Topic Questions

1. Centrioles: These are involved in cell division and are responsible for organizing the microtubules during cell division.

2. Lysosomes: These organelles contain digestive enzymes that break down waste materials and cellular debris.

3. Flagella: Some animal cells have flagella, which are whip-like structures that help with cell movement.

4. Peroxisomes: These organelles are involved in the breakdown of fatty acids and the detoxification of harmful substances.

5. Intermediate filaments: These provide structural support and help maintain the shape of the cell.

What organelles are in animal cells, but not in plant cells?

1. Chloroplasts: These organelles are responsible for photosynthesis, converting sunlight into energy for the plant.

2. Cell wall: Plant cells have a rigid cell wall made of cellulose, providing structural support and protection.

3. Central vacuole: Plant cells have a large central vacuole that stores water, nutrients, and waste products.

What organelles are in plant cells, but not in animal cells?

Ribosomes play a crucial role in protein synthesis, which is the process of translating the instructions encoded in DNA into functional proteins. They accomplish this by reading the messenger RNA (mRNA) molecule, which is a copy of the DNA sequence, and using it as a template to assemble amino acids into a polypeptide chain. This chain then folds into a specific protein based on the instructions encoded in the DNA. In summary, ribosomes help carry out the instructions encoded in DNA by facilitating the translation of mRNA into proteins.

How to ribosomes help carry our instructions encoded in the DNA?

If a cell has a high rate of protein synthesis, you would expect it to have a large number of ribosomes. Ribosomes are the organelles responsible for protein synthesis in cells. They are involved in the translation of mRNA into proteins. Therefore, a higher number of ribosomes would facilitate and increase the efficiency of protein synthesis in the cell.

If a cell has a high rate of protein synthesis, what organelle would you expect it to have a large number of? Why?

The rough endoplasmic reticulum (ER) is studded with ribosomes, giving it a rough appearance. It is involved in protein synthesis and modification. The smooth ER lacks ribosomes and is involved in lipid metabolism, detoxification, and calcium storage.

Differentiate between the rough and smooth er

The main differences between prokaryotic and eukaryotic cells are:

1. Structure: Prokaryotic cells lack a nucleus and membrane-bound organelles, while eukaryotic cells have a nucleus and various membrane-bound organelles.

2. Size: Prokaryotic cells are generally smaller (1-10 micrometers) compared to eukaryotic cells (10-100 micrometers).

3. DNA: Prokaryotic cells have a single circular DNA molecule, called a nucleoid, while eukaryotic cells have multiple linear DNA molecules organized into chromosomes within the nucleus.

4. Reproduction: Prokaryotic cells reproduce asexually through binary fission, while eukaryotic cells reproduce both sexually and asexually.

5. Complexity: Eukaryotic cells are generally more complex and specialized, with a greater variety of organelles and cellular structures.

These are the main differences between prokaryotic and eukaryotic cells.

Identify the main differences between prokaryotic and eukaryotic cells.

The endomembrane system is a network of membranes within a eukaryotic cell that work together to carry out various cellular functions. It includes the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, and plasma membrane. These membranes are interconnected and involved in processes such as protein synthesis, lipid metabolism, and intracellular transport. The endomembrane system plays a crucial role in maintaining cell homeostasis and regulating the flow of molecules within the cell.

Describe the endomembrane system.

The path of a protein starts with transcription, where mRNA is synthesized from DNA in the nucleus. Then, mRNA moves to the cytoplasm and undergoes translation, where ribosomes read the mRNA and assemble amino acids into a polypeptide chain. After translation, the protein may undergo post-translational modifications, such as folding, addition of chemical groups, or cleavage. Finally, the protein assumes its final functional form and carries out its specific role in the cell.

Trace the path of a protein, from mRNA to modifications to final function.

Create a chart to compare the main functions of micro-tubules, micro-filaments, and intermediate filaments.

False. Plants have both a cell wall and a plasma membrane. The cell wall provides structural support, while the plasma membrane controls the movement of substances in and out of the cell.

Plants have a cell wall, therefore they do not have a plasma membrane. Is this true or false?

The Golgi Complex can be compared to a warehouse/mail facility in terms of its function. Just like a warehouse/mail facility, the Golgi Complex receives, modifies, sorts, and packages molecules (such as proteins and lipids) for transport to their final destinations within the cell or outside of the cell. It acts as a processing and distribution center, ensuring that molecules are properly modified and packaged before being sent to their designated locations.

