IB BIO U1 TEST REVIEW

What are cells, and why are they considered the basic unit of life?

What are cells, and why are they considered the basic unit of life?

Cells are the smallest structural and functional units of living organisms.

Can you explain the three tenets of the cell theory?

1. All living organisms are composed of one or more cells.

2. The cell is the basic structural and functional unit of life.

3.  All cells arise from pre-existing cells through cell division.

What are the exceptions to the cell theory?

1. Fungal Hyphae

2. Striated Muscles

3. Red Blood Cells

4. Sieve Element.

What are the main components of a typical animal cell?

1. Cell Membrane

2. Nucleus

3. Cytoplasm

4. Mitochondria

5. Endoplasmic Reticulum

6. Golgi Apparatus

7. Lysosomes

Cell Membrane

Controls the passage of substances in and out of the cell.

Nucleus

Contains genetic material (DNA).

Cytoplasm

Houses organelles and is the site of many cellular processes.

Mitochondria

Produce energy (ATP) through cellular respiration.

Endoplasmic reticulum (ER)

Involved in protein and lipid synthesis.

Golgi apparatus.

Modifies, packages, and transports proteins.

Lysosomes

Contain enzymes for cellular digestion.

How are cells able to maintain a regular metabolism?

1. Regulation of energy production.

2. Waste elimination.

3. Utilization of nutrients.

How do plant cells differ from animal cells, and what unique organelles do plant cells have? What do they do?

1. Plant cells have a cell wall.
   

2. Chloroplasts for photosynthesis.
   

3. Large central vacuoles for storage and support.

What does it mean for a cell to differentiate?

Cell differentiation is the process by which a cell becomes specialized to perform a specific function in the body.

Explain the controls of gene expression during cell differentiation?

Gene expression is controlled by turning specific genes on or off, resulting in the development of specialized cell types.

What are stem cells, and what distinguishes embryonic stem cells from adult stem cells?

Stem cells are undifferentiated cells capable of becoming various cell types. Embryonic stem cells are pluripotent and can differentiate into any cell type, while adult stem cells are multipotent and have a more limited differentiation potential.

What are the potential medical applications of stem cell therapy, such as Stargardt’s disease?

Stem cell therapy may be used to replace damaged or diseased cells in conditions like Stargardt's disease, a genetic eye disorder. It holds promise for regenerative medicine.

What ethical considerations surround stem cell research?

Stem cell research raises ethical concerns related to the use of embryonic stem cells, including potential destruction of embryos.

Discuss the advantages of stem cell research?

Stem cell research has the potential to revolutionize medicine and treat various diseases.

Discuss the disadvantages of stem cell research?

Ethical dilemmas, safety concerns, and technical challenges in stem cell research.

What is a prokaryote?

A prokaryote is a type of cell that lacks a true nucleus and membrane-bound organelles. Bacteria and Archaea are examples of prokaryotes.

What is a eukaryote?

A eukaryote is a cell with a well-defined nucleus and membrane-bound organelles. Plants, animals, fungi, and protists are examples of eukaryotes.

What are the main differences between prokaryotic and eukaryotic cells?

1. Prokaryotic have no nucleus. Eukaryotic cells have a membrane-bound nucleus.

2. Prokaryotes have no bound organelles, whereas eukaryotes have organelles.

3. Prokaryotic DNA is typically a single, circular chromosome, whereas eukaryotes have multiple linear chromosomes.

4. Prokaryotes are generally smaller, 1 to 10 micrometers (µm), and simpler in structure compared to eukaryotes, 10 to 100 µm.

Explain the advantages a eukaryote has over a prokaryote?

1. Compartmentalization/Organelles:

   1. Eukaryotic cells organelles that allow for specialized functions in different compartments, improving efficiency.

2. DNA Protection:

   1. The nucleus protects genetic material from external influences, ensuring genetic stability.

3. Enhanced Metabolism:

   1. Eukaryotes have a more complex metabolism due to organelles.

4. Multicellularity:

   1. Eukaryotes can form complex, multicellular organisms.

5. Adaptability:

   1. Eukaryotic cells can adapt to a wider range of environments and ecological niches.

What is the function of the plasma membrane, and what is its structure?

