Download Cells Check 2 (Solutions)

Name: ___________________________________
Cells and Transport
VCE Biology- Unit 3
1. What is the ‘Cell Theory’?
The cell theory states that all living organisms consist of organized structures called cells or the products of
cells.
2. Make a list of the advances in technology that have allowed scientists to extend their knowledge of cells
and their structures.
Technological advances: hand-held lens, light microscope, phase contrast microscopes, fluorescence
microscopes, transmission and scanning electron microscopes, sectioning equipment and improved staining
techniques.
3. Compare eukaryotic cells and prokaryotic cells, listing the major structural differences between them.
Eukaryotic cells
Relatively large
Unicellular or parts of complex multicellular
organisms
Distinct nucleus
Separate membrane-bound organelles
Prokaryotic cells
Small and lack specification
Unicellular or very simple multicellular organisms
Nuclear material not membrane-bound
Little ‘compartmentalisation’
No membrane- bound organelles
4. Describe the major structural differences between plant and animal cells, paying attention to cell
organelles unique to each cell type.
Cell wall: plant cells have a thick cellulose wall and cell membrane. Animal cells only have a cell
membrane.
Vacuole: large permanent vacuoles are characteristic of plant cells but not animal cells.
Plastids: pigment-filled organelles such as chloroplasts are found in plant cells but not animal cells.
5. Why are cells usually microscopic in size? Discuss in terms of surface area to volume ratio and movement
of materials into and out of cells.
Cells are microscopic in size to increase their surface area to volume ratio. It is through the surface of a cell
that materials enter and leave. An increase in cell volume means a decrease in surface area to volume ratio
and so the rate of exchange of materials (requirements and wastes) between a cell and its surroundings is
decreased. Surface area can be increased to a certain extent by shape. Remember the ‘biconcave disc’ shape
of red blood cells. This increases surface area to volume ratio of red blood cells and thus the ability for
oxygen to diffuse in and out at a rapid rate.
6. How are functions of the ribosomes, endoplasmic reticulum, golgi apparatus, and vesicles related?
Ribosomes are the site of protein synthesis (production). Ribosomes are attached to the endoplasmic
reticulum, which contains a membrane system that provides channels for movement of materials. It is also
the site where the protein is folded and carbohydrates added. Proteins produced in the cell are packaged at
the golgi apparatus (packaging) and moved to the cell membrane in vesicles (export). Protein markers on the
vesicles determine which membranes the vesicles can fuse with. If the vesicle fuses with the cell membrane,
the contents are secreted. The endoplasmic reticulum, the golgi apparatus and the vesicles are membranous
organelles whose function can be summarized as transport, packaging and export.
7. Describe the fluid mosaic model for the structure of the cell membrane.
The fluid mosaic model proposes that cell membranes consist of a bi-layer of phospholipids with embedded
proteins. Fat-soluble materials can pass through the lipid part of the membrane. Other materials can pass
through protein channels.
Name: ___________________________________
VCE Biology- Unit 3
8. How is the structure and function of cell walls different to that of cell membranes?
Cellulose cell walls are found in plant cells and have a support function rather than forming an envelope for
a cell’s living contents. The cell membrane provides little support. Its major role is in determining what
passes in and out of cells. It is described as semipermeable. The cell membrane is made of a double layer of
phospholipid molecules and embedded with lumps of proteins. The proteins form channels that allow larger
molecules to move in and out of the cell.
9. Define and compare the processes: diffusion, osmosis, facilitated diffusion, active transport and vesicle
mediated transport.
Definition
Diffusion
Process where molecules of a substance move
from a region of high concentration to a region
of lower concentration resulting in an even
spread of molecules. Can occur in gases or
liquids.
Comparison
No external energy is required.
Movement is due to random movement of
all molecules. Note, however, that the rate
of diffusion increases with temperature.
Movement of molecules is down the
concentration gradient.
A special case of diffusion- refers to the
movement of water molecules from solutions of
differing concentrations that are separated by a
permeable membrane. Net movement of water
will be to the side with higher concentration of
dissolved materials (solutes).
As above, but note that the movement of
molecules refers to water only.
Facilitated
diffusion
Case of diffusion where movement of materials
is aided (facilitated) by special protein carrier
molecules.
Increases rate of movement of materials
across membranes when the materials
concerned do not dissolve readily in the
lipid bilayer of membranes.
Active
transport
Protein carrier molecules involved in moving
materials across membranes against a
concentration gradient – that is, material
moved to a region where it is higher in
concentration.
Energy is required. This process can only
occur in living cells that are respiring and
so producing ATP. Process is very
important in plant root hairs where ions
are actively absorbed from the soil and in
the mammalian digestive system.
Vesiclemediated
transport
The cell membrane and vesicles are involved in
the movement of large molecules into or out of
the cell.
Energy is required. Involves the
movement of very large molecules and
vesicles fusing with the cell membrane.
Osmosis
Water molecules are moving down their
concentration gradient.