حل أوراق عمل Exam Coverage الأحياء الصف الحادي عشر Elite

حل أوراق عمل Exam Coverage الأحياء الصف الحادي عشر Elite

Question and Answer

Which of the following functions can be attributed to lipids? Select all that apply.
✓ building blocks for cholesterol and other hormones
✓ membrane and barrier formation
information storage
catalyzing biological reactions
✓ energy storage

What is the importance of lipids in most living organisms?
The most biologically important lipids are fats, phospholipids, and steroids and their major function is to store energy.
They are the major component of all cell membranes.
Cholesterol is a steroid that is important in animal cells because it plays a role in maintaining the structure and function of membranes and it is a precursor to vitamin D and some hormones.

Lipids perform three primary biological functions within the body: they serve as structural components of cell membranes, function as energy storage, and function as important signaling molecules (hormones).

Which is the vascular tissue that transports water and dissolved minerals from roots to leaves?
phloem
epidermis
✓ xylem
parenchyma

Explain how a plant tissue’s structure is related to its function.
Plant tissue’s and various cells have different structure which is related to its specific function. As for example vascular tissue cell shape helps to transport water and food throughout the plant, parenchyma cells are thin-walled to help function in storage.

Evaluate why the role of the stomata in a plant is important.
1. They help in gaseous exchange i.e gaining of carbon dioxide and release of oxygen (for photosynthesis) and gaining of oxygen and release of carbon dioxide (for respiration).
2. They help in the regulation of water loss from the plant (Transpiration).

How does the stomata adapt to different climate changes to maintain homeostasis?
In case of extreme conditions like drought or high temperature the guard cells tend to close the stomata to minimize the water loss by the cell thereby maintaining homeostasis.
The closing of the stomata help the plant by preventing dehydration due to loss of water vapor, and helps with maintaining the water necessary for photosynthesis and the homeostasis, or internal balance of the plant.

 Special proteins called Select Choice are the biological catalysts that speed up the rate of chemical reactions in biological processes.
Ans: Enzymes

What are biological catalysts?
The biological catalysts are the specific molecules or substances that speed up the rate at which biochemical reactions occur. The enzymes are the biological catalysts which increases the rate of biological reaction and induce the formation of products.
For example, digestive enzymes like trypsin, pepsin, Amylase etc.

What is the mechanism of the Na+/K+ pump?
The sodium-potassium pump system moves sodium and potassium ions against large concentration gradients
It moves two potassium ions into the cell where potassium levels are high, and pumps three sodium ions out of the cell and into the extracellular fluid.
The sodium-potassium pump is an example of active transport because energy is required to move the sodium and potassium ions against the concentration gradient.

Which of the following factors influence enzyme activity? Select all that apply.
✓ temperature
time of day
whether the reaction is exothermic or endothermic
the activation energy
✓ pH

Explain the effect of extreme conditions on the activity of enzyme
Extreme high temperatures can cause an enzyme to lose its shape (denature) and stop working. pH: Each enzyme has an optimum pH range. Changing the pH outside of this range will slow enzyme activity. Extreme  values can cause enzymes to denature.

Endocytosis & Exocytosis
Exocytosis
Movement of large materials out of the cell.
Vesicles form around a particle.
The vesicles combine with the cell membrane.
The particle is expelled from the cell.

Contrast how facilitated diffusion is different from active transport.
Facilitated diffusion moves molecules/ substances down a concentration gradient (higher to lower concentration) across the plasma membrane without the use of energy, whereas active transport moves molecules against a concentration adient (lower to higher concentration) with the use of energy/ ATP.

OR

Facilitated diffusion moves substances with the gradi- ent and does not require cellular energy to transport a molecule across the plasma membrane. Active transport requires energy because it moves substances against the gradient.

How does the structure of water affect its ability to act as a solvent?
Water is polar molecule, allowing for the formation of hydrogen bonds, which allow ions and other polar molecules to dissolve in water. Therefore, water is an excellent solvent.
Because of its polarity and ability to form hydrogen bonds it can dissolve many different kinds of molecules.

Describe the most important properties of water.
1. Water is polar. Water molecules are polar, with partial positive charges on the hydrogens, a partial negative charge on the oxygen.and a bent overall structure.

2. Water is an excellent solvent. Water has the unique ability to dissolve many polar and ionic substances.

3. Water has high heat capacity. It takes a lot of energy to raise the temperature of a certain amount of water by a degree, so water helps with regulating temperature in the environment. For example, this property allows the temperature of water in a pond to stay relatively constant from day to night, regardless of the changing atmospheric temperature

4. Water has high heat of vaporization. Humans (and other animals that sweat) use water’s high heat of vaporization to cool off. Water is converted from its liquid form to steam when the heat of vaporization is reached. Since sweat is made mostly of water, the evaporating water absorbs excess body heat, which is released into the atmosphere. This is known as evaporative cooling.

5. Water has cohesive and adhesive
properties. Water molecules have strong cohesive forces due to their ability to form hydrogen bonds with one another. Cohesive forces are responsible for surface tension, the tendency of a liquid’s surface to resist rupture when placed under tension or stress. Water also has adhesive properties that allow it to stick to substances other than itself. These cohesive and adhesive properties are essential for fluid transport in many forms of life. For example, they allow nutrients to be transported to the top of a tree against the force of gravity.

6. Water is less dense as a solid than as a liquid. As water freezes, the molecules form a crystalline structure that spaces the molecules further apart than in liquid water. This means that ice is less dense than liquid water, which is why it floats.