Cell stuff: 9

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Questions and Answers

What is the primary role of the cytosol within a eukaryotic cell?

It acts as a barrier to prevent protein leakage.

It serves as the matrix surrounding cell organelles. (correct)

It facilitates the movement of ions across membranes.

It is the site of ATP production.

Which characteristic limits light microscopy in observing small structures?

The wavelength of photons used in visualization. (correct)

The phase variation in light waves.

The thickness of the specimen preparation.

The use of electron beams instead of light.

What happens to an electron in a fluorescent molecule when it absorbs a photon?

It generates additional energy for the matrix.

It becomes ionized and escapes the atom.

It moves to a higher energy orbital. (correct)

It instantly returns to ground state and emits UV light.

Which statement accurately describes the role of a dichroic mirror in fluorescence microscopy?

It reflects light above a certain wavelength and transmits below. Signup and view all the answers

What is a key disadvantage of electron microscopy compared to light microscopy?

It is generally more expensive and requires ultra-thin samples. Signup and view all the answers

Which of the following is NOT a characteristic of biological membranes?

They primarily consist of proteins. Signup and view all the answers

How do small uncharged polar molecules typically diffuse across membranes?

Via hindered diffusion methods. Signup and view all the answers

What process allows ions to pass through membranes more efficiently than simple diffusion?

Facilitated diffusion through ion channels. Signup and view all the answers

What mechanism allows a protein to exhibit fluorescent behavior after the GFP gene is introduced?

The gene for the protein is fused with the GFP gene. Signup and view all the answers

What is the effect of a double bond in the hydrophobic tail of lipids?

It creates a looser bond between adjacent lipids. Signup and view all the answers

Which statement correctly describes the charge of phospholipids in a polarized cell's bilayer?

Phospholipids at the cytosol side are more negatively charged than those at the extracellular side. Signup and view all the answers

What role does cholesterol play in membrane structure?

It increases stability of the membrane. Signup and view all the answers

What is a characteristic of beta-barrel membrane proteins?

They contain hydrophobic side chains on the outside with polar side chains inside. Signup and view all the answers

How does membrane protein localization affect cellular function?

It plays a role in cell communication as well as transport. Signup and view all the answers

What is the significance of sugars attaching to polar head groups of phospholipids?

They contribute to cell recognition and protection. Signup and view all the answers

In relation to cell structures, where is secretion of proteins primarily observed?

At the apical plasma membrane. Signup and view all the answers

What characterizes the interaction of polarized cells with neighboring cells?

They form connections at the lateral plasma membrane. Signup and view all the answers

What type of proteins are primarily involved in the communication between the outside and intracellular environments?

Transporters and channels. Signup and view all the answers

What is a primary feature of membrane proteins related to their structure?

They play significant roles in membrane transport and localization. Signup and view all the answers

Study Notes

Cytoplasm and Cytosol

Cytosol is the fluid contained within the cell membrane.
Cytoplasm comprises the entire content within the cell membrane.

Light Microscopy

Light microscopy relies on the contrast created by the combination of waves out of phase.
Wavelength of light limits light microscopy resolution, making it difficult to observe objects smaller than the wavelength of light.

Fluorescence Microscopy

Fluorescence microscopy uses photons, which have energy and wavelength dependent on their energy level.
In fluorescence microscopy, fluorescent molecules absorb a photon with specific energy, causing an electron to excite to a higher energy orbital.
The excited electron then falls back to the ground state, releasing energy as light with a longer wavelength.

GFP (Green Fluorescent Protein)

GFP allows scientists to make proteins fluorescent.
GFP gene is localized within the cell and fused with the gene for a targeted protein.
The cell then synthesizes the target protein with fluorescent properties.

Electron Microscopy

Electron microscopy uses electron bundles instead of light.
Electron microscopy provides a much higher resolution (around 1nm) compared to light microscopy, allowing the observation of smaller structures.
Electron microscopy requires specialized techniques like ultra-thin sample cutting and is generally more expensive than light microscopy.

Membranes

Membranes are formed by lipids in water.
Lipid bilayers typically measure 5 nm in thickness.
Biological membranes consist primarily of lipids for structural support and proteins.
Membranes are a bilayer, with lipids arranged in two opposing layers.

Membrane Importance

Membranes are crucial for defining cell boundaries and compartmentalizing organelles.
Lipids can diffuse fluidly across the membrane.

Membrane Transport

Passive diffusion allows molecules like oxygen and hydrophobic molecules to pass through the membrane.
Hindered diffusion facilitates the movement of small uncharged polar molecules like water.
Transporter diffusion is specifically used for ions like magnesium and calcium.

Membrane Proteins

Membrane proteins function as transporters and channels.
They facilitate communication between the cell's interior and exterior.
They help localize proteins at the cell surface and in the cytosol.

Beta-barrels

Beta-barrels are a structural motif in membrane proteins.
They have hydrophobic amino acid side chains on the outside and polar side chains on the inside.

Lipid Bilayer Composition

The hydrophilic group of phospholipids contains choline, phosphate, and glycerol.
The hydrophobic tail can vary depending on the presence of double bonds, impacting lipid interactions and membrane structure.
Cholesterol increases membrane stability and decreases permeability.

Membrane Asymmetry

Phospholipids on the cytosol side of the membrane are more negatively charged.
Phospholipids on the extracellular side are more neutral or positively charged.
Sugars attach to the polar head groups of phospholipids on the extracellular side, providing protection and facilitating cell recognition.

Polarized Cells

Polarized cells have distinct regions with specific functions.
The apical plasma membrane is responsible for protein and vesicle secretion.
The lateral plasma membrane connects with other cells.
The basal plasma membrane is firmly attached to the basal lamina.

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Description

This quiz covers key concepts about cytoplasm, cytosol, and various microscopy techniques including light and fluorescence microscopy. It also explores the use of GFP in cellular studies, emphasizing its importance in modern biology. Test your understanding of these critical topics in cell biology!