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Questions and Answers
What is the primary function of microtubules in a cell?
Which structure is primarily responsible for increasing the absorptive area of a cell?
What role do centrioles play during mitosis?
Which of the following best describes the term 'semipermeable' in relation to cell membranes?
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Which structure enables sperm to swim?
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What is the primary function of mitochondria within a cell?
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Which of the following is a role of peroxisomes in the cell?
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What severe condition can Reactive Oxygen Species (ROS) contribute to?
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Which structure in the cell is critical for supporting cell movement?
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How do antioxidants help the body in relation to ROS?
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Which of the following is NOT a cause of oxidative stress?
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What is the role of the electron transport chain in mitochondria?
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What happens when a cell undergoes apoptosis?
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What is the primary function of a gene?
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What role does helicase play in DNA replication?
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How are the nitrogenous bases of DNA paired?
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What is the role of the centromere during cell division?
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Which phase of the cell cycle involves the actual division of the cell's nucleus?
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What happens to chromatin during cell division?
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What is produced during the second step of DNA replication?
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During which phase do spindle fibers align chromosomes at the cell equator?
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What is the main function of the S phase in the cell cycle?
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What is contained within a chromosome?
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What is the significance of the S phase in the cell cycle?
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What happens during the telophase of mitosis?
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What is the sugar component found in DNA?
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Which type of cell is described as having two copies of a chromosome?
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What is the primary event that occurs during anaphase?
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Which phase is considered the resting phase of the cell cycle?
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What is the primary role of tRNA in the translation process?
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Which of the following statements is true regarding mRNA?
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What initiates the transcription process?
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What is the role of the start codon in the translation process?
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Which statement correctly describes the difference between DNA and RNA?
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During transcription, what is the function of the template strand of DNA?
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What is the process of building proteins from amino acids called?
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Which component of the ribosome is primarily responsible for reading the mRNA?
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Study Notes
Mitochondrion
- The mitochondria is the powerhouse of the cell.
- It produces energy for the cell through cellular respiration.
- Cellular respiration is the process of burning carbohydrates to make energy for the cell.
- Mitochondria produce 95% of the ATP a cell uses.
- The inner membrane of the mitochondria performs oxidative phosphorylation.
- Oxidative phosphorylation makes ATP with the electron transport chain.
- Mitochondria are self-replicating.
- Mitochondria have their own DNA and ribosomes to make needed proteins.
- Cells with high energy needs have many thousands of mitochondria.
Peroxisome
- Peroxisomes perform many functions in the cell including:
- Lipid metabolism
- Chemical detoxification
- Peroxisomes contain enzymes that produce hydrogen peroxide (H2O2).
- Peroxisomes then reduce H2O2 to water to reduce oxidative stress from free radicals.
Oxidative Stress
- Reactive Oxygen Species (ROS) are unstable molecules containing oxygen.
- ROS try to donate extra electrons to other molecules, leading to damage.
- Free radicals steal or donate electrons, which can cause cell damage.
- ROS are responsible for the aging process, atherosclerosis, neuronal diseases, mutations, and cancer.
- Examples of ROS include:
- Hydroxyl radical (OH)
- Hydrogen Peroxide (H2O2)
- Superoxide
Sources of ROS
- Oxidative phosphorylation in the mitochondria
- Inflammatory pathways
- Respiratory burst by neutrophils
- Ischemia (lack of blood flow)
External Factors that Create Free Radicals
- Smoking
- Drugs and alcohol
- Pollution
- Chemicals like pesticides
- UV radiation
Cytoskeleton
- The cytoskeleton provides structural support, aids in cell motility, cell reproduction, and transportation of substances within the cell.
- The cytoskeleton is made of three fibrous proteins:
- Microtubules
- Intermediate filaments
- Microfilaments
- Microtubules support and maintain organelle position.
- Intermediate filaments provide cell shape and support.
- Microfilaments are involved in cell movement.
Microvilli
- Microvilli are made of microfilaments of the cytoskeleton.
- Microvilli increase a cell's absorptive area.
Flagellum
- The only human cell that uses flagella are sperm cells.
