Cells Function and Structure PDF

Variation amongst cells External morphology – the size, shape, colour, pattern, and outward appearance of an organism Remember, E. coli and S. cerevisiae are Latin, so should be in italics Prokaryotic cells they lack an enclosed nucleus or membrane bound organelles...

Variation amongst cells External morphology – the size, shape, colour, pattern, and outward appearance of an organism Remember, E. coli and S. cerevisiae are Latin, so should be in italics Prokaryotic cells they lack an enclosed nucleus or membrane bound organelles Examples: Cocci, bacilli, vibrio Eukaryotic cells plants, animals and fungi , Nucleus in an enclosed envelope and membrane bound organelles. Plants cells Most plants are multicellular organisms and obtain their energy via photosynthesis Fungi cells Yeasts, moulds, and mushrooms, they have Heterotrophs with chitin in their cell walls and are Genetically more similar to animals than to plants Note: Heterotrophic – an organism that eats other plants or animals for energy and nutrients Chitin – a polysaccharide chain Animals cells Heterotrophic, motile or non-motile, and have a blastula stage of embryonic development Note: hollow sphere of cells Eukaryotic cells can also be rigid, like calcified bone, be fluid and flexible like neutrophil and be brick shaped and fixed shaped columnar like epithelial cells. Organelles Remember, eukaryotes have lots of membrane bound organelles, whereas prokaryotes have none Nucleus Nucleus has entry and out points called nuclear points Chromatins is a complex of DNA and protein because DNA wraps around the histones, this combination of dna and histones is what we call chromatins. Genes to proteins The central dogma refers to how genetic information can be stored (DNA), and turned into a product (protein) within a biological system Transcription --DNA → messenger RNA Translation --mRNA → protein Only 4 nucleotides, but 20 amino acids Going from the language of dna to the language of protein, 4 to 20 letters Note: Genotype – the genes you have Phenotype – your observable characteristics Translation Going from mRNA → Protein you only need 4 nucleotides, but 20 amino acids Its more complicated than going from DNA → RNA No equivalent of Watson-Crick base-pairing Genotype → Phenotype Ribosomes ribosome is like a molecular machine that helps the cell make proteins. It is made of two parts: 1. Small subunit: This part reads the instructions (the mRNA) that tell the ribosome which amino acids to add to the growing protein. 2. Large subunit: This part links the amino acids together, making a chain (a protein) by forming strong peptide bonds between them. The amino acids are brought to the ribosome by tRNA. Free ribosomes - float around freely in the cell’s fluid (cytosol) and can work together in groups called polysomes to make proteins. All ribosomes in bacteria (prokaryotes) are free-floating. Membrane-bound ribosomes: These are attached to the surface of the endoplasmic reticulum (ER) in eukaryotic cells (like in humans) and help make proteins that are sent to specific places. Its going through the rough er because it has ribosomes attached to it. Mrna will go through it like a tunnel Endoplastic reticulum SER (smooth endoplastic reticulum) has far fewer ribosomes and is much smaller - lipid, phospholipid, and steroid synthesis. Golgi body Also called Golgi apparatus, Golgi complex, or just Golgi. Cisternae are the name of flat stacks found in certain cell structures like endoplasmic reticulum (ER) or Golgi apparatus. These help in the processing and transport of proteins and other molecules. Think of it like A stack of pancakes that made up the Golgi body Proteins arrive from the ER on the cis face and then Modified within the cisternae by enzymes. They are also sorted in the trans Golgi network then sent to the correct destination in the cell either to cell membrane for secretion(meaning to release substances from the cell outside, or to lysosomes for digestion because lysosomes digest or break down larger molecules, waste materials or harmful things like bacteria. the TGN helps direct these molecules by packaging them into small membrane-bound vesicles that are transported. Protein sorting the tgn packages the proteins into vesicles, For constitutive/exocytotic secretion, vesicles continuously transport proteins to the plasma membrane, where they release materials such as lipids and proteins and secretory proteins out the cell note: Constitutive means its occurring all the time The cell membrane is made up of lipids and proteins. By constantly releasing these components, the cell can repair or expand its membrane. Secretory proteins: These are proteins that the cell produces and needs to send outside. They might be hormones, enzymes, or other signaling molecules that help the cell communicate or perform its functions in the body. --In regulated secretion, once the proteins are stored in vesicles they wait