Biology Chapter: Cell Communication and Diabetes

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Questions and Answers

Which of the following best describes the relationship between cells, tissues, organs, and organ systems?

Organ systems are made of organs, which are made of tissues, which in turn are made of cells.

Cells form tissues that are grouped to form organs that work together as organ systems. (correct)

Cells are composed of tissues, which form organs, and organs together create organ systems.

Tissues are the basic unit of life, which come together to form cells, which then become organs, and then create organ systems.

What is a key difference between lipid-based and protein-based chemical signals in terms of cellular transport?

Both lipid and protein based signals cannot cross the membrane directly, and require transmembrane receptor proteins.

Protein-based signals cannot directly cross the cell membrane, whereas lipid-based signals can. (correct)

Lipid-based signals require transmembrane receptor proteins, whereas protein-based signals do not.

Protein-based signals are able to cross the cell membrane directly while lipid-based signals require a transmembrane receptor.

Which of these structures directly facilitate cell-to-cell communication in plants?

Plasmodesmata (correct)

Smooth ER

Transmembrane receptor proteins

Ribosomes

If a cell needs to produce a protein-based hormone, which organelle would be primarily involved in its synthesis?

Ribosomes (C) Signup and view all the answers

Which of the following is a direct example of a lipid-based chemical signaling molecule?

Testosterone (C) Signup and view all the answers

What is the primary method by which insulin travels to reach its target cells?

Through the bloodstream (C) Signup and view all the answers

In type 2 diabetes, what is the initial cellular defect that leads to elevated blood sugar?

Impaired response to insulin (A) Signup and view all the answers

How does GLUT4 facilitate glucose entry into cells?

By facilitated diffusion via a carrier protein (C) Signup and view all the answers

What is the main underlying cause of type 1 diabetes?

Autoimmune destruction of insulin-producing cells (C) Signup and view all the answers

Which of the following is not a typical treatment for type 2 diabetes?

Blood sugar level monitoring and lifestyle management (C) Signup and view all the answers

What is the primary function of gap junctions in animal tissues?

To allow direct communication and passage of substances between adjacent cells. (D) Signup and view all the answers

Which of the following best describes the role of a helper T cell in the immune response?

Binding to antigens and activating the rest of the immune system. (D) Signup and view all the answers

What is the function of cytokines released by helper T cells?

To transmit short distance signals activating the immune response. (D) Signup and view all the answers

Which cellular component is primarily responsible for the 'heat, swelling, and redness' associated with local inflammation?

Mast cells. (A) Signup and view all the answers

What role do chemokines play during a local inflammatory response?

To attract phagocytic cells to the site of infection. (B) Signup and view all the answers

What is the mechanism of action for neurotransmitters at the synapse?

They are released via exocytosis to bind to receptors on the postsynaptic cell. (C) Signup and view all the answers

What does 'quorum sensing' enable bacteria to do?

To express genes only when the population density is high enough. (B) Signup and view all the answers

What is the function of a ligand in signal transduction pathways?

It is a chemical message that binds to a protein receptor. (C) Signup and view all the answers

Where are the protein receptors for lipid-based (steroid) hormones typically located?

Within the nucleus of the cell. (C) Signup and view all the answers

What is the immediate result when a ligand binds to a transmembrane protein receptor?

A conformational change in the receptor protein's shape. (A) Signup and view all the answers

In the G-protein linked receptor pathway, what is the role of adenylyl cyclase?

To convert ATP into cAMP. (A) Signup and view all the answers

What is the purpose of protein kinases in signal transduction pathways?

To modify the activity of other proteins by adding phosphate groups. (D) Signup and view all the answers

What is the primary function of protein phosphatases in signal transduction?

To terminate the signal by removing phosphate groups from proteins. (C) Signup and view all the answers

What is the first step that occurs in Receptor Tyrosine Kinase activation?

