Untitled Flashcards Set

D1.3, A2.1, A2.2, B2.1 Study Guide

1. Define the following:

   1. Codon - A sequence of three nucleotide bases in mRNA that codes for a specific amino acid or signals a start or stop during protein synthesis.

   2. Substitution mutation - A type of genetic mutation where one nucleotide base in a DNA sequence is replaced with another, which may result in a change in the amino acid sequence of a protein.

   3. Insertion mutation - A mutation in which one or more nucleotide bases are added into a DNA sequence, potentially shifting the reading frame and altering protein synthesis.

   4. Deletion mutation - A mutation in which one or more nucleotide bases are removed from a DNA sequence, which can cause a frameshift and significantly impact protein function.

   5. Diffusion - The passive movement of molecules from an area of higher concentration to an area of lower concentration, driven by the concentration gradient.

   6. Endosymbiotic Theory - A scientific theory that explains the origin of eukaryotic cells as a result of symbiosis between ancestral prokaryotic cells, particularly the engulfment of bacteria that eventually became mitochondria and chloroplasts.

2. Describe the Miller-Urey Experiment

   1. The Miller-Urey Experiment (1953) was a groundbreaking experiment conducted by Stanley Miller and Harold Urey to test the hypothesis that early Earth’s conditions could have led to the formation of organic molecules necessary for life.

It was to test the formation of organic molecules from abiotic molecules, or how Earth’s realty conditions could have led to the formation of organic molecules necessary for life.

They designed an apparatus that simulated the conditions of primordial Earth by including:

1. A mixture of gases (methane CH4CH_4CH4​, ammonia NH3NH_3NH3​, hydrogen H2H_2H2​, and water vapor H2OH_2OH2​O) to mimic Earth's early atmosphere.

2. A boiling chamber to simulate the evaporation and condensation of water (ocean).

3. Electrodes that produced electrical sparks to simulate lightning, a source of energy for chemical reactions.

Results: After running the experiment for a week, Miller and Urey found that organic molecules, including amino acids (the building blocks of proteins), had formed in the mixture. This provided strong evidence that life’s essential components could have arisen from simple chemicals under early Earth-like conditions.

Significance:

1. Supported the abiogenesis hypothesis (life originating from non-living matter).

2. Suggested that organic molecules necessary for life could form spontaneously given the right conditions.

3. Inspired further research into the origins of life and prebiotic chemistry.

3. Outline the function of the sodium-potassium pump

A part of active transport.

1. The sodium-potassium pump is a vital active transport protein found in the plasma membrane of cells. It functions to maintain the electrochemical gradient and proper ion balance inside the cell.

In maintaining the ion concentrations, it pumps 3 sodium ions (Na⁺) out of the cell and pumps 2 potassium ions (K⁺). This process occurs against their concentration gradients (low to high), requiring energy from ATP.

Importance: Essential for neuronal signaling, muscle contraction, and kidney function.

Found in almost all animal cells to sustain cellular homeostasis.

Uses ATP, making it an active transport mechanism.

OUTLINE of FUNCTIONS: Maintains Ion Concentrations, Generates Resting Membrane Potential, Regulates Cell Volume, Provides Energy for Secondary Transport. 

4. Compare and contrast simple diffusion and facilitated diffusion

Simple diffusion and facilitated diffusion are both methods of passive transport. Both go along the concentration gradient (higher to lower concentration). Both can involve nonpolar molecules across the membrane, however simple diffusion only is involved with non-polar molecules. 

Simple diffusion doesn’t involve carrier or channel proteins, but facilitated diffusion does. Facilitated diffusion can have both small and large molecules and polar and nonpolar, but simple diffusion only involves small molecules and nonpolar molecules.

5. Identify 3 different examples of atypical cells and explain why they are considered atypical.

Red blood cells, because they lack a nucleus and most organelles. Muscle cells because they have more than one nucleus per cell. Cancer cells are atypical because they have uncontrolled cell division and an abnormal number of chromosomes.

6. Explain why large and polar molecules do not diffuse through the phospholipid bilayer.

For large molecules the bilayer’s hydrophobic interior acts as a barrier; the nonpolar fatty acid tails which block the passage of large, polar, or charged molecules.

7. How do polar molecules move through the cell membrane?

Polar molecules can either move through osmosis, or through facilitated diffusion and active transport NOT simple diffusion.

8. Outline the endosymbiotic theory, including the roles of the mitochondria and chloroplasts.

The endosymbiotic theory suggests that mitochondria and chloroplasts were once free-living prokaryotic organisms that were engulfed by a primitive eukaryotic cell, forming a symbiotic relationship. Over time, these prokaryotes evolved into organelles, with mitochondria responsible for energy production (ATP) through cellular respiration and chloroplasts enabling photosynthesis in plant cells. This theory is supported by evidence such as the similarity in size, shape, and genetic material between these organelles and certain prokaryotes.

9. Compare and contrast prokaryotic and eukaryotic cells.

Both prokaryotic and eukaryotic cells have ribosomes, DNA, and plasma membranes. Prokaryotic cells are smaller, unicellular organisms, and lack a nucleus. Eukaryotic cells are bigger, multicellular, and have nucleus.

10. Describe the role of cholesterol in the cell membrane.

Cholesterol helps support the fluidity of the cell membrane, and it makes sure that the cell membrane is not too rigid or too fluid-like. 

11. Explain the surface area to volume ratio and its limitations on cell size.

The surface area is the combined area of the cell membrane, responsible for the exchange of materials such as nutrients and waste with the environment. The volume is the entire cell, the space inside the cell which contains the organelles and cytoplasm. 

As the cell grows, its volume increases at a faster rate than its surface area, and this is because, for a spherical cell, the surface area increases by a factor of squared length (length^2) and the volume increases by a factor of cubed (length^3).

Limitations on cell size:

• If the volume is too large, diffusion becomes inefficient, and cells rely on diffusion for transporting nutrients and waste. 

• Large cells may struggle to coordinate cellular processes, as signals take longer to travel, as signals take longer to travel. 

Calculation: 

If the diameter is 1 um, the surface area would be 4*pi*(0.5)^2 = 3.14 um^2. The volume would be 4/3*pi(0.5)^3 = 0.52 um^3. The SA divided by the V (SA/V) is the SA:V ratio which would be 3.14/0.52 which equals 6.0

If the diameter is 10 um, the surface area would be 314.159 um^2. The volume would be 523.600 um^3. So then the SA:V ratio would be 314.159/523.600 which equals 0.600.

The small cell (1 um) has efficient diffusion, but the bigger cell (10 um) has inefficient diffusion. 

12. List the different functions of membrane proteins.

Carrier proteins involve the diffusion, and are involved in both active and passive transport, helping to transport large, small, polar, and nonpolar molecules either along the concentration gradient (in passive transport) and against the concentration gradient (in active transport). Channel proteins are only involved with polar molecules and go alongside the concentration gradient in passive transport. 

13. Use a formula to calculate the magnification of a micrograph or drawing.

Formula equals size of image/size of object. 

14. Identify the direction in which transcription occurs. 

5’ to 3’ direction.

15. Identify different organelles found within a eukaryotic cell. 

Mitochondria, centrosome, vacuole, nucleus, Rough ER, Smooth ER.

16. State the function of flagella and ribosomes.

Flagella are tail-like structures that enable cells to move by rotating or whipping, providing locomotion for some prokaryotic and eukaryotic cells. Ribosomes are responsible for protein synthesis, translating messenger RNA (mRNA) into polypeptide chains by linking amino acids in the correct sequence.