Cell Biology: Cellular Fractions and Cell-Free Systems

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Questions and Answers

What is the function of centrifuging at high speeds (100 000 x g for 30 mins) in cell fractionation?

Pelleting DNA

Pelleting proteins

Pelleting ER, golgi apparatus and other membrane fragments (correct)

Pelleting ribosomes

What was the first cell-free system to carry out protein synthesis in vitro?

In 1949 Isolated myofibrils from skeletal muscle cells

In 1955 Ciliary beating

In 1983 In vitro cell cycle

In 1954 First cell free-system to carry out protein synthesis (correct)

What is the basic functional unit of the body?

Cell (correct)

Molecule

Organ

Tissue

What is the purpose of centrifuging at very high speeds (300 000 x g for 3hrs) in cell fractionation?

Pelleting ribosomes Signup and view all the answers

What is the function of cell-free systems?

To study molecular mechanisms involved in cellular processes Signup and view all the answers

What is the name of the process where myofibrils from skeletal muscle cells contract upon the addition of ATP?

Muscle contraction Signup and view all the answers

What is the name of the reference book written by Geoffrey M. Cooper?

The Cell – A Molecular Approach Signup and view all the answers

What is the function of the Golgi apparatus and protein sorting system?

Protein sorting and modification Signup and view all the answers

What is the main goal of cell fractionation?

To isolate and study specific organelles and macromolecules Signup and view all the answers

How can cells be disrupted in cell fractionation?

Through various methods, including osmotic shock, ultrasonic vibration, and grinding Signup and view all the answers

What is the result of careful application of cell disruption procedures?

Leaving organelles such as nuclei, mitochondria, and lysosomes largely intact Signup and view all the answers

What is the next step after homogenization in cell fractionation?

Differential centrifugation Signup and view all the answers

What is the purpose of density gradient centrifugation in cell fractionation?

To separate organelles based on specific gravity Signup and view all the answers

What is the final step in cell fractionation?

Collection of fractions Signup and view all the answers

What is the result of cell fractionation?

Homogeneous sets of organelles, separated from a larger population of cells Signup and view all the answers

What is the first step in cell fractionation?

Homogenization Signup and view all the answers

What is the main advantage of embryonic stem cells?

They can give rise to all the cell types in the body. Signup and view all the answers

What is the purpose of cell-cell fusion?

To produce hybrid cells with desirable characteristics. Signup and view all the answers

What is the main application of microdissection techniques?

To isolate selected cells from tissue slices. Signup and view all the answers

Which of the following is a potential application of embryonic stem cells?

To replace damaged tissues in muscular dystrophy patients. Signup and view all the answers

What is the primary purpose of cell culture?

To understand the process of morphogenesis. Signup and view all the answers

What is the significance of Escherichia coli in biology?

It is the best understood cell in the world of biology. Signup and view all the answers

What is the primary purpose of cytogenetic research?

To diagnose diseases caused by chromosomal abnormalities. Signup and view all the answers

What is the significance of Saccharomyces cerevisiae in biology?

It is the most frequently used single cell eukaryote. Signup and view all the answers

Study Notes

Cell Fractionation

Cells can be disrupted in various ways, including osmotic shock, ultrasonic vibration, being forced through a small orifice, or being ground up.
Carefully applied disruption procedures leave organelles such as nuclei, mitochondria, Golgi apparatus, lysosomes, and peroxisomes largely intact.
Cell fractionation involves breaking up cells and separating their components and organelles to observe them in isolated form.
Cell fractionation methods involve homogenization or destruction of cell boundaries by different mechanical or chemical procedures, followed by separation of subcellular fractions according to mass, surface, and specific gravity.

Steps of Subcellular Fractionation

Homogenization
Differential centrifugation
Further separation and purification by density gradient centrifugation
Collection of fractions
Microdissection techniques allow selected cells to be isolated from tissue slices.

Centrifugation

Centrifugation at high speeds (100,000 x g for 30 minutes) pellets ER, Golgi apparatus, and other membrane fragments.
Centrifugation at very high speeds (300,000 x g for 3 hours) pellets ribosomes.

Cell-Free Systems

Molecular mechanisms involved in cellular processes can be studied using fractionated cell extracts that maintain biological function.
Examples of cell-free systems include:
- In vitro protein synthesis (1954)
- In vitro cell cycle (1983)
- Golgi vesicle trafficking in vitro (1984)
- Analysis of DNA replication and transcription
- Transport along microtubules

Introduction to Cell Biology

Cells are the basic morphological and functional units of the body.
Mammalian tissue is made up of cells and intercellular or extracellular substances.
Cells can be examined using various methods, including fractionation of cells and analyzing their molecules.

Applications of Cell Culture

Embryonic organs can be cultured to study morphogenesis.
Cancer cells can be studied using cell culture.
Cell culture can be used to study cell-virus relations, cytogenetic research, cell-cell interactions, and cell nutrition.
Embryonic stem cells can be used to produce specialized cells for therapy, such as replacing skeletal muscle fibers in muscular dystrophy patients.

Model Organisms

Escherichia coli is the best understood cell in the world of biology.
Saccharomyces cerevisiae (yeast) is the most frequently used single-celled eukaryote.
Studies with bacteria and yeast have established the basic principles of molecular biology.

Cell Fusion

Cell fusion is the process of membrane merging and cytoplasmic mixing of two cell types, such as human and mouse cells.
Hybrid cells are produced by fusion of animal cells.
Cell fusion can be used to study various cellular processes.

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Description

This quiz covers the separation of cellular components through centrifugation and the study of cellular processes using cell-free systems. It includes the isolation of myofibrils and the study of molecular mechanisms.