Cellular Communication Lecture 1

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Questions and Answers

What is the primary characteristic of autocrine signaling?

Cells respond to molecules they produce themselves. (correct)

It affects nearby cells only.

It requires direct membrane contact.

It involves the release of neurotransmitters at synapses.

Which type of signaling involves cells affecting other target cells in their proximity?

Paracrine signaling (correct)

Autocrine signaling

Endocrine signaling

Contant-dependent signaling

What type of receptors do most hydrophilic signaling molecules bind to?

Cell surface receptors (correct)

Intracellular receptors

Cytoplasmic receptors

Nuclear receptors

Which of the following is a characteristic of endocrine signaling?

Hormones are transported via the bloodstream. Signup and view all the answers

What distinguishes synaptic signaling from other forms of cell communication?

It is performed by neurons transmitting signals electrically. Signup and view all the answers

What is true about intracellular receptors?

They require signaling molecules to diffuse through the membrane. Signup and view all the answers

What is a feature of contant-dependent signaling?

It requires membrane-to-membrane contact. Signup and view all the answers

Which type of molecule typically cannot cross the cell membrane directly?

Hydrophilic molecules Signup and view all the answers

What is the primary function of carbohydrates in the human body?

To serve as a major source of energy Signup and view all the answers

Which type of carbohydrate cannot be hydrolyzed into simpler sugars?

Monosaccharides Signup and view all the answers

Which of the following is NOT a function of carbohydrates?

Acting as storage for genetic information Signup and view all the answers

Oligosaccharides are classified as sugars composed of how many monosaccharide residues?

2 to 10 Signup and view all the answers

What distinguishes monosaccharides from other carbohydrates?

They cannot be further hydrolyzed Signup and view all the answers

What sugars are produced from the hydrolysis of pectins?

Galactose, arabinose, and galacturonic acid Signup and view all the answers

Which statement best describes the characteristics of glycoproteins?

They consist mainly of protein with a small amount of carbohydrates. Signup and view all the answers

What role do glycosaminoglycans (GAGs) play in bodily secretions?

They enhance the viscosity and lubrication of mucous secretions. Signup and view all the answers

What are the primary constituents of glycosaminoglycans (GAGs)?

95% carbohydrates and 5% proteins Signup and view all the answers

Which polysaccharide is primarily used as a culture medium for growing bacteria?

Agar-agar Signup and view all the answers

What type of polysaccharide acts as a reserve food and can be hydrolyzed to sugars for respiration?

Starch Signup and view all the answers

Which of the following polysaccharides gives a blue color with iodine?

Starch Signup and view all the answers

What is the primary structural function of cellulose in plants?

Providing rigidity and strength Signup and view all the answers

What characteristic distinguishes glycogen from starch?

It is more branched with α(1→6) linkages. Signup and view all the answers

What happens to cellulose during partial hydrolysis with acids?

It yields cellobiose. Signup and view all the answers

Which of the following properties is NOT true about cellulose?

It is soluble in water. Signup and view all the answers

Inulin serves primarily as what type of compound in dietary contexts?

A diagnostic marker Signup and view all the answers

Which of the following describes dextrins?

They are used as adhesive in tablet preparations. Signup and view all the answers

What is the molecular formula of trioses?

C3H6O3 Signup and view all the answers

How are the carbon atoms in a monosaccharide numbered?

Starting from the aldehyde or ketone functional group Signup and view all the answers

Which of the following statements about monosaccharides is correct?

Monosaccharides exhibit optical activity. Signup and view all the answers

Which sugar derivative is formed by the reduction of a monosaccharide?

Sugar alcohols Signup and view all the answers

What happens to the carbonyl carbon during the oxidation of a monosaccharide to form an aldonic acid?

It gets oxidized to a carboxylic group. Signup and view all the answers

Which compound is produced by the oxidation of glucose to an aldaric acid?

Glucaric acid Signup and view all the answers

Which form do most monosaccharides with five or more carbon atoms predominantly take?

Cyclic form Signup and view all the answers

What type of sugar is deoxyribose classified as?

Deoxy sugar Signup and view all the answers

Which property is not associated with monosaccharides?

