SACE Stage 2 Biology Notes - Cells

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1 SACE Biology Year 2016 Mark Pages 26 Published Jan 4, 2017 SACE Stage 2 Biology Notes - Cells By Elizabeth (99.75 ATAR)

2 Powered by TCPDF ( Your notes author, Elizabeth. Elizabeth achieved an ATAR of in 2016 while attending Seymour College Achievements: Biology subject prize at Seymour College (#1 achieving student) Outstanding Achievement in the Research Project Prize at Seymour College Merit for Physics Merit for Research Project B English Communications subject prize at Seymour College (#1 achieving student) Merit for Biology Merit for English Communications The Hardwicke College Prize for the most outstanding achievement by a female student in SACE Stage 2 Biology Elizabeth says: I graduated from Seymour College, Adelaide with an ATAR of 99.75, studying Maths Studies, English Communications, Biology, Chemistry, Physics, and Research Project B. I received merits in Physics, Biology, English Communications and the Research Project, and credit my success to thorough and dedication revision throughout the year, alongside a balance of cocurricular and social activities. My notes helped me achieve success and I hope they can you too. All the best for Year 12!

3 Stage 2 Biology Topic 2A: Cells Cell Theory The building block of structure in living organisms The functioning unit of life the chemicals of life take place in cells Derived from other cells by cell division Contains information used as instructions for growth, development and functioning Cells are the smallest unit of life which can exist individually as they can grow/develop, reproduce, complex, organised structure, take in energy and use it, respond to stimuli and preserve an internal environment chemically different to its environment. Cell Structure All cells consist of an outer cell membrane, enclosing the cytoplasm which contains organelles carrying out specific functions. Prokaryotic (before nucleus) no nucleus, no membrane bound organelles, does contain ribosomes all bacteria (including cyanobacteria) Eukaryotic (true nucleus) nucleus, membrane bound organelles, ribosomes plants, animals, fungi, protozoa (unicellular organisms), algae Nucleus Controls the structure and function of cells as it contains DNA (forming chromosomes in division, otherwise chromatin, containing a genetic code for the production of proteins) Largest organelle Easily observed using a light microscope Found in all eukaryotic cells (excluding red blood cells which loose theirs in specialisation) Surrounded by double membrane nuclear envelope which controls what enters and leaves the nucleus (nuclear pores allow larger molecules like mrna in) Contains one or more nucleoli (nucleolus=sing.) which produce the rrna to form ribosomes seen by dark spot Mitochondria (mitochondrion = sing.) Site of aerobic respiration s later stages in which energy is released and stored for use by the cell as ATP Rod shaped or cylindrical Are visible through a light microscope Found in all cells, more concentrated in muscle and liver cells Bound by a double membrane o Outer membrane controls what enters and leaves the organelle o Inner membrane is folded into finger-like projections called cristae (crista=sing.) which are coated in stalked granules contain the enzymes and carriers for the electron transport system in aerobic respiration Inside is called the matrix and contains the enzymes required for the Kreb s cycle in aerobic respiration, a loop of DNA and ribosomes so can synthesise its own proteins (so does chloroplasts) this supports the endosymbiotic theory that mitochondria

4 and chloroplasts were once a free-living prokaryotic cell which invaded eukaryotic cells and lived there mutualistically Chloroplasts Site of photosynthesis in which chlorophyll pigments trap light energy and use it to produce glucose and oxygen from carbon dioxide and water (make organic molecules from inorganic molecules) Can be seen in an electron microscope Cells of autotrophic eukaryotic plants/algae which carry out photosynthesis *not present in non-green cells such as roots, petals, tubers Bound by a double membrane o Outer membrane controls what enters and leaves the organelle o Inner membrane gives rise to layers of lamellae (lamella=sing.) which extend across the inside of the chloroplast and form sacs called thylakoids, which stack up to form grana (granum=sing.). Chlorophyll and other photosynthetic pigments which trap light smother these lamellae, thus the grana are the main site of light dependent photosynthesis. The rest is filled with a watery mixture called the stroma which contains enzymes required for the light independent stage of photosynthesis in which glucose is formed, therefore starch grains are also found here, along with lipid droplets, a loop of DNA and ribosomes Ribosomes Site of protein synthesis in which polypeptide chains are formed in translation which then form proteins Are not visible in a light microscope Thousands found in every prokaryotic and eukaryotic cell (smaller in prokaryotic), especially those producing large amounts of proteins also found in mitochondria and chloroplasts Consist of two subunits made of rrna and proteins and lie in the cytoplasm (proteins produced used by cell) or attached to the rough endoplasmic reticulum (released as secretions) Endoplasmic reticulum Found in all eukaryotic cells Network of membranes forming sheets, tubes and flattened sacs running through the cytoplasm, originating from the outer membrane of the nuclear envelope Rough synthesis (by ribosomes) and transport (through membrane network) of proteins, then packaged in membrane vesicles and move in the cell or fuse with cell membrane and are secreted Smooth enzymes inside synthesise and transport lipids (including steroids) (also detoxify drugs and poisons in the liver, and stores calcium in muscles) Golgi Body Modification and packaging of secretions from lipids and proteins received from the ERs to be released by a cell

5 1. Proteins made by RER and lipids made by SER are pinched off of the ER in vesicles which then fuse with the golgi body 2. Additional substances such as sugar groups are added 3. Secretions are packaged into fresh vesicles and pinched off from the golgi body 4. Vesicles are moved to other parts of cell or fuse with cell membrane and release contents as a secretion via exocytosis Produce lysosomes Found in all eukaryotic cells, more prominent in cells which actively secrete molecules Consists of a stack of flattened membrane sacs Lysosomes Contain hydrolytic enzymes (carry out hydrolysis) which break down o Worn out/redundant organelles or damaged macromolecules o Digest solid food particles ingested by unicellular organisms into a food vacuole o Bacteria engulfed by white blood cells o Destroy a dead cell (autolysis) Are not visible in a light microscope Found in all eukaryotic cells Small spherical vesicles bound by a single membrane originating from ER or golgi body Peroxisomes Similar to lysosomes but contain digestive enzymes to break down toxic materials called oxidative enzymes Also absorb nutrients good at digesting fatty acids, alcohol, amino acids Found in all eukaryotic cells more common in liver cells Involved in cholesterol synthesis Vacuoles Fluid filled cavities bound by a single membrane formed by the infolding or pinching off of a part of the cell membrane, or the enlargement of a vesicle cut off by the golgi body Mature plant cell vacuoles are large and permanent and filled with cell sap, surrounded by a tonoplast membrane. The sap contains water, ions, dissolved nutrients, waste products and sometimes pigments. This o Maintains the salt-water balance and hence shape and support of the cell important in cell elongation in growth o Store cell wastes o Store pigments giving rise to petal colours Animal cell vacuoles are small and temporary and o Store food particles which have been engulfed by cells such as amoeba during phagocytosis o Contractile vacuoles pump excess water from unicellular organisms living in fresh water which moves in by osmosis this prevents the cell from lysing

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Organelles. copyright cmassengale 1

Organelles. copyright cmassengale 1 Organelles copyright cmassengale 1 Organelles Very small (Microscopic) Perform various functions for a cell Found in the cytoplasm May or may not be membrane-bound 2 Animal Cell Organelles Nucleolus Nucleus