Biology: Cells as Life's Basic Unit

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Questions and Answers

What is one fundamental property of life that can be observed in cells?

Cells can arise only through division from pre-existing cells. (correct)

Cells require external signal transduction to survive.

Cells do not have a defined lifespan.

Cells can spontaneously generate from non-living matter.

What significant contribution did Henrietta Lacks make to cell culture?

Her cells led to the development of RNA vaccines.

Her cells were used to identify blood type compatibility.

Her cells were immortalized from her tumor and cultured in 1951. (correct)

Her cells were the first to be cloned in a laboratory.

What does death signify in relation to living entities?

It signals that the organism was isolated from its environment.

It indicates that the entity has not reproduced.

It serves as a fundamental property of life. (correct)

It demonstrates the absence of division.

How does the nucleus of a cell respond to signals from its environment?

Signal transduction allows it to recognize changes in genetic material. Signup and view all the answers

Which process is involved in the production of more cells?

Mitosis and Meiosis Signup and view all the answers

What is the primary ethical advantage of induced pluripotent stem (iPS) cells over embryonic stem (ES) cells?

iPS cells do not require the use of an embryo. Signup and view all the answers

Which of the following best describes the totipotency of embryonic stem cells compared to induced pluripotent stem cells?

ES cells are totipotent, while iPS cells are pluripotent. Signup and view all the answers

What potential risk is associated with undifferentiated induced pluripotent stem cells?

They can lead to the development of teratomas. Signup and view all the answers

What role do subunits play in protein formation?

They are responsible for protein signaling and enzymatic functions. Signup and view all the answers

What mechanism allows dyneins to move?

Bending of motor proteins called dynein feet. Signup and view all the answers

How are embryonic stem cells obtained?

By harvesting cells from very young mammalian embryos. Signup and view all the answers

Which theory explains the origin of mitochondria and chloroplasts in eukaryotic cells?

Endosymbiont Theory Signup and view all the answers

How do dynein feet exert a force during movement?

By attaching to and exerting a sliding force on doublets. Signup and view all the answers

What function do proteins on the cell surface serve?

They act as scaffolding for the recruitment of other proteins. Signup and view all the answers

What process is described when proteins recruit more proteins?

Molecular docking. Signup and view all the answers

What is the main function of cholesterol in the plasma membrane?

To hold together protein members by filling gaps Signup and view all the answers

How do cholesterol molecules affect the phospholipid bilayer?

They interfere with movements of the fatty acid tails Signup and view all the answers

What role do sugar molecules play when attached to integral proteins?

They facilitate cell signaling Signup and view all the answers

What causes integral proteins to change their conformation?

Binding with sugar molecules or amino acids Signup and view all the answers

What is the primary characteristic of the hydroxyl group in sphingolipids?

It is hydrophilic and faces the membrane surface Signup and view all the answers

In response to environmental changes, how do lipid membranes alter their composition?

By changing the types and proportions of lipids present Signup and view all the answers

Which of the following describes integral proteins?

They can form glycoproteins when sugar molecules are present Signup and view all the answers

What is altered when integral proteins interact with components found in the cytoplasm?

The shape and folds in their structure Signup and view all the answers

What is the primary function of selectins in cell interactions?

To facilitate transient interactions between cells Signup and view all the answers

Which type of selectin is primarily found in endothelial cells?

E-selectin Signup and view all the answers

Which characteristic describes P-selectin compared to E-selectin?

P-selectin is found in platelets and endothelial cells Signup and view all the answers

What is the role of L-selectin in the body?

To assist leukocytes in navigating vessel walls Signup and view all the answers

Selectins trigger conformation changes in which part of the cell?

Cytoplasmic domain Signup and view all the answers

What type of molecules do selectins recognize and bind to?

Specific arrangements of sugars in oligosaccharides Signup and view all the answers

Which property differentiates E-selectin from other types of selectins?