- Flagella are made of microtubules of the cytoskeleton.
- They propel sperm cells.
- Flagella are longer than cilia.
Cilia
- Cilia are made of microtubules of the cytoskeleton.
- Cilia have the motility to move substances across cell surfaces.
- Cilia are longer than microvilli.
Centriole
- Centrioles make microtubules.
- Microtubules help separate chromosomes during mitosis.
Ribosomes
- Ribosomes make proteins.
Lysosomes
- Lysosomes are digestive sacs.
Golgi Apparatus
- The Golgi apparatus modifies, sorts, and packages material for export.
Smooth ER
- Smooth ER makes cell membrane lipids.
Rough ER
- Rough ER makes protein within a membrane for export.
Nucleus
- The nucleus holds the genome of the cell.
Cytosol
- Cytosol is the liquid-like portion of the cytoplasm absent the organelles.
Cell Membrane and Active and Passive Transport
- The cell membrane acts as:
- A barrier
- A self-identifier
- Contains receptors for hormones
- The cell membrane is semipermeable.
- Some molecules are allowed to pass through the membrane, while others are not.
- Hydrophobic means non-polar and fears water.
- Hydrophilic means polar and likes water.
- Amphipathic means containing both hydrophobic and hydrophilic parts.
- The cell membrane is amphipathic.
DNA and DNA Replication
- A gene is a sequence of DNA that codes for a single protein.
- Chromatin refers to loose strands of DNA.
- Chromosomes are condensed structures of DNA and proteins formed during cell division.
- Human chromosomes are organized in 23 pairs.
Nitrogenous Bases
- DNA is a nucleic acid made of nucleotides containing nitrogenous bases.
- The nitrogenous bases are arranged in complimentary base pairs.
- The two strands of DNA form a double-helix.
- The nitrogenous bases are:
- Adenine (A)
- Thymine (T)
- Cytosine (C)
- Guanine (G)
- DNA also contains deoxyribose and phosphate groups.
- Complementary bases are:
- A-T
- C-G
- Bases are held together by hydrogen bonds.
Chromatin
- DNA is usually found in loose strands called chromatin.
- Chromatin is wound around proteins (histones) for packaging, and called a nucleosome.
Chromosome
- During cell division, chromatin condenses into a visible structure, known as a chromosome.
- Humans have 23 pairs of chromosomes, totaling 46 chromosomes.
Genes
- Both forms of DNA, loose chromatin and densely coiled chromosomes, hold the genes each cell needs to operate.
- A gene is a segment of DNA that codes for a product, usually a protein.
- The sequence of bases found on DNA is the genetic code that is read to make a protein.
- Before a cell can divide, the DNA needs to be replicated.
Helicase
- Helicase is an enzyme needed for replication.
- Helicase separates the hydrogen bonds between base pairs.
DNA Polymerase
- DNA polymerase is a DNA replication enzyme.
- DNA polymerase brings in the complementary base to build a new strand.
- Once two new strands are built, the process stops.
DNA Replication
- The process of DNA duplicating itself.
- Occurs during the S phase of the cell cycle.
- Needed to produce identical daughter cells during mitotic cell division.
- Unwound DNA strands serve as templates for new complementary strands.
- DNA polymerase and other enzymes add nucleotides to the template strands following the base pair rule.
Steps of DNA Replication
- Unwinding of the DNA strand by the helicase enzyme. Breaks hydrogen bonds between nitrogenous bases.
- Creation of two new identical strands by DNA polymerase. Two duplicate DNA molecules are produced.
Phases of the Cell Cycle and Potential Disruptions
- Diploid: A cell with two copies of each chromosome.
- Homologous: A pair of chromosomes, one from each parent.
- Sister Chromatid: Exact copies of DNA molecules found during mitosis.
- Centromere: The structure that attaches two sister chromatids together.
- Somatic Cell: Normal body cell (does not include sex cells: eggs or sperm).
- Sex Cell: Cells containing one half (haploid) of the somatic cells.
Cell Cycle
- The lifespan of a eukaryotic somatic (any cell besides sex cells) cell.
