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Transcript
History of the Cell • Robert Hooke (1665) – Used compound scope to examine thin cork slices. Coined the term “cell” referring to the many little boxes. Actually saw dead plant cells • Anton van Leeuwenhoek (1673) with his simple scope, observed first living cells • Matthias Schleiden (1838) and Theodor Schwann stated that all plants and animals (respectively) are made up of cells . • Rudolph Virchow (1855) – cells come only from other cells The Cell Theory • • • All living things are made up of cells Cells are the basic unit of structure and function in all living things Cells come from pre-existing cells Cells vary by: 1. Size – Range from 2m (giraffe nerve cell from leg to spine) to .2um (bacteria - Mycoplasm) Limited by the ratio between outer surface area and their volume. As the surface area to volume ratio decreases, it makes it difficult for information to get around cell and also nutrients to get and then be circulated around the cell Side Length Surface Area LxWx6 Volume LxWxH Surface area to Volume ratio 1mm 6mm2 1mm3 6 to 1 2mm 24mm2 8mm3 3 to 1 3mm 54mm2 27mm3 2 to 1 2. Shape – Form reflects function. Red Blood Cells are like tubes at Sesame Place so they flow easier Nerve cells are like electrical wires Cheek cells (Epithelial cells) are flat to act like a shield White Blood cells are amoeboid shaped to move and squeeze into all areas 3. Internal Organization – – Organelles – internal structures in a cell. Each has a specific function All cells contain: a. Cell membrane – thin membrane. Porous to certain compounds b. Cytoplasm – “cell’s liquid” Organelles are suspended in it c. Ribosomes – Protein factories in cells d. DNA Types of cells 1. Prokaryotic cells – cells that lack a nucleus and membrane bound organelles - Bacteria & Archaebacteria - Have a cell wall, cell membrane, cytoplasm, DNA & ribosomes - Pigments and enzymes are suspended in cytoplasm suspended in cytoplasm 2. Eukaryotic Cells – contain a membrane bound nucleus and membrane bound organelles. - Much more complex cell - All cells other than bacteria. - Protists, Fungus, Animals and Plants Nucleus Comparing the Two Cytoplasm DNA Cell Membrane Parts of the Eukaryotic cell • Three main components: – Nucleus – Cell membrane – Cell organelles Cell membrane Central Problem #1: A living system MUST be separated from its environment if it is to maintain complex order in a chaotic physical world. Cell Membrane – Separates the cell’s internal environment from the external environment. - Allows for the passage of some substances based on size and concentration – Selectively Permeable Some things can pass through while others can’t • Made up of a bilipid layer (lipid bilayer) – 2 layers of phospholipids with proteins floating through it. • Tails of phospholipids are hydrophobic while the heads are hydrophilic Peripheral membrane proteins do not penetrate the hydrophobic core of the membrane. They can be easily removed without destroying the membrane structure. • Integral proteins : these are fully incorporated into the membrane and are in contact with both the inside and the outside of the cell. Some can act as channel ways for the transport of substances. Others have carbohydrate attached to them – recognition sites Integral proteins Peripheral protein • In the "fluid mosaic model" of membrane structure, the membrane is a fluid phospholipid bilayer in which protein molecules are either partially or wholly embedded. These layers easily move around. Rap Cell Organelles Cytoplasm – area between nuclear envelope and plasma membrane – “cell’s liquid” Made of gelatinous cytosol where nutrients and minerals carried in solution within it. • • Typical Animal Cell Typical Plant Cell Mitochondria - Powerhouse of the cells. – – – - Where cellular respiration occurs and glucose is broken down to release energy (in the form of ATP) to the cell. Found in greater numbers in cells such as muscle cells & liver cells (2500/cell) Double membraned with Cristae (folds) to > surface area for reactions to take place Have their own DNA (mDNA) and ribosomes. Replicate by binary fission as needed Cristae Double Membrane Ribosomes Most numerous organelle in the cell. Site of protein synthesis. Not membrane bound therefore, they are in prokaryotic cells. Made up of RNA and protein. May be free floating in cytoplasm or attached on Endoplasmic Reticulum Endoplasmic Reticulum – Channels or passageways in the cell. There are two types of ER: 1 – Rough with ribosomes attached for the production and distribution of proteins. 