Chapter One - Homeostatis

Question 1

What is homeostatis?

Answer 1

Homeostasis is the tendency to resist change in order to maintain a stable, relatively constant internal environment.

Question 2

Why is homeostasis important?

Answer 2

It’s essential for the survival of all cells.

Question 3

Name and describe an intrinsically controlled organ.

Answer 3

Skeletal muscle. During exercise, skeletal muscle uses up oxygen. The local chemical change causes the smooth muscle to relax allowing the blood vessels to dilate and increase blood flow. This allows more oxygen to flow into the exercising muscle.

Question 4

Name and describe an extrinsically controlled organ.

Answer 4

The heart. When blood pressure drops too low, the nervous system acts simultaneously on the heart and blood vessels throughout the body to increase your blood pressure to a normal level.

Question 5

Give an example of a feedforward control system.

Answer 5

These are responses made by the body in anticipation of change. Just thinking about food can make your mouth start to water and your stomach begin to growl.

Question 6

Describe a physiological example of negative feedback.

Answer 6

When temperature-monitoring nerve cells detect a decrease in body temperature below a desired level, they signal the temperature control center in the brain, which begins a sequence of events that ends in responses, such as shivering, that generate heat and raise the body temperature to the proper level. When the body temperature reaches the set point, the temperature-monitoring nerve cells turn off the stimulatory signal to the skeletal muscles so the body temperature doesn’t continue to fall below the set point.

Question 7

In body temperature regulation, which part is the sensor? Integrator? Effector?

Answer 7

Temperature-monitoring nerve cells. The temperature control center in the brain. The skeletal muscles.

Question 8

Name 6 variables that are homeostatically controlled.

Answer 8

Body temperature, concentration of nutrients, concentration of oxygen and carbon dioxide, concentration of waste products, pH levels, and volume/pressure.

Question 9

How is positive feedback different from negative?

Answer 9

It enhances or amplifies a change so the variable continues to move in the direction of the initial change,.

Question 10

Does positive feedback maintain homeostasis?

Answer 10

No. The goal of homeostasis is to maintain a relatively stable environment and positive feedback continues to move the variable away from the set point.

Question 11

What does anaerobic mean?

Answer 11

Without oxygen.

Question 12

What does aerobic mean?

Answer 12

With oxygen.

Question 13

What is oxygen used for in cells?

Answer 13

The production of energy in the form of ATP.

Question 14

What are NAD+ and FAD+?

Answer 14

Hydrogen carrier molecules in the Citric Acid (Krebs) Cyle.

Question 15

Why is there a “+” in NAD+ and FAD+?

Answer 15

The molecule has a positive charge (proton).

Question 16

What is an endergonic reaction?

Answer 16

A reaction in which energy is absorbed.

Question 17

What is an exergonic reaction?

Answer 17

A reaction where energy is released.

Question 18

How do enzymes affect activation energy?

Answer 18

Enzymes speed up chemical reactions by lowering the activation energy.

Question 19

What is a substrate?

Answer 19

A molecule upon which an enzyme acts.

Question 20

What is a reactant?

Answer 20

A substrate and reactant are the same.

Question 21

What is a product?

Answer 21

The result when a substrate or reactant is changed by an enzyme.

Question 22

Why do cells require energy?

Answer 22

Synthesis of new chemical compounds, membrane transport, and mechanical work.

Question 23

What is the function of glycolysis? Where in cells does it occur? Can all cells do it?

Answer 23

Glycolysis breaks down a 6-carbon sugar molecule into two 3-carbon pyruvate molecules. this process occurs in the cytosol of the cell. All cells are capable of glycolysis.

Question 24

What substrates goes into glycolysis? What are the products?

Answer 24

The substrate is glucose and the products are pyruvate and ATP.

Question 25

Does glycolysis require oxygen?

Answer 25

No. This process can happen aerobically or anaerobically.

Question 26

When and how is lactic acid formed?

Answer 26

When glycolysis happens anaerobically, the product is lactic acid which is stored in the muscles until is removed from the body in the blood.

Question 27

What parts of cell respiration are aerobic?

Answer 27

Citric Acid Cycle and Oxidative Phosphorylation.

