Cholesterol also makes the membrane less fluid by restraining the movement of phospholipids and lowers the temperature required to solidify the membrane. Complete depletion of cholesterol and sphingolipids results in cell death as their presence allows permeability to small molecules such as ions, glucose, and water. How does temperature affect lipid membrane? A membrane remains fluid as the temperature decreases, until it solidifies once it hits a critical temperature. The temperature at which a membrane solidifies depends on its fatty acid composition.
Compounds called proteins and phospholipids make up most of the cell membrane. The phospholipids make the basic bag. The proteins are found around the holes and help move molecules in and out of the cell. Cell Membrane A cell membrane of the cell. It gives the cell its shape, it is the outer covering of the cell made up from phospho-lipid-protein bi-layer, which allows the materials to enter and to exit.
Depending on the contents these are despatched to one of three destinations: Cytoplasm-The cytoplasm consists of all of the contents outside of the nucleus and enclosed within the cell membrane of a cell. This includes the cytosol and in euckaryotic cells, organelles such as mitochondria and ribosomes. Also located within the cytoplasm is the cytoskeleton, a network of fibers that help the cell maintain its shape and give it support. The cytoplasm is clear in colour and has a gel-like appearance. It is composed mainly of water and also contains enzymes, salts, organelles, and various organic molecules.
| | | A) | cytoskeleton | | | B) | fluid mosaic model | | | C) | impermeable membrane | | | D) | genetic material | | | | | | Feedback: Phospholipids in the plasma membrane create a fluid environment in which other molecules can float, allowing selective permeability. This is known as the fluid mosaic model. | | 13 CORRECT | | What effect has eukaryotic evolution had on cells? | | | A) | more simplified structures | | | B) | greater adaptability
SER lacks ribosomes and participates in lipid synthesis and detoxification. The Golgi apparatus is a system of membranous cisternae and vesicles arranged in stacks near the nucleus. The Golgi processes and modifies sugar side chains on proteins that are being secreted or destined for the plasma membrane or other membrane-bound organelles like the lysosome. Therefore, the Golgi apparatus is particularly prominent in cells synthesizing large
A) is neutralized by water B) is surrounded by water molecules C) reacts and forms a covalent bond to water D) aggregates with other molecules or ions to form a micelle in water Answer: B Page Ref: Section 3 11 9) Which would you expect to be most soluble in water? A) I B) II C) III D) IV Answer: A Page Ref: Section 3 10) Solutes diffuse more slowly in cytoplasm than in water because of A) the higher viscosity of water. B) the higher heat of vaporization of water. C) the presence of many crowded molecules in the cytoplasm. D) the absence of charged molecules inside cells.
PROTEINS 6: A difference in the concentration of a chemical on both sides of a membrane leads to which of the following phenomena? DIFFUSION 7: Which of the following eukaryotic organelles is responsible for the production of ATP? MITOCHONDRION 8: Glucose is A MONOSACCHARIDE Glucose is a monosaccharide; it is both an important energy molecule by itself and a building block of more complex carbohydrate 9: Which of the following is considered a neutral pH? 7.2 10: Due to the semipermeable nature of a phospholipid membrane, all of the following types of substances will normally be kept on one side of the membrane EXCEPT NON-POLAR MOLECULES 11: A molecule that gains an electron from another molecule will experience A REDUCTION in its overall electrical charge. 12: Hydrolysis reactions ARE EXOTHERMIC 13: If a molecule is described as "organic," this means it CONTAINS CARBON AND HYDROGEN 14: Glucose is a sugar with six carbons.
The nuclear membrane has a similar structure to the cell membrane but it contains gaps which allow protein to pass through. The nucleus controls almost all of the activities of the cell. Cytoplasm: The cytoplasm refers to anything which is inside the cell boundary and outside the nucleus. It is a semi-fluid material which is capable of flowing slowly. Many chemical reactions are carried out in the cytoplasm.
The protein molecule is able to float in the membrane – part of it is embedded in the membrane, part of it sticks into the cytoplasm, and part of it sticks out into the aqueous environment of the cell. What do you suspect about its structure, including its amino acid sequence, to make it behave as it does? * Examine the diagram of the cell membrane below. Is the diagram a “good” illustration of the fluid mosaic model of the cell membrane? What aspects of cell membrane structure are accurately illustrated by it?
The bilayer is selectively permeable which enables it to act as a barrier that keeps proteins, ions and other molecules where they are needed and prevents them from diffusing into areas where they are not (Wisegeek.com/bilayer. 2011). Small molecules can move through the layer automatically, this is diffusion from a high concentration to an area of low concentration, whereas water diffuses from highly concentrated areas to low concentrated areas. This process is known as osmosis and its purpose is to maintain equilibrium within the cell in order for it to function properly (Wisegeek.com/bilayer. 2011).