What are the surface appendages that allow a bacterium to stick to a surface?
What is the name of the structure that allows bacteria to stick to a surface?
Which is the bacterial structure that acts as a selective barrier?
Which of the following structures are used by prokaryotes for attaching to surfaces?
Prokaryotes often have appendages (protrusions) on their surface. Flagella and some pili are used for locomotion, fimbriae help the cell stick to a surface, and sex pili are used for DNA exchange.
Which plant structure is most like gap junctions in animal cells?
What happens when a cell is exposed to a substance that prevents it from dividing?
A cell is exposed to a substance that prevents it from dividing. The cell becomes larger and larger. This situation will eventually be problematic, since the cell’s ability to absorb nutrients through its outer membrane will not keep increasing as quickly as its cytoplasmic needs.
Does the cytoskeleton play a role in amoeboid motion?
The cytoskeleton plays an important role in amoeboid motion. The cytoskeleton helps to support cells. The cytoskeleton is composed of three types of fibers: microfilaments, microtubules, and intermediate filaments. Once laid down, the elements of the cytoskeleton are fixed and remain permanently in place.
What cell lacks a membrane enclosed nucleus?
Which of the following is a typical feature of an ATP driven active transport mechanism?
Which of the following is a typical feature of an ATP-driven active transport mechanism? Active transport moves solutes against their concentration gradient; facilitated diffusion moves substances down their concentration gradient. Macrophages are white blood cells that roam the body searching for invading microbes.
When particles move across membranes without expending ATP it is called?
Passive transport is the movement of substances across the membrane using their own kinetic energy, without the expenditure of chemical energy. In contrast, active transport is the movement of substances across the membrane using energy from the hydrolysis of adenosine triphosphate (ATP).
Which of the following describes phagocytosis?
Phagocytosis, process by which certain living cells called phagocytes ingest or engulf other cells or particles. The phagocyte may be a free-living one-celled organism, such as an amoeba, or one of the body cells, such as a white blood cell.
What molecules are responsible for membrane transport?
Carrier proteins and channel proteins are the two major classes of membrane transport proteins. Carrier proteins (also called carriers, permeases, or transporters) bind the specific solute to be transported and undergo a series of conformational changes to transfer the bound solute across the membrane (Figure 11-3).
Are channel proteins always open?
Channel proteins facilitate the transport of substances across a cell membrane. The charge of the channel, as well as the size and shape, indicate what can cross the cell membrane. The channel protein has a pore that can always be open or may open and close depending on the needs of the cell
Can channel proteins be saturated?
Once the channels operate at their maximal rate, a further increase in particle numbers no longer increases the apparent rate of diffusion. At this limited rate we describe the protein channel as being saturated.
What happens to facilitated diffusion when protein carriers become saturated?
What happens to facilitated diffusion when the protein carriers become saturated? The maximum rate of transport will occur. The protein carriers fall apart. The solutes can diffuse through the pores and the concentration of solutes is the same on both sides of the membrane.
What is the difference between channel protein and carrier protein?
Unlike channel proteins which only transport substances through membranes passively, carrier proteins can transport ions and molecules either passively through facilitated diffusion, or via secondary active transport. These carrier proteins have receptors that bind to a specific molecule (substrate) needing transport.
Can facilitated diffusion be saturated?
Facilitated diffusion requires specific membrane transport proteins. Since the number of such membrane transport proteins is limited, they can be saturated if the concentration of molecules to be transported is high.
Why does the rate of uptake slow and then eventually plateau with facilitated diffusion?
As the external concentration of the compound is increased, the rate of uptake increases until it reaches a point where it slows and then begin to plateau. At this point, the number of carriers and the time it takes the carriers to translocate the compound across the membrane limits transport.
What are the features of facilitated diffusion?
the transport relies on molecular binding between the cargo and the membrane-embedded channel or carrier protein. the rate of facilitated diffusion is saturable with respect to the concentration difference between the two phases; unlike free diffusion which is linear in the concentration difference.
What must happen when a concentration gradient is eliminated?
it is the random motion of the molecules that causes them to move from an area of high concentration to an area with a lower concentration. Diffusion will continue until the concentration gradient has been eliminated