Biochemistry Course - Introduction to Cell Structure

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Questions and Answers

What property does density gradient centrifugation primarily use for separating particles?

Size and density (correct)

Temperature and pressure

Shape and color

Magnetic fields

How does the spinning motion of a centrifuge affect particle separation in density gradient centrifugation?

It allows more dense particles to move to the outside edge due to inertia. (correct)

It mixes the particles evenly throughout the solution.

It enables less dense particles to move outward.

It causes all particles to rise to the top.

What is the main difference between differential centrifugation and density gradient centrifugation?

Differential centrifugation is used for smaller particles only.

Density gradient centrifugation uses magnetic fields for separation.

Density gradient centrifugation separates based on density and size. (correct)

Differential centrifugation requires special reagents.

Which method is more suitable for separating smaller particles?

Density gradient centrifugation Signup and view all the answers

What characterizes differential centrifugation as a separation method?

It separates based on mass without special reagents. Signup and view all the answers

What type of cell lacks an endoplasmic reticulum?

Prokaryotic cell Signup and view all the answers

Which of the following statements is true about ribosomes in prokaryotic cells?

Ribosomes are smaller than in eukaryotic cells Signup and view all the answers

What is the primary goal of subcellular fractionation?

To isolate a particular subcellular organelle for study Signup and view all the answers

During the homogenization process, which condition is optimal for preserving organelles?

pH 7.4 and temperature 0 - 4 ͦ C Signup and view all the answers

What does centrifugation separate in the context of subcellular fractionation?

Soluble cell fluid from particulate matter Signup and view all the answers

Which of the following organelles is absent in prokaryotic cells?

Endoplasmic reticulum Signup and view all the answers

What characteristic differs between prokaryotic and eukaryotic cells regarding the cytoskeleton?

Eukaryotic cells possess a cytoskeleton Signup and view all the answers

Which method is used to determine the separation based on components' different mass-to-volume ratios during subcellular fractionation?

Rate-zonal centrifugation Signup and view all the answers

What is the primary advantage of preparative density gradient ultracentrifugation over differential centrifugation?

It can resolve particles with greater accuracy. Signup and view all the answers

In the context of cell fractionation, what does the term 'fractionation' specifically refer to?

The separation of various cellular components. Signup and view all the answers

What is one function of using centrifugation in scientific research?

To remove contamination and impurities. Signup and view all the answers

What does chromatography specifically aid in during the purification process?

Eliminating contaminants from proteins. Signup and view all the answers

What describes the mobile phase in column chromatography?

A buffered aqueous solution. Signup and view all the answers

Which of the following statements about the stationary phase in chromatography is true?

It consists of a porous solid material. Signup and view all the answers

During the chromatographic process, what happens to the protein mixture placed at the top of the column?

It dissolves in the buffer as it travels. Signup and view all the answers

From where does the term 'chromatography' derive, and what does it signify?

Greek for color. Signup and view all the answers

What is the primary function of ribosomes in cells?

Synthesize polypeptides and proteins Signup and view all the answers

Which of the following statements is true regarding prokaryotic cells?

They have ribosomes but lack a nuclear envelope Signup and view all the answers

Which domain includes organisms that do not have peptidoglycan in their cell walls?

Archaea Signup and view all the answers

In the three domain system, which group is characterized as 'true bacteria'?

Bacteria Signup and view all the answers

What distinguishes eukaryotic cells from prokaryotic cells?

Eukaryotic cells contain organelles Signup and view all the answers

Which kingdom is characterized by multicellular organisms that perform photosynthesis?

Plantae Signup and view all the answers

Which characteristic is NOT associated with Prokaryotic organisms?

Presence of a nuclear envelope Signup and view all the answers

Which of the following groups is classified under Eukarya?

Fungi Signup and view all the answers

What is the primary focus of the module on cell structure?

The cell as the most basic unit of life Signup and view all the answers

Which statement accurately describes a genome?

It includes all genes organized into chromosomes. Signup and view all the answers

What is a coenzyme?

An organic compound that assists enzymes in reactions Signup and view all the answers

What is one learning outcome of the module on cell structure?

Outline differences between eukaryotic and prokaryotic cells Signup and view all the answers

Which features differentiate eukaryotic cells from prokaryotic cells?

Eukaryotic cells contain membrane-bound organelles. Signup and view all the answers

What method is commonly used for fractionation and separation of cell components?

Centrifugation Signup and view all the answers

Which of the following is NOT a function associated with organelles in cells?

External environment interaction Signup and view all the answers

How many chromosomes make up the full complement of DNA in humans?

46 chromosomes in total Signup and view all the answers

What happens to proteins with a net negative charge in ion exchange chromatography?

They are carried quickly down the column by the buffer. Signup and view all the answers

In cation exchange chromatography, what is the role of Na+ ions?

They exchange with positively charged proteins. Signup and view all the answers

What method can be used to decrease the interaction of positively charged proteins with the stationary phase in cation exchange chromatography?

Adjust the pH of the buffer to a higher value. Signup and view all the answers

What is the primary characteristic of anion exchange chromatography?

It binds proteins with a net positive charge. Signup and view all the answers

Which resin is commonly used for protein purification in anion exchange chromatography?

DEAE resin Signup and view all the answers

What happens to small proteins during size exclusion chromatography?

They fit into the pores of the beads. Signup and view all the answers

Why might proteins with a large net positive charge remain attached to the column in cation exchange chromatography?

