Bio 120 Structured Study Session

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Questions and Answers

What is the role of cholesterol in the plasma membrane?

Decreases the movement of fatty acid tails at high temperatures (correct)

Facilitates the transport of proteins across the membrane

Increases the fluidity of the membrane at all temperatures

Repels water molecules from associating with the membrane

Which situation would most likely result in increased membrane fluidity?

Phospholipids that are saturated

Phospholipids with double bonds (correct)

Phospholipids that tightly associate with each other

Phospholipids with long tails

Which of the following is NOT a role of membrane proteins?

Signal transduction

Cell surface attachment and recognition

Energy production in mitochondria (correct)

Transport of molecules across the membrane

What characterizes phospholipids that contribute to their behavior in a membrane?

Hydrophilic head and hydrophobic tail Signup and view all the answers

Which factor contributes to the decrease in membrane fluidity?

Saturated phospholipids Signup and view all the answers

What type of molecules can pass through the plasma membrane without assistance?

Small nonpolar molecules Signup and view all the answers

How do desaturases affect membrane fluidity as temperature decreases?

They add double bonds to fatty acids, increasing fluidity Signup and view all the answers

What happens to phospholipids with long tails in terms of membrane fluidity?

They lead to tighter packing in the membrane Signup and view all the answers

What term describes a solution with a lower concentration of solutes compared to another solution?

Hypotonic Signup and view all the answers

What is the primary movement of water during osmosis?

Into an area with a higher solute concentration Signup and view all the answers

How does temperature affect desaturase concentration?

It would decrease Signup and view all the answers

In a hypertonic solution, how will water move in relation to the cell?

Water will move out of the cell Signup and view all the answers

Which organism is likely to have cholesterol in its cell membrane?

Wolf Signup and view all the answers

What is the role of aquaporins in osmosis?

They facilitate the movement of water Signup and view all the answers

What happens when a cell is placed in an isotonic solution?

There will be no net movement of water Signup and view all the answers

What defines a hypertonic solution?

It has a higher concentration of solutes than another solution Signup and view all the answers

What is the role of membrane fluidity in the plasma membrane?

It affects the permeability and movement of proteins within the membrane. Signup and view all the answers

Which statement accurately describes passive transport?

It can occur through simple diffusion or facilitated diffusion. Signup and view all the answers

What type of transport occurs when potassium moves out of the cell via a channel protein?

Facilitated diffusion Signup and view all the answers

What type of molecules can pass directly through the cell membrane via simple diffusion?

Small, uncharged molecules like oxygen Signup and view all the answers

Which of the following best characterizes glucose transport across the plasma membrane?

It requires a carrier protein due to its size and polarity. Signup and view all the answers

What type of transport is exemplified by the Na-K-ATPase which moves 3 sodium out of the cell and 2 potassium into the cell?

Antiport Signup and view all the answers

What is primary active transport primarily responsible for?

Utilizing ATP to move molecules against their concentration gradient. Signup and view all the answers

What characterizes passive transport?

It includes processes like simple diffusion and osmosis. Signup and view all the answers

Which process involves a cell engulfing a large particle such as a bacterial cell?

Phagocytosis Signup and view all the answers

Receptor-mediated endocytosis begins with a ligand binding to what structure on the cell's surface?

Receptor Signup and view all the answers

What does diffusion refer to?

The tendency of substances to spread out and increase entropy. Signup and view all the answers

What distinguishes facilitated diffusion from simple diffusion?

Facilitated diffusion involves specific transporter proteins. Signup and view all the answers

What role do channel proteins play in the plasma membrane?

They form openings that allow specific substances to pass through the membrane. Signup and view all the answers

Which of the following accurately describes simple diffusion?

It does not require energy and occurs down the concentration gradient. Signup and view all the answers

What is the process where a cell expels large molecules, such as metabolic wastes, from itself?

Exocytosis Signup and view all the answers

Which of these describes an example of secondary active transport?

Transporting glucose into the cell along with sodium ions. Signup and view all the answers

Which endocytic process is often referred to as 'cellular drinking'?

Pinocytosis Signup and view all the answers

What happens to the scent molecules from cooking food in a kitchen?

They spread out into available space due to diffusion. Signup and view all the answers

Why do larger molecules like glucose require assistance to cross the cell membrane?

They cannot pass through the membrane directly due to their size or charge. Signup and view all the answers

The Na-K-ATPase transport mechanism utilizes what kind of energy?

Chemical energy Signup and view all the answers

Why is a carrier protein necessary for glucose transport?

Glucose is too large and polar to pass through the lipid bilayer unaided. Signup and view all the answers

What is a concentration gradient?

The difference in concentration of molecules across a membrane. Signup and view all the answers

What distinguishes receptor-mediated endocytosis from pinocytosis?

Specificity of molecule uptake Signup and view all the answers

What role does the clathrin-coated pit play in receptor-mediated endocytosis?

Forms the vesicle for uptake Signup and view all the answers

Which of the following statements about osmosis is true?

It involves the movement of water across a semi-permeable membrane. Signup and view all the answers

During exocytosis, the contents of the vesicle are expelled into the environment after what event?

Fusing with the cell membrane Signup and view all the answers

What is required for facilitated diffusion to occur?

A concentration gradient Signup and view all the answers

Which transport mechanism requires energy input?

Active transport Signup and view all the answers

What is the primary role of ion channels in facilitated diffusion?

To allow ions to move through the membrane Signup and view all the answers

Which type of transporter moves two molecules in the same direction?

Symport Signup and view all the answers

Which method involves the breakdown of ATP to facilitate transport?

