Biology

• Golgi apparatus modifies and packages proteins

  and lipids before transporting them to other cell components.
• Proteins and lipids move from the endoplasmic reticulum to the cis face to the cisternae to the trans face
• Cisternae are responsible for packaging and molecules are packaged into Golgi vesicles
• Golgi found in eukaryotic cells
• Ribosomes reform protein synthesis. Faster sedimentation means higher s number.
• 70s ribosomes in prokaroytes and subunits are 50s and 30s while 80s ribosomes in eukaryotes and subunits 60s and 40s. Chloroplasts and mitochondria have 70s ribosomes revealing prokaryotic origins.
• ribosomal RNA combines with proteins to form the subunits of the ribosome
• lysosomes are organelles whose function is to break down cellular wastes and debris by engulfing it with hydrolytic enzymes
• lysosomes break down excess or worn-out cell parts, may be used to destroy invading viruses and bacteria. If cell is damaged beyond repair, lysosomes can help it to self-destruct in process called programmed cell death, or autolysis
• Centrioles present in animal cells only and aid in cell division and spindle fibers formation that separate the chromosomes during the cell cycle. They also produce cilia
• Secretory vesicles form from the trans Golgi network, and they release their contents to the cell exterior by exocytosis
• Rough Endoplasmic reticulum provides surface area for chemical reactions to take place eg. post-translational modifications, folding, and sorting and is adjacent to the cell nucleus, and its membrane is continuous with the outer membrane of the nuclear envelope
• function of smooth ER is the synthesis of lipids, steroids, and carbohydrates and metabolism of exogenous substances, such as drugs or toxins
• Endoplasmic reticulum has network of membranes called cisternae held together by the cytoskeleton
• A prokaryote is a single-cell organism whose cell lacks a nucleus and other membrane-bound organelles. They have circular DNA
• Eukaryote is a single-celled or multicellular organism with a distinct, membrane-bound nucleus and linear dna bound to proteins and rna to form chromatin
• Chromatin is a genetic material comprising DNA, RNA, and proteins, which constitute chromosomes in the nucleus of a eukaryotic cell
• The nuclear envelope separates the contents of the nucleus from the cytoplasm and provides the structural framework of the nucleus and has double membrane
• The nuclear pore allows molecules, ions, and macromolecules (proteins and RNAs) to travel between the nucleus and the cytoplasm. RNAs that are synthesized in the nucleus must be exported to the cytoplasm, where they function in protein synthesis.
• Nucleolus is site of ribosome biogenesis (ribosome synthesis). More than one may be present
• Cytoskeleton is the structure that maintains the shape and internal organization of the cell, and provides it mechanical support enabling cells to carry out division and movement
• Microtubules are about 25nm in diameter. They make up part of the cytoskeleton. They allow movement of cell components on their outside surface, form spindle during nuclear division, form part of centrioles
• Microtubules made of protein called tubulin with 2 forms: alpha Tubulin and beta tubulin which combine to form dimers which join end to end to form 13 protofilaments which line up in a ring with a hollow centre. microtubules found in eukaryotic cells.
• Centriole consists of 9 groups of microtubules, each group made of 3 microtubules.
• Cell wall of bacterium contains murein, a peptidoglycan. Pili used to attach to other surfaces and in sexual reproduction.
• Mitochondria are membrane bound organelles found in eukaryotic cells and the site of aerobic respiration. Mitochondria produce adenosine Triphosphate (ATP) which stores and transports chemical energy within cells and facilitates biosynthesis of DNA and RNA.
• many folds form a layered structure called cristae, which increase surface area thus giving the mitochondrion more locations for ATP production to occur.
• The matrix of a mitochondrion is internal spaces enclosed by the inner membrane. Many steps in cellular respiration occur in the matrix due to its high concentration of enzymes
• Chloroplasts are membrane-bound organelles. Light energy absorbed by photosynthetic pigments eg. Chlorophyll
• A thylakoid is a flattened, membrane-bound, fluid-filled sac and site of light dependent reactions of photosynthesis in a chloroplast
• Grana are stacks of thylakoids and allow for optimum surface area, maximizing the amount of photosynthesis that can happen.
• stroma is liquid found in the cavity of the chloroplast and provide volume around the different structures for protection
• Chloroplasts can only be seen under electron microscope