Receptor Tyrosine Kinases autophosphorylate each other. (C) Signup and view all the answers

How do ligand-gated ion channels elicit a cellular response?

They alter the membrane potential by opening ion channels. (C) Signup and view all the answers

What is the immediate effect of a ligand binding to its receptor protein?

A change in the shape of the receptor's intracellular domain. (A) Signup and view all the answers

How do steroid hormones typically initiate a cellular response?

By binding to intracellular protein receptors and regulating gene expression. (B) Signup and view all the answers

What is the role of the IRS family of proteins in the insulin signaling pathway?

They activate PI 3-Kinase, which is involved in lipid metabolism and glycogen synthesis. (B) Signup and view all the answers

What is the first step in the signal transduction of ethylene in plants when the hormone is present?

Activation of EIN2 due to the inhibition of CTR1. (C) Signup and view all the answers

Which of the following is a consequence of a mutation in the extracellular domain of a receptor protein?

Failure of the receptor to bind its ligand, disrupting signal transduction. (A) Signup and view all the answers

Which of the following exemplifies a negative feedback loop in the human body?

The regulation of blood sugar levels through insulin release. (D) Signup and view all the answers

If a cell receives a signal to divide and passes the G1 checkpoint, what is the immediate consequence?

The cell is committed to undergoing cell division irreversibly. (C) Signup and view all the answers

What is the primary function of the S phase in the cell cycle?

Synthesis of a complete copy of the DNA in the cell nucleus. (A) Signup and view all the answers

Which process is directly supported by the presence of GLUT 4 transport vesicles?

Facilitated diffusion of glucose into cells. (C) Signup and view all the answers

Which of the following describes the function of the osmoreceptors within the hypothalamus?

Monitor and regulate the osmolality of blood and release ADH from the posterior pituitary. (A) Signup and view all the answers

What is the primary distinction between Type I and Type II diabetes?

Type I diabetes is an autoimmune disease leading to lack of insulin production, while Type II diabetes involves insulin resistance. (B) Signup and view all the answers

A mutation in which type of protein is most likely to cause continuous cell division?

A relay protein, because it is involved in signal transduction. (C) Signup and view all the answers

Which of the following best describes the role of a ligand in cell signaling?

To bind with a receptor protein, initiating a specific cellular response. (B) Signup and view all the answers

What is the function of the G1 checkpoint in the cell cycle?

To ensure that the cell has all resources for division, and the DNA is error-free. (D) Signup and view all the answers

Which signaling molecule triggers a positive feedback loop during fruit ripening?

Ethylene (A) Signup and view all the answers

Which of the following best describes the role of the kinetochore during mitosis?

It is the region of DNA where microtubules connect during anaphase, separating sister chromatids. (C) Signup and view all the answers

What cellular event is directly controlled by the M phase checkpoint?

Attachment of microtubules to all kinetochores. (B) Signup and view all the answers

At what stage of the cell cycle is the DNA in its most condensed state?

Prophase (D) Signup and view all the answers

Which of the following is a key function of cyclins in cell cycle regulation?

To activate cyclin-dependent kinases (CDKs) at specific phases. (C) Signup and view all the answers

What would be the immediate consequence of a mutation that inactivates the p53 tumor-suppressor gene?

The cell will continue to divide in the presence of DNA damage. (A) Signup and view all the answers

The formation of a new nuclear envelope around the separated chromosomes is characteristic of which phase of mitosis?

Telophase (C) Signup and view all the answers

What is the role of microtubules during mitosis?

They attach to the kinetochores and move chromosomes during cell division. (C) Signup and view all the answers

What is the primary function of the G2 checkpoint in the cell cycle?

To confirm that DNA replication is complete and without damage. (D) Signup and view all the answers

What directly causes the activation of cyclin-dependent kinases (CDKs)?

Binding to their respective cyclin proteins. (B) Signup and view all the answers

If a cell does not pass the G1 checkpoint, what is the most likely outcome?