They interact strongly with negatively charged functional groups. Signup and view all the answers

What is the effect of using a buffer of lower pH in cation exchange chromatography?

It increases the positive charge on proteins. Signup and view all the answers

Study Notes

Biochemistry Course - BIO119

Course Lead: Ms. Jean
Course Code: BIO119

Biochemistry Definition

Biochemistry is the application of chemistry to the study of biological processes at the cellular and molecular level.

Introduction to Cell Structure - Module 1

Focuses on the cell as the fundamental unit of life.
Provides a brief overview of cell structure for the course introduction.
Outlines the differences between animal and plant cells.
Reviews various organelles within cells.

Learning Outcomes for Introduction to Cell Structure

Define terms associated with cells.
Describe organelles found in various cell types.
Outline the function of each organelle.
Outline fractionation and separation methods for cell components.
Differentiate between eukaryotic and prokaryotic cells.

Genome Definition

The genome is the complete genetic complement of an organism.
It encompasses all organic bases within an organism's DNA.
A genome includes all the genes.
It contains the information needed to develop and maintain an organism.
The full DNA complement is organized into 23 pairs or 46 chromosomes.

Coenzymes (Organic Cofactors)

Coenzymes are organic, non-protein compounds.
They bind with enzymes to catalyze reactions.
Often referred to broadly as cofactors, but have different chemical structures.
Can be reused multiple times when paired with an enzyme.

Definitions of Pili, Flagella, and Plasmids

Pili: Protein structures on bacterial cell envelopes used for cell attachment. (Includes Sex Pili).
Flagella: Slender thread-like structures enabling movement in protozoa, bacteria, and spermatozoa.
Plasmids: Small, extrachromosomal DNA molecules, separate from chromosomal DNA, that replicate independently, typically found in circular, double-stranded form in bacteria. Plasmids can also be in archaea and eukaryotic organisms.

Cytosol Definition and Function

Cytosol is the liquid inside cells.
It's the water-based solution where organelles, proteins, and other structures float.
Its properties support vital cellular functions.
Its contents include proteins, amino acids, mRNA, ribosomes, sugars, ions, messenger molecules, and more.
Acts as the medium for intracellular processes, including enzyme activities.
Supports cell structure and enables chemical movement/processes within.
Virtually all life functions in prokaryotes occur in the cytosol.
Messenger molecules diffuse through cytosol to modify enzyme function, organelle activity, or DNA transcription.

Ribosomes

Minute particles found in large numbers in the cytoplasm of living cells.
Composed of RNA and proteins.
Bind mRNA and tRNA to synthesize polypeptides and proteins.

Cell Structure and Function

The cell has a nucleus or nucleoid.
It has a plasma membrane.
It has cytoplasm.

Three Domain System

Recognizes three types of cells based on a comparison of ribosomal RNA genes.
Classifies microorganisms into: Bacteria, Archaea, and Eukarya (eukaryotes).
Archaea, prokaryotes lacking peptidoglycan in the cell walls.

Classification by Energy Source

Organisms can be classified by their energy source (light or chemical compounds).
They are also classified according to their carbon source (CO2 or organic compounds).
The categories include: Phototrophs, Chemotrophs, Autotrophs, Heterotrophs.

Eukarya Kingdoms

Plantae: Multicellular organisms with eukaryotic cells, organized tissues, cell walls, for photosynthesis, and nutrient absorption.
Animalia: Multicellular organisms with eukaryotic cells, organized tissues, and no cell walls, primarily for nutrient ingestion.
Protista: Simple, mostly single-celled eukaryotic organisms.
Fungi: Single-celled or multicellular organisms, with eukaryotic cells, cell walls (but no organized tissues). Nutrients absorbed.

Archaea

Often called extremophiles (live in extreme environments - e.g., high salt).
Are prokaryotes, unlike bacteria ,having different lipids in their cell membrane and no peptidoglycan.
Ribosomal structure is similar to eukaryotic ribosomes.
DNA transcription is also similar to eukaryotes.
Examples include Halobacterium salinarum (which lives in high salt environments like the Dead Sea).

Prokaryotic vs. Eukaryotic Cells (key differences)

Prokaryotes lack a true nucleus and membrane-bound organelles; eukaryotes contain a true nucleus and membrane-bound organelles.
The DNA in prokaryotes is circular; in eukaryotes, it is linear.
Ribosomes are 70S in prokaryotes; 80S in eukaryotes.

Subcellular Fractionation

Process of isolating/separating subcellular components of cells according to the parameters of size, mass, and/or density.
Involves homogenization that is the process of breaking down cells.
Centrifugation used is the method of separating the component using different speeds of centrifugation.
Methods to assess purity of components: Microscopy/electron microscopy; using markers (chemicals/enzymes); immunological techniques.

Chromatography- Fractionation Methods

A process to separate components of a mixture (like proteins, using a column).
Types: Column Chromatography: Ion Exchange, Size Exclusion (Gel Permeation), Affinity methods, HPLC.
Mobile phase - a buffered aqueous solution.
Stationary phase - a porous solid material (like fine sand) within the column.

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Description

This quiz covers the fundamentals of cell structure as part of the Biochemistry course BIO119. It addresses the differences between animal and plant cells, identifies organelles, and outlines their functions. Understanding the cellular components is crucial for grasping biological processes at a molecular level.