2 – Smooth – Synthesis of steroids (lipids) in gland cells, Ca+ regulation in muscle cells and breakdown of toxins 1 2 3 4 5 6 7 8 - 10 Nuclear Envelope Nucleopore Rough endoplasmic reticulum (RER) Smooth endoplasmic reticulum SER) Ribosome on the RER Proteins that are transported in …Transport vesicle Golgi apparatus Golgi Apparatus (Bodies) o Stack of smooth flat sacs. o Processing, packaging and secreting organelle of the cell. o Much like a processing & exporting plant. Work in close association with ER Lysosomes Single membrane - are the cells' garbage disposal system. They breakdown worn out organelles such as mitochondria & produce hydrolytic enzymes to that degrade DNA, proteins, lipids &carbohydrates Responsible for the un-webbing of hands of fetus while developing in utero These are rare in plant cells Cytoskeleton Network of protein strands that provide support and mobility of organelles in cytoplasm. 2 components of cytoskeleton - Microfilaments – made of actin (protein threads). Involved with cellular movement and muscle contractions – Microtubules – larger structures. Involved in cell division, make up flagella and cilia. Also make up spindle fibers that assist in chromosome migration during cell division. 9 – 2 arrangement Cilia and Flagella Extensions from cell membrane. Assist in movement. Have 9-2 arrangement like microtubules Cilia - when short and multiple numbers. Covering of Paramecium, lining of respiratory tract and nasal passages. Flagella- long and usually only 1 to a few. Sperm cells, Euglena. Used for propulsion Nucleus • • • • • • Only in Eukaryotic cells. Stores hereditary information in DNA. Surrounded by a double nuclear envelope. Nuclear pores perforate membrane. Chromatin - strands of a combination of DNA & protein within nucleus. These will later become chromosomes. Nucleolus (1 or >) produces ribosomes Plant Cells • Are eukaryotic and have most of the same organelles as animal cells except: 1. Cell Walls Made up of cellulose & pectin (glue between walls) Gives cells rigidity, protection & support. Is also porous. Cell Wall Primary cell wall Forms just on the outer surface. Expands by adding on more cellulose. Grows as cell grows Secondary cell wall Develops between primary and cell membrane. Tough and woody. No more growth 2. Vacuoles - Store enzymes, food, water and wastes. - Huge water vacuole (Central Vacuole) in plant cells. - Gives plant cell “turgor” (full of water and fully supported) – 90% of cells may be water. - Some contain metabolic wastes which may be toxic to other organisms (poison ivy). 3. Plastids Double membrane, DNA containing to store starch, fats or Pigments such as chlorophyll. Chloroplast – where photosynthesis occurs. Made up of stacks called Thylakoids. Here is where the energy conversion occurs. Leucoplast/Amyloplasts store starch Typical Animal Cell 1. _______________ 2. _______________ 3. _______________ (Dots) 4. _______________ 5. _______________ 6. _______________ 7. _______________ 8. _______________ 9. _______________ 10._______________ 11._______________ 12._______________ 13._______________ 1 7(folds) 2 8 9 (Dots) 10 3 11 12 4 13 5 6 Typical Plant Cell Epithelial (Cheek) Cells Cell Membrane Nucleus Cytoplasm Cyclosis Elodea Onion Cells Potato Cells Red Blood Cells (& 2 White Blood Cells) Organelle Function Plant Cells Animal Cells Mitochondria Site of cellular respiration - transfer of energy - Folds called Cristae Yes Yes Ribosomes Site of Protein synthesis Yes Yes Endoplasmic Reticulum Rough - Protein packaging & transport site Smooth - Sythesis of lipids Yes Yes Golgi Apparatus Processing & packaging center for cell secretions Few Many Lysosomes Produce hydrolytic enzymes Few Many Cytoskeleton Network of protein filaments - keep cell's shape and for movement Yes Yes Microfilaments & microtubules Support, movement and cell division Yes Yes Cilia & Flagella Cell movement & circulation Cilia - many & short, Flagella 1or 2 & long Yes Yes Nucleolus Production of ribosomes Yes Yes Nucleus Contains DNA, synthesizes RNA & Ribosomes Yes Yes Chromatin DNA & protein - genetic information Yes Yes Cell Wall Outmost layer of plant cell - support & protection Made of cellulose & pectin glue between walls Yes No Vacuole Stores enzymes, wastes, water & food Large water in plants - support Yes, large water vacuole Many Plastid Stores food and pigments - Chloroplasts (photosynthesis) & leucoplasts (stores starch) Yes No Centrioles Microtubules that function during cell division No Yes Cell Membrane Selectively permeable - made of a bilipid layer & proteins Yes Yes