Cells and Tissues

Question 1

Name the three types of lipids found in cell membranes

Answer 1

1. Phospholipids
2. sphingolipids
3. cholesterol

Question 2

Describe the three types of membrane proteins and how they are associated with the cell membrane.

Answer 2

Integral proteins are tightly bound to the membrane. Peripheral proteins are loosely bound to membrane components. Proteins may be transmembrane, lipid anchored, or loosely bound to other proteins.

Question 3

Why do phospholipids in cell membranes form a bilayer instead of just a single layer?

Answer 3

To hide the hydrophobic tails of phospholipids from direct contact with aqueous body fluids

Question 4

How many phospholipid bilayers will a substance cross passing into a cell?

Answer 4

One

Question 5

Name the three sizes of cytoplasmic protein fibers?

Answer 5

Microfilaments (actin filaments), intermediate filaments, and microtubules

Question 6

Examining tissue from a previously unknown species of fish, you discover a tissue containing large amounts of smooth endoplasmic reticulum in its cells. What is one possible function of these cells?

Answer 6

This suggests that the tissue synthesizes large amounts of lipids, fatty acids, or steroids, or that it detoxifies foreign molecules

Question 7

How would the absence of a flagellum affect a sperm cell?

Answer 7

It would be unable to swim to find an egg to fertilize

Question 8

What is the difference between cytoplasm and cytosol?

Answer 8

Cytoplasm is everything inside the cell membrane except the nucleus. Cytosol is the semi-gelatinous substance in which organelles and inclusions are suspended

Question 9

What is the function of motor proteins?

Answer 9

Motor proteins use energy to create movement

Question 10

What is the difference between a cilium and a flagellum?

Answer 10

Cilia are short, usually are very numerous on a cell, and move fluid or substances across the cell surface. Flagella are longer, usually occur singly (on human sperm) and are used to propel a cell through fluid

Question 11

What distinguishes organelles from inclusions?

Answer 11

A membrane separates organelles from the cytosol; inclusions have no membrane.

Question 12

What is the anatomical difference between rough endoplasmic reticulum (ER) and smooth ER? What is the functional difference?

Answer 12

Rough ER has ribosomes attached to the cytoplasmic side of its membrane; smooth ER lacks ribosomes. Functionally, Rough ER synthesizes proteins, smooth ER synthesizes lipids.

Question 13

Name the functional categories of cell junctions.

Answer 13

• Gap (communicating)
• Tight (occluding)
• Anchoring

Question 14

Which type of cell junction:

1. Restricts movement of materials between cells?
2. Allows direct movement of substances from the cytoplasm of one cell to the cytoplasm of an adjacent cell?
3. Provides the strongest cell-cell junction?
4. Anchors actin fibers in the cell to extracellular matrix?

Answer 14

1. tight
2. gap
3. anchoring (specifically desmosome)
4. anchoring (specifically focal adhesion)

Question 15

Where do secretions from endocrine glands go?

Answer 15

Endocrine glands secrete hormones into the blood.

Question 16

Where do secretions from exocrine glands go?

Answer 16

Exocrine glands, with ducts, secrete their products outside the body–onto the surface of the skin or into the lumen of an organ that opens into the environment outside of the body.

Question 17

List the five functional types of epithelia

Answer 17

1. protective
2. secretory
3. transporting (regulated & rapid passage)
4. ciliated (surface movement via cilia)
5. exchange

Question 18

Define secretion

Answer 18

secretion = the process by which a cell releases a substance into its environment

Question 19

Name two properties that distinguish endocrine glands from exocrine glands

Answer 19

Endocrine glands do not have ducts and they secrete into the blood

Exocrine glands have ducts and secrete into the external enviornment

Question 20

The basal lamina of epithelium contains the protein fiber laminin. Are the overlying cells attached by focal adhesions or hemidesmosomes?

Answer 20

hemidesmosomes

Question 21

You look at a tissue under a microscope and see simple squamous epithelium. Can it be a sample of the skin surface? Explain.

Answer 21

No, skin has many layers of cell to protect the internal environment. A one-cell thick simple squamous epithelium would not be protective

Question 22

A cell of intestinal epithelium secretes a substance into the extracellular fluid, where it is picked up by the blood and carried to the pancreas. Is the intestinal epithelium cell an endocrine or exocrine cell?

Answer 22

endocrine cell, because it secretes its product into the ECF for distribution in the blood.

Question 23

What is the distinguishing characteristic of connective tissues?

Answer 23

extensive matrix

Question 24

Name four types of protein fibers found in connective tissue matrix and give characteristics of each.

Answer 24

1. collagen provides strength & flexibility
2. elastin provides elastance
3. fibrin provides elastance
4. fibronectin helps anchor cells to matrix

Question 25

Name six types of connective tissues

Answer 25

1. bone
2. cartilage
3. blood
4. dense connnective tissues (ligaments and tendons)
5. loose connective tissue
6. adipose tissue

Question 26

Blood is a connective tissue with two components: plasma and cells. Which of these is the matrix in this connective tissue?

