Introduction to Cells Part 1

Introduction to Cells part 1 Building Blocks of Life Learning objectives: • You should understand the: - Basic structure and function of a eukaryotic cell - Major cellular organelles and their roles Eukaryotes vs. prokaryotes ✓ Eukaryotic cells are found in animals, plants, algae, protozoa, and fungi. ✓ Prokaryotic cells are found in bacteria and archaea. Viruses • Not classified as a living cell. Thus, they are not classified as eukaryotic or prokaryotes. Cells ✓ 1 million seconds = 11.6 days ✓ 1 billion seconds = 31.7 years ✓ 1 trillion seconds = 31709 years Each type of cells performs a different function. Retinal Ganglion cells: The morphology of cells can vary greatly, usually because they have different functions. Protoplasm is the living substance if a cell • Cytoplasm Cytosol- fluid suspension: This is where all the bits inside the cell sit in ✓ Organelles ✓ Cytoskeleton ✓ Inclusions Karyoplasm (Things that are found within the nucleus) - Contents of a nucleus - • Typical features if cells Primary Processes 1. Maintenance of structural integrity. ✓ Cytoskeleton: keeps everything organised and keeps the shape of the cell. 2. Obtain nutrients from the surrounding aqueous environment. Cells communicate with other cells and the outside environment to obtain nutrients such as glucose and oxygen. It has to select for this by having cell membrane. ✓ Cell membrane 3. Make and secrete proteins: Cells make the proteins we need. ✓ A large percentage of the cell’s machinery is dedicated to making proteins. Humans are primarily made out of proteins and our cells are make those proteins. 4. Convert glucose to ATP. We need energy to do all of the body processes. This process is governed by the mitochondria. ✓ Mitochondria 5. Replicate. 6. Remove waste products. There are lots of storage disorders that can be cause bad diseases, due to cells not getting rid of wastes. Cells can recycle a lot of stuff, but they need to be able to remove wastes, otherwise they will just build up. ✓ Lysosomes Maintenance of structural integrity • • Cytoskeletal proteins - Microfilaments: Microfilaments, also called actin filaments, are protein filaments in the cytoplasm of eukaryotic cells that form part of the cytoskeleton. They are primarily composed of polymers of actin. - Intermediate: These are a type of cytoskeletal element that is composed of multiple strands of fibrous proteins wound together. Their main function is the provide mechanical support for the plasma membrane where it comes into contact with other cells or with the extracellular matrix. Unlike microfilaments and microtubules, intermediate filaments do not participate in CELL MOTILITY. - filaments Microtubules: Microtubules, like actin filaments, are dynamic structures: they can grow and shrink quickly by the addition or removal of tubulin proteins. Also similar to actin filaments, microtubules have directionality, meaning that they have two ends that are structurally different from one another. Microtubules act as a scaffold to determine cell shape and provide a set of "tracks" for cell organelles and vesicles to move on. Microtubules also form the spindle fibres for separating chromosomes during mitosis. When arranged in geometric patterns inside flagella and cilia, they are used for locomotion. Functions of the cytoskeleton integrity - Provides a structural framework - Cell motility (crawling, cilia, flagella). The cytoskeleton will be involved in cell crawling and it does this really quickly. - Cell-cell and cell-basement membrane attachment. Important in terms of skin. This allows us to stretch our skin without it breaking away from each other. These cells are tailored to one another by really strong connections. When we have mutations in the intermediate fibres for example, we get blistering diseases because these cells are able to be pulled apart. - Movement of chromosomes during cell division. - Movement of vesicles and organelles Obtain nutrients from the surrounding aqueous environment. You have plasma membrane that surrounds every cell. Within these membranes there are membrane proteins. ✓ The mitochondria, the endoplasmic reticulum they all covered with a membrane. ✓ Plasma membrane is the one that covers the cell. ✓ Biolipid layers that enclose these different organelles. Make and secrete proteins: A large percentage of the cell’s machinery is dedicated to making proteins. • • • The nucleus is the largest organelle Central dogma The way that we make proteins, the way we make any stuff that we secrete in our bodies, the way we make new parts of cells, the way that cells grow, is through transcription and translation. We start with the instructions, which are the DNA. That DNA is transcribed into mRNA. The messenger mRNA will come out the nucleus and then that messenger mRNA will be translated into protein. • The nucleus - Largest organelle in any cell Contains DNA which is the genetic material of the cell. That is called chromatin. - • Chromatin: DNA will wrap around histones, and those histones plus the DNA are called chromatin. - Chromatin (histones plus DNA are called the chromatin). ✓ Genetic material of the cell - The nucleolus ✓ Site of ribosomal RNA synthesis. Ribosomes are important for the translation step. - Nucleoplasm/karyoplasm ✓ Macromolecules and nuclear particles involved in cell membrane. Involved in transcription, DNA replication etc. DNA and Chromatin - The DNA wraps around the histones, and then the histones wrap together and then we get condensed a chromosome. - DNA is the genetic material housed within the nucleus of the cell. ✓ Polymer of the nucleotides (sugar, phosphate, nitrogen base) in the shape of a double helix. - Chromatin strands of DNA and histone proteins ✓ Heterochromatin – densely backed The two types of chromatins ✓ Euchromatin transcription Electron micrographs allows us to see chromatins, just like the above picture. The Nuclear Envelope • • • • It is not just the plasma membrane that has a membrane. This is a membrane itself. It is a double membrane. Parallel membranes separated by 10-30 nm perinuclear cisterna The nuclear pore (found within the membrane (nuclear envelope)). These allow things to be imported and exported into the nucleus. gated by glycoproteins. But there are small molecules that can get permeable to small molecules and ions. - Selective transport Exportins carry large molecules to the cytoplasm. (This is selective transport) - Importins carry large molecules to the nucleus. (This is selective transport) Formation of proteins We make things through transcription and translation. Transcription – translation