Transcript document
By the end of this session you should be able to: – Recall the basic structure of an animal cell – Describe the functions of cell organelles Cell Structure – KS3/4 nucleus cytoplasm cell membrane Cells • Basic living unit • Consist of organelles, each of which has a specific structure and function • Ideal animal cell shows all organelles • Cells are specialised in living organisms – working together to form tissues; tissues work together to form organs; organs work together to form organ systems. Cellular Ultrastructure • Cytoplasm is a matrix full of structures – organelles • Each organelle has a specific structure and function Cellular Ultrastructure • • • • • Nucleus Nucleolus Centrioles Ribosomes Smooth Endoplasmic Reticulum • Rough Endoplasmic Reticulum • • • • • • Golgi Apparatus Mitochondria Lysosomes Plasma Membrane Cilia Flagella Endoplasmic Reticulum STRUCTURE • Complex system of sheet like double membranes continuous with the nuclear membrane • Fluid filled spaces/sacs between the membranes called CISTERNAE which allow materials to be transported through cell • Two types of ER – – smooth – has no ribosomes attached (RER) – rough – has ribosomes attached (SER) • • • • FUNCTION Forms an extensive transport system Site of protein synthesis (Rough ER) Site of lipid, steroid and carbohydrate synthesis (smooth ER) Stores and transports these materials Rough Endoplasmic Reticulum (RER) is arranged in flat sheets Smooth Endoplasmic Reticulum (SER) is arranged in tubules: Endoplasmic reticulum Ribosomes STRUCTURE • Small dense structures found in huge numbers. • Made up of RNA and protein • Can be attached to the rough ER of floating in the cytoplasm. • Are about 20 – 25 nm in diameter in eukaryotic cells and slightly smaller in prokaryotic cells • (80s type – prokaryotic) • (70s type – eukaryotic) • Made up from two sub units FUNCTION • Synthesize proteins • Synthesize enzymes Subunit of ribosome found in Thermus thermophilus Proteins – blue; single strand RNA - orange Golgi Apparatus •A system of membranes and folded vesicles found in both animal and plant cells •Involved in storage and transport of products that are secreted from the cell •e.g. hormones and enzymes In which types of tissue would you expect to find cells with large numbers of Golgi apparatus? Golgi apparatus STRUCTURE • Formed from small pieces of rough ER • Chemicals made in the ER collect in the Golgi body where they are modified • Small vesicles can then be ‘pinched’ off the Golgi body • Some of the vesicles become lysosomes • Others are secreted from the cell FUNCTION • Assembling glycoproteins (such as mucin) by combining carbohydrate and protein • Transporting and storing lipids • Formation of lysosomes • Producing digestive enzymes Lysosomes STRUCTURE FUNCTION • Small vacuoles formed when small pieces of Golgi body are pinched off • Contain hydrolytic enzymes which digest materials in the cell • Release enzymes which destroy worn out organelles • Digest material taken into the cell (eg white blood cells which have engulfed a bacterium) – phagocytosis • Completely break down cells after they have died – autolysis Task: Put the statements about lysosomal action into the correct order Timescale: 5 minutes 0:00 0:10 0:20 0:30 1:00 1:30 2:00 2:30 3:00 3:30 4:00 4:30 5:00 Time’s up! Membrane forms around old/unwanted structures Lysosome fuses with membrane around unwanted structures Digestive enzymes are released within the membrane Old/wanted structures are broken down Cell reabsorbs products back into cytoplasm Plasma (cell surface) membrane STRUCTURE FUNCTION • This is the boundary between the cell cytoplasm & the environment • Partially permeable • Made up 45% protein & 45% phospholipids with the remaining 10% cholesterol, glycoprotein & glyolipids • Controls movement of substances in & out of the cell • Recognition site so that the body’s immune system can recognize its own cells • Receptor site for the attachment of specific hormones and neurotransmitters. Nucleus, Nucleolus & Nuclear envelope STRUCTURE • Largest organelle in the cell (10um diameter) • Surrounded by a nuclear membrane / envelope • Double membrane – outer is continuous with the ER • Nuclear pores in the membrane allow the passage of large molecules in & out (eg messengerRNA) • Material inside the nucleus is called nucleoplasm – this contains chromatin which makes up the DNA of the cell – in non-dividing cells it is spread out and during cell division it condenses to form the chromosomes • Nucleolus makes ribosomal RNA and assembles the ribosomes. FUNCTION • Acts as the control centre of the cell through the production of mRNA and protein synthesis • Retains the genetic material in the cell in the form of DNA / chromosomes • Manufactures ribosomal RNA (rRNA) & ribosomes • Starts the process of cell division Cilia STRUCTURE • 3-10 um in length, 0.2um in diameter • Made of rings of 9 pairs of microtubules • Have basal body embedded in cytoplasm • Rest extends from basal body • Only a few types of cell possess cilia • On cells which have cilia there are large numbers FUNCTION • To move an entire organism (eg in paramecium it propels it through the water) • To move material within an organism ( eg cilia in the lining of the respiratory tract) Centrioles Structure • Two short bundles of hollow cylinders (microtubules) positioned at right angles to each other • Found just outside the nucleus in a clear area of cytoplasm called the centrosome • Wall of each centriole is made of 9 triplets of tubes arranged at an angle Function • During cell division they migrate to opposite poles to produce the spindle – which helps to move the chromosomes during cell division Mitochondria •Ave. 1000 per cell •Sausage shaped •Have an inner & outer membrane •Inner membrane is highly folded, producing fingers called CRISTAE •Fluid filled internal area – matrix •It is the site of respiration •ATP is produced here The cristae are folded to increase the surface area increased respiration More energy needed by the cell = more mitochondria required. • Sperm tails • Mammalian muscle fibres • Wings of insects Task: • In discussion with your group, answer the questions below. – Either write out the question or use full sentence answers 1. What are the basic units of all living things? 2. What is the function of the cell membrane? 3. How do you describe similar cells working together? 4. Where is the DNA located in a cell? 5. Where in the body would you find ciliated cells (cells with cilia attached)? 6. The cells of the retina have few mitochondria – why do you think this is?