Biology

Exam 1

What is matter and what states can it exist in?

Matter is anything that takes up space, by having a volume, and has mass. Matter can exist in a solid, liquid, gaseous (vapor), or plasma state. All matter is made up of certain basic substances called elements

Explain the difference between essential and trace elements.

Essential elements are required for human life. Trace elements are required only in small quantities

Hydrogen Bonds form what kind of bond?

Relatively weak bonds that are easily broken

True or False; If false, make the statement true: Anions are positively charged ions, and cations are negatively charged ions.

False; Cations are positively charged ions, and anions are negatively charged ions

Which of the following are not one of the organic compounds that make up biomacromolecules?

 

Lipids

 

Proteins

 

Ribosomes

 

Carbohydrates

Ribosomes

What are carbohydrates?

Carbohydrates, commonly referred to as sugars, are the primary source of fuel for organisms and have the same three elements in their main structure: carbon, hydrogen, and oxygen (C, H, and O, respectively)

Why are lipids unique among the biomacromolecules?

Lipids are unique among the biomacromolecules because most of them are insoluble in water. Additionally, lipids are not monomers but are assembled from smaller molecules that are chemically linked together

Why are lipids insoluble in water?

Lipids are insoluble in water because they are made mostly of non-polar hydrocarbon chains. As water is polar, it will only dissolve other polar or ionically bonded substances. Lipids are non-polar, and this is why they are insoluble in water but can be dissolved with nonpolar solvents such as alcohol

Describe the structure of a phospholipid.

Phospholipids contain two main components: (1) a polar head group joined to (2) a non-polar tail group. The head group is composed of a charged phosphate group and (usually) a nitrogen-containing group. The head is attracted to polar substances, such as water, and is therefore hydrophilic (water loving). The tail group is a hydrocarbon—a molecule containing an H and C—composed of non-polar fatty acid chains. The tail repels water and is therefore hydrophobic (water fearing)

Name the functions of proteins as mentioned in the module.

-Proteins can act as enzymes and regulate metabolic functions

-Proteins can store amino acids

-Proteins can act as hormones

-Proteins form antibodies for immunological defense

-Proteins can act as carriers for transport and also form membrane channels

-Proteins can form cell surface receptors to receive chemical messages

-Proteins can act as structural molecules for support and movement

Describe how the shape of a protein is related to its function.

Proteins can be assembled into a variety of shapes which allows them to serve a variety of functions. Some functions of proteins are to make many needed protective tissues such as skin, hair, and fingernails. Proteins also form enzymes (catalysts that speed up chemical reactions) and are used to make needed substances such as hemoglobin, which carries oxygen in red blood cells

What are the roles of the two major types of nucleic acids?

There are two major types of nucleic acids: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). DNA contains a vast amount of hereditary information and is responsible for the inheritable characteristics of living organisms. RNA is responsible for deciphering the hereditary information in DNA and using it to synthesize proteins

Describe the structure of DNA and RNA.

DNA and RNA exist as chains of nucleotides. The sugar of one nucleotide is linked to the phosphate of the next nucleotide, while the nitrogenous base protrudes from each sugar in the string. RNA is most commonly a single chain of nucleotides, whereas DNA is a double chain held together by hydrogen bonds between protruding bases

What are some of the main differences between prokaryotic and eukaryotic cells?

Prokaryotic cells (also called prokaryotes) are considered simple cells and have three defining characteristics: (1) size, (2) non-enclosed genetic material and (3) lack of organelles and other internal membrane bound structures.

Eukaryotic cells are more complex than prokaryotic cells. Most organisms are composed of eukaryotic cells. Unlike prokaryotes, eukaryotes are 10-100 times larger, possess a nuclear membrane (eukaryotic means “true nucleus”) and contain membrane-bound organelles

What structures of the cells are complexes of tiny manufacturing plants that assemble proteins?

 

Endoplasmic reticulum

 

Lysosomes

 

Nucleus

 

Ribosomes

Ribosomes

What 3 types of protein fibers make up the cytoskeleton?

Microtubules, microfilaments, and intermediate filaments

Which type of cell junctions are mechanical structures that wrap around the cell to prevent extracellular fluid from leaking?

 

Gap junctions

 

Synaptic junctions

 

Tight junctions

 

Desmosomes

Tight junctions

What is the purpose of the cell membrane?

