Measuring Cells and Organelles

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Questions and Answers

What is the primary function of ribosomes as mentioned in the content?

Sorting of cellular materials

Synthesis of lipids

Modification of carbohydrates

Synthesis of proteins (correct)

Which sequence correctly describes the transport process of proteins from the endoplasmic reticulum?

Endoplasmic Reticulum → Cis-Golgi Network → Trans-Golgi Network (correct)

Trans-Golgi Network → Ribosomes → Lysosomes

Plasma Membrane → Endoplasmic Reticulum → Golgi Apparatus

Ribosomes → Golgi Apparatus → Plasma Membrane

What are vesicles primarily used for in the Golgi apparatus?

Transporting waste products out of the cell

Transporting proteins and lipids between cisternae (correct)

Synthesis of cellular enzymes

Modifying carbohydrates and steroids

Which face of the Golgi apparatus is located near the nucleus?

Cis face Signup and view all the answers

What happens to proteins that are incorrectly exported from the Golgi apparatus?

They return to the endoplasmic reticulum Signup and view all the answers

What structures do chromatins condense to form during cell division?

Chromosomes Signup and view all the answers

Which function does the nucleus NOT serve?

Generates ATP Signup and view all the answers

What is the shape of mitochondria commonly described as?

Variable Signup and view all the answers

What is the main function of the inner membrane of the mitochondria?

Generates ATP Signup and view all the answers

How does mitochondria replicate?

By dividing into daughter mitochondria Signup and view all the answers

Where are chloroplasts predominantly found in plants?

Palisade mesophyll Signup and view all the answers

Which component is found in the stroma of chloroplasts?

Photosynthetic enzymes Signup and view all the answers

What is the primary role of plastids in high-level plants?

Photosynthesis and starch storage Signup and view all the answers

What is the main purpose of an eye-piece graticule in microscopy?

To measure the size of specimens accurately Signup and view all the answers

What is the actual size of one eyepiece graticule division given that 100 divisions equal 0.25 mm?

0.0025 mm Signup and view all the answers

Which type of electron microscope provides the best resolution?

Transmission electron microscope (TEM) Signup and view all the answers

Which of the following is NOT a limitation of using an electron microscope?

It can only be used for transparent specimens Signup and view all the answers

How is the diameter of a cell calculated using eyepiece graticule measurements?

By multiplying the number of divisions by the size of each division Signup and view all the answers

Which characteristic differentiates a scanning electron microscope (SEM) from a transmission electron microscope (TEM)?

SEM produces 3-dimensional images of surfaces Signup and view all the answers

Why is the cost of operation relatively low for light microscopes compared to electron microscopes?

Electron microscopes require specialized environments and procedures Signup and view all the answers

What physical form do specimens require when viewed under an electron microscope?

Fixed and plastic-embedded Signup and view all the answers

What is the primary function of centrioles within the centrosome?

To organize microtubules that attach to chromosomes during cell division Signup and view all the answers

What distinguishes cilia from flagella in terms of movement?

Cilia have a back-and-forth motion, while flagella undulate Signup and view all the answers

Which of the following correctly describes the arrangement of microtubules in cilia and flagella?

Both have a '9+2' pattern Signup and view all the answers

What role does the cytoskeleton play within a cell?

It provides mechanical support and maintains cell shape Signup and view all the answers

Which characteristic is shared between basal bodies and centrioles?

Both have a '9+0' microtubule pattern Signup and view all the answers

In terms of cellular locomotion, which statement is true regarding flagella?

Flagella propel cells in the same direction as their axis Signup and view all the answers

Which component is NOT a part of the cytoskeleton?

Lipid bilayers Signup and view all the answers

During cell division, centrioles help organize which structures?

Microtubules Signup and view all the answers

What is the primary composition of the cell wall?

Cellulose Signup and view all the answers

Which component of the plasma membrane is involved in maintaining fluidity?

Cholesterol Signup and view all the answers

What structure allows for the lateral movement of proteins in the plasma membrane?

Phospholipid bilayer Signup and view all the answers

What characterizes peripheral proteins in the plasma membrane?

They are found on the surfaces of the membrane. Signup and view all the answers

Which statement about the structure of membranes is true?

Most proteins can move laterally within the membrane. Signup and view all the answers

What are the hydrophilic parts of phospholipids called?

Polar heads Signup and view all the answers

What term describes the model that explains the arrangement of proteins in the plasma membrane?

