Unit 5 - Cells Textbook Work

What materials need to be exchanged across a cell membrane?

Cell membranes must control the exchange of nutrients, wastes, water, and communication signals.

What limits the size of cells?

Cell size is limited by the ability of diffusion to transport adequate nutrients into the cell and to remove wastes from the cell.

What is the significance of a membrane's being selectively permeable?

A cell membrane must selectively permeable so that the cell can exert some level of control over which types of molecules can pass through the membrane.

What is a concentration gradient? How does it affect diffusion?

A concentration gradient refers to the gradual change in solute concentration, either from a low concentration to a high one or the opposite. Diffusion can move molecules down a concentration gradient (that is from an area of high concentration to an area of low concentration), but it cannot transport molecules against a concentration gradient.

Explain the difference between tissues and organs.

A group of cells working together is defined as a tissue and several tissues working together comprise an organ. The heart is used as an example of an organ which is made up from muscle and valve tissue.

Can a single cell form a system or a tissue? Explain your answer.

A single cell cannot form a system or a tissue since, by definition, these terms describe collections of cells with a specialized function.

What type of evidence demonstrates active transport?

Active transport moves substances against their concentration gradients and thus requires energy. Since substances can't move against concentration gradient, there has to be active transport since some substances do more work against the concentration gradient, cells can move substances against their concentration gradient because we can see more of a substance inside a cell then outside of a cell.

Explain the differences between active and passive transport. Why is each important to a cell?

Active transport uses energy (often supplied by ATP) to move molecules against their concentration gradient. Passive transport describes the transport of molecules down their concentration gradient and is accomplished without the input of energy.

In what way is an organism a protected compartment?

An organism is a protected compartment in the sense that whether it is made of a single or many cells, each cell is completely surrounded by a protective membrane.

How are cells organized in multicellular organisms? What are the advantages of that organization?

Cells are organized into tissues in multicellular organisms. Tissues are further organized into organs. This organization allows for the localization and isolation of biological processes.

What is the cell theory?

Cells, or products made by cells, are the units of structure and function in organisms. All cells come from preexisting cells.

Biologists have been able to keep isolated chloroplasts or mitochondria for a few hours or days. Can these structures be considered alive?

Chloroplasts and mitochondria are organelles which both have DNA and can have the capability of replicating and reproducing itself, which means they can stay alive for a certain amount of hours or days.

Some medicines are delivered in capsules of artificial vesicles to be swallowed. Would this method be best for delivering medicines that act on target proteins in the plasma membrane, the mitochondria, or the cytosol? Explain your answer.

Cytosol, because a swallowed vesicle would not reach the plasma membrane, or the mitochondria.

Compare the differences and similarities of prokaryotic and eukaryotic cells.

Eukaryotic cells contain many membrane-enclosed, large, complex organelles in the cytoplasm whereas prokaryotic cells do not contain these membrane-bound organelles. Only eukaryotes possess a membrane-bound nucleus and membrane-bound organelles such as the mitochondria, golgi apparatus, lysosomes, peroxisomes and ER.

What three organelles enable eukaryotic cells to move?

Flagella, cilia, and pseudopodia.

In what way is a cell membrane selective?

It allows small molecules to pass through but restricts the movement of large molecules. It uses a variety of transport proteins to help move certain large molecules either with or against their concentration gradients. It also contains transport proteins that help transport ions across the membrane.

How do membranes regulate the movement of molecules into and out of the cell?

Membranes regulate the movement of molecules by providing barriers to certain larger molecules. Other molecules are regulated by specific transport proteins or by coupling the movement of one type of molecule to the movement of another type of molecule.

Explain why metabolism in eukaryotic cells depends on the endoplasmic reticulum, but prokaryotes have survived quite well without such an internal transport system.

Metabolism in eukaryotic cells depends on the ER because it transports materials between membrane-bound organelles within a cell. Prokaryotic cells do not have membrane-bound organelles and therefore do not need an ER.

Which membrane gives eukaryotes an advantage over prokaryotes in protecting their genetic material from damaging chemical changes?

The nuclear membrane.

In centimeters, how long is your pencil? How does its size compare with that of a bacterium? Of a eukaryotic cell?

My pencil is around 18 centimeters long. A centimeter is 1000 micrometers and the size of a bacterium it's around 1 to 10 micrometers in size, while a eukaryotic cell is a bit bigger, being around 10-50 micrometers in size. if we compare, for a bacterium, it is about .005 of a cm and a eukaryotic cell is about .025 of a cm.

What are the important characteristics of prokaryotic cells?

No membrane enclosed organelles, singular circular chromosome, no streaming in the cytoplasm, cell division without mitosis, simple flagella, small ribosomes, no known cytoskeletal, no cellulose in cell walls, proteins bound to DNA.

List three cell parts found in both prokaryotes and eukaryotes.

Plasma membrane, flagella, and ribosomes.

In what ways does the study of cells depend on technology?

Progress depended on the technology of improved microscopes, better techniques to prepare cells for observation, and studies of cell function. Even modern light microscopes cannot uncover all the detailed wonders of the cell—some of its structures are too small to see without the electron microscope.

Give three reasons why specialized systems are necessary in large multicellular organisms.

Specialized systems are necessary in large multicellular organisms since there is a division of labor between cells, many individual cells cannot work together without coordination, and most of the cells are not in direct contact with the outside environment.

What cell part specializes in packaging materials for export? Give an example of how the plasma membrane also can package materials for export.

The Golgi Apparatus packages materials for export from the cell. Materials in the plasma membrane can be packaged inside vesicles that bud off from the plasma membrane.

What is one advantage of using a light microscope rather than a more powerful electron microscope?

The biggest advantage is that they have a higher resolution and are therefore also able of a higher magnification. Light microscopes can show a useful magnification only up to 1000-2000 times.

Arrange these terms in increasing order of complexity: cells, systems, organs, tissues, organisms.

The terms in order of increasing complexity are cells, tissues, organs, organ systems, and organelles.

What differences are likely to exist between unicellular organisms and cells of larger organisms?

Unicellular organisms are those with one cell. These are organisms that belong to the kingdoms of Monera and Protista. On the other hand, multicellular organisms have many cells, some of which have different functions.

Would you expect osmosis and diffusion to stop when substances are evenly distributed? Explain your answer.

When substances attain equal distribution over an area, there is no longer any net movement of the substance and diffusion (or osmosis) stops (but the molecules themselves do not stop moving).