Presence of more than six carbon atoms Signup and view all the answers

Which of the following correctly identifies the bond type in maltose?

α(1→4) glycosidic bond Signup and view all the answers

Which monosaccharide is known to be reduced into sorbitol?

Fructose Signup and view all the answers

Galactonic acid is produced from which monosaccharide?

Galactose Signup and view all the answers

Which component forms the glycosidic bond in disaccharides?

Hydroxyl group of anomeric carbon Signup and view all the answers

What is the molecular formula for lactose?

C12H22O11 Signup and view all the answers

Isomaltose is formed from which type of glycosidic bond?

α(1→6) Signup and view all the answers

Which sugar is an example of an amino sugar found in chondroitin?

Galactosamine Signup and view all the answers

Study Notes

Lecture 1: Cellular Communication

Cell communication is a process where living cells in an organism interact. This happens via direct contact or chemical signals.
Chemical signals are carried by neurotransmitters, hormones, or cyclic AMP.

Modes of Cell Communication

Contact-dependent: Surface molecules on one cell bind to surface molecules on another. This requires direct membrane contact
Paracrine: Signaling molecules only affect target cells in the proximity of the signaling cell. Example: electrical signal transmission between nerve and muscle cells (neurotransmitters).
Autocrine: Cells respond to molecules they produce themselves. Examples include growth factors and prostaglandins, which often function in paracrine and autocrine signaling.
Endocrine: Hormones produced by an endocrine gland travel through the bloodstream and reach distant target cells

Cell Communication Definition

Any way living cells in an organism communicate with each other, whether by direct contact or chemical signals.

Types of Cell Communication

Autocrine: Signaling a cell to itself.
Paracrine: Signaling a neighboring cell.
Endocrine: Signaling a distant cell through the bloodstream.
Direct: Signaling a neighboring cell through a gap junction.

Binding of Extracellular Signal Molecules to Receptors

Cell-surface receptors: Hydrophilic (water-soluble) signal molecules attach to these receptors on the exterior of the target cell's membrane.
Intracellular receptors: Hydrophobic (lipid-soluble) signal molecules pass through the membrane and bind to receptors inside the cell. These receptors are often located in the cytoplasm or the nucleus.

Intracellular Receptors

Signaling molecules are hydrophobic, and can diffuse through the cell membrane.
Typically, polar molecules (e.g., hormones) cannot rapidly cross the cell membrane. Instead, they bind to a plasma membrane receptor.

Cell Surface Receptors

Most signal molecules are hydrophilic, so they cannot pass through the cell membrane.
These bind to cell-surface receptors which then generate a signal inside of the target cell.

Hormones

Hormones are chemicals that coordinate different functions in the body via carrying messages through the blood to organs, skin, muscles, and other tissues.

Classification of Hormones

Group I (Lipophilic):
- Steroids and thyroid hormones
- Long half-life (hours to days)
- Intracellular receptors
- Receptor-hormone complex
Group II (Hydrophilic):
- Amino acid derivatives
- Short half-life (minutes)
- Cell surface receptors
- Second messengers (e.g., cAMP, Ca2+, etc.)

Broad Classification of Hormones (by Structure)

Hydrophilic: Proteins, peptide hormones, catecholamines. Primarily act via second messengers
Lipophilic: Steroid and thyroid hormones. Primarily act by activating genes within the nucleus.

Lipid-Soluble Hormones

Pass easily through the plasma membrane.
Have receptors inside the cell, in the cytoplasm
Binding to receptors activates enzymatic activity for changes in biochemical processes. Hormones like testosterone, progesterone, estrogen, cortisol, and thyroxine have receptors in the nucleus.

Hydrophillic Hormones

Bind to specific receptor proteins on the cell surface of the target cells.
Do not enter the cytosol or nucleus.
Cell-surface receptors convert extracellular signals to intracellular signals.

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Description

Explore the fascinating world of cellular communication in this quiz. Learn about the different modes of communication including contact-dependent, paracrine, autocrine, and endocrine signaling mechanisms. Test your understanding of how cells interact and convey signals within an organism.