Chapter 3: A Tour Of The Cell 3.1 Quiz

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Questions and Answers

What is the main function of the plasma membrane?

To separate the living cell from its surroundings (correct)

To synthesize proteins for the cell

To allow the passage of all substances in and out of the cell

To provide a rigid structure for the cell

What is the structure of the plasma membrane?

A double layer of phospholipids (correct)

A single layer of phospholipids

A triple layer of proteins

A quadruple layer of lipids and proteins

What is the role of the nucleolus within the nucleus?

To store the DNA

To organize the chromosomes

To control the entry and exit of molecules

To synthesize ribosomal RNA (rRNA) (correct)

What is the function of ribosomes?

To synthesize proteins Signup and view all the answers

What is the purpose of the nuclear envelope?

To enclose the nucleus and separate it from the cytoplasm Signup and view all the answers

What is the role of the chromatin in the nucleus?

To organize the genetic material (DNA) of the cell Signup and view all the answers

What is the primary function of the nuclear envelope?

Separate the nucleus from the cytoplasm Signup and view all the answers

Which region of the endoplasmic reticulum (ER) is responsible for the production and secretion of glycoproteins?

Rough ER Signup and view all the answers

What is the primary function of the Golgi apparatus?

Modify and package materials into transport vesicles Signup and view all the answers

What is the primary function of lysosomes?

Digest and hydrolyze macromolecules Signup and view all the answers

Which type of vacuole is found in many mature plant cells and carries organic compounds and water?

Central vacuole Signup and view all the answers

Which region of the endoplasmic reticulum (ER) is responsible for the metabolism of carbohydrates?

Smooth ER Signup and view all the answers

What is the function of the secondary cell wall in plant cells?

To provide support and maintain the shape of the cell Signup and view all the answers

What is the primary component of the extracellular matrix (ECM) in animal cells?

Glycoproteins Signup and view all the answers

Which of the following is a characteristic of a catabolic pathway?

It releases energy by breaking down complex molecules into simpler compounds Signup and view all the answers

What is the role of ATP in driving endergonic reactions in the cell?

ATP is broken down to release energy that can be used to drive endergonic reactions Signup and view all the answers

What is the purpose of plasmodesmata in plant cells?

To allow for communication and signaling between adjacent plant cells Signup and view all the answers

Which of the following is an example of an anabolic pathway in cells?

Protein synthesis Signup and view all the answers

What is the main function of a light microscope?

To pass visible light through a specimen and magnify the image Signup and view all the answers

Which type of microscope provides 3D images of the surface of a specimen?

Scanning electron microscope Signup and view all the answers

What is a characteristic feature of prokaryotic cells?

Cytoplasm bound by plasma membrane Signup and view all the answers

Which cell component is correlated to its cellular function?

Organelles Signup and view all the answers

Why can't a light microscope be used to see organelles within cells?

Organelles are too small to be visible with a light microscope Signup and view all the answers

Where is the DNA located in prokaryotic cells?

In the cytoplasm, in a nucleoid region Signup and view all the answers

What is the main function of the Calvin cycle?

To convert carbon dioxide into organic molecules using ATP and NADPH Signup and view all the answers

Which of the following is a by-product of the light reactions in photosynthesis?

Oxygen Signup and view all the answers

What is the primary role of chloroplasts in photosynthesis?

To convert light energy into chemical energy stored in ATP and NADPH Signup and view all the answers

What is the overall equation for photosynthesis?

$6CO_2 + 12H_2O + \text{Light energy} \rightarrow C_6H_{12}O_6 + 6O_2 + 6H_2O$ Signup and view all the answers

Where do the light-dependent reactions of photosynthesis take place?

In the thylakoid membranes of the chloroplast Signup and view all the answers

Why do leaves appear green?

