Chapter 3 - Cell Structure and Genetic Control

What is the cell?

The basic unit of structure and function in the body.

What does "structure determines function" mean?

The structure or shape of a cell or cellular component helps determine what it can do.

What are the main components of a cell?

Membranes, nucleus, cytoplasm, ribosomes, endoplasmic reticulum, Golgi apparatus, mitochondria, and other organelles.

What are membranes used for in cells?

They form internal and external partitions.

What is the function of the nucleus?

It contains genomic DNA and controls cell activities.

What is cytoplasm?

The aqueous contents of the cell inside the plasma membrane.

What is the function of ribosomes?

Protein synthesis.

What are the functions of the endoplasmic reticulum?

Protein synthesis, lipid synthesis, detoxification, and calcium dynamics/storage.

What is the function of the Golgi apparatus?

It modifies, sorts, packages, and distributes proteins.

What is the function of mitochondria?

ATP synthesis and energy production.

What is an organelle?

A specialized structure within a cell that performs a specific function.

Do organelles have membranes?

Many organelles have their own membranes that separate their internal environment from the cytoplasm.

What is the plasma membrane?

The membrane that surrounds each cell.

What is the structure of the plasma membrane?

A double layer of phospholipids with proteins embedded in it.

What does the plasma membrane do?

It provides cellular structure and separates the internal cell environment from the extracellular environment.

What does selectively permeable mean?

The membrane allows some substances to cross while restricting others.

Why is the plasma membrane important for cell communication?

It receives chemical messages and allows communication between intracellular and extracellular regions.

What is the fluid-mosaic model?

A model describing the plasma membrane as a fluid phospholipid bilayer with various proteins embedded within it.

What are the two major types of membrane proteins?

Integral proteins and peripheral proteins.

What are integral membrane proteins?

Proteins bound to molecules within the membrane.

What are transmembrane proteins?

Integral membrane proteins that extend across the lipid bilayer.

Can transmembrane proteins cross the lipid bilayer more than once?

Yes, some can cross the lipid bilayer multiple times.

What are peripheral membrane proteins?

Proteins that are partially embedded in or attached to one face of the membrane.

What does the nucleus contain?

DNA.

What does the nucleus control?

Cell activities.

What is the rough endoplasmic reticulum?

Endoplasmic reticulum with ribosomes attached to its surface.

Why does rough ER appear rough?

It has ribosomes attached to its surface.

What is the primary function of rough ER?

Protein synthesis and processing.

What are ribosomes?

The cellular structures where proteins are synthesized.

What is smooth endoplasmic reticulum?

Endoplasmic reticulum without ribosomes attached to its surface.

What are the functions of smooth ER?

Lipid synthesis, detoxification, and calcium storage.

Which ER is involved in protein synthesis?

Rough ER.

Which ER is involved in lipid synthesis?

Smooth ER.

Which ER stores calcium?

Smooth ER.

Which ER is involved in detoxification?

Smooth ER.

What is the function of the Golgi apparatus?

It modifies proteins from the ER and packages them into vesicles for distribution.

What are vesicles?

Small membrane-bound sacs used to transport and store substances.

Where does cellular energy production occur?

In the mitochondria.

What is the primary product synthesized by mitochondria?

ATP.

What is ATP?

A molecule that stores and provides usable energy for cellular processes.

What is the function of lysosomes?

They perform cellular cleanup and destroy bacteria, damaged organelles, and other cellular materials.

What does the cytoskeleton consist of?

A network of interconnected protein filaments, including microtubules.

What are microtubules?

Protein filaments that are part of the cytoskeleton.

What are the functions of the cytoskeleton?

Movement and structural support.

What are proteins made of?

Amino acids.

How many amino acids are used to build proteins?

20 amino acids.

What are proteins?

Large molecules made of sequences of amino acids, often containing more than 100 amino acids.

What are some functions of proteins in the body?

Cell signaling, membrane receptors, enzymes, ion channels, cell attachment, cytoskeleton, locomotion, and hormones.

What directs protein synthesis in the cell?

DNA and RNA.

What does each DNA molecule contain?

Many genes.

What is a gene?

A region of DNA that contains the instructions for making a polypeptide.