Compare the Golgi Complex to a warehouse/mail facility. How is its function similar?

Disagree. While plant cells do obtain energy from photosynthesis, they also require mitochondria for various other cellular processes. Mitochondria are responsible for producing ATP, the energy currency of cells, and are involved in other metabolic pathways. Additionally, mitochondria play a role in programmed cell death and calcium signaling. Therefore, plant cells do have mitochondria alongside chloroplasts for photosynthesis.

Plant cells get their energy from photosynthesis, therefore they do not have mitochondria. Do you agree or disagree with this statement? Why?

The mitochondria are responsible for cellular respiration, producing energy in the form of ATP. They break down glucose and other molecules to release energy. Chloroplasts, on the other hand, are found in plant cells and are responsible for photosynthesis. They convert sunlight, water, and carbon dioxide into glucose and oxygen.

Describe the roles of both the mitochondria and the chloroplasts.

The Krebs cycle, also known as the citric acid cycle, is a series of chemical reactions that occur in the mitochondria. It involves the breakdown of glucose and produces energy-rich molecules such as ATP, NADH, and FADH2. The electron transport chain, on the other hand, is a process that takes place in the inner mitochondrial membrane. It uses the high-energy molecules produced in the Krebs cycle to generate ATP through a series of redox reactions. In summary, the Krebs cycle generates energy-rich molecules, while the electron transport chain uses those molecules to produce ATP.

Differentiate between the Krebs cycle and the electron transport chain in mitochondria.

Light dependent reactions occur in the thylakoid membrane of the chloroplasts. The Calvin cycle occurs in the stroma of the chloroplasts. The Krebs cycle occurs in the mitochondrial matrix. ATP synthesis occurs in the inner mitochondrial membrane. The Electron transport chain (ETC) occurs in the inner mitochondrial membrane.

Identify the location where each process occurs:

1. Light dependent reactions

2. Calvin cycle

3. Krebs cycle

4. ATP synthesis

   1. Electron transport chain (ETC)

Pigments, like chlorophyll, are important to plants because they play a crucial role in photosynthesis. Chlorophyll absorbs light energy from the sun and converts it into chemical energy, which is used to produce glucose and oxygen through the process of photosynthesis. Without pigments, plants would not be able to capture and utilize sunlight effectively, resulting in a lack of energy and inability to produce food.

Why are pigments, like chlorophyll, important to plants?

The surface area-to-volume ratio of cells should be high in order to optimize the exchange of materials through the plasma membrane. This is because a higher surface area allows for more efficient diffusion and transport of substances across the membrane, while a smaller volume ensures that the distance for diffusion is minimized. Therefore, cells with a larger surface area relative to their volume have a greater capacity for exchanging materials with their environment.

Describe how the surface area-to-volume ratio should be in order for cells to optimize the exchange of material through the plasma membrane.

As a single cell keeps getting larger over time, several problems may arise:

1. Nutrient and waste exchange: As the cell grows, its surface area to volume ratio decreases. This makes it difficult for nutrients to enter the cell and for waste products to exit efficiently. This can lead to cellular starvation and accumulation of toxic waste.

2. DNA replication and gene expression: The larger the cell, the more DNA it needs to replicate and the more genes it needs to express. This can put a strain on the cell's machinery and lead to errors in DNA replication and gene expression, potentially causing genetic abnormalities.

3. Cellular communication: Larger cells may have difficulty in effectively communicating with other cells. Signaling molecules may have a harder time reaching all parts of the cell, leading to impaired intercellular communication and coordination.

4. Structural integrity: As a cell grows larger, its internal structures may struggle to support the increased size. This can result in structural instability, leading to cell deformation or even cell rupture.

Overall, the problems associated with a single cell getting larger over time highlight the importance of cell division and the need for multicellular organisms to maintain a balance between cell size and function.

Propose problems that would occur if a single cell were to keep getting larger and larger over time.

The following lists will compare the surface area of the cell that will have the most efficient exchange across its cell

1. 2.0; 0.9; 1.2

2. 0.9; 0.6; 1.1

   1. 0.6; 0.7; 0.5

You have a set of data regarding the surface area-to-volume ratios of four cells. Circle the ratio belonging to the cell that would be best suited for storage.