It has a moderate length structural domain Signup and view all the answers

During which physiological processes do selectins primarily mediate interactions?

Inflammation and clotting Signup and view all the answers

Study Notes

Cells are the Basic Unit of Life

Cells are the building blocks of all living organisms.
Unlike isolated cellular parts, whole cells can be cultured in a laboratory and will grow and reproduce.
Death is also a property of life, as all living entities face this possibility.
The first human cell culture was started in 1951 from a malignant tumor.
This culture, known as the HeLa cell line, was obtained from Henrietta Lacks.

### Cell Division

All cells arise from the division of pre-existing cells.

Heredity

Genetic abnormalities, such as nullisomy (lack of a chromosome pair) or trisomy (an extra copy of a chromosome), often lead to abortion or reduced lifespan.
The phenotype of a cell can influence its maintenance and ability to produce necessary components.

### Cell Differentiation

Embryonic stem cells (ES cells) are isolated from very young mammalian embryos.
ES cells can be induced to differentiate into various cell types.
The ethical concerns associated with ES cell research stem from the use of embryos.
Induced pluripotent stem cells (iPS cells) offer an alternative to ES cells and provide an ethically sound approach to stem cell research.
Unlike ES cells, iPS cells do not require embryonic material.

### Endosymbiont Theory

The theory suggests that eukaryotic cells evolved from large prokaryotes that engulfed aerobic prokaryotes.
Mitochondria, energy-producing organelles, are thought to have originated from aerobic prokaryotes.
Chloroplasts, photosynthetic organelles in plants, are believed to have derived from photosynthetic cyanobacteria.

### Proteins

Proteins are assembled from subunits called polypeptides.
Subunits can form functional proteins that perform tasks like signaling and enzymatic reactions.
Proteins found on the cell surface can act as scaffolds, recruiting other proteins for various functions.
This recruitment process, known as molecular docking, involves the interaction of proteins with each other, building upon the initial scaffold.

### Cellular Membranes

Phospholipid bilayers are the primary component of cell membranes.
Cholesterol molecules within the membrane influence the fluidity of the fatty acid tails.
The proportion of phospholipids, cholesterol, and sphingolipids varies based on environmental factors.

### Integral Proteins

Integral proteins are embedded in the membrane.
They can be modified by the addition of sugars, forming glycoproteins.
The sugars attached to glycoproteins play important roles in recognition and signaling between cells.
Selectins are a family of integral membrane glycoproteins that recognize and bind to specific sugar arrangements.

### Selectins

Selectins are involved in cell-cell interactions.
They are classified into three types based on size and location:
- E-selectin: found on endothelial cells.
- P-selectin: found on platelets and endothelial cells.
- L-selectin: found on leukocytes (white blood cells).
Selectins regulate the adhesion and detachment of cells, particularly leukocytes, during inflammation and clotting.
Selectins play a role in the movement of white blood cells from the bloodstream to sites of infection and inflammation.

### Dyneins

Dyneins are motor proteins that move by bending "feet."
These feet attach to microtubules and exert a sliding force, propelling cellular structures within the cell.

### Cytoplasmic Domain

The cytoplasmic domain of a protein is located at the intracellular end of the membrane.
The cytoplasmic domain can interact with cytoplasmic components, triggering conformational changes and potentially recruiting other proteins.

### Cell to Cell interactions

Glycoproteins, specifically those containing sugar molecules, play a crucial role in cell-cell recognition and communication.
The arrangement of sugar molecules on a glycoprotein acts like a signal, which can be recognized by receptors on other cells.
These interactions trigger changes within the receptor protein leading to a chain of events within the cell, potentially influencing cell behavior and function.

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Description

Explore the fundamental concepts surrounding cells, including their role as the basic unit of life, cell division, and heredity. This quiz delves into cell differentiation and the ethical concerns regarding stem cell research. Test your knowledge on these essential biological topics!