Exam 2 Review

Question 1

What are the components of prokaryotic cells?

Answer 1

Cell Wall- Provides structural support and protection

Ribosomes- protein synthesis

Nucleoid – A region containing the circular DNA molecule (chromosome), which carries genetic information.

Question 2

What makes up the phospholipid bilayer?

Answer 2

Hydrophilic head- Composed of a phosphate group and glycerol, facing outward toward the aqueous environment.

Hydrophobic (water-repelling) tails – Made of fatty acid chains, facing inward away from water.

Proteins (integral and peripheral) – Aid in transport, signaling, and enzymatic activity.

Cholesterol (in eukaryotic cells) – Maintains fluidity and stability.

Question 3

What is the function of the cell membrane?

Answer 3

Selective Permeability- Regulates what enters and exits the cell, maintaining homeostasis.

Protection and Support – Acts as a barrier, shielding the cell’s internal environment.

Cell Communication – Contains receptor proteins that receive signals from other cells.

Transport of Materials – Facilitates passive transport (diffusion, osmosis) and active transport (using ATP).

Cell Recognition – Glycoproteins and glycolipids help in immune responses and cell identification.

Question 4

How do eukaryotic cells differ from prokaryotic cells?

Answer 4

Eukaryotic cells are more complex, have a nucleus, and contain membrane-bound organelles.

Prokaryotic cells are simpler, lack a nucleus, and do not have membrane-bound organelles.

Question 5

What organelles make up the endomembrane system?

Answer 5

The Endoplasmic Reticulum (ER), Golgi apparatus, Vesicles, Lysosomes, Peroxisomes, and plasma membrane.

Question 6

ER rough and smooth

Answer 6

Rough ER – Studded with ribosomes; involved in protein synthesis and modification.

Smooth ER – Lacks ribosomes; synthesizes lipids, detoxifies toxins, and stores calcium.

Question 7

Golgi Apparatus

Answer 7

Modifies, sorts, and packages proteins and lipids for transport within or outside the cell.

Question 8

Vesicles

Answer 8

Small membrane-bound sacs that transport substances between organelles.

Question 9

Lysosomes

Answer 9

Contain digestive enzymes to break down waste, cellular debris, and foreign invaders.

Question 10

Peroxisomes

Answer 10

Break down fatty acids and detoxify harmful substances.

Question 11

Nucleus functions

Answer 11

-stores genetic information: contains DNA in the form of chromatin or chromosomes

-RNA synthesis

-regulates cell cycle (cell division)

Question 12

Ribosomes

Answer 12

Function: Synthesize proteins by translating mRNA into amino acid chains.

Question 13

Vacuoles

Answer 13

Function: Storage of water, nutrients, and waste; maintains turgor pressure in plants.

Question 14

Cytoskeleton components

Answer 14

Microtubules, microfilaments, and intermediate filaments

Question 15

Microfilaments

Answer 15

Narrowest, made of 2 intertwined strands of globular protein actin. Function in cellular movement and shape.

Question 16

Microtubules

Answer 16

Small hollow tubes and provide structural support, facilitate intracellular transport and form the mitotic spindle.

Question 17

Intermediate Filaments

Answer 17

several strands of fibrous proteins that are wound together. Maintain shape, strength and stability of the cell.

Question 18

Purpose of the extracellular matrix

Answer 18

complex network that provides structural support for cells and tissues, allowing them to adhere to each other, communicate with one another, and regulate various cellular functions like growth, migration, and differentiation by acting as a scaffold and signaling platform within the body

Question 19

Tight Junctions

Answer 19

Function: Tight junctions create a seal between adjacent cells, preventing the leakage of molecules between them. They are found in tissues where a barrier function is crucial, such as in the intestines and kidneys.

Structure: These junctions are made up of proteins like claudins and occludins that link cells tightly together, forming a “zipper-like” seal.

Purpose: To control paracellular transport (movement of substances between cells) and maintain tissue polarity.

Question 20

Desmosomes

Answer 20

Function: Desmosomes provide strong adhesion between cells, helping tissues withstand mechanical stress. They are especially abundant in tissues subjected to stretching, like skin and heart muscle.

Structure: These junctions are formed by cadherin proteins that link to intermediate filaments inside the cell, anchoring adjacent cells together.

Purpose: To provide mechanical stability and resist shearing forces.

Question 21

Gap Junctions

Answer 21

Function: Gap junctions allow for communication between adjacent cells by permitting the passage of ions, small molecules, and electrical signals.

Structure: They consist of connexins, which form channels (connexons) that connect the cytoplasm of two cells.

