Cell Biology: Structure and Function

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Questions and Answers

What is the main function of the cell wall in prokaryotes?

To facilitate the transmission of signals between cells

To provide structural support and barriers against outside forces (correct)

To regulate the movement of molecules in and out of the cell

To synthesize proteins

What is a characteristic feature of plant cells?

They have a true nucleus

They are typically small in size

They have a distinct compartment for metabolism

They have a cell wall with a rigid outer layer (correct)

What is the typical size range of cells?

1-100 centimeters in diameter

1-10 micrometers in diameter

100-1000 micrometers in diameter

10-100 micrometers in diameter (correct)

What is a characteristic of prokaryotes?

They have a single circular molecule of DNA Signup and view all the answers

What is the function of ribosomes in prokaryotes?

To synthesize proteins Signup and view all the answers

How do prokaryotes differ from other cells?

They have genetic material not separated from the cytoplasm Signup and view all the answers

What is the main function of the plasma membrane?

To separate the internal environment of the cell from the outside environment Signup and view all the answers

What is the characteristics of the nucleus in eukaryotic cells?

It is a membrane-bound organelle that contains DNA Signup and view all the answers

What is the primary function of ribosomes?

To synthesize proteins Signup and view all the answers

What is the term for the ability of the plasma membrane to allow certain molecules to pass through while keeping others out?

Selective permeability Signup and view all the answers

What is the main component of the cytosol and extracellular fluids?

Water Signup and view all the answers

What is the function of membrane proteins?

To act as channels for molecules to pass through Signup and view all the answers

What is the main characteristic of Peripheral Membrane Proteins?

Associated with polar heads at inner or outer surface Signup and view all the answers

What type of protein is permanently attached to the membrane from only one side?

Integral monotopic protein Signup and view all the answers

What is the primary function of Enzymes in the cell membrane?

To carry out chemical reactions on the interior surface of the plasma membrane Signup and view all the answers

What is the main difference between Passive and Active Transportation?

The requirement of energy Signup and view all the answers

What is the process called when the plasma membrane extends outward and envelopes food particles?

Endocytosis Signup and view all the answers

What is the purpose of Cell Adhesion Proteins?

To allow cells to glue themselves to one another Signup and view all the answers

What is the term for the movement of molecules from a region of high concentration to a region of low concentration?

Diffusion Signup and view all the answers

What type of protein is involved in the active transportation of ions and molecules across the cell membrane?

Carrier protein Signup and view all the answers

What is the purpose of Cell Surface Receptors?

To act as antennae for chemical messages Signup and view all the answers

What is the process called when vesicles fuse with the plasma membrane to release their contents outside the cell?

Exocytosis Signup and view all the answers

Study Notes

Cell Biology

Cells are the building blocks of all living things, performing necessary maintenance, recycling parts, disposing of waste, and adapting to changes in their environment.
Cells can be single-celled (e.g., bacteria) or multi-celled (e.g., plants and animals) and come in a wide range of sizes and shapes.

Types of Cells

Cells can be classified into two main categories based on how their genetic material is packaged:
- Prokaryotes: genetic material is not separated from the cytoplasm, no distinct interior compartments, no true nucleus, and ribosomes are not surrounded by a membrane.
- Eukaryotes: genetic material is found in a nucleus, and cells can be single-celled or multi-celled, with organized complex structures.

Cell Structure

All cells have four common components:
- Cell membrane
- Cytoplasm
- Ribosomes
- DNA
Cell structure helps maintain proper homeostasis in the body and its environment.

Cell Membrane

The cell membrane separates the internal environment of the cell from the outside environment.
It has selective permeability, allowing certain molecules to pass through while keeping others out.
The cell membrane is a lipid bilayer with embedded proteins, which provide mechanical support and perform various functions.

Membrane Proteins

Proteins attached to the cell membrane can be classified into two groups:
- Peripheral membrane proteins: not embedded in the membrane, associated with the polar heads at the inner or outer surface, and have surface functions.
- Integral membrane proteins: embedded in the plasma membrane, can act as cell receptors, and have functions such as transporting molecules across the membrane.

Cell Membrane Proteins

Transporters: selective membrane proteins that allow certain substances to enter or leave the cell.
Enzymes: proteins that carry out chemical reactions on the interior surface of the plasma membrane.
Cell surface receptors: sensitive to chemical messages and act as antennae.
Cell surface identity markers: carry cell surface markers that identify them to other cells.
Cell adhesion proteins: cells use specific proteins to glue themselves to one another or form permanent bonds.

Transportation Across Cell Membrane

Transportation across the cell membrane can be classified into two types:
- Passive transportation:
  - Diffusion: net movement of substances from high to low concentration without energy expenditure.
  - Facilitated diffusion: passage of molecules through channels in the membrane.
  - Osmosis: movement of molecules from high to low concentration through a selectively permeable membrane.
- Active transport:
  - Bulk passage into and out of cells:
    - Endocytosis: plasma membrane extends outward and envelops food particles.
    - Exocytosis: discharge of material from vesicles at the cell surface.
  - Active transportation of ions and molecules: process requires energy expenditure, typically ATP, and involves highly selective protein carriers within the membrane.

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Description

Learn about the cell membrane, the building block of all living things, and its various functions, including maintenance, recycling, and adaptation to its environment.