Question 28

Where does the Krebs Cycle occur?

Answer 28

In the mitochondrial matrix.

Question 29

What substrate goes into the Krebs Cycle. How does pyruvic acid become this form?

Answer 29

Acetyl-CoA is the substrate in the Krebs Cycle. One of the carbons in pyruvic acid is removed in the form of carbon dioxide. One of the hydrogens is released and transferred to NADH. The remaining 2-carbon molecule combines with coenzyme A to produce acetyl-CoA.

Question 30

How many carbon atoms enter Krebs? What molecule do they bind to? What molecule does it become?

Answer 30

Six carbons enter the Krebs Cycle from one round of glycolysis. It binds with coenzyme A (CoA) to form Acetyl-CoA.

Question 31

What are the products of Krebs? Where do they go?

Answer 31

The Krebs Cycle (per 2 molecules of pyruvic acid) two ATP molecules, ten NADH molecules, and two FADH2 molecules. The NADH and the FADH2 will be used in the electron transport system.

Question 32

Explain the steps of the ETC. Include the chemiosmotic theory.

Answer 32

NADH and FADH2 from the Krebs Cycle harvest electrons and carry them to the ETC. Electrons provide the energy to pump protons across the inner mitochondrial membrane. Oxygen combines with protons and electrons to form water. Protons diffuse back in over their concentration gradient which drives the synthesis of ATP. The chemiosmotic theory explains the functioning of electron transport chains. According to this theory, the transfer of electrons down an electron transport system through a series of oxidation-reduction reactions releases energy.

Question 33

Which stage of cell respiration makes the most ATP?

Answer 33

The majority of ATP is created in the ETC.

Question 34

What does selective permeability mean? How does a cell achieve this?

Answer 34

The actual structure of the cell membrane allows free passage or restricts movement of substances across the membrane. Three ways in which the cell membrane controls the movement of substances is by simple diffusion, facilitated diffusion, and active transport.

Question 35

Name the components of a cell membrane and provide a brief description of each function.

Answer 35

1) Phospholipid - Lipid made of glycerol, two fatty acids tails, and a phosphate linked head group. Biological membranes usually involve two layers of phospholipids with their tails pointing inward, an arrangement called a phospholipid bilayer.
2) Cholesterol - Another lipid composed of 4 fused carbon rings. Found alongside phospholipids in the core of the membrane.
3) Membrane Proteins - Extend partway into the plasma membrane, cross the membrane entirely, or be loosely attached to its inner or outer surface.
4) Carbohydrate Groups - Present only on the outer surface of the plasma membrane and are attached to proteins, forming glycoproteins, or lipids forming glycolipids.

Question 36

How are cells held together?

Answer 36

Extracellular Matrix - An intricate meshwork of fibrous proteins embedded in a watery gel-like substance composed of complex carbohydrates. Biological ‘glue’.

Question 37

Describe 3 structures within the extracellular matrix.

Answer 37

1) Desmosomes - Act like ‘spot rivets’ that anchor together two adjacent but non-touching cells. Most abundant in tissues that are subject to a lot of stretching like the skin, heart, and uterus.
2) Tight Junctions - Adjacent cells bind firmly with each other at points of direct contact to seal off the passageway between the two cells. Found primarily in sheets of epithelial tissue which covers the surface of the body and line its internal cavities.
3) Gap Junctions - A gap exists between two adjacent cells which are linked by small connecting tunnels formed by connexons. The small diameter of the tunnels permits small water soluble particles to pass between the connected walls without entering the ECF.

Question 38

Describe simple diffusion.

Answer 38

With simple diffusion, certain substances such as water, oxygen, and carbon dioxide move from an area of high concentration to an area of low concentration. This type of movement does not require energy because the substances move down their concentration gradients.

Question 39

Describe osmosis.

Answer 39

Osmosis is the process where particles diffuse over a semi-permeable membrane from a lower concentration to a higher concentration.

Question 40

What are hypotonic, hypertonic, and isotonic?

Answer 40

A less concentrated solution is called hypotonic. A more concentrated solution is called hypertonic. A balanced solution is called isotonic.