Cell Structure and Functions

• A cell is the smallest unit of life, and organisms can be single-celled or multicellular.

Cell Structure and Function

• The three main parts of a cell include:
  • Cell membrane
  • Nucleus
  • Cytoplasm
• Single-celled organisms carry out all life functions within one cell.
• Multicellular organisms have cells specialized for specific jobs.
• Cells provide structure, take in nutrients, and convert them to energy.
• Cells contain hereditary material and can replicate to facilitate organism growth and reproduction.

Types of Cells

• Eukaryotic and prokaryotic cells are the two primary categories.
• Prokaryotic cells are simpler and lack membrane-bound organelles, such as a nucleus or mitochondria; bacteria consist of prokaryotic cells.
• Eukaryotic cells are more complex, containing membrane-bound organelles like a nucleus; plants, animals, and fungi are made up of eukaryotic cells.
• DNA, the hereditary material, remains in the nucleus in eukaryotic cells and contains the code for necessary proteins.
• Prokaryotic cells have DNA in a nucleoid region without a membrane.

Cell Division

• Multicellular organisms originate from a single cell, necessitating cell division for growth.
• The cell cycle includes interphase, mitosis, and cytokinesis.
• During interphase, DNA replicates, forming chromosomes; replicated chromosomes consist of two sister chromatids connected at a centromere.

Mitosis

• Following interphase, mitosis occurs, replicating the cell nucleus.
• Cytokinesis follows mitosis, splitting the cytoplasm into two new cells.
• Meiosis is a cell division that produces reproductive cells with half the number of chromosomes.
• Prokaryotic cells divide via binary fission using a single circular chromosome.
• Mitosis generates identical nuclei via prophase, metaphase, anaphase, and telophase.
• In prophase, the nuclear membrane breaks down, chromosomes condense from chromatin, and spindle fibers form.
• During metaphase, chromosomes line up at the metaphase plate, and spindle fibers attach to centromeres.
• Anaphase involves shortening spindle fibers and splitting centromeres, pulling sister chromatids apart.
• Telophase includes nuclear membrane reformation and cell elongation.
• Cytokinesis happens after telophase.

Meiosis

• Meiosis, reproductive cell division, produces gametes with half the normal chromosome number.
• Gametes are genetically diverse cells that combine during fertilization to produce zygotes.
• Meiosis consists of two divisions: meiosis I and meiosis II, each with phases similar to mitosis.
• Prophase I involves homologous chromosomes pairing up into tetrads.
• Crossing over occurs during prophase I, where chromosomes in tetrads exchange genetic information.
• Metaphase I aligns tetrads along the metaphase plate.
• Anaphase I separates homologous chromosomes.
• Telophase I results in two genetically different cells.
• Meiosis II then occurs, ending with four genetically distinct cells with half the original chromosome number.

Binary Fission

• Binary fission is a method of asexual reproduction in which DNA replicates, and the cell divides into two identical cells.
• Binary fission is the primary reproduction method of prokaryotes.

Explore the fundamental unit of life: the cell. This includes cell structure, the differences between prokaryotic and eukaryotic cells, and their specific functions. Understand the major parts of a cell, including the cell membrane, nucleus, and cytoplasm.