Bio100 (Cytology~A)

What is defined as the structural and functional unit of the living body?

The cell.

What is the smallest unit that has all the characteristics of life?

A single cell.

List the 6 general characteristics of a cell.

1. Needs nutrition and oxygen 2. Produces its own energy for growth/repair 3. Eliminates carbon dioxide and metabolic wastes 4. Maintains the medium (environment for survival) 5. Shows immediate response to invaders 6. Reproduces by division.

Which specific type of cell is a notable exception because it does not reproduce by division?

Neurons.

Define a "tissue".

A group of cells having similar function.

What are the four primary tissues of the body?

1. Muscle tissue 2. Nervous tissue 3. Epithelial tissue 4. Connective tissue.

Give the three examples of connective tissue mentioned in the text.

Cartilage, bone, and blood.

What types of cells comprise nervous tissue?

Neurons and supporting cells.

What is defined as a structure formed by two or more primary types of tissues?

An organ.

Organs are generally classified into what two structural categories?

1. Tubular or hollow organs 2. Compact or parenchymal organs.

Define a "system" in the context of general physiology.

A group of organs that work together to carry out specific functions of the body.

Which system is responsible for the transport of substances between the organs?

The cardiovascular system.

Which system is concerned with the growth of the body and regulation/maintenance of normal life?

The endocrine system.

Which system eliminates unwanted substances?

The excretory system.

What is the specific function of the digestive system?

Concerned with digestion of food particles.

What is the specific function of the respiratory system?

Concerned with the supply of oxygen and removal of carbon dioxide.

What is the specific function of the reproductive system?

Involved in the reproduction of species.

What is the specific function of the musculoskeletal system?

Responsible for stability and movements of the body.

What is the specific function of the nervous system?

Controls the locomotion and other activities including the intellectual functions.

A cell is formed by what two main structural components?

The cell body and the cell membrane.

The cell body is comprised of what two main parts?

The nucleus and the cytoplasm.

What are two alternative names for the cell membrane?

Plasma membrane and plasmalemma.

What two fluid compartments does the cell membrane separate?

The extracellular fluid (ECF) and the intracellular fluid (ICF).

What is the typical thickness of the cell membrane?

75 to 111 Å.

What are the three primary substances that compose the cell membrane, and what are their relative percentages?

1. Proteins (55%) 2. Lipids (40%) 3. Carbohydrates (5%).

Under an electron microscope, the cell membrane appears as a three-layered structure. Describe the properties of these three layers.

One central electron-lucent layer (formed by lipids) sandwiched between two electron-dense layers (formed by proteins).

Who proposed the 'Danielli-Davson model' of the cell membrane in 1935?

James F Danielli and Hugh Davson.

How did the Danielli-Davson model describe the basic structure of the cell membrane?

As a "sandwich of lipids" covered by proteins on both sides.

Who proposed the 'Unit membrane model' in 1957?

JD Robertson.

Who proposed the currently accepted 'Fluid mosaic model' of the cell membrane in 1972?

SJ Singer and GL Nicholson.

Briefly describe the membrane arrangement according to the 'Fluid mosaic model'.

It is a fluid membrane with a mosaic of proteins (a pattern formed by arrangement of different pieces) within the lipid layer.

Is the central lipid layer of the cell membrane a solid structure or fluid in nature?

It is fluid in nature (not a solid structure).

Because the lipid layer is fluid, what happens to portions of the membrane and dissolved materials?

They move from one point to another point along the surface of the cell to all areas of the cell membrane.

What are the two major classes of lipids that make up the lipid bilayer of the cell membrane?

Phospholipids and Cholesterol.

Name the 6 specific phospholipids present in the lipid layer mentioned in the text.

Aminophospholipids, sphingomyelins, phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylserine, and phosphatidylinositol.

Describe the shape and polarity of a phospholipid molecule.

It resembles a pin shape, with a hydrophilic (water-soluble) head and a hydrophobic (water-insoluble) tail.

How does the text describe the physical structure/texture of phospholipids?

Soft and oily structures.

How are phospholipid molecules spatially arranged within the cell membrane bilayer?

The hydrophobic tails meet in the center, while the hydrophilic heads face outward (towards ECF on the outside, ICF on the inside).

Where are cholesterol molecules physically located within the cell membrane?

Arranged in between the phospholipid molecules.

What are the two primary structural functions of cholesterol in the cell membrane?

It helps 'pack' the phospholipids and is responsible for the structural integrity of the lipid layer.

The lipid layer acts as a semipermeable membrane that allows the passage of what type of substances? Give three examples.

Fat-soluble substances (e.g., oxygen, carbon dioxide, alcohol).

The lipid layer is largely impermeable to what type of substances? Give three examples.

Water-soluble substances (e.g., glucose, urea, electrolytes).