- Happens in 4 phases:
- Interphase
- M Phase (Cell Division)
Interphase
- Occurs when a cell is not dividing.
- The cell performs normal functions and prepares for division.
- Consists of G0, G1, S, and G2 phases.
- G0: Resting phase of the cell cycle.
- G1: First growth phase, the cell is growing and performing normal functions.
- S: Cell enters S (Synthesis) phase when it grows too large to function well, and needs to divide. A copy of DNA is being made (DNA replication).
- G2: Growth 2/Gap Phase 2. Further cell division preparation (Mitosis).
M Phase (Cell Division)
- Consists of Mitosis and Cytokinesis.
Mitosis
- The division of the cell's nucleus.
- Further divided into 4 phases:
- Prophase
- Metaphase
- Anaphase
- Telophase
Prophase
- The longest phase of mitosis.
- Chromatin begins to condense into the shape of chromosomes.
- The nucleolus and nuclear membrane disappear.
- Chromosomes begin to appear.
- Spindle fibers begin to form.
- Sister chromatids are held together by centromeres in the middle.
Metaphase
- Centrioles complete movement and chromosomes line up to the middle of the cell (equator).
- Spindle fibers align the chromosomes in the middle.
Anaphase
- The spindle fibers separate the sister chromatids at their centromere into two separate groups of chromosomes. Pull towards poles.
- Now individual chromosomes, spindle fibers shorten, and they are a V shape.
- Move to opposite sides of the pole towards the centrioles. Centrioles are at the poles.
Telophase
- The nuclear membrane and nucleolus reforms around chromosomes, then chromosomes spread out into chromatin.
Cytokinesis
- The division of the cytoplasm.
Codon
- Part of a gene containing the code for each specific amino acid in a protein (3 nitrogenous bases).
Triplet
- The process of protein synthesis starts in the nucleus and ends at the ribosome.
- Proteins are shape dependent and run many of the cells function as enzymes.
- Protein synthesis is called gene expression.
- Not all genes are expressed at all times.
- DNA > RNA > Protein
- Triplet > Codon > Amino Acid
- Most types of RNA, including mRNA, are single-stranded and contain no complementary strand.
- RNA is important for building proteins.
- RNA contains ribose, whereas DNA has deoxyribose.
- Instead of thymine, RNA contains the base uracil.
- Adenine will always pair up with uracil during the protein synthesis process.
Transcription
- Transcription is the process of building messenger RNA.
- Transcription takes place in the nucleus.
- Transcription is not related to replication.
- Transcription is the process of copying genetic ‘code’ into mRNA.
Transcription Process
- The first step in the process of using the genetic code in DNA to synthesize different proteins.
- Proteins are made outside the nucleus (in ribosomes).
- DNA uses mRNA (messenger RNA) to carry the genetic code from the nucleus to the ribosome.
- Transcription begins when the enzyme RNA polymerase attaches to a gene.
- The gene contains the code to build protein.
- RNA polymerase causes a specific area of a DNA strand to unwind and separate into two strands.
- Template strand- transcribed by RNA, contains complementary bases.
- Non-template strand- not transcribed.
- DNA is written in three base groups called a triplet.
- RNA is written in three bases called codons.
- mRNA is a copy of the non-template strand with uracil instead of thymine.
Translation
- Uses the mRNA and ribosomes to create a protein.
- Begins at a start codon (AUG) and ends when it reaches a stop codon.
- mRNA leaves the nucleus through a pore and associates with a ribosome (made of rRNA) either in the cytoplasm or attached to the endoplasmic reticulum.
- The ribosome “reads” the mRNA, and tRNA carries in the complimentary anticodon that matches the codon on mRNA. If the codon is AUG then the anticodon is UAC.
- Each tRNA drops off the amino acid it carries, and the amino acids are joined together by peptide bonding.
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Description
Explore the fascinating functions of mitochondria and peroxisomes in cellular biology. This quiz covers energy production, oxidative phosphorylation, lipid metabolism, and the role of reactive oxygen species. Test your knowledge of these essential organelles and their importance in maintaining cellular health.