The plasma membrane, also known as the cell membrane, serves as a selectively permeable barrier that separates the cell's interior from its external environment.

What is the structure of the plasma membrane?

The plasma membrane is primarily composed of a phospholipid bilayer with embedded proteins. It encloses the cell and regulates the passage of molecules in and out of the cell. There is also cholesterol, to maintain flexibility. There are integral and peripheral proteins. Carbohydrates are on the surface of the cell layer, attached to peripheral proteins and are for cell recognition and communication with other cells.

What is the fluid mosaic model of the cell membrane, and what does it explain about membrane structure?

The fluid mosaic model describes the plasma membrane as a dynamic structure where phospholipids and proteins are not static but move within the lipid bilayer.

What does the fluid mosaic model of the cell membrane explain about membrane structure?

This model explains that the membrane is not rigid but rather flexible and constantly changing, allowing for the movement of molecules and proteins within the membrane.

How does the phospholipid bilayer contribute to the selective permeability of the cell membrane?

The phospholipid bilayer is selectively permeable because its hydrophilic heads face outward and interact with water, while the hydrophobic tails are oriented inward. This arrangement prevents the passage of large, charged molecules while allowing smaller, nonpolar molecules to pass through.

What are membrane proteins, and what roles do they play in cellular processes?

Membrane proteins are molecules embedded in the lipid bilayer of the plasma membrane. They can be integral (spanning the membrane) or peripheral (attached to the surface).

What roles do membrane proteins play in cellular processes?

1. Transport of molecules in and out of the cell.

2. Cell adhesion and recognition.

3. Structural support.

Why is cholesterol important in the plasma membrane?

Cholesterol molecules are interspersed within the lipid bilayer of the plasma membrane. They play a crucial role in maintaining membrane fluidity and stability. Cholesterol helps regulate the membrane's rigidity, preventing it from becoming too fluid at high temperatures and too solid at low temperatures. It is essential for the proper functioning of the cell membrane.

How do different types of molecules move across the cell membrane through passive transport?

Passive transport mechanisms, such as diffusion and facilitated diffusion, allow molecules to move from areas of high concentration to low concentration without requiring energy. Oxygen and carbon dioxide can diffuse directly through the lipid bilayer, while larger or charged molecules may use protein channels or carriers in facilitated diffusion.

What is active transport?

Active transport is a process that requires the expenditure of energy (usually ATP) to move molecules against their concentration gradient, from areas of low concentration to high concentration.

How does active transport differ from passive transport in terms of energy requirements?

Unlike passive transport, active transport moves molecules against the concentration gradient, so it requires energy to work against this gradient.

How do cells maintain a concentration gradient, and why is it important for various cellular processes?

Cells use active transport mechanisms to pump molecules against their concentration gradient, which helps maintain concentration differences. This is vital for processes such as membrane permeability and metabolic purposes.

What is osmosis?

Osmosis is the passive movement of water molecules across a semipermeable membrane from areas of low solute concentration to high solute concentration.

How does Osmosis affect cell volume in different solutions?

In hypertonic solutions, water moves out of the cell, causing it to shrink. In hypotonic solutions, water moves into the cell, leading to cell swelling. Isotonic solutions result in no net water movement.

What are the differences between facilitated diffusion and active transport in terms of mechanisms?

Facilitated diffusion uses membrane proteins to assist the passive movement of molecules, while active transport moves molecules against their gradient using energy.

What are the differences between facilitated diffusion and active transport in terms of energy usage?

Facilitated diffusion does not require energy, whereas active transport relies on the expenditure of energy, usually in the form of ATP.

How do ion channels facilitate the movement of ions across cell membranes?

Ion channels are transmembrane proteins that form pores allowing specific ions to pass through. They open or close in response to various signals.

How do carrier proteins facilitate the movement of ions across cell membranes?

Carrier proteins bind to specific ions and undergo conformational changes to transport them across the membrane.

Can you explain how endocytosis works, and provide examples of their biological significance?

Endocytosis is the process by which cells engulf external material by forming vesicles from the cell membrane. It includes phagocytosis (cell eating) and pinocytosis (cell drinking).

Can you explain how exocytosis works, and provide examples of their biological significance?