Most of the proteins present in the electron-dense layers of the cell membrane exist in what specific chemical form?

As glycoproteins.

What are the two main categories of proteins found in the cell membrane?

1. Integral (transmembrane) proteins 2. Peripheral membrane proteins.

Describe the physical placement of integral proteins in the cell membrane.

They pass through the entire thickness of the cell membrane from one side to the other.

Are integral proteins tightly or loosely bound to the cell membrane?

Tightly bound.

Name the 7 examples of integral proteins mentioned in the text.

Cell adhesion proteins, cell junction proteins, carrier (transport) proteins, channel proteins, hormone receptors, antigens, and some enzymes.

Describe the physical placement of peripheral proteins in the cell membrane.

They are partially embedded in the outer and inner surfaces, but do not penetrate the membrane.

Are peripheral proteins tightly or loosely bound to the cell membrane?

Loosely bound (they dissociate readily).

Name the 3 examples of peripheral proteins mentioned in the text.

Proteins of the cytoskeleton, some carrier proteins, and some enzymes.

Which type of membrane proteins primarily provide structural integrity to the cell membrane?

Integral proteins.

What is the primary function of channel proteins in the cell membrane?

They help in the diffusion of water-soluble substances (like glucose and electrolytes).

What is the primary function of carrier proteins?

They transport substances across the membrane by means of active or passive transport.

Carrier proteins that act as 'pumps' facilitate what specific physiological process?

Active transport (moving ions actively across the cell membrane).

What function do receptor proteins serve in the cell membrane?

They serve as receptor sites for hormones and neurotransmitters.

Which membrane proteins are responsible for inducing the process of antibody formation?

Antigens.

What is the primary function of cell adhesion molecules (integral proteins)?

Responsible for the attachment of cells to their neighbors or to the basal lamina.

What function do membrane-bound enzymes provide?

They control chemical (metabolic) reactions within the cell membrane.

Carbohydrate molecules in the cell membrane attach to proteins and lipids to form what two respective structures?

Glycoproteins (carbs + proteins) and glycolipids (carbs + lipids).

What is another term used in the text for the glycoproteins formed by carbohydrates attaching to proteins?

Proteoglycans.

What is the thin, loose covering over the entire surface of the cell membrane formed by carbohydrate molecules called?

The glycocalyx.

Are carbohydrate molecules in the cell membrane positively or negatively charged?

Negatively charged.

How does the negative charge of membrane carbohydrates affect transport?

It does not permit negatively charged substances to move in and out of the cell.

What role does the glycocalyx play regarding cellular interaction?

It helps in the tight fixation of cells with one another.

Aside from charge limitation and fixation, what is another function of some carbohydrate molecules on the cell membrane?

They function as receptors for some hormones.

List the 6 overarching functions of the cell membrane.

1. Protective function 2. Selective permeability 3. Absorptive function 4. Excretory function 5. Exchange of gases 6. Maintenance of shape and size of the cell.

Describe the "protective function" of the cell membrane.

It protects the cytoplasm and the organelles present in the cytoplasm.

Describe the "selective permeability" function of the cell membrane.

It acts as a semipermeable membrane, which allows only some substances to pass through it and acts as a barrier for other substances.

Describe the "absorptive function" of the cell membrane.

Nutrients are absorbed into the cell through the cell membrane.

Describe the "excretory function" of the cell membrane.

Metabolites and other waste products from the cell are excreted out.

Describe the "exchange of gases" function of the cell membrane.

Oxygen enters the cell from the blood and carbon dioxide leaves the cell and enters the blood through the cell membrane.

Describe how the cell membrane contributes to the "maintenance of shape and size".

The cell membrane is responsible for the maintenance of shape and size of the cell.

Define the cytoplasm and note its primary constituent.

It is the jelly-like material formed by 80% water that contains a clear liquid portion and various particles/organelles.

What is the clear liquid portion of the cytoplasm specifically called?

Cytosol.

The cytoplasm is structurally divided into what two zones?

1. Ectoplasm 2. Endoplasm.

Describe the location of the Ectoplasm.

It is the peripheral part of the cytoplasm, situated just beneath the cell membrane.

Describe the location of the Endoplasm.

It is the inner part of the cytoplasm, interposed between the ectoplasm and the nucleus.

What are cytoplasmic organelles?

Cellular structures embedded in the cytoplasm, considered the "tiny organs" of the cell.

Cytoplasmic organelles are categorized based on the presence or absence of what structural feature?

A limiting membrane.

Based on the introductory text provided, describe the Endoplasmic Reticulum.

It is a network of tubular and microsomal vesicular structures which are interconnected with one another (and is an organelle with a limiting membrane).

The limiting membrane of the endoplasmic reticulum is formed by what two components?

Proteins and bilayered lipids.