Biology: Cell Structure and Function

Study Notes

Cell Structure and Function

Cells are the basic units of life, and all living organisms are composed of one or more cells.
Cells exhibit a remarkable diversity in their shapes and sizes, reflecting their specialized functions.
Cell structures perform specific functions essential for maintaining life.
Prokaryotic cells (bacteria and archaea) are simpler, lacking a nucleus and other membrane-bound organelles.
Eukaryotic cells (plants, animals, fungi, and protists) are complex, possessing a nucleus and a variety of membrane-bound organelles.

Cell Membrane

The cell membrane, also known as the plasma membrane, is a selectively permeable barrier that encloses the cell's contents.
It is primarily composed of a phospholipid bilayer interspersed with proteins and cholesterol.
The phospholipid bilayer provides a hydrophobic barrier that regulates the passage of substances into and out of the cell.
Membrane proteins play crucial roles in transport, enzymatic activity, cell signaling, and cell adhesion.
Different kinds of transport mechanisms across the membrane include passive transport (e.g. diffusion, osmosis) and active transport (requiring energy).

Cytoplasm

The cytoplasm is the jelly-like substance that fills the cell and surrounds the nucleus.
It contains various organelles – specialized structures that carry out specific functions within the cell.
Cytosol, the liquid component of cytoplasm, contains water, dissolved ions, small molecules, and macromolecules.
Cytoskeleton – a network of protein fibers (microfilaments, intermediate filaments, microtubules) in the cytoplasm which gives shape to the cell, and enables movement.

Nucleus

The nucleus is the control center of the cell, containing the cell's genetic material (DNA).
It is enclosed by a double membrane, the nuclear envelope, with pores that regulate the passage of substances between the nucleus and cytoplasm.
Within the nucleus is the nucleolus, a region involved in ribosome biogenesis.
The DNA in the nucleus is organized into tightly coiled structures called chromosomes.

Organelles

Mitochondria are the "powerhouses" of the cell, generating ATP (energy) through cellular respiration.
Ribosomes are responsible for protein synthesis.
Endoplasmic reticulum (ER) is a network of membranes involved in protein synthesis, folding, and transport.
Golgi apparatus modifies, sorts, and packages proteins.
Lysosomes contain digestive enzymes, breaking down waste and cellular debris.
Vacuoles, primarily in plant cells, store water, nutrients, and waste products.
Peroxisomes contain enzymes that detoxify harmful substances.
Chloroplasts (only in plants) are responsible for photosynthesis converting light energy into chemical energy.

Cell Division

Cell division is a fundamental process enabling growth, repair, and reproduction in organisms.
Two main types of cell division are mitosis (for somatic cells) and meiosis (for gametes).
Mitosis results in two genetically identical daughter cells from a single parent cell.
Meiosis results in four genetically diverse daughter cells (gametes) from a single parent cell.

Cell Communication

Cells communicate with each other through various mechanisms, including direct contact, signaling molecules, and receptor proteins.
These interactions are essential for coordinating cellular activities and maintaining homeostasis.

Description

Explore the fascinating world of cells, the basic units of life. This quiz covers the characteristics, structures, and functions of prokaryotic and eukaryotic cells, including the essential role of the cell membrane. Test your understanding of cellular diversity and membrane dynamics.