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CET - Cell Structure
Cells, Exchange and Transport, OCR A level Biology F211
| Question | Answer |
|---|---|
| Magnification? | Increases size of image, does not increase detail level. |
| Resolution? | Ability to see two distinct points separately; the higher the resolution the more detail one can see. |
| Why stain? | Image shows on microscope because different amounts of light or electrons are absorbed, but sometimes a specimen lets light or electrons pass straight through. |
| How do you stain for a light microscope? | Dye added, taken in better by some parts than others, cause a contrast. |
| How do you stain for an electron microscope? | Object dipped in solution of heavy metals which is taken in better by some parts than others. Metal ions scatter electrons, creating a contrast. |
| What is the maximum resolution and magnification of a light microscope? | 200nm, x1500. |
| Maximum resolution and magnification of transmission electron microscope? | 0.1nm, over x1,000,000. |
| Maximum resolution and maginification of scanning electron microscope? | 5nm, less then 1,000,000. |
| Describe the plasma membrane? | Membrane found on surface of animal cells and just inside cell wall of plant cells and prokaryotic cells; made of lipids and protein. |
| WWhat is the function of the plasma membrane? | Regulates movement of substances into and out of cell. Has receptors which allow it to respond to chemicals like hormones. |
| Describe the cell wall? | Rigid structure that surrounds plant cells, made mostly of the carbohydrate cellulose. |
| What is the function of the cell wall? | Supports plant cells. |
| Describe the nucleus? | Large, surrounded by nuclear envelope (double membrane) containing many pores. Contains chromatin, and often a nucleolus. |
| What is the function of the nucleus? | Chromatin made from proteins and DNA, which controls cell activity. Pores allow substances to move between nucleus and cytoplasm. Nucleolus makes ribosomes. |
| Describe a lysosome? | Round organelle surrounded by a membrane; no clear internal structure. |
| What is the function of an lysosome? | Contains digestive enzymes; used to digest invading cells or break down worn components of cell. |
| Describe a ribosome? | Very small, either floats free in cytoplasm or attached to rough ER. |
| What is the function of a ribosome? | Site where proteins are made. |
| Describe rough endoplasmic reticulum? | System of membranes enclosing a fluid filled space; surface is covered with ribosomes. |
| What is the function of rough endoplasmic reticulum? | Folds and processes proteins that have been made at the ribosomes. |
| Describe smooth endoplasmic reticulum? | Similar to rough ER but no ribosomes. |
| What is the function of smooth endoplasmic reticulum? | Synthesises and processes lipids. |
| Describe a vesicle? | Small, fluid filled sac in the cytoplasm, surrounded by a membrane. |
| What is the function of a vesicle? | Transports substances in and out of the cell and between organelles. Some formed by Golgi apparatus or ER, others at cell surface. |
| Describe Golgi apparatus? | Group of fluid filled flattened sacs, vesicles often seen at edges of sacs. |
| What is the function of Golgi apparatus? | Processes and packages new lipids and proteins; also makes lysosomes. |
| Describe mitochondria? | Usually oval shaped. Double membrane, inner folded forming cristae, inside is matrix, contains enzymes involved in respiration. |
| What is the function of mitochondria? | Site of aerobic respiration, where ATP is produced. Found in large numbers in cells which require a lot of energy. |
| Describe a chloroplast? | Small, flattened structure in plant cells. Surrounded by double membrane; has membranes inside called thylakoid membranes which are stacked up in some parts to form grana, which are linked by lamellae - thin, flat pieces of thylakoid membranes. |
| What is the function of a chloroplast? | Site of photosynthesis. Some parts happen in the grana, and others in the stroma, a thick fluid found in chloroplasts. |
| Describe a centriole? | Small, hollow cylinders, containing a ring of microtubules. |
| What is the function of a centriole? | Involved with separation of chromosomes during cell division. |
| Describe cilia? | Small, hair like structures on surface membrane of some animal cells. In cross section have outer membrane and ring of nine pairs of microtubules inside, with a single pair of microtubules in the middle. |
| What is the function of cilia? | Microtubules allow to move, used by cell to move substances along cell surface. |
| Describe the flagellum? | On Eukaryotic cells - like cilia but longer. Stick out from the surface and are surrounded by plasma membrane. A pair of microtubules surrounded by nine pairs around the edge. |
| What is the function of a flagellum? | Microtubules contract to make flagellum move. Flagella used to propel cell forward. |
| Where are different types of protein made? | Ribosomes on rough ER make proteins that are excreted or stay attached to the cell membrane. Free ribosomes make proteins that stay in the cytoplasm. |
| Where are proteins produced at rough ER folded and processed? | In the rough ER. |
| What are proteins transported from rough ER to Goldi apparatus in? | Vesicles. |
| What happens at the Golgi apparatus? | Proteins undergo further processing. |
| What happens after proteins are processed in the Golgi apparatus? | Enter more vesicles to be transported around cell. |
| How are the protein threads of the cytoskeleton arranged in eukaryotic cells? | As microfilaments (small solid strands) and microtubules (tiny protein cylinders). |
| What are the four main functions of the cytoskeleton? | 1. Support the cells organelles. 2. Strengthen cell / maintain its shape. 3. Transporting materials within cell. 4. Causes cell to move. |
| What is the diameter of a prokaryotic and eukaryotic cell? | Prokaryotic: less then 2um. Eukaryotic: 2-200um. |
| Difference in DNA between prokaryotic and eukaryotic? | Prokaryotic: Circular. Eukaryotic: Linear. |
| Difference in nucleus between prokaryotic and eukaryotic? | Prokaryotic: No nucleus; DNA free in cytoplasm. Eukaryotic: Nucleus present; DNA inside nucleus. |
| Cell wall? Prokaryotic and eukaryotic. | Prokaryotic: Murein cell wall. Eukaryotic: None in animals; cellulose in plants; chitin in fungi. |
| Number of organelles? Prokaryotic vs. eukaryotic. | Prokaryotic: Few organelles, no mitochondria. Eukaryotic: Lots of organelles, mitochondria present. |
| Ribosome size in prokaryotic vs. eukaryotic? | Prokaryotic: Smaller. Eukaryotic: Larger. |
| Size difference? Prokaryotic vs. eukaryotic. | Prokaryotic roughly 1/10 size of eukaryotic, so need to be viewed through electron microscoope. |
| What do plant cells have which animal cells don't? | 1. Cell wall with plasmodesmata ('holes' for substance exchange). 2. Vacuole (compartment containing cell sap). 3. Chloroplasts for photosynthesis. |
Created by:
emm142
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