1. 4.5; 7.2; 3.1; 5.5

Calculate and compare the SA:V ratios of the cubes below. Then identify which will have the best exchange of material through the plasma membrane.

side = 5

side = 2 (3 cubes per side)

A plasma membrane is composed of various components.

1. Phospholipid Bilayer: Consists of two layers of phospholipids, with hydrophilic heads facing outward and hydrophobic tails facing inward.

2. Integral Proteins: Span the entire width of the membrane and are embedded within the phospholipid bilayer.

3. Peripheral Proteins: Attached to either the inner or outer surface of the membrane.

4. Cholesterol: Scattered within the phospholipid bilayer, providing stability and fluidity to the membrane.

5. Glycoprotein: Protein with attached carbohydrate chains, involved in cell recognition and signaling.

6. Glycolipid: Lipid with attached carbohydrate chains, also involved in cell recognition.

7. Transport Proteins: Facilitate the movement of specific molecules across the membrane.

8. Receptor Proteins: Bind to specific molecules, triggering cellular responses.

9. Cell Surface Markers: Proteins and carbohydrates that help identify the cell type and aid in cell-cell recognition

Draw a small section of a plasma membrane. Label all parts.

The plasma membrane is often referred to as a fluid mosaic model because it is composed of a fluid lipid bilayer with embedded proteins that form a mosaic pattern. The lipid bilayer is fluid, allowing for the movement of molecules within the membrane. The proteins within the membrane are also dynamic and can move laterally, contributing to the mosaic-like appearance. This model accurately represents the dynamic nature of the plasma membrane.

Why is a plasma membrane often referred to as a fluid mosaic model?

The purpose of the plasma membrane is to regulate the movement of substances in and out of the cell, maintain cell integrity, and facilitate cell communication.

What is the purpose of the plasma membrane?

The difference between unsaturated and saturated tails of phospholipids lies in their chemical structure. Unsaturated tails have double bonds between carbon atoms, resulting in a kinked shape and a more fluid membrane. Saturated tails, on the other hand, have no double bonds and a straight shape, leading to a more rigid membrane.

Think back to unit 1, what is the difference between unsaturated and saturated tails of phospholipids?

The presence of double bonds in the fatty acid tails of phospholipids causes kinks in their structure.

What causes kinks in the tails of phospholipids?

The molecule that embeds itself within the membrane and affects fluidity is called a phospholipid. Phospholipids have a hydrophilic (water-loving) head and a hydrophobic (water-fearing) tail. They arrange themselves in a bilayer, with the hydrophilic heads facing the aqueous environment and the hydrophobic tails facing each other. This arrangement allows phospholipids to regulate the fluidity of the membrane. By adjusting the saturation and length of their fatty acid tails, phospholipids can either increase or decrease the fluidity of the membrane.

What molecule embeds itself within the membrane and affects fluidity? How does it affect fluidity?

Integral proteins are embedded within the cell membrane and span across its entire width. They have hydrophobic regions that interact with the lipid bilayer. Peripheral proteins, on the other hand, are not embedded in the membrane and are found on either side of it. They are attached to the membrane through weak interactions with integral proteins or lipids.

Differentiate between integral and peripheral proteins.

Human cells are able to maintain membrane fluidity in cold temperatures through the incorporation of unsaturated fatty acids into their cell membranes. Unsaturated fatty acids have double bonds in their carbon chains, which introduce kinks and prevent the fatty acids from packing tightly together. This prevents the cell membrane from becoming too rigid and allows it to remain fluid even in cold temperatures. Additionally, cells may also produce special proteins called antifreeze proteins that help prevent ice crystal formation and maintain membrane integrity.

How are human cells able to maintain membrane fluidity when they are in cold temperatures?

An integral protein embedded within the plasma membrane consists of a long chain of amino acids that spans across the lipid bilayer of the membrane. The hydrophobic regions of the protein are embedded within the lipid bilayer, while the hydrophilic regions are exposed to the aqueous environment on either side of the membrane.

Draw an integral protein embedded within the plasma membrane. Label its hydrophobic and hydrophilic regions.