The cell cycle stops, and the cell may enter a G0 resting state or undergo apoptosis. (B) Signup and view all the answers

Which of these is a characteristic of an oncogene?

It promotes uncontrolled cell growth. (C) Signup and view all the answers

How are sister chromatids defined after the start of anaphase?

They become individual chromosomes. (D) Signup and view all the answers

What is a key difference between chromatin and chromosomes?

Chromatin is the relaxed form of DNA while chromosomes are the condensed forms of DNA. (D) Signup and view all the answers

What is the primary purpose of cytokinesis?

To divide the cytoplasm into two new identical daughter cells. (C) Signup and view all the answers

What is the role of a centromere in cell division?

It is the region that holds the sister chromatids together. (B) Signup and view all the answers

Study Notes

Cell Communication

Cells are the fundamental units of life, working together in multicellular organisms like humans.
Cell functions & body functions rely heavily on cellular communication.
Tissues: groups of cells with shared functions. Example: beta cells in pancreas produce insulin.
Organs: structures formed by multiple tissues, performing specific tasks.
Organ systems: groups of organs, working together for particular functions (e.g., circulatory, endocrine, digestive).
Cells communicate through chemical signals.
Two major chemical signals: lipids (nonpolar, can cross membranes) and proteins (polar, water-soluble).
Lipid-based signals (e.g., steroid hormones like testosterone) and protein hormones derived from amino acids, polypeptides can pass right through the membrane (epinephrine).

How Cells Communicate

Direct cell-to-cell communication:
In plants, plasmodesmata (channels connecting plant cell cytoplasms) facilitate direct transfer of molecules between cells.
In animals, gap junctions (channels linking animal cell cytoplasms) allow direct molecules transfer. Also, tight junctions (hold cells together) form barriers in tissues (e.g., intestines).
Immune system communication: Helper T cell recognizes antigens (part of pathogen), activates, releases cytokines (messages) which help other immune cells fight infection. Cytotoxic T cells damage infected cells by creating holes.
Local regulators: short-distance communication through chemical signals. Example: mast cells release histamine (inflammatory substance), causing localized inflammation (redness, swelling, heat). Chemokines attract phagocytic cells.
Neurotransmitters: chemical signals in nerve cells; released from presynaptic cell; travel across synapse to postsynaptic cell; calcium ions are vital.

How cells communicate over long distances

Hormones: chemical signals that travel within the bloodstream for long-distance communication. The endocrine system utilizes hormones to regulate many body functions. Released from glands to bloodstream, needing receptor proteins in target cells.

### Signal Transduction

Signal transduction pathways: linking signal reception to cellular responses.
Ligand: chemical message; binds with a receptor. Example: epinephrine.
Signal reception: ligand attaches to a receptor protein.
Intracellular receptors: located inside the cell; for lipid-based hormones (e.g., steroids).
Extracellular receptors: located on the cell surface. For protein-based hormones (e.g., epinephrine).
3 types of surface receptors:
G protein-coupled receptors: (using epinephrine as an example)
Ligand binding changes the receptor shape which activates a G protein.
The activated G protein subunits initiate a signal transduction cascade:
The receptor changes shape → activates a g protein → g protein has an activated alpha subunit which separates from the rest of the protein, → activate adenylyl cyclase → adenyl cyclase converts ATP to cAMP → cAMP activates protein kinase A (PKA).
PKA activates other enzymes, creating a phosphorylation cascade, amplifying the signal.
cAMP is a second messenger.
The phosphorylations and dephosphorylation cascades that occur with the different proteins cause the signal to increase (amplify)
The original ligand causes a metabolic response, ex: raised blood sugar levels.
Receptor tyrosine kinases:
Signaling starts when ligand binds to the receptor tyrosine kinase (RTK) and activates the receptor.
The activated receptors cause themselves to "auto-phosphorylate" (add phosphate groups to themselves).
Relay proteins bind to the phosphorylated tyrosines, initiating a cascade of further signals to the cell.
Ligand-gated ion channels:
When a signaling molecule (ligand) binds to the ligand-gated ion channel, it causes the gate to open, allowing ions to flow in and out of the cell, and initiating a cell response.
Binding of a ligand opens the gate; ions flow across the membrane causing a response.

