Chapter 4

Who first discovered the cells in 1665 by observing through a microscope?

Robert Hooke

Which two scientist proposed the Cell Theory?

Mathias Schleiden (1838) and Theodor Schwan (1839)

What affect the cells size?

Diffusion

What affects the rate of diffusion?

• Temperature

• Concentration gradient

• Surface area

• Distance (size of the particles involved)

Relationship between many small cells and fewer large cells

many small cells have an advantage

When the cell size increases what increases first?

Volume increases much faster than surface area

How do some cells overcome a higher volume rather than surface area?

By being long and narrow (EX: neurons)

What are the 4 components of the Cell Theory?

• All organisms are composed of cells

• cells are the smallest living things

• cells arise only from pre-existing cells

• all cells today represent a continuous line of descent from the first living cells.

The minimum distance two points that care apart and still be distinguishes as two separate points

Resolution

• Uses magnifying lenses with visible light

• resolve structures that are 200nm apart

• limit to resolution using light

Light Microscope

• Use beam of electrons

• Resolve structures that are 0.2 nm apart

• Transmission electron microscopes transmit electrons through the material

• Scanning electron microscopes beam electrons onto the specimen surface

Electron microscope

What cells are ce;ed

Prokaryotic Cells

The simplest organisms that lack a membrane-bound nucleus. DNA is present in the nucleoid, and they have cell walls outside of the plasma membrane. Prokaryotic cells also possess ribosomes and a cytoskeleton.

Bacterial Cell Walls

Most bacterial cells are encased by a strong cell wall composed of peptidoglycan. The cell wall protects the cell, maintains its shape, and prevents excessive uptake or loss of water. The structure of bacterial cell walls can determine their susceptibility to antibiotics.

Archaea

Prokaryotes that have cell walls but lack peptidoglycan. They have a greater diversity in cell wall components and their membrane lipid structure helps distinguish them from bacteria.

Flagella

Tail-like structures present in some prokaryotic cells that function in locomotion. They may have one or more flagella, and the rotary motion propels the cell.

Eukaryotic Cells

More complex than prokaryotic cells and possess a membrane-bound nucleus. Eukaryotic cells are characterized by compartmentalization achieved through membrane-bound organelles and the endomembrane system. They also have a cytoskeleton for support and structure maintenance.

Animal VS Plant Cell

Both animal and plant cells have a plasma membrane and contain most of the same organelles. Plant cells have additional features such as a cell wall made of cellulose, chloroplasts for photosynthesis, and specialized vacuoles.

Nucleus

The repository of genetic information in eukaryotic cells. It is enclosed by the nuclear envelope and contains the nucleolus, where ribosomal RNA synthesis takes place. Most eukaryotic cells have a single nucleus.

Ribosomes

The cell's protein synthesis machinery. They are found in all cell types and consist of ribosomal RNA (rRNA) and protein complexes. Ribosomes can be free in the cytoplasm or associated with internal membranes.

Central Dogma

The flow of genetic information in cells. It involves the transcription of DNA into RNA in the nucleus and the translation of RNA into proteins in the cytoplasm. The nucleotides in RNA differ from those in DNA, and the process is regulated by the nuclear envelope and nuclear pores.

Chromatin

The combination of DNA and proteins that make up chromosomes. Chromatin is not easily accessible and must undergo condensation to form visible chromosomes during cell division.

Protein Synthesis

The process of creating proteins using ribosomes, messenger RNA (mRNA), and transfer RNA (tRNA). Ribosomes consist of large and small subunits that come together to read mRNA and bring tRNA to build polypeptide chains.