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| Frage | Antworten |
| What are prokaryotic organisms? | Single-celled organisms |
| What is a cell ultrastructure? | A cell's organelles and the internal structure of most of them. This can be examined using an electron microscope |
| Name the organelles found in plant cells, but not animal cells | Cell wall with plasmodesmata Vacuole Chloroplasts |
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Describe the structure and function of the plasma membrane
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STRUCTURE: Mainly made of lipids and protein Has receptor molecules FUNCTION: Found on the surface of animal cells and just inside the cell wall of plant cells and prokaryotic cells Regulates movement of substances into or out of the cell Receptor molecules allow it to respond to chemicals like hormones |
| Describe the structure and function of the cell wall | STRUCTURE: A rigid structure that surrounds plant cells Mainly made of the carbohydrate cellulose FUNCTION: Provide support for the cell by allowing it to become turgid As water enters the vacuole by osmosis, the plant cell expands - the cell wall is strong enough to resist this expansion |
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Describe the structure and function of the nucleus
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STRUCTURE: Large organelle surrounded by nuclear envelope (double membrane), which contains many pores Contains chromatin (made from DNA and proteins) and often a nucleolus DNA contains instructions to make proteins FUNCTION: Controls the cell's activities (by controlling the transcription of DNA) Pores allow substances (e.g. RNA) to move between nucleus and cytoplasm Nucleolus makes ribosomes |
| Describe the structure and function of the lysosome | STRUCTURE: A round organelle surrounded by a membrane, with no clear internal structure Contains hydrolytic enzymes that digest material within the cell FUNCTION: Can be used to digest invading cells or break down worn out components of cell Membrane prevents lysosome from digesting the cell itself |
| Describe the structure and function of the ribosome | STRUCTURE: A very small organelle, made up of one small sub-unit and one large sub-unit, that either floats free in the cytoplasm or is attached to the rough ER Made up of proteins and RNA 80S = 20nm in diameter, found in eukaryotic cells 70S = slightly smaller than 80S, found in prokaryotic cells FUNCTION: Site where proteins are made (translation) |
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Describe the structure and function of the rough endoplasmic reticulum (RER)
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STRUCTURE: A system of membranes enclosing a fluid-filled space Surface is covered with ribosomes FUNCTION: Folds and processes proteins made at ribosomes |
| Describe the structure and function of the smooth endoplasmic reticulum (SER) | STRUCTURE: No ribosomes Large amounts located in cells that make lipids and steroids (e.g. liver and testis cells) FUNCTION: Makes cellular products e.g. hormones and lipids |
| Describe the structure and function of a vesicle | STRUCTURE: Small fluid-filled sac in the cytoplasm, surrounded by a membrane Some are formed by the Golgi apparatus or the ER, while others are formed at the cell surface FUNCTION: Transports substances in and out of the cell (via the plasma membrane) and between organelles |
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Describe the structure and function of the Golgi apparatus
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STRUCTURE: A group of fluid-filled, membrane-bound, flatted sacs Small pieces of RER are pinched off at the ends to form small vesicles Vesicles join and fuse together to make a Golgi apparatus Vesicles are often seen at the edges of the sacs FUNCTION: Processes and packages new lipids and proteins Makes lysosomes |
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Describe the structure and function of the mitochondrion
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STRUCTURE: Usually oval-shaped Has a double membrane - the inner one is folded to form cristae Inside is the matrix, which contains enzymes involved in respiration Found in large numbers in cells that are very active and require a lot of energy FUNCTION: The site of aerobic respiration, where ATP is produced |
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Describe the structure and function of the chloroplast
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STRUCTURE: A small, flattened structure found in photosynthetic tissues of plants and some protoctists Large starch grains form a temporary store for products of photosynthesis Surrounded by double membrane Thylakoid membranes inside the chloroplast are stacked up in some parts to form grana Grana are linked together by lamellae - thin, flat pieces of thylakoid membrane FUNCTION: Site of photosynthesis Some parts of photosynthesis occur in the grana, and other parts occur in the stroma (thick fluid found in chloroplasts) |
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Describe the structure and function of the centriole
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STRUCTURE: Small, hollow cylinders, made of microtubules (tiny protein cylinders) Located just outside the nucleus in the centrosome Found in animal cells, but only some plant cells Wall of each centriole is made up of 9 triplets of microtubules arranged at an angle FUNCTION: Involved with the separation of chromosomes during cell division Arrangement assists the movement of chromosomes |
| Describe the structure and function of the cilia | STRUCTURE: Small, hair-like structures found on the surface membrane of some animal cells In cross-section, they have an outer membrane and a ring of 9 pairs of protein microtubules inside, with a single pair of microtubules in the middle FUNCTION: Microtubules allow the cilia to move This movement is used by the cell to move substances along the cell surface |
| Describe the structure and function of the flagella (undulipodia) | STRUCTURE: Flagella on eukaryotic cells are like cilia but longer They stick out from the cell surface and are surrounded by the plasma membrane Inside they are like cilia - two microtubules in the center and 9 pairs around the edge FUNCTION: Microtubules contract to make the flagellum move Used like outboard motors to propel cells forward |
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How are organelles involved in protein production?
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1. Proteins are made at the ribosomes (the ribosomes on the RER make proteins that are excreted or attached to the cell membrane, whereas the free ribosomes in the cytoplasm make proteins that stay in the cytoplasm) 2. New proteins produced at the RER are folded and processed (e.g. sugar chains are added) in the RER 3. They are transported from the RER to the Golgi apparatus in vesicles 4. At the Golgi apparatus, the proteins may undergo further processing (e.g. sugar chains trimmed or more added) 5. Proteins enter vesicles to be transported around the cell (e.g. glycoproteins move to the cell surface and are secreted) |
| What are the four main functions of the cytoskeleton? | 1. Microtubules and microfilaments support the cell's organelles, keeping them in position 2. Help to strengthen the cell and maintain its shape 3. Responsible for the transport of organelles and materials within the cell 4. The proteins of the cytoskeleton can cause the cell to move |
| Compare the size of prokaryotic cells and eukaryotic cells | PROKARYOTIC = extremely small (less than 2µm diameter) EUKARYOTIC = larger cells (about 10-100µm diameter) |
| Compare the DNA of prokaryotic cells and eukaryotic cells | PROKARYOTIC = circular DNA EUKARYOTIC = linear DNA |
| Compare the cell wall of prokaryotic cells and eukaryotic cells | PROKARYOTIC = cell wall made of polysaccharide EUKARYOTIC = no cell wall (in animals), cellulose cell wall (in plants), or chitin cell wall (in fungi) |
| Compare the organelles of prokaryotic cells and eukaryotic cells | PROKARYOTIC = few organelles and no membrane-bound organelles (e.g. mitochondria) EUKARYOTIC = many organelles and other membrane-bound organelles present |
| Compare the flagella of prokaryotic cells and eukaryotic cells | PROKARYOTIC = flagella (when present) made of the protein flagellin, arranged in a helix EUKARYOTIC = flagella (when present) made of microtubules, arranged in a '9+2' formation |
| Compare the ribosomes of prokaryotic cells and eukaryotic cells | PROKARYOTIC = small ribosomes (20nm or less) EUKARYOTIC = larger ribosomes (over 20nm) |
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Why can't normal microscopes see the internal structure of bacterial cells?
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Prokaryotes like bacteria are roughly a tenth the size of eukaryotic cells. Normal microscopes aren't powerful enough to look at their internal structure |
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