Signal Transduction Pathways- Examples

Glucose regulation:
Insulin binds to its receptor, which initiates intracellular signaling pathways. Signaling starts with insulin.
These pathways result in the activation of enzymes related to lipid metabolism & glycogen synthesis.
GLUT4 protein activation (a carrier for glucose): GLUT4 transport vesicles embed in the cell membrane, increasing glucose uptake.
Ethylene signaling (plants):
A gaseous plant hormone that triggers fruit ripening in a positive feedback loop, activates genes that result in a positive feedback loop. The activation of downstream target proteins activate more genes, which causes the ripening to speed up.

Changes in Signaling Pathways

Mutations in signaling pathway components can disrupt the transduction of signals. This can lead to aberrant cellular responses like those seen in cancer.
Changes in extracellular or intracellular domains of receptors can block signal transduction.
Mutations in relay proteins can lead to uncontrolled cell division, a hallmark of cancer.

Feedback Mechanisms

Feedback mechanisms: regulate cellular processes, maintaining homeostasis.
Negative feedback loops: maintain a steady-state within the body or cells. Often involve hormones, regulate blood sugar levels.
Example (blood sugar regulation):
High blood sugar → promotes insulin release → lowers blood sugar. Receptor proteins detect high blood sugar in the bloodstream, & release insulin → target cells take up the glucose until blood sugar decreases.
Positive feedback loops: amplify a response.
Examples (childbirth, blood clotting):
Childbirth: contractions cause further contractions.
Blood clotting: initiated clotting produces more clotting.

Cell Cycle

The cell cycle: series of events that result in cell division.
Interphase: G1, S, G2 phases.
M phase (mitosis): division of nucleus, produces two identical daughter cells.
The nucleus is dividing.
Phases: prophase, metaphase, anaphase, telophase.
Control points (checkpoints): crucial for the cell to move from one stage to the next. Checkpoints ensures DNA replication is complete, chromosomes are correctly aligned, and no damage.
G1 checkpoint: checks cell size, nutrients, growth factors, and DNA integrity before DNA replication begins.
G2 checkpoint: checks the integrity of the DNA after replication, and prepares for M phase.
M checkpoint: checks if chromosomes are properly attached to spindle fibers (microtubules) before the cell divides.
Cyclins/CDK: proteins that control the progression of the cell cycle.
Genes regulating cell division: Normal genes (proto-oncogenes); mutated can be oncogenes, leading to cancer; also tumor suppressor genes limit cell division.
P53: a tumor suppressor gene, regulates cell cycle checkpoints; vital for DNA damage repair and initiating apoptosis.

Feedback loops and Diabetes

Diabetes: imbalance of blood glucose regulation.
Type 1: autoimmune disease; body doesn't produce insulin.
Type 2: insulin resistance; cells don't respond properly to insulin.
Mechanisms for maintaining homeostasis; Negative feedback loops maintain homeostasis, so when one component increases, it activates a cascade of other factors to decrease it.
Hypothalamus: Monitors blood osmolarity, regulating ADH release from the posterior pituitary. Negative feedback loop.
Insulin resistance/Type 2: Impaired insulin signaling pathways, preventing glucose uptake even if insulin is bound to its receptor.

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Description

This quiz covers the fundamental concepts of cell communication, the roles of various organelles in hormone synthesis, and the biochemical pathways involved in diabetes. Test your understanding of lipid-based vs protein-based signals, as well as the mechanisms of glucose transport within cells. Prepare to explore essential topics that connect cellular biology and medical knowledge.