Answer 26

Plasma is the extracellular matrix.

Question 27

Why does torn cartilage heal more slowly than a cut in the skin?

Answer 27

Cartilage lacks a blood supply, so oxygen and nutrients needed for repair must reach the cells by diffusion, a slow process.

Question 28

List the four general functions of the cell membrane

Answer 28

1. barrier between cell & ECF
2. regulate exchange of material between cell & ECF
3. transfer information between the cell and other cells
4. provide structural support

Question 29

Name the two types of cell junctions

Answer 29

1. Cell-Cell Junctions
2. Cell-Matrix Junctions

Question 30

Name the three types of Cell-Cell Junctions and describe them.

Answer 30

1. Desmosomes (anchor/avoid shearing)
2. Tight Junctions (occlude space between)
3. Gap Junctions (intercellular communication)

Question 31

The larger the _____ ____ , the more nutrients it (cell) can absorb

Answer 31

The larger the Surface Area, the more nutrients it (cell) can absorb

Question 32

Desmosomes

Answer 32

Desmosomes (anchor/avoid shearing)

• held together by a protein called cadherin
• used to prevent tearing
• used when cells need to be strongly held together

Example: Skin

Question 33

Tight Junctions

Answer 33

Tight Junctions (occlude space between)

• held together by protein called occludin
• “zippers” the cells together so that nothing can pass inbetween the cells → instead, information must go through the cells

Example: Intestines

Question 34

Gap Junctions

Answer 34

Gap Junctions (intercellular communication)

• held together by a protein called connexion
• has a “bridge” between the cells
• allows information to flow from cell to cell

Example: smooth and cardiac muscle

Question 35

What is the membrane protein of desmosomes?

Answer 35

cadherin

Question 36

What is the membrane protein of tight junctions??

Answer 36

occludin

Question 37

What is the membrane protein of gap junctions?

Answer 37

connexion

Question 38

Cell-Cell Junctions

Answer 38

Cell-cell junctions

Three types:

1. Desmosomes (anchor/avoid shearing)
   
   • Held together by a protein called cadherin
   • Used to prevent tearing
   • Used when cells need to be strongly held together
   • Ex: skin
2. Tight junctions (occlude space between)
   
   • Help together by a protein called occludin
   • “Zippers” the cells together so that nothing can pass inbetween the cells→ instead, information must go through the cells
3. Gap junctions (intercellular communication)
   
   • Held together by a protein called connexion
   • Has a “bridge” between the cells
   • Allows information to flow from cell to cell

Question 39

Cell-Matrix Junctions

Answer 39

Cell-matrix junctions

• Focal adhesion: Cells joining indirectly
  
  • structural and regulatory
  • indirectly hold cells together
• Main protein involved is integrin
  
  • Integrins in cell membrane interact with extracellular proteins, such as fibronectin, which hold cells in meshwork
• Fibronectin (an extracellular protein) helps connect the cells
• These types of junctions are both static (holds cells in place) and dynamic/functional (signaling due to interactions with extracellular proteins)
  
  • Angiogenesis is an example of regulatory function
    
    • FAK-mediated angiogenesis (making blood vessels)
      
      • Fibronectin talks to some endophilial cells→ clumps the integrin together→ causes a growth factor to be made→ new blood vessel begins to form

Question 40

Epithelial Tissue

Answer 40

Epithelial Tissue

• Separates internal and external environment
  
  • Physiologists refer to “outside” as any place that hasn’t crossed a cell barrier
    
    • includes GI, respiratory, and urinary tracts
• Epithelial cells secrete a basal lamina (basement membrane)
  
  • Basal lamina is made of collagen
  • Provides structural base for epithelial layer
  • Sometimes promotes organ function (kidney filtration)
    
    • Alport syndrome:
      
      • Caused by a basal lamina defect in podocytes
      • Results in blood and protein in the urine
• Epithelial cells have two layers
  
  • Simple epithelial→ one cell width
  • Striated epithelial→ several layers wide
    
    • Ex: skin
• Epithelial cell layers have various functions
  
  1. Protection
  2. Transport (regulated and rapid passage)
  3. Surface movement (via cilia)
  4. Secretion

Question 41

Connective Tissue

Answer 41

Connective Tisuse

• Defined as cells + extracellular matrix (ECM)
  
  • Fibroblast cells secrete collagen (the ECM protein)
    
    • Collagen forms triple helix structure to make rigid and strong fiber
      
      • These fibers cross-link to each other for structural integrity
        
        • Forms a meshwork of particular consistency
    • Depending on how much collagen is secreted, fibroblasts can form different types of connective tissues of very different consistencies and function
      
      • Ex: loose connective tissue, dense connective tissue, cartilage, bone connective tissue, etc.
        