Because chlorophyll absorbs red and blue light and reflects green light Signup and view all the answers

Study Notes

Cell Structure and Function

Cell components: molecules, atoms, organelles (not non-living components)
Cell structure correlates with cellular function

Microscopy

Light Microscope:
- Uses visible light to magnify image
- Cannot be used to see organelles due to size limitations
Bright-field Microscope:
- Uses direct light to create image
- Suitable for cells with natural pigmentation or artificial staining
Electron Microscopes:
- Scanning Electron Microscopes (SEMs): provide 3D images of surface structures
- Transmission Electron Microscopes (TEMs): study internal structures of cells (e.g., organelles)

Types of Cells

Prokaryotic Cells (Bacteria & Archaea):
- No nucleus
- DNA in nucleoid region
- No membrane-bound organelles
- Cytoplasm bound by plasma membrane
Eukaryotic Cells (Protists, Fungi, Animals, & Plants):
- Has nucleus
- DNA in nucleus bounded by membranous nuclear envelope
- Membrane-bound organelles
- Cytoplasm between plasma membrane and nucleus

Plasma Membrane

Boundary separating living cell from surroundings
Selective permeability allows passage of certain substances
Function: regulates exchange of oxygen, nutrients, and waste
Structure: double layer of phospholipids

Phospholipids in Plasma Membrane

Most abundant lipid in plasma membrane
Amphipathic molecules (hydrophobic and hydrophilic regions)

Fluid Mosaic Model

Membrane is a fluid structure with embedded proteins
Phospholipids can move within bilayer
Most lipids and some proteins can move laterally (sideways)
Rare vertical movement (flip-flop) across membrane

Nucleus

Contains most of the DNA in eukaryotic cells
Ribosomes use DNA information to make proteins
Nuclear envelope separates nucleus from cytoplasm
Nuclear membrane is a double membrane with lipid bilayer
Pores control entry and exit of molecules from nucleus

Nucleus Components

DNA organized into discrete units called chromosomes
Each chromosome has a single DNA molecule with proteins
Chromatin condenses into discrete chromosomes when cell prepares to divide
Nucleolus is where rRNA synthesis occurs

Ribosomes

Make proteins in cytosol (free ribosomes) and on endoplasmic reticulum (bound ribosomes)
Particles made of rRNA and protein

Endomembrane System

Biosynthesis: uses small molecules to build substances
Feedback mechanisms: regulate enzyme activity and strategic points in catabolic pathways
Photosynthesis: occurs in chloroplasts with structural organization

Photosynthesis

Chloroplasts split water into hydrogen and oxygen, incorporating hydrogen into sugar molecules
Photosynthesis reverses the direction of electron flow
Redox process where water and oxygen are reduced
Endothermic process with energy provided by light

Light Reactions

Occur in thylakoids
Split water and release oxygen
Reduce NADP+ to NADPH
Generate ATP from ADP by photophosphorylation

Calvin Cycle

Occurs in stroma
Dark reaction that forms sugar from carbon dioxide using ATP and NADPH

Chloroplasts

Major location for photosynthesis in leaves, particularly mesophyll tissue
Plasmodesmata: channels between adjacent plant cells
Cell wall protects plant cell, maintains shape, and prevents excessive water uptake

ECM of Animal Cells

No cell wall, but covered by an extracellular matrix (ECM)
ECM made up of glycoproteins (collagen, proteoglycans, fibronectin)
Function: support, adhesion, movement, and regulation

Metabolism

Chemical reactions in organisms
Emergent property of life resulting from interactions between molecules within the cell
Metabolic pathway: begins with a specific molecule and ends with a product
Each step catalyzed by a specific enzyme
Catabolic pathway: releases energy by breaking down complex molecules into simpler compounds
Anabolic pathway: consumes energy to build complex molecules from simpler ones

ATP

Composed of ribose, adenine, and 3 phosphate groups
Bonds between phosphate groups can be broken by hydrolysis, releasing energy
Chemical reactions: exergonic (release energy) and endergonic (consume energy)
In cells, energy released from exergonic reactions can be used to drive endergonic reactions

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Test your knowledge on cell components and the structure-function correlation in cells. Learn about molecules, atoms, macromolecules, and microscopy techniques like light microscopes.