Exocytosis is the reverse process, where cells expel material by fusing vesicles with the cell membrane. Endocytosis is crucial in immune response (phagocytosis) and nutrient uptake (pinocytosis). Exocytosis is important in cell secretion and neurotransmitter release.

What are the main theories about the origin of life on Earth, including abiogenesis?

Abiogenesis is the theory that life can arise from non-living matter. It was once believed that life originated spontaneously from inanimate substances.

What are the main theories about the origin of life on Earth, including biogenesis?

Biogenesis is the current scientific consensus that life arises from pre-existing living matter, and it has replaced the idea of abiogenesis.

How do prokaryotic cells, specifically bacteria and archaea, provide insights into early life forms?

Bacteria and archaea are ancient, simple, single-celled organisms that resemble early life forms. They lack a true nucleus and membrane-bound organelles, providing clues about the simplicity of early life.

What is the endosymbiotic theory?

The endosymbiotic theory suggests that eukaryotic organelles like mitochondria and chloroplasts originated from free-living prokaryotic cells that were engulfed by ancestral eukaryotic cells.

How does the endosymbiotic theory explain the origin of eukaryotic organelles such as mitochondria and chloroplasts?

These prokaryotes established a symbiotic relationship, with the host cell providing protection and nutrients while the engulfed cells contributed functions like energy production (mitochondria) and photosynthesis (chloroplasts).

Can you describe the evidence supporting the endosymbiotic theory?

Supporting evidence includes similarities between organelles and free-living prokaryotes in terms of DNA structure, replication, and ribosomes. Additionally, organelles like mitochondria and chloroplasts have double membranes, which may result from the engulfment process.

What is the significance of the Miller-Urey experiment in understanding the chemical origins of life?

The Miller-Urey experiment simulated early Earth conditions and demonstrated that organic molecules, including amino acids, could spontaneously form from inorganic precursors. This provided evidence that the building blocks of life could have arisen through abiogenesis.

What did Pasteur's Experiment show?

Louis Pasteur's experiment disproved the idea of spontaneous generation (abiogenesis) by demonstrating that microorganisms did not spontaneously arise from non-living matter but instead came from pre-existing microorganisms. His experiments provided strong support for the concept of biogenesis, the idea that life arises from other living organisms.

What is the purpose of cell division, and how does it relate to growth, repair, and reproduction?

Cell division is essential for the growth, repair, and reproduction of organisms. It allows for the production of new cells for development, tissue regeneration, and the creation of offspring in multicellular organisms.

What are the key events of the cell cycle, including interphase, mitosis, and cytokinesis?

• Interphase: The cell prepares for division, including the growth phase (G1), DNA synthesis (S phase), and a final growth phase (G2).

• Mitosis: The nucleus divides into two identical daughter nuclei.

• Cytokinesis: The cell divides into two daughter cells, each with its nucleus.

How does mitosis differ from meiosis, and what are their respective roles in multicellular organisms?

• Mitosis: Mitosis is a type of cell division that results in two genetically identical daughter cells. It is essential for growth and tissue repair in multicellular organisms.

• Meiosis: Meiosis is a specialized form of cell division that produces four genetically distinct haploid cells (gametes) and is necessary for sexual reproduction.

What are cyclins in cell cycle regulation?

Cyclins: Cyclins are proteins that regulate the progression of the cell cycle by binding to cyclin-dependent kinases.

What are cyclin-dependent kinases (CDKs) in cell cycle regulation?

CDKs: Cyclin-dependent kinases are enzymes that control the various checkpoints in the cell cycle, and their activity is dependent on the presence of specific cyclins.

Why are checkpoints important in the cell cycle?

Checkpoints in the cell cycle are control mechanisms that ensure accurate DNA replication and division. They prevent the cell from progressing to the next phase if errors or DNA damage are detected, thereby maintaining genomic integrity.

What are the consequences of uncontrolled cell division, and how do these relate to cancer development?

Uncontrolled cell division can lead to the development of cancer. Cancer occurs when cells divide uncontrollably, forming a mass of abnormal cells (tumor) that can invade nearby tissues and spread to other parts of the body. It results from mutations or dysregulation in cell cycle control mechanisms and can have severe health implications.