The cell membrane (plasma membrane) is the outermost constituent of the cell. This membrane is responsible for enclosing the cell’s cytoplasm and organelles (discussed above) and separates the extracellular (external) environment from the intracellular (internal) cellular environment

Explain the main difference between passive and active transport and provide an example of each.

Passive transport occurs when substances move through the membrane without the input of energy. Examples include (1) simple diffusion, (2) osmosis (3) filtration, and (4) facilitated diffusion. Active transport occurs when an input of energy is required to move substances through the membrane. An example includes the sodium-potassium pump

Why is the electrochemical gradient important for cellular function?

The electrical potential of ions across the cell membrane is an important element for nerve conduction, muscle contraction, mitochondrial metabolism, and hormone secretion

Passive Transport Overview

Cells rely on their membranes to regulate what comes in and out. Passive transport requires no cellular energy (ATP). Instead, molecules move down their concentration gradients. The four types are: simple diffusion, osmosis, filtration, and facilitated diffusion.

Simple Diffusion in Physiology

Simple diffusion allows molecules like oxygen and carbon dioxide to move freely across the lipid bilayer. Because oxygen is constantly used up inside the cell during cellular respiration, oxygen diffuses in from the extracellular space, while carbon dioxide, a waste product, diffuses out.

Osmosis and Solvent Balance

Osmosis refers to the movement of water across a selectively permeable membrane. Water moves toward the side with more solute, seeking to equalize solute concentration on both sides. Osmotic balance is critical, as shifts can disrupt cellular structure and function.

Isotonic Environments

In an isotonic solution, solute concentration is equal inside and outside the cell. Water movement occurs in both directions equally, maintaining stable cell size. This is the condition most compatible with normal physiology.

Hypertonic environments

When extracellular fluid is hypertonic, it has more solutes than the cell’s cytoplasm. Water flows out of the cell, causing it to shrink (crenation). This condition is seen in severe dehydration or hypernatremia (high sodium levels).

Hypotonic environment

In a hypotonic solution, extracellular fluid has fewer solutes than the cell’s cytoplasm. Water rushes into the cell, causing swelling and possibly lysis. This is the situation Lina faced when she consumed large amounts of pure water without electrolytes.

Filtration in the body

Filtration is another passive process, dependent on pressure gradients rather than concentration gradients. In the kidneys, filtration allows small molecules like water and glucose to pass through membranes while retaining larger proteins and blood cells.

Facilitated diffusion

Some molecules, like glucose, cannot freely cross the lipid bilayer and require transport proteins. Facilitated diffusion allows these molecules to move passively down their concentration gradients without energy expenditure.

Clinical Implications of Osmosis

In medical settings, understanding osmosis is critical. Administering the wrong IV fluid can cause cells to swell or shrink dangerously. For example, giving a hypotonic solution to a hyponatremic patient could worsen brain swelling.

Lina’s Case and Hyponatremia

By drinking too much water without electrolytes, Lina diluted her blood sodium levels. Her extracellular fluid became hypotonic relative to her cells. Water entered her cells, causing them to swell. Brain cells are especially sensitive, and swelling can result in seizures, coma, or even death.

Restoring Balance

Treatment involves carefully reintroducing sodium and electrolytes. Hypertonic saline may be used under close monitoring to draw water back out of swollen cells without causing them to shrink too rapidly.

Which of the following best explains why cells must maintain isotonic extracellular conditions?

To avoid swelling or shrinking due to osmotic imbalance

Why was giving Lina a hypertonic saline solution medically beneficial?

It restored the isotonic balance of her cells.

Filtration differs from diffusion in that it relies on:

Pressure gradients

In the lungs, oxygen moves from the alveoli into blood capillaries because:

The concentration of oxygen is higher in the alveoli than in the blood.

If a patient receives an IV of pure water, what will likely happen to their red blood cells?

They will swell and possibly burst.

Which transport mechanism is responsible for glucose entering cells via carrier proteins without ATP use?

Facilitated Diffusion

Osmotic pressure is defined as:

The force required to stop osmosis.

What happens to a red blood cell in a hypertonic solution?

It shrinks

In Lina’s case, why did her brain cells swell?

The extracellular fluid was hypotonic compared to the intracellular fluid.

Which of the following molecules crosses the membrane primarily through simple diffusion?

Oxygen