https://padlet.com/GemmaGreenow/7z8ydyw9f21r organelle functions en-us 2016-11-30 20:51:10 UTC 2025-11-26 11:55:39 UTC hello@padlet.com GemmaGreenow https://padlet.com/GemmaGreenow/7z8ydyw9f21r/wish/140966661 Usually spherical; 10-20 μm. Contains DNA & protein comprising chromosomes. Chromosomes direct protein synthesis & are the site of transcription. DNA provides a template for DNA replication.

• Bounded by two membranes: called the nuclear envelope with pores: allows the passage of large molecules (i.e. mRNA). Outer membrane is continuous with the endoplasmic reticulum.
• Granular material: nucleoplasm which contains chromatin (made of coils of DNA bound to protein). During cell division: chromatin condenses into chromosomes.
• Within the nucleus: nucleolus: sites of formation of rRNA.

]]> 2016-11-30 20:52:56 UTC https://padlet.com/GemmaGreenow/7z8ydyw9f21r/wish/140966661 GemmaGreenow https://padlet.com/GemmaGreenow/7z8ydyw9f21r/wish/140966704 Often cylindrical: 1-10μm (length).

• 2 membranes: separated by a narrow, fluid-filled inter-membrane space. Inner membrane folds inwards to form cristae. 
• Organic matrix: contains many compounds (lipids & proteins).
• Small 70S ribosomes & circular DNA: enable mitochondria to make their own protein & self-replicate.
• Function: produce ATP in aerobic respiration. Reactions occur in matrix or on inner membrane. Cristae: large surface area for enzymes attachment in respiration.
• Metabolically active cells (muscles): have many mitochondria.

]]> 2016-11-30 20:53:08 UTC https://padlet.com/GemmaGreenow/7z8ydyw9f21r/wish/140966704 GemmaGreenow https://padlet.com/GemmaGreenow/7z8ydyw9f21r/wish/140966735 Occur in cells of photosynthesising tissue. Each chloroplast: two membranes forming chloroplast envelope. Mainly found in the palisade mesophyll cells.

• Stroma: fluid-filled & contains some photosynthesis products
• 70S ribosomes & circular DNA: make protein & self-replicate
• In the storm; flattened sacs: thylakoids. Stack of thylakoids: granum. Each granum: comprises between 2 & 100 parallel sacs. Photosynthetic pigments (chlorophyll) are found in thylakoids. This arrangement: large surface area, efficient for trapping light energy.

]]> 2016-11-30 20:53:15 UTC https://padlet.com/GemmaGreenow/7z8ydyw9f21r/wish/140966735 GemmaGreenow https://padlet.com/GemmaGreenow/7z8ydyw9f21r/wish/140966795 System of parallel double membranes forming flattened sacs with interconnected, fluid-filled spaces between them: cisternae.
These are pink in the electron microscope. ER is connected w/ nuclear envelope. Two types: 

• Rough ER, RER: has ribosomes on outer surface, transports proteins made there, present in large amounts in cells that makes lots of protein e.g. cells that make amylase.
• Smooth ER, SER: comprises membranes that lack ribosomes. It's associated w/ synthesis & transport of lipids.

]]> 2016-11-30 20:53:31 UTC https://padlet.com/GemmaGreenow/7z8ydyw9f21r/wish/140966795 GemmaGreenow https://padlet.com/GemmaGreenow/7z8ydyw9f21r/wish/140966817 Smaller in prokaryotic cells; 70S than eukaryotic; 80S (in cytoplasm where they occur singly or attached to RER). Ribosomes have one large subunit & one small subunit. Assembled in nucleolus from rRNA and protein. Important in protein synthesis: site of translation, mRNA is used to assemble the polypeptide chain. ]]> 2016-11-30 20:53:36 UTC https://padlet.com/GemmaGreenow/7z8ydyw9f21r/wish/140966817 GemmaGreenow https://padlet.com/GemmaGreenow/7z8ydyw9f21r/wish/140966846 Most plant cells: large, permanent vacuole which consists of a fluid-filled sac bounded by a single membrane: tonoplast. Vacuoles contain cell sap which stores chemicals, i.e. glucose, amino acids & minerals. May store vitamins & pigments. Play a major role in supporting soft plant tissues.]]> 2016-11-30 20:53:43 UTC https://padlet.com/GemmaGreenow/7z8ydyw9f21r/wish/140966846 GemmaGreenow https://padlet.com/GemmaGreenow/7z8ydyw9f21r/wish/140966886 Occur in animal cells, not in cells of higher plants. Located outside the nucleus. Centrioles are two rings of microtubules which make hollow cylinders positioned at right angles to one another. Together may be called centrosome. During cell division, centrioles organise the microtubules that make the spindle.]]> 2016-11-30 20:53:56 UTC https://padlet.com/GemmaGreenow/7z8ydyw9f21r/wish/140966886 GemmaGreenow https://padlet.com/GemmaGreenow/7z8ydyw9f21r/wish/140966913 of a plant consists largely of cellulose. Cellulose molecules: held together in microfibrils which are held in bundles of fibres which are embedded in a polysachharide matrix called pectin. Functions:

• Transport: gaps between cellulose fibres makes the cell wall fully permeable to water & dissolved molecules and ions. This space outside the cell through which solution moves: apoplast. Apoplast pathway is the main way water crosses the plant root.
• Mechanical strength: structure of cellulose microfibrils and their laminated arrangement makes the cell wall very strong. When vacuole is full of solution, the cell contents pushes against cell wall and makes cell turgid. 
• Communication between cells: cell walls have pores through which strands of cytoplasm called plasmodesmata pass. Plamodesmata occurs where there is no cellulose thickening between 2 cells. Strand of cytoplasm runs from one cell tot he next. Network of cytomplasm in connected cells: symplast. Symplast pathway is important in water transport through a plant.

]]> 2016-11-30 20:54:02 UTC https://padlet.com/GemmaGreenow/7z8ydyw9f21r/wish/140966913 GemmaGreenow https://padlet.com/GemmaGreenow/7z8ydyw9f21r/wish/140966927 structure resembles the ER, but is more compact. Vesicles containing the polypeptide are pinched off the RER and fuse with the stack of membranes comprising the Golgi body. Proteins are modified & packaged in the Golgi body. Then, vesicles containing the modified proteins are pinched off the golgi body and fuse with the cell membrane secreting the modified proteins by exocytosis. Functions:

• Producing secretory enzymes, packaged into secretory vesicles
• Secreting carbohydrates
• Producing glycoprotein
• Transporting & storing lipids
• Forming lysosome, containing digestive enzymes

]]> 2016-11-30 20:54:06 UTC https://padlet.com/GemmaGreenow/7z8ydyw9f21r/wish/140966927 GemmaGreenow https://padlet.com/GemmaGreenow/7z8ydyw9f21r/wish/141071115 Small, temporary vacuoles which are surrounded by a single membrane, formed by being pinched off from the Golgi body. Contain & isolate potentially harmful digestive enzymes from the remainder of the cell. Release lytic enzymes which recycle worn out organelles and digest some bacteria.]]> 2016-12-01 12:21:34 UTC https://padlet.com/GemmaGreenow/7z8ydyw9f21r/wish/141071115