Answer: Large molecules and wastes move through the membrane through forms of active transport- endocytosis and exocytosis.
Explanation:
Molecules are moved across the cell membrane via different mechanisms like diffusion, facilitated diffusion and passive transport; however, some very large molecules require specialized types of active transport to cross over- these are endocytosis and exocytosis.
During endocytosis large molecules cells and cell fragments moved across the plasma membrane through a process of <em>invagination;</em> piece of the external cell membrane falls into itself and forms a small pocket that surrounds the target molecule this breaks off from the membrane to form an intracellular vesicle. Different methods of endocytosis such as <em>phagocytosis, pinocytosis </em>and receptor-mediated <em>endocytosis</em>, take in cells, water and targeted substances respectively.
Like endocytosis, the particles (signal proteins, neurotransmitters and waste material) are surrounded by a phospholipid membrane. However, in exocytosis, this membrane is formed in the cytoplasm, and merges with the plasma membrane’s interior in a process <em>opposite to </em>endocytosis; material is removed from the cell and exported into the cell’s exterior called the extracellular space.
Answer: The hepatic portal vein is one of the most important vein that receives blood from the body and transports it into the liver for filtration and processing. This vein is part of the hepatic portal system that receives all of the blood draining from the abdominal digestive tract, as well as from the pancreas, gallbladder, and spleen.
‘Hepatic’ means of or relating to the liver, therefore the hepatic portal vein is a blood vessel that sends nutrient-rich blood from the gastrointestinal tract and spleen to the liver, but also delivers toxins to the liver that will be chemically modified in the proces of detoxication
Answer:
Rough endoplasmic reticulum differ from smooth endoplasmic reticulum by the presence and absence of ribosomes in their surface.
Explanation:
Rough endoplasmic is named so because RER contain ribosomes at their surface and due to the presence of ribosomes rough endoplasmic reticulum play an importnt role in protein synthesis or translation.
Whereas smooth endoplasmic reticulum does not contain any ribosome in its surface.smooth endoplasmic reticulum helps in the biosynthesis of lipid and steroids along with detoxification of toxic compounds.
Answer:
Glucose entering the intestines from the villus.This is by active transport.The latter is defined as the movement of molecules and solutes from the region of lower concentration to the region of higher concentration against the concentration gradient.
Explanation:
All the above options depends on the diffusion gradients from one higher region to another.e.g oxygen passing from high concentration from outside to lower concentration in blood stream,like wise Co2 from higher concentration from inside to outside,with passive diffusion lipids and water enter the small intestine(note amino acid and glucose,and fructose are different).
Active transport( through sodium dependent transporter) transports glucose to the intestine from the villus.This is movements against concentration gradient because,glucose molecule are concentrated in intestine,and needed by the cells, in the body.Therefore they must be transported as a fast rate inn the blood .
However the absorption by the villi is very slow,therefore active transport is needed to move these against the concentration gradient into the intestine.And finally the blood.
If this were to be moved by passive diffusion,the high concentration in the intestine will force this back into the villi
Therefore extra energy is needed by active transport for the glucose molecules to enter the intestine from the villus.