Primary active transport Signup and view all the answers

What type of transport is exemplified by the sodium-glucose transporter?

Secondary active transport Signup and view all the answers

What happens to a carrier protein during primary active transport?

It undergoes a conformational change Signup and view all the answers

In which scenario does potassium typically have a higher concentration?

Inside the cell compared to outside Signup and view all the answers

Which of the following statements about active transport is true?

It requires energy input. Signup and view all the answers

Study Notes

Structured Study Sessions

Structured Study Sessions (SSS) are peer-led study sessions
Bio 120
Led by Janelle and Steve
October 1, 2024
Sessions are developed by peer mentors, not course professors
Session materials selected based on peer mentor experience and input from the SSS Peer Mentor Team

Question of the Day

Students asked their names and favorite season

Topics Covered Today

Plasma membrane structure - review
Membrane fluidity
Diffusion
Passive and active transport

Glucose Transport

Glucose requires a carrier protein for passage through the plasma membrane
It does NOT cross the membrane via simple diffusion

Primary Active Transport

Directly uses ATP energy to move a molecule against its concentration gradient.
Does not use concentration gradients for movement

Plasma Membrane

Composed of phospholipids and proteins
Phospholipids have hydrophilic heads and hydrophobic tails
Tails of phospholipids cluster together to form the membrane to avoid contact with water
Proteins are embedded in and move within the phospholipid bilayer

Membrane Protein Roles

Transport of molecules
Enzymatic activity
Signal transduction
Cell surface attachment and recognition

Membrane Fluidity

Some phospholipids have more freedom of movement than others
Membrane fluidity is affected by tail length and presence of double bonds.
Saturated phospholipids have longer tails and less movement, making the membrane less fluid.
Unsaturated phospholipids have shorter tails and double bonds, allowing for more movement and making the membrane more fluid
Other factors like desaturases and temperature affect fluidity
Desaturases add double bonds to fatty acids as temperature decreases

Cholesterol in the Membrane

Found only in animal cells
Regulates membrane fluidity at different temperatures.
At low temperatures, cholesterol prevents fatty acid tails from tightly associating, maintaining fluidity
At high temperatures, it reduces fatty acid tail movement, reducing fluidity.

Molecules Passing Through the Membrane

Small, uncharged molecules (e.g., oxygen, carbon dioxide) can pass directly through the plasma membrane
Larger molecules, charged molecules and ions need the help of membrane proteins

Diffusion

Substances move from areas of high concentration to low concentration to increase entropy (randomness)
Explains molecule dispersal in environments like smells spreading through a house
Also, explains how molecules move across cell membranes

Passive Transport

Any membrane transport that does not require energy input
Molecules move down their concentration gradient (higher to lower concentration)
Examples include simple diffusion, facilitated diffusion, and osmosis

Simple Diffusion

Passive transport of small, uncharged molecules across the cell membrane
Molecules move from a higher to lower concentration area
Doesn't require energy

Concentration Gradient

A difference in the concentration of a substance across a distance.
Molecules move from areas of higher to lower concentration

Osmosis

The movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration
Doesn't require energy input
Can occur directly across the membrane or through aquaporins, protein channels.

Osmosis - Important Terms

Hypotonic, Hypertonic, and Isotonic solutions are defined by the concentration of solutes within them and their effect on the movement of water into or out of a cell

Desaturase Concentration

Increases when temperature decreases

Hypertonic Solution

Water moves out of the cell

Cholesterol: Organism

Found in wolves (animals)

Facilitated Diffusion

Still passive transport, no energy input
Molecules can't move through the phospholipid bilayer, need help from special channels (e.g., ion channels) or carrier proteins to pass.
Important for transporting ions and larger molecules like glucose

Facilitated Diffusion Examples

Sodium and potassium ion channels are essential for generating electrical signals in cells
Channels are specific to the ion they transport due to differences in their shape and size

Active Transport

Requires energy input (e.g., ATP)
Molecules move against the concentration gradient (lower to higher concentration)
Three types: primary active, secondary active, and vesicular

Primary Active Transport Example

Na-K ATPase moves 3 sodium out and 2 potassium into the cell

Secondary Active Transport

Uses energy stored in a concentration gradient of one molecule to move another molecule against its gradient
Example: sodium-glucose transporter.

Types of Transporters

Uniport (one molecule)
Antiport (different directions)
Symport (same direction)

These transporters can be involved in secondary active transport or other types of membrane transport using carrier proteins

Potassium Transport

Potassium moves out of the cell via a channel protein in facilitated diffusion

Endocytosis

Used to transport larger molecules that can't be transported across membranes using membrane proteins.
Three types: phagocytosis, receptor-mediated endocytosis, and pinocytosis

Phagocytosis

Cell engulfs a large particle (e.g., bacteria) by extending its plasma membrane around it, forming a phagosome.

Receptor-Mediated Endocytosis

Ligand binds to a receptor on the cell's surface
Receptor and lignad migrate to a coated pit
Indentation folds inward to form a vesicle and moves ligand into the cell

Pinocytosis

Cellular "drinking"
Less specific.
Cell takes in some of the fluid surrounding, collecting any nutrients or other small molecules in that fluid.
Membrane folds inward to form a vesicle

Exocytosis

Large molecules expelled from the cell.
Vesicle fuses with the cell membrane and expels contents to the outside of the cell

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Description

Join the peer-led Structured Study Session for Bio 120, focusing on essential topics like plasma membrane structure, diffusion, and transport mechanisms. Led by Janelle and Steve, this session is designed to enhance your understanding through collaborative learning among peers.