Biology Exam 2 Review Questions

Questions and Answers

What is the difference between integral and peripheral membrane proteins?

Integral proteins are embedded in the whole bilayer, whereas peripheral proteins are located on the inner or outer surface of the phospholipid bilayer.

How do transmembrane proteins become embedded in the plasma membrane?

Transmembrane proteins are anchored into the membrane by translocation and are stopped by a membrane anchor sequence.

What are 6 functions of the cell membrane?

Cell compartmentalization, anchoring cytoskeleton, protein sorting, adhesion of cells, cell signaling, selective uptake and export of ions and molecules.

What 3 types of macromolecules compose the plasma membrane?

Lipids, Proteins, and Carbohydrates. Signup and view all the answers

What is glycosylation and what does it produce?

Glycosylation is the process of adding a carbohydrate to a lipid or protein, forming glycolipids or glycoproteins. Signup and view all the answers

What are phospholipids and how does their structure affect their role?

Phospholipids are made up of a phosphate head and a lipid tail; their structure contributes to the fluidity of the membrane. Signup and view all the answers

Why is the phospholipid bilayer termed a semifluid?

Some proteins can float through the membrane while some proteins are anchored into the membrane. Signup and view all the answers

What does it mean to be semi-permeable?

Small molecules can pass through easily like water, but large molecules have a difficult time. Signup and view all the answers

What is selective permeability?

Selective permeability is the ability of the cell membrane to allow some molecules to enter and exit while preventing others. Signup and view all the answers

What is the difference between active and passive transport?

Active transport requires energy (ATP), while passive transport does not (e.g., diffusion and osmosis). Signup and view all the answers

What is the difference between osmosis and diffusion?

Osmosis is the movement of water across the membrane, while diffusion is the movement of solutes. Signup and view all the answers

How can you tell whether a solution is hypertonic, hypotonic, or isotonic to a cell placed within it?

Isotonic solutions have the same amount of solutes, hypertonic solutions have a lot of solute, and hypotonic solutions have little solute. Signup and view all the answers

What happens to plant/animal cells when placed in either a hypotonic, hypertonic, or isotonic solution?

Isotonic: ideal for animal cells, but will cause plant cells to wilt. Hypertonic: plant cells become plasmolyzed, and animal cells experience crenation. Hypotonic: plant cells become turgid, while animal cells undergo lysis. Signup and view all the answers

What is the difference between exocytosis and endocytosis?

Exocytosis packages and ships materials outside of the cell, while endocytosis packages materials from outside the cell to the interior. Signup and view all the answers

What are the differences between an antiporter, a symporter, and a uniporter?

Uniporter moves one type of molecule across; Symporter moves two or more in the same direction; Antiporter moves two or more in opposite directions. Signup and view all the answers

What is the difference between a channel protein and a transport protein?

Channel proteins have an open structure that allows molecules to move back and forth, while transport proteins facilitate the movement of ions and molecules passively or actively. Signup and view all the answers

Describe 3 ways a cell can communicate with cells immediately around it.

Gap junctions, tight junctions, and desmosomes. Signup and view all the answers

Describe how a cell communicates with cells very far removed from it.

Cells communicate through endocrine signaling by secreting hormones into the circulatory system. Signup and view all the answers

Describe the stages of cell signaling.

<ol> <li>Reception 2. Transduction 3. Response.</li> </ol> Signup and view all the answers

Study Notes

Membrane Proteins

Integral proteins are fully embedded in the phospholipid bilayer, while peripheral proteins associate with the membrane's surface.
Transmembrane proteins act as receptors and traverse the membrane multiple times, anchored by translocation and a membrane anchor sequence.

Functions of the Cell Membrane

Provides compartmentalization for cellular processes.
Facilitates cytoskeleton anchoring for structural integrity.
Assists in protein sorting for cell function.
Promotes cellular adhesion.
Engages in cell signaling for communication.
Supports selective uptake and export of ions and molecules.

Composition of Plasma Membrane

Composed of three primary macromolecules: lipids, proteins, and carbohydrates.

Glycosylation

A biochemical process where carbohydrates are added to lipids or proteins, producing glycolipids and glycoproteins.

Phospholipid Structure

Consists of a hydrophilic phosphate head and hydrophobic lipid tails; structural elements influence membrane fluidity through length, kinks, and cholesterol content.

Membrane Properties

The phospholipid bilayer is termed semifluid due to the mobility of some proteins and the anchoring of others.
Semi-permeable membranes allow small molecules like water to pass freely, while large molecules face barriers.

Transport Mechanisms

Selective permeability allows certain molecules to enter or exit while restricting others.
Active transport requires energy (ATP), contrasting with passive transport, which occurs without energy (e.g., diffusion, osmosis).
Osmosis refers to water movement, while diffusion pertains to solute movement.

Tonicity and Cell Response

Isotonic solutions have equal solute concentrations; they are ideal for animal cells but not for plant cells, which may become flaccid.
Hypertonic solutions cause plasmolysis in plants and crenation in animal cells.
Hypotonic solutions lead to turgidity in plant cells due to water influx and lysis in animal cells.

Vesicular Transport

Exocytosis involves packaging materials to be expelled from the cell.
Endocytosis entails engulfs external materials into vesicles for intracellular processing.

Transport Proteins

Uniporters transport a single type of molecule across the membrane.
Symporters move two or more different molecules in the same direction; antiporters move them in opposite directions.

Protein Types

Channel proteins form open structures that allow selective molecule passage through the membrane.
Transport proteins facilitate ion and molecular movement via passive diffusion or secondary active transport.

Cellular Communication

Local communication occurs through gap junctions, tight junctions, and desmosomes.
Distant communication utilizes endocrine signaling, where hormones travel through the circulatory system to target cells.

Cell Signaling Process

Involves three sequential stages: reception (signal detection), transduction (signal processing), and response (cellular action).

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Prepare for your Biology Exam 2 with these flashcards that cover essential concepts related to membrane proteins. Explore the differences between integral and peripheral membrane proteins, along with insights on transmembrane protein embedding. Test your knowledge and get ready for success!