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Structure
Interesting Questions, Facts and Information
- There are a total of 45 general entries. We are selecting 30 for display.
Special Topics
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 Interesting Questions, Facts, and Information
 Cell and Molecular Biology
nucleolus. Ribosomal RNA is used to produce ribosomes which are necessary for protein synthesis.
| Which type of organelle forms a membranous system of tubular canals, which is continuous with the nuclear envelope and branches throughout the cytoplasm?
| Basic Cell Biology
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Rough endoplasmic reticulum. mRNA moves from the nucleus and may attach to the rough E.R. to produce certain proteins. The mRNA may also attach to other ribosomes in the cytoplasm.
| Which organelle will produce steroid hormones in the testes and adrenal cortex while detoxifying alcohol in the liver?
| Basic Cell Biology
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Smooth endoplasmic reticulum. The main function of the smooth ER which does not contain ribosomes is to produce steroid hormones or lipids.
Golgi apparatus. The Golgi apparatus looks like a bunch of pancakes or balloons squished together and packages materials into vesicles for use inside the cell or to be secreted by the cell.
mitochondria. The cristae are the folds in the mitochondria that increase the surface area for production of ATP.
Cytochrome. The energy released from the electrons as they move from cytochrome to cytochrome is used to actively transport hydrogen ions into the inner-membrane space.
Terminal Cytochrome. An oxygen (electron acceptor) molecule accepts the electron from the terminal cytochrome and bonds to two hydrogen ions to form water.
2nd and 3rd bonds. A phosphate group is composed of three individual phosphate. Between the 2nd and 3rd phosphate groups is a relatively weak bond that is often prone to release energy and a phosphate. When this event happens, ATP is desynthesized and becomes ADP.
Carries the acetate to the Krebs cycle. In aerobic respiration, the main function of coenzyme A is to carry the acetate from the acetyl CoA in the transition reactions directly to the Krebs cycle.
Electron acceptor. An oxygen (electron acceptor) "accepts the electron from the terminal cytochrome and bonds to two hydrogen ions to form water.
Mitochondrion. The purpose of the mitochondrian is to supply energy to the cell, and the only way it can achieve this goal is to obtain energy from the ATP molecules that are produced during both the Krebs cycle and the electron transport system.
| Which situation is accurate for describing when the energy from the hydrogen ions is transferred into ATP molecules? | Biology, Breathing, and You
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Hydrogen ions diffuse back into the matrix. The hydrogen ions in the inner-membrane space contain energy, and as the hydrogen ions diffuse back into the matrix (the site of the Krebs cycle), that energy is transferred into the ATP molecules so that the cell can directly use it.
Cristae. By definition, the cristae is the foldinsg of the inner mitochondrial membrane that form a series of "shelves" that contain the electron transport systems involved in ATP formation.
| The cell membrane is the outermost part of an animal cell, and, is situated underneath the cell wall in plant cells. What is another name for the cell membrane? | Cell Membrane: Structure and Function
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Plasma Membrane. In animal cells, the cell or plasma membrane is a structure which helps keep the cytoplasm and the cell organelles in place. The cell membrane is composed of many different substances and structures. The terms plasma membrane and cell membrane can be used interchangeably.
| Through many studies, including imagery of cells using an electron microscope, it has been determined that the cell membrane consists of two layers. This is known as the bilayer. What is this bilayer composed of? | Cell Membrane: Structure and Function
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Phospholipids. The cell membrane is composed of what is known as a phospholipid bilayer. Lipid is the biological name for a fat (fatty acids and glycerol). The phospholipid bilayer is arranged due to certain properties of the phospholipids. The bilayer has two protein layers and a layer containing more protein molecules in between.
| The component molecules of the cell membrane have two main parts, the head and the tail. These parts are either hydrophobic (repelled by water) or hydrophilic (attracted to water). Which is which? | Cell Membrane: Structure and Function
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Hydrophilic Head and Hydrophobic Tail. The environment both inside and outside the cell contains water. The cell membrane is therefore subjected to water on both the inner and outer sides of its structure. This is where the orientation of the phospholipid head and phospholipid tail comes in to importance. Due to the tails being hydrophobic they turn away from the water and are therefore found nearer the centre of the cell membrane structure. As the heads are hydrophilic, they are attracted to the water in the surrounding environments and are therefore found nearer the edges of the cell membrane structure. Due to the cell membrane being composed of a phospholipid bilayer, one layer of hydrophilic heads are found on one side of the membrane, and, another layer of hydrophilic heads are arranged on the other side of the membranous structure. The tails of both of these layers will then meet in the middle.
