Biology: Construction of a Cell

Study Notes

Cell Theory and Components

Cell theory emphasizes that the cell is the basic unit of life.
Cells differ in size, shape, structure, and function.
Fundamental components of all cells:
- Cytoplasm: gel-like substance for growth.
- Plasma membrane: encloses the cytoplasm.
- Chromosomes: genetic blueprints inside the cytoplasm.
- Ribosomes: structures for protein synthesis.

Cytoplasm

Surrounds the plasma membrane; composed of 70-80% water.
Contains nutrients, enzymes, and suspended organic molecules.
Includes glucose, amino acids, fatty acids, and nucleic acids.
Dissolved ions like sodium and potassium present.
Site for metabolic reactions, including protein synthesis.

Plasma Membrane

All cells possess a plasma membrane with selective permeability.
Described by the fluid mosaic model, indicating mobility of membrane components.
Composed of a bilayer of phospholipids and diverse proteins.
Eukaryotic membranes contain sterols (e.g., cholesterol) for fluidity.
Archaeal membranes differ, featuring ether linkages and branched phospholipid chains.
Surface proteins aid in cell communication and environmental sensing.
Glycoproteins and glycolipids allow for interaction with the external environment.

DNA

Double-stranded DNA organized into chromosomes carries essential life information.
Prokaryotic chromosomes: circular, haploid, and lack a nuclear membrane.
In humans, there are 46 chromosomes; fruit flies have 8.
Chromosomes are visible during cell division; otherwise, they exist as chromatin (unwound form).
Extrachromosomal DNA (plasmids) carry advantageous traits, such as antibiotic resistance.
Plasmids are primarily found in bacteria, but can also exist in archaea and eukaryotes.

Ribosomes

All cellular life utilizes ribosomes for protein synthesis.
Ribosomes consist of proteins and ribosomal RNA.
Differences in ribosomes between domains (bacterial, archaeal, eukaryotic):
- Bacterial and archaeal ribosomes contain distinct proteins and rRNA; archaeal are closer to eukaryotic ribosomes.
- Eukaryotic ribosomes are 80S with a small and large subunit.
Ribosomes are abundant in cells with high protein synthesis needs, like pancreatic cells producing digestive enzymes.

Cell Types: Prokaryotic vs. Eukaryotic

Prokaryotic cells:
- Lack a nucleus and membrane-bound organelles.
- Usually contain a single, circular chromosome in a nucleoid.
Eukaryotic cells:
- Have a nucleus surrounded by a nuclear membrane.
- Contain multiple linear chromosomes and various membrane-bound organelles.

Description

This quiz focuses on the fundamental components of a cell and the cell theory, which highlights the cell as the basic unit of life. You will explore the structures that make up cells, including the cytoplasm and plasma membrane, and their varying functions. Test your knowledge on cell biology essentials.