Answer:
The correct answer is: is controlled by the somatic nervous system.
Explanation:
The urethra is an organ that is part of the urinary system, and consists of a tube that connects the urinary bladder to the urinary meatus, which is important for the excretion of urine. The urethra has two sphincters, which are muscles with the function to control the exit of the urine: <u>the internal urethral sphincter and the external urethral sphincter</u>.
The external urethral sphincter, unlike the internal one that is composed of smooth muscle, is made of skeletal muscle and is controlled by the somatic nervous system - this is what makes urination voluntary. Being the most external sphincter, it opens after the internal urethral sphincter during the micturition reflex.
Any damage in either sphincter can produce incontinence.
Answer:
B. Animals that eat the seeds
Explanation:
The pine trees and the trees alike, in general tend to rely on the animals to disperse their seeds. The seeds of the plants like this usually fall on the ground bellow the tree. As they fall, the animals are able to eat them and they do as they are very nutritional to them. While the animals manage to digest the majority of the cones, they are not able to do so with the seeds, so they release them by defecting them. As the seeds get on the ground, they are able to grow, thus giving rise to new trees, and achieving the goal of dispersal.
No- the question isn’t too clear but since the plasma membrane is the only part of the cell responsible for movement of molecules, there doesn’t need to be other molecules to replicate the same process
Answer:
A stork eating fish with its beak = Predator/Prey
Fungi absorbing nutrients = Parasitism
Barnacles = Commensalism
Explanation:
A stork eating a fish is hunting, the stork is predator and the fish is prey.
The fungi is parasitism because it is benefiting while causing harm to its host.
The barnacles are commensalism, because they benefit from the whale but don't harm it.
The cell membrane is selectively permeable and is a barrier to the movement of ions and molecules, particularly polar molecules such as glucose and amino acids that are repelled by the non-polar, hydrophobic lipids of the membrane.
<span>Facilitated diffusion is the movment of a polar, charged substance by transport proteins from a region of higher concentration to a region of low concentration (down a concentration gradient) across a membrane with no direct use of energy. </span>
<span>The role of transport proteins is to facilitate diffusion of substances that are insoluble in the phospholipid bilayer by: </span>
<span>1) providing hydrophillic channels in the form of transmembrane channel proteins </span>
<span>2) acting as carrier proteins that carry the substance across the membrane via conformational change </span>
<span>Diffusion can occur through the channel in either direction. Transport proteins are also highly specific. </span>
<span>Channel Proteins have a fixed shape and are transmembrane proteins. They provide a hydrophillic channel across the membrane that is selective for a particular solute. Eg. water channel proteins (aquaporins) found in the cells lining collecting ducts in kidney allow water molecules to flow very quickly from one side of the membrane to the other. Some channel proteins function as gated channels, where a chemical or electrical stimulus will cause them to open or close. </span>
<span>Carrier Proteins are proteins which exists in two alternate conformations. They undergo rapid changes in shape when the molecule being transported binds to it. Thus moving a solute across the membrane as the shape of the protein changes. Eg. entry of glucose molecules into red blood cells. </span>
<span>Factors affecting facilitated diffusion include: </span>
<span>1) Concentration of substances </span>
<span>Transport proteins can take up substances from both sides of the membrane, but direction of flow depends on the relative concentrations of the substrate across the membrane. It also depends on the chance collision between transport protein and substrate. </span>
<span>2) Number of carriers/channel proteins </span>
<span>Increaseing the number of carriers will result in an increased rate of facilitated diffusion. </span>
<span>3) Number of substrate binding sites on the carrer </span>
<span>Increasing the number of binding sites will increase the rate of facilitated diffusion. </span>
<span>Another way to transport substances across the membrane is by active transport. This is the energy (ATP)-consuming transport of molecules or ions across a membrane against a concentration gradient via carrier proteins. </span>
<span>Active transport is a major factor in the ability of a cell to maintain internal concentrations of small molecules that differ from concentrations in its external environment. Movement is usually in one direction only (unlike diffusion which is reversible). Energy is required because in the substance is moved against its natural tendency to diffuse in the opposite direction. The energy supplied is ATP (andosine tri-phosphate) which is manufactured by the process of respiration. Active transport is achieved by carrier proteins situated in the cell membrane which need a supply of energy (ATP) to keep changing shape. </span>
<span>One type of carrier protein in the sodium-potassium pump (as mentioned by the answerer above). Since the cell expends energy when transporting the ions, it is also referred to as an ion pump. This transport system pumps ions against steep concentration gradients. The pump ocscillates between two conformational states in a pumping cycle that translocates 3 Na+ out of the cell for every 2 K+ pumped into the cell. ATP powers the changes in conformation by phosphorylating the transport protein. </span>
<span>Other mechanisms that transport substances into or out of a cell include diffusion, osmosis and bulk transport (endocytosis and exocytosis).</span>