifying the “warehouse” This complex is made up 3-20 flattened membranous sacs called cisternae, stacked on top of one another (“pita bread”) Functions: modify, sort, package and transport proteins received from the rough ER using enzymes in each cisternae Formation of: secretory vesicles (proteins for exocytosis) membrane vesicles (PM molecules) transport vesicles (molecules to lysosome) Secretory cells have extensive Golgi, eg. Goblet cells, Lab 2 Histology Campbells, 11th edition, Fig 6.12 Objective Three Golgi apparatus : to destination Each sac or cisternae contains enzymes of different functions proteins move cis to trans from sac to sac mature at the exit cisternae travel to destination Modifications occur within each sac (formation of glycoproteins, glycolipids and lipoproteins) ENDOMEMBRANE SYSTEM : Fred ( ) can be a well travelled phospholipid! Objective Three Lysosomes contain powerful digestive enzymes vesicles formed from Golgi membrane membrane proteins pump H+ in to maintain acidic pH rest of cell protected by membrane Main function is digestion of: substances that enter a cell cell components e.g. organelles - autophagy entire cells - autolysis Once digested, all building blocks (amino acids, lipids, etc.) are recycled Objective Three Mitochondria Main function: generation of ATP through cellular respiration Mitochondria are made up of: Outer mitochondrial membrane Inner mitochondrial membrane, with folds called cristae Fluid filled interior cavity, called the mitochondrial matrix Despite all of these membranes, mitochondria are not part of the endomembrane system!! The more energy a cell requires, the more ATP it must make, and the greater the number of mitochondria present Mitochondria carry a separate small (37 genes) genome encoding mitochondrial specific products Objective Five Cytoskeleton structural support system of the cell Fibres or filaments that help to maintain the size, shape and integrity of the cell: Act as scaffolding across the cell Involved in intracellular transportation and cell movement Three types of fibers (from smallest to largest): Microfilaments Intermediate filaments Microtubules You have met the first two in Lecture 2, here we add microtubules. Objective Five Cytoskeleton : microfilaments Diameter: ~7 nm Comprised of actin molecules assembled in two long chains, twisted around each other Found around the periphery and lining the interior of cell Function: Bear tension and weight by anchoring cytoskeleton to plasma membrane proteins, and promote amoeboid motility if required (eg. macrophage) Assembled and disassembled as required – they are dynamic Q : what do I mean by dynamic? Objective Five Cytoskeleton : intermediate filaments Diameter: 8-12 nm. Comprised of diverse range of different materials; one example: keratin Found in the cytoplasm of the cell. Function: bear tension and weight throughout cell, e.g., during cell anchoring, act as scaffold for cellular organelles, e.g., the nucleus. Usually the most permanent of cytoskeletal structures – they are less dynamic Objective Five Cytoskeleton : microtubules Diameter: tubular structure, 25 nm with central lumen of 15 nm diameter Comprised of tubulin dimers (alpha and beta), coiled, to form a tube Extends from centriole into cytoplasm/nucleus Functions: Support cell shape and size Guide for movement of organelles, e.g., vesicles from Golgi to membrane Chromosome organization – cell division Support and movement of cilia /flagella Assembled and disassembled as required - are dynamic The Inner Life of the Cell (XVIVI Scientific Animation) https://xvivo.com/examples/the-inner-life-of-the-cell/ Watch the assembly and disassembly at about 1:10m to see what I mean by “dynamic” Some additional resources for this topic / lecture Pearson BioFlix movie 4.5 minutes –is within CANVAS for this module textbook readings listed in your course guide for this lecture Self-directed (ie. we don’t provide answers) study questions are in the lecture guide (page 49) The Inner Life of the Cell (XVIVI Scientific Animation) https://www.youtube.com/watch?v=FzcTgrxMzZk Complete the table on page 45 as part of your revision The video shown at the start of the lecture: https://youtu.be/gFuEo2ccTPA Plus another Frank Gregorio video (Cell organelles) https://www.youtube.com/watch?v=TG_FqCWam4I https://www.youtube.com/user/khanacademy/ Publisher permission was granted for lecture slide use of images/resources from the 107 texts (Tortora and Campbell). Unless otherwise stated content was sourced from these texts or were lecturers own Next CSF lecture: Harvesting Chemical Energy Tip: please try to watch the video on my Canvas module BEFORE the lecture tomorrow