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Cell Structure
Cell and Molecular Biology
| Question | Answer |
|---|---|
| Unicellular organisms contain | one cell |
| Multicellular organisms contain | more than one cell |
| What is a cell? | The smallest unit of an organism capable of surviving independently. |
| What is resolution/resolving power? | The minimum distance apart that two objects can be in order for them to appear as separate items. |
| What is magnification? | This is how many times bigger an image is when compared to the object. Magnification = size of image/ size of object |
| Differentiate between a light microscope and an electron microscope. | Light (simple, cheaper) -magnifies objects up to 1500 x only - low resolution - living and dead material can be observed Electron (complex, larger) - magnifies objects more than 500 000 x -high resolution -only dead material can be observed |
| Rough endoplasmic reticulum | One of two types of ER ( networks of tubules and flattened sacs which are continuous with the outer nuclear membrane) -Rough ER has ribosomes present on the outer surfaces of the membranes. - Provides pathway for transport of proteins throughout cell |
| Smooth endoplasmic reticulum | One of two types of ER ( networks of tubules and flattened sacs which are continuous with the outer nuclear membrane) - Smooth ER lacks ribosomes on its surface and is often more tubular in appearance. - Synthesizes, stores and transports lipids |
| Golgi body( apparatus) | - similar to smooth ER but more compact - stack of membranes made up of flattened discs (cisternae) and hollowed vesicles. - receives, sorts, processes and delivers proteins and lipids. |
| Mitochondria | rod-shaped structures within which the reactions of aerobic respiration occur - parts include : double membrane, cristae and matrix |
| Ribosomes | small. spherical structures found in all cells and are important in protein synthesis. 80S ribosomes (22nm) - found in eukaryotic cells 70S ribosomes (17 nm) - found in prokaryotic cells + mitochondria and chloroplasts S - Svedburg's unit |
| Lysosomes | vesicles produced by the Golgi body which contain enzymes such as proteases and lipases. - they isolate potentially harmful enzymes from the rest of the cell before releasing them either to outside the cell or into a phagocytic vesicle within the cell. |
| Chloroplasts | flat discs found in eukaryotic cells which photosynthesize - parts include: chloroplast envelope, stroma, grana (stacks of thylakoids) and starch grains |
| Cell membrane | a phospholipid bilayer containing proteins that control the movement of materials into and out of the cell |
| Nuclear envelope | - double membrane which surrounds the nucleus - outer membrane is continuous with the endoplasmic reticulum and has ribosomes on its surface - controls entry and exit of materials in and out of nucleus and contains the reactions taking place within it |
| Centrioles | a pair of hollow cylinders involved in cell division |
| Nucleus | made up of one or more nucleoli (singular nucleolus) and thread-like chromatin in a fluid nucleoplasm |
| Nucleolus | small, spherical region (there may be more than one) that manufactures ribosomal RNA (rRNA) and assembles the ribosomes. |
| Prokaryotic cell | Does not contain nucleus; unicellular |
| Eukaryotic cell | Contains nucleus; multicellular |
| Distinguish among cell, tissue and organ using plant structure as examples. | Cell - smallest unit of living organism which can exist on its own e.g. parenchyma Tissue - group of cells working together e.g. ground tissue Organ - group of tissues working together e.g. root |
| Distinguish between the appearance of a dicotyledonous root vs stem | Stem vascular bundle is seen near to the cell membrane's circumference. Root vascular bundle appears X shaped |
| What are 5 structures which can only be seen in plant cells? | 1) Cellulose cell wall 2) Pits and plasmodesmata in cell wall 3) Chloroplasts 4) Large, permanent vacuole 5) Starch grains |
| What are 3 structures which can only be seen in animal cells? | 1) Centrioles 2) Small, temporary vacuoles 3) Glycogen granules |
| What is the endosymbiont theory (endosymbiosis)? | The theory that organelles such as mitochondria an chloroplasts originated from prokaryotes that entered ancestors of eukaryotic cells. This is based on mitochondria, chloroplasts and prokaryotes having a few similar structures. |
| Cytoplasm | watery material with jelly-like consistency |
| Glycogen granules | small particles found in some cells |
| Cell wall | a tough wall containing cellulose fibres that surrounds the cell |
| Vacuole | a large permanent structure that contains a solution of mineral salts and sugars known as cell sap |
| Tonoplast | a membrane that surrounds the vacuole |
| Starch grains | spherical bodies that store carbohydrate |
| This is the most prominent feature of a eukaryotic cell when viewed under a microscope. | nucleus |
| State 3 functions of the nucleus | 1) Act as the control centre of the cells, controlling cell activities through the production of mRNA and tRNA and protein synthesis 2) Protect the DNA from the rest of the cell 3) Manufacture rRNA and ribosomes |
| List the 4 parts of the nucleus. | 1) Nuclear envelope 2) Nuclear pores 3) Chromatin 4) Nucleolus |
| Chloroplast envelope | double membrane which controls the entry and exit of substances in and out of the chloroplast |
| Stroma | - colourless, gelatinous matrix which contains the enzymes necessary for the light dependent stage of photosynthesis - small, circular DNA, 70 S ribosomes and oil droplets can be found here |
| Grana | coin-like, flattened stacks of thylakoids (lamellae) which carry out the light dependent stage of photosynthesis. |
| Cristae | - infoldings of the inner membrane of the double membrane which surrounds mitochondria. - they contain enzymes and other molecules involved in aerobic respiration |
| Matrix | - semi rigid material containing protein, lipids, 70 S ribosomes and small circular DNA - many enzymes involved in aerobic respiration found here |
| Describe 5 functions of the Golgi body. | 1) Add carbohydrates to proteins to form glycoproteins 2) Produce secretory enzymes 3) Secrete carbohydrates 4) Transport, modify and store lipids 5) Form primary lysosomes |
| Describe 4 functions of lysosomes. | 1) Break down material ingested by phagocytic cells 2) Digest worn out organelles so that useful chemicals within then can be re-used 3) Break down cells that have died 4) Some release hydrolytic enzymes to destroy material outside of cell |
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CAPE Biology Unit 1
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