AP Biology - Unit 4: Overall Review

Cell Communication

Quiz Answers

• Plasmodesmata (plants) = gap junctions (animals)
• Signal molecules change the receptor protein in some way!
• A signal transmitted via phosphorylation of a series of proteins brings a conformational change to each protein
• Morphogens are defined as synthesized locally signaling molecules that diffuse and act over long distances to induce cellular responses and control growth and pattern throughout a tissue region. Ex: Paracrine Signaling

Additional Information

• Plasmodesmata are specialized junctions found in plant cells. They create channels that allow direct cytoplasmic exchange between adjacent plant cells.
• Increasing the permeability of the plasmodesmata would likely help plant viruses travel from one plant cell to another.
• Desmosomes are essential in tissues that experience stretching, such as the skin and cardiac muscle, where they ensure that cells remain connected and maintain structural integrity.
• When a ligand binds, GPCRs activate G proteins by exchanging GDP for GTP. The activated G protein separates into α and βγ subunits, initiating intracellular signaling cascades
• RTKs are a class of enzyme-linked receptors that transfer phosphate groups to tyrosine residues. They often dimerize when two ligands bind to nearby receptors.
• Water-soluble ligands = cannot cross plasma membranes
• Lipid-soluble ligands = pass through the plasma membranes
• The GPCR undergoes a conformational change, and the alpha subunit activates adenylate cyclase, leading to the production of cyclic AMP (cAMP).

Immune and Nervous System

Quiz Answers

• The Sodium potassium pump moves sodium ions out of the cell and potassium ions into the cell
• Most organelles are in the cell body
• Myelinated axons speed up action potentials
  1. Action potential depolarizes the membrane of the axon terminal
  2. Calcium ions rush into the neuron’s cytoplasm
  3. The synaptic vesicles release neurotransmitters into the synaptic cleft
  4. Neurotransmitters bind with receptors associated with the postsynaptic membrane
  5. The ligand-gated ion channels open (Require a neurotransmitter)
• A toxin that binds specifically to voltage-gated sodium channels in axons would be expected to prevent the depolarization phase of the action potential
• Saltatory Conduction = Conduction of impulses jumping from one node of Ranvier to the next in a myelinated neuron
• Creation of the action potential is during depolarization and repolarization
• Immune cells are produced in the bone marrow
• T cells are produced in the thymus
• When referring to immune responses, cytokines are referred to as messengers
  • Any of a number of substances, such as interferon, interleukin, and growth factors, which are secreted by certain cells of the immune system and have an effect on other cells
    • Act like a neurotransmitter
• Antigens = pieces of biological materials that can trigger an immune response (Ligand)
• Antibodies = can bind to antigens, neutralize pathogens, and mark them for destruction (Receptor)
• B cells produce antibodies
• T and B cells have “memory”

Additional Information

• Helper T Cells- They not only help activate B cells to secrete antibodies and macrophages to destroy ingested microbes, but they also help activate cytotoxic T cells to kill infected target cells.
• Killer T Cells- They directly kill cells that have already been infected by a foreign invader.
• B Cells- They produce antibodies that destroy antigens or the pathogen associated with a particular antigen. B-cells can also remember specific antigens so your immune system can launch an effective defense if the pathogen ever enters your body again.

Feedback Mechanisms and the Endocrine System

Quiz Answers

• When ADH is released, water will be reabsorbed
• The reason why small animals often have higher metabolic rates than larger animals is that smaller animals have a higher ratio of surface area to volume. This means that small animals lose body heat faster than larger animals.
• Androgen, cortisol, estrogen, and testosterone are all steroid hormones
• Oxytocin and prolactin help a mother produce milk
• The adrenal cortex produces hormones that control sex (androgens, estrogens), salt balance in the blood (aldosterone), and sugar balance (cortisol)

Additional Information

• Hormones from the pituitary gland include thyroid-stimulating hormone (TSH), which stimulates the thyroid gland to produce thyroid hormones, as well as other hormones like ACTH, which acts on the adrenal cortex.
• The adrenal glands are located on top of the kidneys and produce hormones like cortisol, aldosterone, and adrenal androgens.
• Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) are released by the pituitary and act on the gonads (testes in males and ovaries in females) to regulate the production of sex hormones.
• Other hormones from the pituitary include growth hormone (GH) and prolactin.
• Steroid and thyroid hormones =primary messengers

Regulation of the Cell Cycle

Quiz Answers

• IPMAT!
  • Interphase
  • Prophase
  • Prometaphase
  • Metaphase
  • Anaphase
  • Telophase
• Centromere = region in which chromatids remain attached to one another until anaphase
• Altering the spindle apparatus will affect metaphase the most
• The daughter cells have the same number of chromosomes and the same amount of DNA at the end
• Anaphase = centromeres uncoupling, sister chromatids separating, and two new chromosomes moving to opposite poles of the cell
• Chromosomes become visible during prophase
• Chromosomes coil during mitosis to allow the chromosomes to move without becoming entangled and breaking
• MPF protein complex turns itself off by activating a process that destroys the cyclin component
• The decrease in the amount of cyclin at a specific point is due to its destruction by a process initiated by the activity of its complex within a cyclin
• G1 Checkpoint Requirements: No DNA damage, sufficient resources, favorable condition
• S Checkpoint Requirements: No errors in DNA replication
• G2 Checkpoint Requirements: DNA replication is complete, Chromosome set complete, DNA without damage
• M Checkpoint Requirements: All sister chromatids are attached to the mitotic spindle

Additional Information

• Prophase: condenses into visible, compact structures, each chromosome is composed of two sister chromatids connected by a centromere.
• Metaphase: align along the cell's equator, microtubules extending to the kinetochores of each chromosome, and positioned correctly
• Anaphase: sister chromatids of each chromosome are pulled apart, exerting tension
• Telophase: reaches the opposite poles of the cell. envelope begins to reform two distinct nuclei and de-condensed back into chromatin.
• Cancerous cells often produce abnormal forms of cell-cycle regulators, allowing them to divide even when it is not appropriate to do so.
• Binary fission is a form of asexual reproduction in which an organism divides into two, each part carrying one copy of genetic material
  • (Like mitosis but without the spindle apparatus and it’s a form of asexual reproduction)

Quick Reminders

Glands:

• The pituitary gland (TSH) (ACTH) (LH) (FSH) (GH) (Prolactin)
• The thyroid (Thyroxine) (T4) (T3)
• The parathyroid gland (PTH)
• The adrenal (Cortisol) (Aldosterone) (Adrenal Androgens)
• The pancreas (Glucagon) (Insulin)
• Endotherms regulate their body temperature internally, while ectotherms rely on external environmental sources to control their body temperature.