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Transcript
Cell Review Cells The Cell Theory • All living things are made of one or more CELLS. • Cells are the basic unit of structure and function in an organism. • New cells are produced from existing cells. 2 types of cells • Prokaryotes – Cells without a nucleus or organelles surrounded by membranes • Eukaryotes – Cells with a nucleus and organelles surrounded by membranes. Prokaryotes • Single celled organism • Has DNA that is circular floating all around in the cytoplasm • Only has ribosomes and no other membrane bound organelles • Most common = bacteria – Some can make their own food, most get food from other sources Eukaryotes • There can be singled celled eukaryotes as well as multicellular • Highly organized • More complex than prokaryotes Cell membrane (plasma membrane) • Made mainly of phospholipids (2 layers) and proteins Outside of cell Proteins Carbohydrate chains Cell membrane Inside of cell (cytoplasm) Protein channel Lipid bilayer Cell membrane made of: • Phospholipids have 3 kinds of proteinshydrophobic tails made • channel-provides a path of lipids and hydrophilic for materials to move in heads. and out • marker- used for recognition • receptor- receive signals Cell membrane • Acts as a boundary • Controls what enters and leaves cell • Fluid (fluid mosaic model) – Molecules in cell membranes are constantly moving and changing (ex. cholesterol and carbohydrates) Nucleus • LARGEST organelle in animal cells • Surrounded by nuclear envelope • Contains nuclear pores = openings that allow molecules to move in and out of nucleus • Contains genetic material (DNA) • Control center of the cell Nucleolus • Dark spot in nucleus • Assembles RNA and also ribosomes Cytoskeleton • Helps cell maintain shape • Help move organelles around • Made of proteins – Microfilaments – Microtubules Centrioles • Made of microtubules • Only seen in animal cells during cell division • Function: Guide chromosomes during PMAT Mitochondria • • • • • “Powerplant of cell” Site of cellular respiration Burns glucose to release energy Stores energy as ATP Surrounded by double membrane – Inner membrane = cristae Ribosomes • Can be free in cytoplasm or attached to rough ER • Made of rRNA • Function: assembles proteins • Called the site of protein synthesis Endoplasmic reticulum (internal network of membranes) • Rough ER – Attached ribosomes make proteins which are modified and transported to Golgi for export • Smooth ER – Makes membrane lipids (steroids) – Regulates calcium in muscles – Breaks down toxins in liver Golgi Apparatus • Looks like a “stack of pancakes” • Made of membranes • Modify, sort, and package substances from ER for storage or export out of cell Lysosomes • Sac containing digestive enzymes • Digests food molecules and unwanted cells/cell parts • Plays a role in apoptosis “programed cell death” – Cell suicide for the good of the organism Movement • Pseudopodia = “false feet” help amoebas with movement and eating (phagocytosis) • Cilia = many and short microtubules (little hairs) – Move cells – Move substances past cells • Flagella = few and long microtubules (like a tail) – Move cells What’s special about plant cells? • • • • Cell wall HUGE central vacuole Chloroplasts No centrioles!! Cell wall • Found outside the cell membrane • Provides support and protection • Made of Cellulose (carbohydrate) makes plant sturdy • Bacteria have cell walls made of peptidoglycan instead • Cell walls of fungi are made of chitin Vacuoles • Storage space for: proteins, carbohydrates, water, waste • Contractile vacuoles control excess water in a paramecium (homeostasis) • Huge in plant cells, small animal cells, not in bacteria Chloroplast • Surrounded by double membrane • Thylakoids = membrane sacs inside • Contains chlorophyll where photosynthesis happens • Found photosynthetic cells (plants, some bacteria and protozoans) Molecule Movement and Cells • Passive Transport = does not require energy by the cell • Active transport = requires energy! Passive transport • No energy required • Move due to gradient – Differences in concentration, pressure, charge • Move to equalize gradient (equilibrium) – High concentration moves toward low concentration • 3 Types – Diffusion, osmosis, facilitated diffusion Diffusion • Molecules move to equalize concentration Osmosis • Special form of diffusion • Fluid flows from lower solute concentration • Always involves movement of water – Into cell – Out of cell Hypotonic = solutes in cell more than outside, fluid will flow into cell Isotonic = solutes equal inside and out of cell Hypertonic = solutes greater outside cell, fluid will flow out of cell Facilitated Diffusion • Channels (are specific) help molecule or ions enter or leave the cell • Channels usually are transport proteins Active transport • Molecular movement • Requires energy (against gradient) • Example: sodium-potassium pump Endocytosis • Phagocytosis – cell eating • Pinocytosis – cell drinking Exocytosis • Reverse of endocytosis • Cell discharge material Cellular reproduction • 5 ways – 1. Fission – 2. Budding – 3. Vegetative propagation – 4. Mitosis – 5. Meiosis Binary Fission • • • • Prokaryotes (bacteria) Asexual reproduction Cell makes copy of DNA and grows in size Membrane will divide and two new cells formed Budding • Asexual reproduction • Hydra bud to form new hydra • Yeast cells undergo budding Vegetative propagation • Asexual reproduction in plants • Runners will grow off from the parent plant and root to form a new identical plant.