        • Dermis connective tissues use more water to make it “squishy”
        • Bone and cartilage connective tissues use less water to form a more dense tissue
• Connective tissue defect: Fibrodysplasia ossificans progressiva
  
  • Injury results in repair pathway mistakenly activating stem cells to become bone tissue
    
    • Defect is an overactive receptor for bone formation molecule
  • Those stem cells, since they are in the same “class” of stem cells as all tissues, get the wrong signal and become bone tissue instead of the tissue needed to repair the injury

Question 42

Fibrodysplasia ossificans progressiva

Answer 42

Connective tissue defect:

Injury results in repair pathway mistakenly activating stem cells to become bone tissue

Defect is an overactive receptor for bone formation molecule

Those stem cells, since they are in the same “class” of stem cells as all tissues, get the wrong signal and become bone tissue instead of the tissue needed to repair the injury

Question 43

Alport Syndrom

Answer 43

Epithelial tissue defect

• caused by basal lamina defect in podocytes
• results in blood and protein in urine

Question 44

Resting Membrane Potential

Answer 44

Resting Membrane Potential (RMP)

Basics:

• Na+/K+ pump
• Electrochemical gradient
  
  • The charge that occurs on one side of the membrane when an ion passes through to the other side
• Ion equilibrium potential
  
  • When a membrane is selectively permeable, only certain ions can cross through the membrane
  • When the sides of the membrane have unequal concentration, the ions that can cross through will diffuse through the membrane to even out the concentration→ causes a charge gradient
  • The charge gradient will then cause those ions to go back the other way through the membrane until the charge gradient and concentration create an equilibrium

Membrane establishes RMP (-70 mV) by “using” two ion equilibrium potentials (K+ and Na+)

• Three things promote RMP of -70 mV:
  
  1. Disequilibrium of K+ and Na+ on either side of membrane
     
     • Na+/K+ pump uses primary active transport
     • Keeps K+ concentration high inside the cell
     • Keeps Na+ concentration high outside the cell
  2. Ion equilibrium potential of K+
     
     • Leaky K+ channels leak K+ from the cell
       
       • Leaky K+ channel is very active
         
         • The main channel established in RMP
       • Allows K+ to reach its ion equilibrium potential
  3. K+ leaks from the cell easily
     
     • ​Note: there are also leaky Na+ channel
       
       • BUT they are less active and not as many→ Na+ hardly leaks in
       • Na+ doesn’t reach its ion equilibrium potential

Proteins can’t leave cell

• Most proteins have a net negative charge

Question 45

Membrane Transport

Answer 45

• Cell membrane contains function-defining proteins that govern the basic membrane behavior
  
  • Channel/carrier proteins
    
    • A.k.a. Transporters
  • Receptor proteins
• Cell membrane is in “dynamic disequilibrium”
  
  • Dynamic disequilibrium: important solutes differentially concentrated on either side of the membrane
  • When solutes move across the membrane→ allows work to be done across the membrane
• How does a cell membrane allow information to be moved across? (2 ways)
  
  1. Bind a molecule and allow information to be transmitted into the cell
  2. Transport a molecule in/out

Question 46

Transporting a molecule in/out

BASIC DIFFUSION

Answer 46

Basic diffusion:

• Water and steroid hormones can pass through the membrane itself

Question 47

Transporting a molecule in/out

PROTEIN MEDIATED TRANSPORT

Answer 47

PROTEIN MEDIATED TRANSPORT

1. Channel proteins
   
   • Gated (at least most of them)
     
     • However, it doesn’t allow just anything in or out
       
       • Ex: Voltage-gated K+ transporter
   • Form a pore in the membrane (a.k.a. makes a channel)
   • Energy requirements for channel proteins:
     
     • Always use facilitated diffusion
       
       • Ex: ion channel→ ions flow in or out depending on the concentration gradient
2. Carrier proteins
   
   • Physically interacts with a molecule
   • Binds with the substrate→ changes its conformation to move it across membrane
     
     • Ex: glucose transporter uses facilitated diffusion→ requires a carrier protein
     • Ex: sodium-potassium pump uses active transport→ uses ATP to carry things across the membrane
   • Energy requirements for carrier proteins:
     
     • If molecule moves with concentration gradient→ use facilitated diffusion
     • If molecule moves against concentration gradient→ active transport (requires ATP)
   • Types of active transport (used when molecules move against concentration gradient)
     
     • Primary active transport:
       
       • Direct ATP use
         
         • Ex: H+/K+ pump in parietal cells
     • Secondary active transport:
       
       • Indirect ATP use
         
         • Concentration gradient of one molecule established
           
           • set up by using ATP
         • That potential energy is then used for transport of second molecule against the concentration gradient
       • Ex: Sodium/glucose transporter in intestinal epithelial cells
         
         • 1. Na+ has high concentration outside of the cell due to Na+/K+ pump
              * Na+/K+ pump uses ATP directly
         • 2. Na+/glucose transporter brings Na+ back in (along the concentration gradient→ using the energy from facilitated diffusion) to simultaneously move glucose (against the concentration gradient) into the cell