The term "selectively permeable" refers to the property of the plasma membrane to allow certain substances to pass through while restricting the passage of others. It acts as a barrier, controlling the movement of molecules and ions in and out of the cell. This selectivity is achieved through various mechanisms such as transport proteins, ion channels, and receptor-mediated endocytosis. Essentially, the plasma membrane regulates the entry and exit of substances to maintain the cell's internal environment and ensure proper functioning.

In your own words, what dos it mean that the plasma membrane is selectively permeable?

The plasma membrane is selectively permeable due to its lipid bilayer structure and embedded proteins. The hydrophobic interior of the membrane prevents the passage of hydrophilic molecules, while allowing the diffusion of small, nonpolar molecules. Membrane proteins, such as transporters and channels, regulate the movement of specific substances across the membrane. Additionally, the presence of cholesterol helps maintain the fluidity and stability of the membrane, contributing to its selective permeability.

What qualities of the plasma membrane make it selectively permeable?

Nonpolar molecules are hydrophobic, meaning they repel or do not mix well with water. This has implications for their passage across the plasma membrane. Since the plasma membrane is composed of a phospholipid bilayer, which is also hydrophobic, nonpolar molecules can easily pass through the membrane by simple diffusion. They can move across the membrane without the need for any specific transport proteins or energy expenditure.

Are nonpolar molecules hydrophobic or hydrophilic? What does this mean in terms of their passage across the plasma membrane?

Polar molecules are hydrophilic, meaning they have an affinity for water. This affects their passage across the plasma membrane as the membrane is primarily composed of hydrophobic lipid bilayers. Polar molecules have difficulty crossing the hydrophobic region of the membrane and often require the assistance of transport proteins or specialized channels for transport.

Are polar molecules hydrophobic or hydrophilic? What does this mean in terms of their passage across the plasma membrane?

Carbon Dioxide: (b) nonpolar Ions: (a) polar Oxygen: (b) nonpolar Water: (a) polar Glucose: (a) polar

Identify the following as (a) polar or (b) nonpolar:

1. Carbon Dioxide

2. Ions

3. Oxygen

4. Water

5. Glucose

False. Plant cells can exchange materials through their plasma membrane despite having a cell wall. The plasma membrane is selectively permeable, allowing the passage of certain substances. The cell wall provides structural support and protection but does not hinder the exchange of materials through the plasma membrane via processes such as diffusion, osmosis, and active transport.

If plant cells have a cell wall, then they cannot exchange material through their plasma membrane. True or False. Why?

Cell walls are composed of cellulose, a complex carbohydrate that provides structural support to plant cells.

What are cell walls composed of?

Plant cells have a cell wall. The purpose of a cell wall is to provide structural support and protection to the cell, maintaining its shape and preventing it from bursting under osmotic pressure.

What kind of cells have a cell wall? What is the purpose of a cell wall?

Passive transport is the movement of molecules across a cell membrane without the use of energy, while active transport requires the expenditure of energy. In passive transport, molecules move along their concentration gradient, from an area of high concentration to low concentration. Active transport, on the other hand, moves molecules against their concentration gradient, from an area of low concentration to high concentration. Passive transport includes processes like diffusion and osmosis, while active transport includes processes like protein pumps and endocytosis/exocytosis.

What are the main differences between passive and active transport?

The example you provided is an example of passive diffusion, which is a type of passive transport. In passive diffusion, molecules move from an area of higher concentration to an area of lower concentration without the need for energy input.

Imagine a room is a cell and someone brings in freshly popped popcorn (gas molecules). The smell slowly drifts through the room What type of transport is this an example of?

In passive transport, molecules move from an area of higher concentration to an area of lower concentration.

Fill in the blanks: in passive transport, molecules move from _______ to ________ concentration.

Molecules are able to move through diffusion due to their random thermal motion. This motion causes molecules to spread out from an area of high concentration to an area of low concentration, resulting in a net movement of molecules. Diffusion does not require an input of energy and is driven by the inherent kinetic energy of the molecules.

How are molecules able to through diffusion?

Animal cells maintain a high internal concentration of potassium compared to their external environments through the active transport mechanism. This process involves the use of ATP energy to pump potassium ions into the cell against their concentration gradient. The sodium-potassium pump, a protein embedded in the cell membrane, actively transports three sodium ions out of the cell while simultaneously bringing two potassium ions into the cell. This constant pumping of potassium ions helps to establish and maintain the high internal concentration of potassium in animal cells.