Fluid mosaic model Signup and view all the answers

Which type of protein extends through the entire membrane?

Integral protein Signup and view all the answers

Study Notes

Measuring Cells

Accurate measurement of cells and organelles is essential for scientific research.
Two essential tools:
- Eye-piece graticule: Transparent scale with 100 divisions in the microscope eyepiece.
- Stage micrometer: Miniature ruler placed on the microscope stage.
Magnification formula: Magnification = Size of image / Actual size of specimen.
100 eyepiece graticule divisions = 0.25 mm, resulting in 1 division = 2.5 µm.
Example: A cell with a diameter of 20 divisions measures 50 µm.

Electron Microscopy Principles

Electron Microscope: Uses electrons to illuminate specimens, capable of resolving sub-cellular structures due to effective wavelength < 1 nm.
Limitations:
- Specimens must be dead and fixed in plastic for viewing in a vacuum.
- Susceptible to damage from electron beams.
- Requires staining with heavy metals (e.g., osmium, lead, gold).
Types:
- Transmission Electron Microscope (TEM): Transmits electrons through thin specimens; provides the best resolution.
- Scanning Electron Microscope (SEM): Scans specimens with a fine electron beam, providing 3D images but poorer resolution.

Comparison of Microscopes

Light microscopes:
- Cost-effective (RM400 – 2000).
- Easy to operate and portable.
- Simple sample preparation.
Electron microscopes:
- High cost (over RM500,000).
- Expensive operation and complex sample preparation.

Cell Division and Chromosomes

During division, chromatin condenses into chromosomes, composed of DNA and histone proteins.
Non-dividing nucleus appears grainy due to chromatin presence.
Functions of the nucleus include housing genetic material, controlling cellular activities, and producing ribosomes and RNA.

Mitochondria

Present in all cells except red blood cells; shapes can vary (oval, rod, sphere).
Average dimensions: ~2.5 µm (length), ~1 µm (diameter).
Primarily generates ATP through aerobic respiration; features two membranes (outer smooth, inner folded into cristae).
Contains own DNA and ribosomes; replicates independently via division but cannot replicate outside the cell.

Chloroplast

Found primarily in the mesophyll of high-level plants, especially palisade mesophyll.
Conducts photosynthesis and stores starch; typical diameter: 8-10 µm.
Contains stroma, DNA, ribosomes, and photosynthetic enzymes.

Ribosomes

Key functions include synthesizing proteins and enzymes.
Ribosomes on the endoplasmic reticulum (ER) transfer proteins to the Golgi apparatus for processing.

Golgi Apparatus

Composed of stacked membrane sacs; functions like a cell's post office.
Processes proteins from the ER, modifies them, sorts them, and directs them to their destinations.
Contains two faces: cis (near ER) and trans (further from nucleus).
Vesicles transport proteins and other materials between sacs.

Centrosome and Centrioles

Contains centrioles made of microtubules in a "9+0" pattern.
Organizes microtubules that attach to chromosomes during cell division.

Cilia and Flagella

Cilia: Short projections used for cellular movement; found in paramecium and oviducts.
Flagella: Longer, whiplike structures seen in algae, protozoa, and some bacteria, generating thrust with undulating motion.
Both organelles feature a "9+2" tubule arrangement.

Cytoskeleton

Network of fibers providing mechanical support, maintaining cell shape, and enabling cellular movement.
Composed of microtubules, actin filaments, and intermediate filaments.

Cell Wall

Thick structure outside the plasma membrane, providing strength and rigidity.
Primarily made of cellulose, freely permeable to solutes.

Plasma Membrane

Separates the cell's internal environment from its surroundings, composed of a phospholipid bilayer.
Fluid mosaic model describes dynamic structure where proteins and phospholipids move laterally.

Fluid Structure of Membranes

Layers of membrane components move over one another; lateral diffusion is common, while flip-flop is rare.
Integral and peripheral proteins embedded in the phospholipid framework.

Extracellular Matrix

Contains glycoproteins, glycolipids, and proteins, contributing to cellular communication and structure.
Hydrophilic heads of phospholipids face outward, while hydrophobic tails are oriented inward, forming a bilayer for cell homeostasis.

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Description

This quiz focuses on the techniques used to measure cells and organelles accurately, including the eye-piece graticule and stage micrometer. Understand the principles of magnification and how to apply these methods in microscopy. Test your knowledge on the accurate measurement of microscopic objects!