Cell Structure/Function
The organelle not part of the endomembrane system: Endoplasmic reticulum, mitochondria, plasma membrane, nuclear envelope, vesicles, vacuoles
What is Mitochondria?
Phospholipids are composed of a ___ backbone attached to phosphate group and two fatty acid tails
Glycerol
Which type of transport moves molecules like glucose down their concentration gradient with the help of a carrier protein?
Facilitated diffusion
A red blood cell placed in pure water will swell and burst. What term describes this type of solution relative to the cell?
Hypotonic
Which organelle is responsible for generating ATP in eukaryotic cells?
Mitochondria
The cellular compartment responsible for synthesizing lipids as well as carrying out some detoxification processes
What is Smooth endoplasmic reticulum
How does the structure of a liposome model the structure of a cell membrane, and how does this structure affect its function?
A liposome is a spherical vesicle with a phospholipid bilayer, just like a cell membrane. In both structures, the hydrophilic heads face outward toward water, while the hydrophobic tails face inward, forming a barrier. This arrangement allows the liposome to be selectively permeable, separating its internal environment from the external one. This enables compartmentalization and regulates the movement of molecules
What specific type of transport would cortisol, a steroid hormone, likely utilize to pass through the phospholipid bilayer? (Active/Passive and what type)
Passive; simple diffusion
What structure in plant cells prevents them from bursting in hypotonic environments?
Plant cell
Why is compartmentalization in eukaryotic cells advantageous?
Allows eukaryotic cells to separate different chemical reactions into specialized organelles preventing reactions from interfering with each other, increases the efficiency of different cellular processes, and allows the cell to maintain necessary conditions (such as pH, enzyme concentration, etc) for each reaction related to its function.
Calculate SA/V ratio for a rectangle with l=4, w=5, h=6
SA=2lh+2lw+2wh
V= lwh
What is 1.23?
Give one specific structural feature that leads to dynamic properties of a plasma membrane
1. Phospholipid tails interact with Van der Waals forces (WEAK and TEMPORARY H bonds) that are easily broken and formed so phospholipids can move around within membrane
2. Phospholipids rotate rapidly allowing lipids to spin without moving
(etc)
The sodium–potassium pump moves sodium and potassium ions across the membrane. How many of each ion are moved, and in which direction?
Moves 3 sodium ions (Na⁺) out of the cell and 2 potassium ions (K⁺) into the cell for each cycle.
In osmoregulation, how does a contractile vacuole in freshwater protists help maintain homeostasis?
The vacuole collects excess water and periodically expels it from the cell, preventing the cell from swelling and bursting
What is one structural feature of a lysosome that aids in its function?
Acidic interior denatures proteins, contains various enzymes to help with waste digestion, etc
Give an example of an organelle whose function is most directly dependent on having a large surface area, and how does this structural feature support its role in the cell?
Ex: Mitochondria
The inner mitochondrial membrane is highly folded into cristae, which increase the membrane’s surface area. This large surface area maximizes the organelle's ability to produce ATP
Explain how the presence of cholesterol in animal cell membranes modifies membrane structure at both high and low temperatures
At higher temperatures, cholesterol decreases fluidity because its ring structure interacts more closely with phospholipid tails. At lower temperatures, cholesterol increases fluidity by preventing phospholipids from packing together
The Na⁺/K⁺ pump is an ATPase. Explain how this ATP hydrolysis provides the energy for this pump to work.
ATP is split into ADP and a phosphate. The phosphate group temporarily attaches to the pump, causing a conformational change in the protein. This shape change allows the pump to move 3 Na⁺ ions out of the cell and 2 K⁺ ions in, both against their concentration gradients. Once the ions are transported, the phosphate is released, and the pump returns to its original shape
Salmon migrate between freshwater and saltwater. Which type of transport mechanism do their gill cells use to actively excrete excess salts in seawater?
Active- Na/K pump
What evidence supports the endosymbiotic theory for the origin of mitochondria and chloroplasts?
Similar DNA structure
How does the structure of grana in a chloroplast affect its function?
Grana are stacks of thylakoid membranes that increase the surface area available for light-dependent reactions. This large surface area maximizes the chloroplast’s ability to capture light energy and produce ATP.
Predict how replacing unsaturated fatty acids in the membrane with saturated fatty acids would affect membrane permeability, and justify your answer in terms of molecular interactions.
More saturated fatty acids would lead to a decrease in membrane fluidity. Saturated fatty acids do not have kinks, so they are packed more tightly. Van der Waals forces depend on distance, so packed phospholipids lead to stronger forces.
A white blood cell engulfs a bacterium. After digestion of the bacterium inside the cell, some of the digested molecules (like amino acids) are released back into the bloodstream. Identify the two types of vesicular transport involved in this process.
Endocytosis- engulfing the bacterium
Exocytosis- releases digested molecules back into bloodstream
A plant cell is placed in a hypertonic solution. Predict what happens to both the plasma membrane and the cell wall, and explain how this affects overall cell function.
Water leaves the cell by osmosis. The plasma membrane shrinks away from the cell wall in a process called plasmolysis, while the rigid cell wall remains intact. This loss of turgor pressure reduces the cell’s ability to maintain structural support, which can lead to wilting and impaired function in tissues and organs.
Eukaryotic cells carry out both hydrolytic enzyme activity and ATP synthesis, but in very different organelles. Predict what would happen if the membranes separating these organelles were disrupted.
Ex: If the membranes separating these organelles were disrupted, the hydrolysis could occur in areas where the cell is trying to perform synthesis, causing the cell’s building processes to be disrupted and could destroy important molecules.