Biology Cell Basics

Study Notes

Cell Membrane

Also known as plasma membrane
Thin, semi-permeable layer of lipid and protein molecules surrounding the cell
Regulates what enters and leaves the cell through active and passive transport
Composed of:
- Phospholipid bilayer (hydrophobic tails facing inward, hydrophilic heads facing outward)
- Embedded proteins (receptors, enzymes, transport proteins)
- Cholesterol (stabilizes membrane structure)

Mitosis

Type of cell division that results in two daughter cells with same number of chromosomes as parent cell
Occurs in somatic cells (non-reproductive cells)
Phases:
1. Interphase (cell grows, replicates DNA, and prepares for division)
2. Prophase (chromatin condenses, nuclear envelope breaks down, and spindle fibers form)
3. Metaphase (chromosomes line up at center of cell)
4. Anaphase (sister chromatids separate and move to opposite poles)
5. Telophase (chromosomes uncoil, nuclear envelope reforms)
6. Cytokinesis (cytoplasm divides, and cell splits)

Meiosis

Type of cell division that results in four daughter cells with half the number of chromosomes as parent cell
Occurs in reproductive cells (gametes: sperm and egg cells)
Phases:
1. Interphase (cell grows, replicates DNA, and prepares for division)
2. Prophase I (chromatin condenses, nuclear envelope breaks down, and spindle fibers form)
3. Metaphase I (homologous pairs of chromosomes line up at center of cell)
4. Anaphase I (homologous pairs separate and move to opposite poles)
5. Telophase I (chromosomes uncoil, nuclear envelope reforms)
6. Prophase II (chromosomes condense, nuclear envelope breaks down, and spindle fibers form)
7. Metaphase II (chromosomes line up at center of cell)
8. Anaphase II (sister chromatids separate and move to opposite poles)
9. Telophase II (chromosomes uncoil, nuclear envelope reforms)
10. Cytokinesis (cytoplasm divides, and cell splits)

Photosynthesis

Process by which cells convert light energy into chemical energy
Occurs in chloroplasts of plant cells and some algae
Equation: 6 CO2 + 6 H2O + light energy → C6H12O6 (glucose) + 6 O2
Steps:
1. Light-dependent reactions (light energy excites electrons, which generate ATP and NADPH)
2. Light-independent reactions (Calvin cycle: ATP and NADPH are used to convert CO2 into glucose)

Cell Signaling

Process by which cells communicate with each other through signals
Types of signals:
- Hormones (endocrine signals: released into bloodstream, affect distant cells)
- Neurotransmitters (released by neurons, affect nearby cells)
- Paracrine signals (released by nearby cells, affect adjacent cells)
- Autocrine signals (released by cells, affect same cell)
Steps:
1. Signal reception (signal binds to receptor on target cell)
2. Signal transduction (signal is transmitted through cell, often involving second messengers)
3. Response (target cell responds to signal, often involving changes in gene expression)

Animal Cells

Characteristics:
- Lack cell wall
- Have true nucleus
- Have mitochondria
- Have centrioles (involved in formation of cilia, flagella, and spindle fibers)
- Have lysosomes (contain digestive enzymes)
- Have Golgi apparatus (involved in protein modification and transport)
- Can be totipotent (capable of giving rise to entire organism)

Description

Test your knowledge of cell biology, covering topics such as cell membranes, cell division, photosynthesis, cell signaling, and animal cells. Learn about the structure and functions of cells, including mitosis and meiosis.