Download Ch 3 Check Your Progress Answers BC Biology 12 3.1 p 67 1

Ch 3 Check Your Progress Answers BC Biology 12
3.1 p 67
1. Explain why humans are made up of trillions of cells.
Having many cells allows the surface area-to-volume ratio to be quite large and
allows materials to be exchanged more easily. Smaller cells have a higher metabolic
rate. Also, having many different cells allows an organism to have areas of
specialization for different functions.
2. Describe what happens to the surface area to volume ratio as the cell size increases.
SA:volume ratio decreases. If a cell doubles in size, its surface area increases
fourfold but its surface area increases 8 fold .
3.2 p 77
1. Explain the function of the cell wall in eukaryotes.
Cell wall provides support and protection
2. Explain the function of select organelles within the cell.
Organelles each provide a specific function necessary to cell life.
3. Describe the advantages that different compartments provide for the cell.
Having different compartments allows the organelles to specialize and provide
specific jobs. Also, the raw materials get delivered or eliminated from specific
places, minimizing transportation energy requirements.
3.3 p 80
1. Identify the structural makeup of actin filaments, intermediate filaments and
microtubules
Actin: long, extremely thin, flexible fibers that occur in bundles or meshlike
networks, 2 chains of globular actin monomers twisted about each other in a helical
manner
intermediate: intermediate in size between actin and microtubules; rope-like
assembly of fibrous polypeptides
microtubules: small hollow cylinders about 25nm in diameter and .2um in length;
made of globular protein, dimer; 13 rows around an empty core
2. Describe the structure of cilia, flagella, and centrioles.
cilia and flagella: hair-like projections that can move like a whip or an oar. Cilia are
shorter than flagella but have similar construction. Both are membrane bound
cylinders. The cylinders are nine microtubule doublets arranged in a circle around
two central microtubules.
centrioles: short cylinders of microtubules with a 9+0 pattern of microtubule
triplets, with none in the middle; They replicate at right angles to one another and
separate during cell division
3. Explain how cilia and flagella move.
They move when the microtubules doublets slide past each other. In the presence of
ATP, the dynein side arms reach out to their neighbours and bending occurs.
3.4 p 82
1. Describe the role of proteins, steroids, and phospholipids in the fluid mosaic model
peripheral proteins: structural; they help stabilize and shape the plasma membrane
and play a role in signaling pathways
integral proteins: determine a membrane’s specific functions
2. Distinguish between the roles of the various integral proteins in the plasma
membrane
identify pictures on page 82 Fig 3.16
a) channel proteins: allow substances to pass through; like H ions for ATP
formation
b) carrier proteins: selectively interacts with a specific molecule or ion so that it
can cross the plasma membrane (eg. GLUT transfers glucose)
c) cell recognition protein: glycoproteins that help the body recognize self vs
others and can help recognize invaders like bacteria
d) receptor proteins: have a shape that allows a specific molecule to bind to it.
The binding causes the shape of the protein to change and to have a cellular
response (eg. liver stores glucose after insulin from pancreas tells it to do so)
e) enzymatic proteins: carry out metabolic reactions directly; some reactions
occur as a result of them (like final steps in electron transport chain)
3.5 p 91
1. Contrast diffusion with facilitated transport
diffusion is the movement of molecules from an area of high concentration to an
area of low concentration (down the concentration gradient); usually lipid soluble
molecules and gas
facilitated transport: down concentration gradient but they have channels or a
carrier; some sugars and amino acids
2. Explain the movement of water between hypotonic and hypertonic environments.
If a cell is placed in a relatively hypertonic environment, water will flow out of the
cell
If a cell is placed in a relatively hypotonic environment, water will flow into the cell
3. Describe the differences between facilitated and active transport
facilitated transport requires a carrier but no input of energy since it flows toward
lower concentratio while active transport requires a carrier plus energy since it
flows toward higher concentration of particles (eg, sugars, amino acids and ions).
4. Discuss the potential benefits of receptor-mediated endocytosis.
This is a form of pinocytosis that is selective and efficient. It has a specific protein
receptor shape so that the specific molecule can bind to it and no other.