Cell Shape and Function Quiz

Cell Shape and Function

• Cell Dimensions and Ratios:
• Cell A: 4cm x 4cm x 4cm
• Cell B: 5cm x 5cm x 5cm
• Cell C: 6cm x 6cm x 6cm
• Surface Area calculations: A = 96 sq cm, B = 150 sq cm, C= 216 sq cm
• Volume calculations: A = 64 cu cm, B = 125 cu cm, C = 216 cu cm
• SA:Vol Ratio calculations: A = 1.5, B = 1.2, C = 1
• Ranking (greatest to least SA:Vol ratio): A, B, C
• Efficient Cell Function:
• Cell A, with the highest SA:Vol ratio, will function most efficiently.
• A larger surface area allows for quicker exchange of materials across the cell membrane, facilitating its functions.
• The exchange of materials with the surroundings is crucial for cellular processes.

Transport Types

• Transport Comparison:

  Transport Type	Defining Characteristics	Direction of Movement?	Energy Required?	Proteins Involved?	Example
  Passive (simple diffusion)	Movement from high to low concentration. No energy required.	Down the concentration gradient	No	No	Oxygen into a cell
  Facilitated Diffusion	Movement from high to low concentration, aided by protein channels or carriers.	Down the concentration gradient	No	Yes	Glucose into a cell
  Active Transport	Movement against the concentration gradient. Requires energy.	Against the gradient	Yes	Yes	Sodium/Potassium pump

Feedback Loops

• Positive vs. Negative Feedback:
• Positive Feedback: Output enhances the initial stimulus, causing a snowball effect.
• Negative Feedback: Output resists or reverses the initial stimulus, maintaining homeostasis.
• Identify feedback type from graphic: (Require graphic)
• How to identify: Observe the pattern of change. Positive loops have an escalating trend, negative loops have a stabilizing trend.

Solutions and Cell Response

• Tonicity:
• Hypertonic: Solution with higher solute concentration than the cell. Water moves out of the cell.
• Hypotonic: Solution with lower solute concentration than the cell. Water moves into the cell.
• Isotonic: Solution with same solute concentration as the cell. No net water movement.
• Determining direction: Water always moves from an area of high water concentration to low water concentration.
• Graphic needed for further response: (Require graphic)

Cell Membrane Structure

• Cell Membrane Layer:
• Sketch should depict a phospholipid bilayer, with:
• Polar/hydrophilic heads facing the aqueous environment (inside and outside of the cell).
• Non-polar/hydrophobic tails facing inward.
• Transport proteins embedded within the bilayer.

Polarity and Permeability

• Water (H₂O) Polarity:

• Water molecule is polar because of the unequal sharing of electrons between oxygen and hydrogen atoms.

• Oxygen acquires a slight negative charge, and hydrogen acquires a slight positive charge.

• This difference in charge creates a dipole moment, making water polar.

• Hydrogen (H₂) Non-Polarity:

• The Hydrogen molecule is nonpolar because electrons are shared equally by the nuclei of both atoms. It has no dipole moment.

• Polarity and Membrane Permeability:

• The polar nature of the cell membrane (hydrophilic heads) allows water, and other polar molecules to diffuse across more readily or through transport proteins, while non-polar molecules, due to the hydrophobic tails, have a harder time diffusing through the membrane.

Sodium-Potassium Pump

• Membrane Permeability:
• Sodium and potassium ions cannot pass directly through the cell membrane due to their charge and relatively large size.
• Resting Membrane Potential:
• Inside the cell is relatively negative compared to the outside.
• Sodium Binding:
• 3 sodium ions bind to the pump.
• Sodium Pump Action:
• Sodium ions are pumped out of the cell.
• ATP Activation:
• ATP provides energy to change the shape of the pump.
• Potassium Binding:
• 2 potassium ions bind to the pump.
• Potassium Pump Action:
• Potassium ions are pumped into the cell.
• Active Transport Characteristics:
• Against concentration gradient.
• Requires energy.
• Body Functions:
• Nervous system signaling.
• Muscle contraction.