Bio test 2

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The main lipids found in the cell membranes are what?

phospholipids

In general, which of the following is largely responsible for moving substances across the plasma membrane, communicating with other cells, and identifying the cell?

proteins

Plasma membranes are BEST described as what?

double layer of phospholipids with hydrophobic tails oriented toward one another.

When a mouse cell and a human cell are fused, the membrane proteins of the two cells become uniformly distributed over the surface of the hybrid cell. This occurs because?

many proteins can move around within the bilayer.

Cell membranes do all of the following EXCEPT which one?

provide shape and structure to a cell.

The rate of facilitated diffusion of a molecule across a membrane will increase as the concentration gradient of the molecule across the membrane increases to a certain point. Eventually, an increase in the concentration of the molecule will not cause any further increase in facilitated diffusion. This is because what?

there are a limited number of carrier proteins in the membrane.

To say that a cell is "selectively permeable" means what?

only certain molecules can pass through.

The process in which white blood cells engulf bacteria is termed what?

phagocytosis.

Two aqueous solutions are separated by a selectively permeable membrane that allows water to pass through but does not allow starch to pass through. Solution A is 10% starch and solution B is 5% starch. What will occur?

Water will diffuse from solution B to solution A

Cells use exocytosis to do what?

release substances from the cell.

What is the correct order of the steps below as they relate to enzyme catalysis? 1. The substrate and enzyme change shape. 2. The substrate enters the active site. 3. The enzyme reverts to its original configuration. 4. The product is expelled.

2, 1, 4, 3

Which of these statements regarding enzymes is FALSE?

Enzymes provide energy for the reactions they catalyze.

Which of the following is the organic molecule that is sometimes required for certain enzyme activity?

a coenzyme

Energy is defined as the capacity to do work. True or False?

TRUE

Competitive and noncompetitive enzyme inhibitors differ with respect to what property?

the precise location on the enzyme to which they bind.

Imagine you are conducting an experiment on a yeast enzyme known as sucrase. This enzyme is used by yeast cells to break down sucrose into glucose and fructose. What type of reaction is this?

exergonic

All of the following statements are true of the first law of thermodynamics EXCEPT which one?

the amount of useful energy decreases

Imagine you are conducting an experiment on an enzyme known as sucrase. This enzyme is synthesized and used by yeast cells to break down the disaccharide sucrose (table sugar) into the monosaccharides glucose and fructose. You decide to conduct an experiment to test whether the sucrase enzyme can break down the artificial sweetener sucralose. Sucralose (a "chlorinated" carbohydrate) has some chemical similarity to sucrose, but is different in that three of its hydroxyl groups are missing and replaced with chlorine atoms instead. Based on the details provided in this scenario, do you think the sucrase enzyme will be able to interact with sucralose?

No; all enzymes are highly specific and can react with only a specific substrate.

Preservatives such as citric acid are added to foods to interfere with bacterial growth. This creates an acidic pH in the food. Why does this affect the bacteria that are present?

An acidic enviroment causes bacterial enzymes to fail or work less efficiently

What is the ultimate source of energy for almost all forms of life on Earth?

solar energy

Light reactions produce:

ATP, NADPH, and O2

Specifically, molecules of chlorophyll are located in the membranes of sacs called:

thylakoids

Before photosynthesis evolved, ________ was rare in Earth's atmosphere.

O2

In C4 photosynthesis, where does the carbon in newly synthesized glucose come from?

atmospheric CO2

The role of water in photosynthesis is to:

provide electrons

During photosynthesis, when is CO2 utilized?

during the Calvin cycle only

Carbon dioxide is required in the light reactions of photosynthesis. True or False?

FALSE

Suppose that you are experimenting with different types of lighting for your indoor green plants. Which of the following colors of light will be most effective?

red & blue

The products of photosynthesis are:

glucose and oxygen

NADPH is synthesized during which of the following reactions?

the light reactions only

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