What does it mean when a gene "codes for" a protein?

The gene contains the instructions that determine the amino acid sequence of a polypeptide/protein.

What is gene expression?

The process by which instructions in a gene result in the synthesis of a functional protein.

What are the three major steps of gene expression?

Transcription, splicing, and translation.

What is genetic transcription?

The synthesis of pre-messenger RNA using DNA as a template.

What is genetic translation?

The synthesis of a protein according to the code contained in messenger RNA.

What is pre-messenger RNA?

The initial RNA molecule produced during transcription before introns are removed.

What is messenger RNA (mRNA)?

RNA that carries genetic instructions from DNA to the ribosome for protein synthesis.

What is transfer RNA (tRNA)?

RNA that links mRNA codons to their corresponding amino acids during translation.

What is the correct order of protein synthesis?

Transcription → splicing → translation.

What happens during transcription?

DNA genetic information is copied into pre-messenger RNA.

What happens during splicing?

Introns are removed and exons are joined together to form mature mRNA.

What happens during translation?

The mRNA code is used to determine the sequence of amino acids in a polypeptide.

Where does transcription occur?

In the nucleus.

Where does splicing occur?

In the nucleus.

Where does translation occur?

At ribosomes in the cytoplasm.

What is the first step of protein synthesis in the nucleus?

DNA provides the information/template for synthesizing a specific protein.

What is transcribed from DNA during transcription?

The DNA triplet code is transcribed into pre-messenger RNA.

What are introns?

Non-coding regions of pre-messenger RNA that are removed during splicing.

What are exons?

Coding regions that remain and are joined together during splicing.

What happens to introns during splicing?

They are removed.

What happens to exons during splicing?

They are spliced together.

What happens to mRNA after splicing?

It exits the nucleus and enters the cytoplasm.

What does mRNA bind to after leaving the nucleus?

A ribosome.

What is a codon?

A three-nucleotide sequence on mRNA that specifies an amino acid.

What is an anticodon?

A three-nucleotide sequence on tRNA that is complementary to an mRNA codon.

How does the cell determine which amino acid to add to a protein?

The mRNA codon pairs with a complementary tRNA anticodon, which brings the appropriate amino acid.

What is the relationship between mRNA and tRNA during translation?

tRNA anticodons pair with complementary mRNA codons.

What is the role of tRNA in protein synthesis?

It acts as the link between mRNA codons and the amino acid sequence of the protein.

What results from the translation of mRNA?

A sequence of amino acids forming a polypeptide.

What is a polypeptide?

A chain of amino acids.

What are mRNA triplets called?

Codons.

What are tRNA triplets called?

Anticodons.

What does "genes code for proteins" mean?

Genes contain DNA instructions that determine the amino acid sequence of proteins.

What happens after a polypeptide chain is synthesized?

The amino acids interact to form secondary structure, and the protein folds and bends to form tertiary structure.

What is secondary protein structure?

Local folding of a polypeptide, such as alpha helices and beta sheets.

What is tertiary protein structure?

The overall three-dimensional shape formed when a polypeptide folds and bends.

Why is protein folding important?

The final shape of a protein helps determine its function.

What can happen to a synthesized protein?

It can be used within the cell or secreted to another destination.

Where are proteins destined for secretion sorted?

In the Golgi apparatus.

How does the Golgi apparatus prepare proteins for secretion?

It sorts proteins according to their function and destination and packages them into vesicles.

What packages proteins before secretion?

Vesicles formed by the Golgi apparatus.

What is the overall pathway for a secreted protein?

DNA → transcription → pre-mRNA → splicing → mRNA → ribosome → translation → polypeptide → folding → Golgi apparatus → vesicle → secretion.

What organelle contains genomic DNA?

The nucleus.

What organelle is the site of protein synthesis?

Ribosomes.

What organelle contains ribosomes on its surface?

Rough endoplasmic reticulum.

What organelle synthesizes lipids and stores calcium?

Smooth endoplasmic reticulum.

What organelle modifies and packages proteins?

The Golgi apparatus.

What organelle produces ATP?

Mitochondria.

What organelle destroys bacteria and damaged organelles?

Lysosomes.