Answer: Lungs
Explanation: The pleura encloses each lung by a double layered serous membrane
Answer:
Both facilitated diffusion and active transport are selective processes. Only selective molecules are allowed to cross the membrane. They utilize carrier proteins to move across the membrane.
Explanation:
Diffusion is the process by which molecules move across a membrane respective of the concentration gradient. The plasma membrane is a <em>selectively permeable membrane</em> which allows specific molecules to move across the concentration gradient.
Molecules migrate from a region of higher concentration to a lower concentration in case of diffusion. It can be classified into simple diffusion and facilitated diffusion. These are examples of <em>passive transport</em>.
In facilitated diffusion molecules move across the concentration gradient with the help of <em>carrier proteins or channel proteins</em>. The carrier proteins bind to the molecule which has to be transported and change conformation to allow it to cross the membrane. For example glucose molecule is carried across through <em>GLUT transporter</em>. <em>Channel proteins</em> open a channel inside the membrane and molecules get transported across the gradient.
Active transport carries molecules against the concentration gradient with the assist of energy. ATP hydrolysis is utilized to generate energy. As a result of active transport, the molecules are aggregated on one side of the membrane.
Atoms are the most basic confirmed building block of life. Everything is made up of atoms. Atoms are made the positively charged protons, neutral charged neutrons, and negatively charged electrons.
Echinoderms have radial symmetry.