until a specific signal trigger their release. Once they receive that signal, they can rlease hormones, neurotransmitters and enzymes. Regulated secretion When something specific is happening Proteins destined for lysosomes, such as digestive enzymes (lysozymes), are synthesized in the rough endoplasmic reticulum (RER). Lysosomal exocytosis (proteins to be digested can be sent to the lysosome to be destroyed by digestive lysozyme enzymes, or lysozymes are sent to digest something outside of the cell) Lysosomes are the vesicle that lysozymes lives in. Their job is to destroy proteins Remember, a lysoSOME and a lysoZYME are different terms. Lysosomes are a type of vesicle, lysozymes are a type of enzyme How do things move inside the cell? nm – nanometre (1 millimetre = 1,000 micrometres = 1,000,000 nanometres) Pseudopodia – a temporary protrusion of the surface of a cell for movement and/or feeding. Microfilaments (actin) Actin filaments, also known as microfilaments, are the smallest elements of the cytoskeleton and are among the most common proteins found in eukaryotic cells. They are made up of globular actin proteins (G-actin)(monomers) that polymerize to form long, thin strands called filamentous actin (F-actin)(polymer). These actin filaments play several important roles in the cell, including changing the cell's shape and length, which is particularly crucial for muscle contraction. They help extend the cell membrane to form structures like pseudopodia for movement, assist in dividing the cell during the process of cytokinesis, and contribute to cell adhesion by connecting neighbouring cells. Overall, actin filaments are essential for maintaining the structure and function of cells. Note: Pseudopodia – a temporary protrusion of the surface of a cell for movement and/or feeding Look over this again Cytoskeletal elements are protein-based structures within cells that provide support, shape, and organization. They play crucial roles in various cellular functions, including movement, division, and maintaining the integrity of the cell. The three main types of cytoskeletal elements are: Microtubules (made from tubulin, hollow tubes, 25 nm Ø) Intermediate filaments (8 – 12 nm Ø) Microfilaments Microtubules help move organelles and vesicles inside the cell. Motor proteins (kinesin and dynein) attach the cargo to the outside of the microtubule. Kinesin moves towards the cell's edge (+ end), while dynein moves towards the nucleus (– end). Remember kinesin to Dundee, moving away and dynein To Edinburgh moving to the nucleus Cargo refers to various materials, such as organelles, vesicles, proteins, or other cellular components, that are transported within the cell by motor proteins like kinesin and dynein Note: Kinesin and dynein are examples of mechanoenzymes, which can convert chemical energy (ATP) into kinetic energy (movement) Mitochondria Mitochondria are bacilli-shaped, divide by binary fission, produce ATP, and have two membranes. The inner membrane forms cristae, creating two compartments (intermembrane space and matrix), and they contain their own DNA. Binary fission—they get longer then divide in half Cristae, the folds of the inner mitochondrial membrane, create two compartments by dividing the space within the mitochondrion: 1. Intermembrane space: The area between the outer and inner membranes. 2. Mitochondrial matrix: The space inside the inner membrane, where metabolic reactions occur. The cristae increase the surface area of the inner membrane, enhancing the mitochondrion's ability to produce ATP. Mitochondrion – singular for mitochondria They have their own Dan separate from rest of the DNA Chloroplast chloroplast Shaped like a bacilli and divide by binary fission Synthesise ATP (energy) through a photosynthetic pigment called chlorophyll Two membranes with an intermembrane space Has its own DNA Cell junctions Help hold cells together and Allow communication between neighbouring cells Permit movement of water and solutes between cells (osmotic regulation) Gap junctions Are Chemical communication between cells and Connexon cylinder made from 6 connexin proteins Moving much smaller structures within cells because of Very smaller middle Adheren and desmosome Several different methods to anchor cells to each other  ◉ Adherens junctions – cells linked actin-to-actin via cadherin or integrins ◉ Desmosomes – cells linked keratin-to-keratin via cadherin ◉ Hemidesmosomes – cytoskeleton of cells linked to extracellular matrix via integrins Tight juctions Tight junctions control water and solute movement between epithelial cells. They line organs and blood vessels. More tight junctions mean tighter barriers, while fewer create leakier barriers. Examples: Tight epithelia like kidneys, don’t want everything to leak out so you might have more tj Your gut you will have more tj so you don’t want all the water to be trapped there Moving much smaller structures within cells Very smaller middle