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3.3.5 Practice: Cells

Biology Sem 1

Points Possible:25

Practice

Name:

Date:

In this practice you will apply what you have learned in this unit. Please answer the questions below. Submit this to your teacher when you are done.

Instructions: Read the article below and answer the following questions.

"Francesco Redi was a scientist that performed an experiment to determine whether maggots formed from rotting meat. Versions of his experiments are described below.

Meat was placed in two beakers. One of the beakers was left open to the air. The other beaker was covered with a fabric that only allowed air to get in. As the meat rotted, flies landed on the meat in the open beaker but were unable to get to the meat with the fabric over it. After a few days, maggots appeared on the meat in the open beaker, but not in the closed beaker.

In the next experiment, rotting meat was placed in two beakers. Dead flies were placed in one beaker, and live flies were placed in the other beaker. Both beakers were sealed, allowing no air in. Maggots appeared in the beaker with live flies, but not in the beaker with dead flies."

1. Explain how this experiment disproves the theory of spontaneous generation. (3 points)

These maggots come from the egss laid by flies on the meat as it is only found on open meat jar where flies can go and lay their egss. I disaproves the spontaneous generation theory as if it was true open or closed jar every rotting meat jar must carry maggots on them.

2. Explain how the surface area and volume of cells affect the rate of exchange of materials in and out of cells in multicellular organisms. (2 points)

An organism must have a arge area to volume ratio in order to exchange materials easier. Having a flat concave shape allows them to carry more haemooblin and also increases its surface area to volume ratio so that the length and availability of a surface is less for the material to travel. Mutli cellular organism tend to have flat and elongated respiratory surfaces to allow for a larger/ higert surface area and volume ratio in order to increase the rate of gas exchange.

3. a) The flowchart below shows the pathway a protein takes from its production to its destination either inside or outside the cell.

Ribosomes → rough endoplasmic reticulum → vesicle → Golgi apparatus → vesicle → within the cell or outside the cell

Explain where in this pathway the process of exocytosis plays a role. (1 point)

The process of exocytosis plays a role during vesicle transport. Exocytosis is a process of secretion of cell contents of the vacuole to the exterior environment. Vesicle membrane fuses with the cell membrane and releases its content to the different cell compartments.

b) Antibiotics destroy a bacterial infection by disabling ribosomes in the bacteria. Eukarotic cells contain mitochondria that themselves contain ribosomes while bacterial cells have no organelles and thus have uncontained ribosomes. How do chemists use this fact to create antibiotics that can destroy a bacterial infection without harming human cells? (1 point)

Antibiotics attack proteins only found in bacteria. Each one targets a specific area, be it their cell wall, cell membrane or protein synthesis centers, and really any area that differs enough from human cells.

c) Explain how the structures that are unique to plant cells help a cactus survive a harsh desert climate. (1 point)

Cacti have a hard structure that protects them an holds in water in them.

4. a) Cell membranes are made up of a bilayer of phospholipids that are very selective about what substances can pass through.

The table below shows the different types of molecules that can enter a cell. It compares the concentration on the outside to the inside of the cell, its relative size, and whether it is polar, nonpolar, or an ion. Determine how each molecule can pass into the cell. Is it by passive transport, active transport, or endocytosis? (3 points)

Oxygen: Passive transport, Carbon dioxide passes through, fructose endocytosis, Glutamine active transport, Glutamine active transport, sodium ions active transport, potassium ions active transport, protein molecules, passive transport or endocytosis.

b) Review the results of your table and summarize your observations about how the different substances cross membranes. (2 points)

If the concentration of the molecule is higher on the outside of the cell, than it is most likely passive transport, If the concentration of the molecule is higher on the inside, it is most likely active transport. If the molecule is known to be bigger, it is likely to be the process of endocytosis.

5. Membrane receptors are specialized proteins that take part in communication between the cell and the outside world. The membrane protein receptor can be subdivided into three

parts or domains. The portion of the protein in the E zone is extracellular (outside of the cell). The P zone is the plasma membrane and the I zone is intracellular (inside of the cell).

A glucagon hormone is a molecule that stimulates a reaction inside liver cells. Based on the diagram, where do you think a glucagon hormone most likely binds to send its signal to the cell? (1 point)

The E Domain

6. a) The important factor in osmosis is not the number of molecules. Instead, it is the number of particles in a given volume of solution. For example, one glucose molecule

dissolved in water yields one particle, but one NaCl molecule can yield two ions: Na+ and Cl-. Water moves osmotically in response to the total concentration of particles in the solution.

If there is a 10% glucose solution on one side of a semipermeable membrane and 5% salt solution on the other side, what will most likely happen to the flow of water? (1 point)

The water will flow out of the cell because there is less water outside the cell and ther needs to be equal concentration.

b) The Atlantic salmon lives in the ocean for most of its life. Every year, it returns to freshwater rivers to spawn. Based on what you've learned so far about membrane proteins, diffusion, and osmosis, what kind of mechanism allows the salmon cells to adapt to freshwater after leaving saltwater? (1 point)

By altering function and excreting a huge wolume of diluye urine, the salmon’s kidney is able to adapt with the change from saltwater to freshwater.

c) Explain what would happen to the salmon's cells if this process did not occur. (1 point)

Metsulfuron will inhibit cell division and animo acid synthesis.

7. a) Below is a picture of a tomato plant. It is a multicellular organism with many parts that work together to keep the plant alive. Select at least four structures on the plant and describe how cells in those structures specialize to help the plant stay alive. (2 points)

b) Fusarium oxysporum is a fungus that attacks tomato plants, causing them to wilt and die. The fungus initially blocks the xylem and grows extensively within parenchyma. As the plant continues to wilt, the blockage of both xylem and phloem can be observed. The result is the suppression of both the xylem sap circulation in the plant and photosynthetic activity in the leaves.

Based on these observations, explain how the fungus affects the role of both the xylem and the phloem. (1 point)

The xylem transports water to the plant, so if the fungus blocks the xylem, the plant would eventually dehydrate, affecting the role of the xylem.The phloem transports glucose,

nutrients and such, therefore the fungi may try to steal the nutrients for the plant, affecting its role.

c) Describe the gradual effects of suppressing xylem and phloem on the tomato plant (that is, the effect on plant structure, supply of water, supply of carbohydrates, and the plant overall). (1 point)

The plant will droop, wilt, and start to die because the plant isn’t etting the things it needs in order ro stay alive and grow

8. The continuum below shows the development of the human embryo into an adult and the types of stem cells involved.

a) List the four types of stem cells, give an example of each type, and explain how much each type can differentiate. (2 points)

Totipotent: Zygote

Pluripotent: Embryonic stem cells

Multipotent: Neural stem cells

Unipotent: epidermal stem cells

b) Many people feel the use of stem cells has great potential for scientific and medical progress, while others have been opposed to it. Today there is a great deal of debate about stem cell research using pluripotent stem cells from an embryo. Provide an argument for people in favor of continuing stem cell research. Include in your answer the uses of stem cell research and a suggestion for obtaining a source of stem cells without risk to life. (2 points)

Regenerative medicines and therapeutic cloning are very effective to control many dreadful diseases.By studying stem cells, scientists can study how to treat an ailment whose cure was otherwise unknown. As diseases like cancer occur due to inappropriate divisions, study of stem cells enable scientists to learn the mechanism of differentiation and how it gives rise to cancer.One of the methods through which stem cells can be obtained is the method of induced pluripotency. By this method, pluripotent stem cells can be made from adult stem cells....