Purpose: To facilitate intercellular communication and coordinate activities in tissues like cardiac and smooth muscle, where synchronized contraction is essential.

Question 22

What is the difference between integral and peripheral proteins?

What are the main functions of each?

Question 23

Integral Proteins Structure and Function

Answer 23

Integral proteins are embedded within the lipid bilayer, with some spanning the entire membrane, allowing them to interact with both the inner and outer environments of the cell. They primarily function in transport, serving as channels or carriers, and in cell signaling as receptors for various molecules.

Question 24

Peripheral Protein structure and function

Answer 24

Peripheral proteins are loosely attached to the inner or outer surface of the cell membrane, often interacting with integral proteins or the lipid bilayer. They play key roles in cell signaling, maintaining cell shape by interacting with the cytoskeleton, and facilitating cell recognition.

Question 25

How do ions use facilitative diffusion?

Answer 25

Ions use facilitated diffusion to move across the cell membrane through specialized transport proteins because they cannot easily pass through the hydrophobic lipid bilayer on their own due to their charge and size.

Question 26

Ion channels

Answer 26

These are specific proteins that form pores in the membrane, allowing ions (like sodium, potassium, calcium, etc.) to pass through. The movement occurs down the ion's concentration gradient, from an area of higher concentration to one of lower concentration

Question 27

Carrier Proteins

Answer 27

These proteins bind to the ion on one side of the membrane, undergo a conformational change, and release the ion on the other side, allowing it to move down its concentration gradient.

Question 28

What is membrane potential

Answer 28

Membrane potential refers to the difference in electric charge across a cell's membrane, creating an electrical potential difference between the inside and outside of the cell.

Question 29

How is membrane potential generated in the sodium potassium pump?

Answer 29

The sodium-potassium pump generates membrane potential by actively transporting 3 sodium ions out of the cell and 2 potassium ions into the cell, using energy from ATP. This creates an imbalance of ion concentrations, with a higher concentration of sodium outside and potassium inside, establishing a negative charge inside the cell and contributing to the resting membrane potential.

Question 30

Secondary active transport

Answer 30

a type of transport that uses the energy stored in the form of ion gradients, created by primary active transport (like the sodium-potassium pump), to move other substances across the cell membrane. Unlike primary active transport, which directly uses ATP, secondary active transport relies on the movement of ions down their concentration gradients to power the transport of other molecules

Question 31

Symport and an example

Answer 31

Definition: In symport, two or more substances are transported in the same direction across the membrane. Example: Sodium-glucose cotransporter (SGLT): In the intestine and kidney, sodium ions (Na+) move down their concentration gradient into the cell, and glucose is simultaneously transported into the cell against its gradient. Both Na+ and glucose move in the same direction into the cell.

Question 32

Antiport and example

Answer 32

Definition: In antiport, two substances are transported in opposite directions across the membrane. Example: Sodium-calcium exchanger (NCX): In many cells, sodium ions (Na+) enter the cell while calcium ions (Ca²⁺) are pumped out of the cell. The sodium and calcium move in opposite directions, with sodium moving into the cell and calcium moving out.

Question 33

Endocytosis

Answer 33

the process by which cells engulf and internalize large molecules, particles, or fluids from the extracellular environment by forming a vesicle from the cell membrane.

Question 34

Phagocytosis

Answer 34

Description: Known as "cell eating," phagocytosis involves the engulfment of large particles such as debris, foreign substances, or microorganisms. Example: White blood cells (like macrophages) engulf and digest bacteria or dead cells.

Question 35

Pinocytosis

Answer 35

Description: Known as "cell drinking," pinocytosis involves the non-specific uptake of extracellular fluid and dissolved substances into small vesicles. Example: The cell takes in extracellular fluid containing nutrients or other small molecules.

Question 36

Receptor Mediated Endocytosis

Answer 36

Description: This is a more specific form of endocytosis where the cell surface contains receptors that bind to specific molecules (ligands), which are then internalized in a clathrin-coated vesicle. Example: The uptake of cholesterol by cells via low-density lipoprotein receptors.

Question 37

Exocytosis

Answer 37

the process by which cells release substances, such as waste or proteins, by vesicles fusing with the cell membrane and expelling their contents into the extracellular space.

Question 38

What do endocytosis and exocytosis provide for a cell?

Answer 38

Endocytosis and exocytosis provide a way for a cell to take in essential materials (like nutrients, fluids, and signaling molecules) and export waste products, proteins, or other substances, allowing the cell to maintain homeostasis, communicate with its environment, and regulate its internal composition.