Cell membrane structure ; Week 3 (Cell) Assignment 1
Which of the following statements about cells is FALSE?
Cells join together to form organelles, which then form our organs and organ systems.; Organelles are the functional parts of cells—they are inside the cells, in the cytoplasm. Cells join to form tissues, and the tissues then join to form the organs that work together in organ systems.
What is the basic difference between simple diffusion and facilitated diffusion across a cell membrane?
In facilitated diffusion, molecules only move with the aid of a protein in the membrane. ; Facilitated diffusion allows molecules that cannot pass through the lipid component of the membrane to pass through via a more compatible protein channel or carrier. This includes ions and polar molecules.
Which of the following is most likely to move through the cell membrane by facilitated diffusion?
Na+ ; Ions move easily through water, which is polar, but cannot pass directly through the lipid (nonpolar) part of the cell membrane.
If a person is severely dehydrated, their extracellular fluids will become hypertonic to the intracellular fluid. What do you predict will happen to the person's cells?
The cells will lose water and shrink; The hypertonic extracellular fluid will draw water out of the hypotonic intracellular fluid, so the cells will shrink. This is called crenulation.
Which of the following is not required for osmosis to occur?
energy; Osmosis is a special type of diffusion, which is always a passive process
What is not a major function of proteins in the cell membrane?
forming the entire glycocalyx; The glycocalyx is composed mostly of carbohydrates.
Which of the following solutions contains the most solute?
hypertonic; "Hyper" means "high," so a hypertonic solution has a higher solute concentration than the solution to which it is being compared.
Where in a typical eukaryotic cell would you expect to find genes?
in the DNA within the cell's nucleus; The nucleus houses the DNA, which contains the genes. Genes determine what proteins the cell can make, which in turn determines what the cell can do.
In general, to maintain homeostasis the relationship between our intracellular and extracellular fluids should be which of the following?
isotonic to each other; In order to prevent the cells from either swelling or shrinking, the body fluids should be isotonic, meaning that they are at equilibrium
Which of the following acts as the digestive system of the cell, breaking down materials?
lysosome; Lysosomes use their enzymes to break down material, much as our digestive system breaks down the foods we consume. The root "lyse" means to loosen or separate, which is what the enzymes in lysosomes do to the chemical bonds in the items they digest.
Which of the following best explains diffusion?
movement of molecules from an area of high concentration to an area of low concentration; By diffusion, molecules spread out to maximize their space.
What part of a cell membrane is usually in contact with the interstitial fluid?
phosphate heads of phospholipids; The phosphate heads of the phospholipids are polar, so they are attracted to the polar water molecules.
What is the main component of the cell membrane?
phospholipids; Although phospholipids have a polar head, the long fatty acid tails are nonpolar, making the membrane mostly nonpolar.
Which of the following is NOT one of the three major components of a typical eukaryotic cell?
ribosome; Ribosomes are organelles and they are located within one of the major components of the cell.
What is a characteristic of the cell membrane?
semipermeable; The cell membrane is semipermeable, or selectively permeable, because some things can easily pass through it while others cannot.
Which of the following is least likely to increase the rate of diffusion?
small concentration gradient; The larger the concentration gradient, the faster the rate of diffusion. Higher concentration means there are more collisions, so the molecules bounce away from each other more rapidly.