How is it possible that animal cells have a high internal concentration of potassium in comparison to their external environments?

In active transport, ATP (adenosine triphosphate) molecules are necessary for the movement of molecules across a cell membrane against their concentration gradient.

What molecules is necessary for active transport?

Draw two diagrams: one of a cell going through endocytosis and one of a cell going through exocytosis

Facilitated diffusion is a type of passive transport. It does not require energy expenditure by the cell. Instead, it relies on the assistance of specific carrier proteins to transport molecules across the cell membrane along their concentration gradient.

Is facilitated diffusion a type of active or passive transport? Why?

The two types of transport proteins are channel proteins and carrier proteins.

Identify the two types of transport proteins.

Two ways water can pass through the cell membrane are through simple diffusion and through aquaporins.

What are two ways water can pass through the cell membrane?

Facilitated diffusion increases the rate of diffusion by using carrier proteins or channel proteins to transport specific molecules across the cell membrane. These proteins create a pathway for molecules that cannot pass through the lipid bilayer on their own. By providing a facilitated pathway, the rate of diffusion for these molecules is enhanced, allowing them to move more rapidly across the membrane.

How does facilitated diffusion affect the rate of diffusion?

If there was a mutation that changed the amino acid sequence of the proteins that make up aquaporins, it could potentially affect the structure and function of the aquaporins. Aquaporins are responsible for facilitating the transport of water across cell membranes. Any alteration in their amino acid sequence could lead to a change in their shape and impair their ability to transport water effectively. This could result in a decrease in water transport across the cell membrane, potentially leading to cellular dehydration or impaired cellular processes that rely on water transport.

Predict the effect on a cell if there was a mutation that changed the amino acid sequence of the proteins that make up aquaporins.

A chemical gradient can be a source of energy for the cell through a process called chemiosmosis. In this process, the cell utilizes the potential energy stored in the gradient to generate ATP, the cell's main energy currency. This occurs when ions or molecules move across a membrane, driven by the gradient, and their movement is coupled with the synthesis of ATP. This mechanism is crucial for various cellular processes, including active transport, muscle contraction, and ATP synthesis in mitochondria.

How can a chemical gradient be a source of energy for the cell

A concentration gradient refers to the gradual change in the concentration of a substance across a space or membrane. It can be a difference in concentration from one side to another. On the other hand, a chemical gradient refers to the change in the concentration of a specific chemical substance, such as ions or molecules, across a space or membrane. In summary, while a concentration gradient is a general term for any change in concentration, a chemical gradient specifically refers to the change in concentration of a chemical substance.

Contrast “concentration gradient” to “chemical gradient”

Hypertonic solution has a higher solute concentration than the cell. In a plant cell, water will move out, causing the cell to shrink (plasmolysis). In an animal cell, water will move out, causing the cell to shrink (crenation).

Isotonic solution has the same solute concentration as the cell. In a plant cell, water will move in and out, maintaining cell shape (flaccid). In an animal cell, water will move in and out, maintaining cell shape (normal).

Hypotonic solution has a lower solute concentration than the cell. In a plant cell, water will move in, causing the cell to swell and become turgid. In an animal cell, water will move in, causing the cell to swell and potentially burst (lysis).

defines hypertonic, isotonic and hyponic in terms of solute concentration. Describe what would happen to a plant and animal cell if placed in each of these solutions.

A saltwater fish lives in a hypertonic solution. To survive in this solution, the saltwater fish must consume a lot of water.

Circle one: a salwater fish lives in a (hypertonic, isotonic, hypotonic) solution. To survive in this solution the saltwater must consume a lot of (salt, water)

The water will diffuse out of the plant cell into the 0.25M solution.

If the concentration of NaCL inside of a plant cell is 0.45M, which way will water diffuse if the cell is placed in a 0.25M solution

Solute potential (Ψ) = -iCRT

Where:

• i is the ionization constant (for NaCl, i = 2)

• C is the molar concentration of the solution (0.3M)

• R is the ideal gas constant (0.0831 L·bar/(mol·K))

• T is the temperature in Kelvin (25°C + 273 = 298K)

Plugging in the values:

Ψ = -2 * 0.3 * 0.0831 * 298

Calculating this expression will give you the solute potential of the NaCl solution in bars.

Calculate the solute potential of a 0.3M NaCLsolutation at 25C. FInd your answers in bars.