Glycocalyx. The glycocalyx is a structure that produces carbohydrates such as glycoproteins. These carbohydrates protect the cell membrane from damage from organisms outside of the cell.
The term calyx is also used botanically to describe the outer sepals of a flower.
| The net movement of a gaseous substance will follow a concentration gradient (at normal atmospheric pressure) from an area of high concentration of that gas, to an area of lower concentration of that same gaseous substance. What is the name of this biological process? | Cell Membrane: Structure and Function
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Diffusion. Diffusion, as described above, was studied by a scientist named Adolf Fick. He stated that, amongst other things, the rate of diffusion across a membrane is dependent upon the concentration gradient and the size of the membrane itself. Evidently, the greater the concentration gradient, the faster the rate of diffusion. Also, the thinner the membrane, the faster the rate of diffusion. Other things are taken in to account such as the size of the molecules being diffused through the membrane.
Refraction is a term used in physics, particularly optics when describing the bending of rays of light with the use of, amongst many other objects, a prism. Integration is used in calculus, a concept formulated independently by both Sir Isaac Newton and Gottfried Liebniz. Finally, sublimation is when a solid changes directly into a gaseous substance, and vice versa.
| What process is described as being the net movement of WATER molecules from an area of low concentration of solute to an area with a higher concentration of solute? (Normal atmospheric pressure). | Cell Membrane: Structure and Function
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Osmosis. Osmosis is a spontaneous process. It follows a concentration gradient and the net movement is from a more dilute solution to a higher solute concentration until equilibrium is reached. An important aspect to this is that it occurs across a partially permeable membrane and requires no ATP energy (Adenosine Triphosphate).
Hydrolysis is a reaction in chemistry whereby a substance or compound is broken down by water. Galvanisation is another industrial chemical process where a particular metal, generally iron (Fe) or steel, is coated with zinc (Zn). Differentiation is an area of calculus alongside integration.
| Water moves from one region to another due to differences in water potential. This is how water moves from one side of a cell membrane to the other. What has the water potential of 0 if we assume that there is normal atmospheric pressure? | Cell Membrane: Structure and Function
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Pure water. Pure water has the water potential of 0 and any water that has impurities will have a lower number. So, the quantification of water potential works with only negative numbers and 0. Obviously, the closer the water potential is to 0, the more pure the water.
Psi. The Greek alphabet is commonly used in all aspects of science from electronics to astrophysics. The letter psi in particular is used to denote, as well as water potential, a subatomic particle. It is also used in quantum mechanics where it is shorthand for wave function.
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Molecules being removed from the cell. Endocytosis is the process of molecules being taken into the cell in intracellular vesicles.
Programmed Cell Death. This is the controlled form of cell death. The uncontrolled form of cell death is called necrosis.
| What organelle is the site of most of the protein synthesis that occurs in the cell? | Cell Biology
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Rough endoplasmic reticulum. The rough endoplasmic reticulum is covered with ribosomes and it is this that synthesizes proteins.
| How many hydrogen bonds does thymine form in DNA? | Cell Biology
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2. Thymine and adenine two form hydrogen bonds and guanine and cytosine form three hydrogen bonds.
| The phospholipid bilayer in the membrane is made up of which two molecules? | Cell Biology
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Hydrophobic tail and hydrophilic head. Other molecules found in the membrane are cholesterol, proteins and glycolipids.
| What is the process that makes the most ATP called? | Cell Biology
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Oxidative Phosphorylation. The process of chemiosmosis occurs across the cell membrane.
Cytoplasm. Glycolysis breaks down one molecule of glucose into two molecules of pyruvate.
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