Cell Membrane and Proteins Overview

Cholesterol

• Cholesterol is a lipid found in animal cells, it is non-polar
• Cholesterol helps maintain membrane fluidity
• Cholesterol is important for cell function
• Cholesterol is difficult to transport because it doesn't dissolve in water

Receptor Proteins

• Receptor proteins are located on the cell membrane
• They bind to specific chemicals (e.g. tastebud receptors)
• They allow cells to respond to specific chemicals

Enzymes

• Enzymes are proteins that facilitate reactions
• They are essential for many cellular processes

Identification Markers

• Identification markers are proteins that allow cells to be recognized by other cells
• For example, blood types

Junction Proteins

• Junction proteins bind cells together

Cytosis

• Cytosis is a type of transport that involves the folding of the cell membrane
• Endocytosis: bringing material into the cell
• Exocytosis: expelling material from the cell

Plant Cells

• Plant cells are multicellular
• Plant cells contain a cell wall and a central vacuole
• The central vacuole is a storage space for water and other molecules
• The cell wall provides structural support for the plant

Glycolysis

• Glycolysis is a metabolic pathway that breaks down glucose into two molecules of pyruvate
• Glycolysis can operate with or without the presence of oxygen
• Requires an investment of 2 ATP molecules to begin the process
• The process can be divided into three stages:
  • Stage 1 begins with glucose (6 carbon molecules) and uses 2 ATP molecules to generate more energy, thus becoming ADP
  • Stage 2: glucose is broken down into two 3-carbon molecules (G3P) with the help of phosphate groups from ATP
  • Stage 3: Each G3P molecule contains a phosphate and NAD+
    • NAD+ gets reduced (an electron is added) into NADH
    • 2 ADP molecules turn into 2 ATP molecules
    • The two G3P molecules turn into pyruvate
• Glycolysis results in a net energy gain of 2 ATP molecules
• It occurs in the cytoplasm of both prokaryotic and eukaryotic cells

Meiosis

• Meiosis is a process of cell division that produces gametes (sex cells)
• It involves two rounds of division, resulting in four haploid daughter cells
• Each daughter cell has half the number of chromosomes as the parent cell
• Meiosis is essential for sexual reproduction

Stages of Meiosis I

• Prophase I: Chromosomes condense next to their homologue forming pairs (homologous pairs) and become visible, the cytoskeleton breaks down, the nucleolus disappears and the spindle starts to form
• Metaphase I: Homologous pairs line up along the metaphase plate.
• Anaphase I: Homologous pairs of chromosomes are pulled apart and pulled to opposite ends of the cell
• Telophase I: Each daughter cell receives one chromosome (with two chromatids) from each pair.

Meiosis II

• Prophase II: Chromosomes condense, spindle fibers form, and the nuclear envelope breaks down.
• Metaphase II: Chromosomes line up at the metaphase plate.
• Anaphase II: Sister chromatids of each chromosome separate and move to opposite poles of the cell.
• Telophase II: The nuclear envelope reforms.
• Cytokinesis: The cytoplasm divides, forming four haploid daughter cells.

Haploid and Diploid

• Diploid cells have two sets of chromosomes (2n), one from each parent.
• Haploid cells have one set of chromosomes (n).

Sexual Reproduction

• Haploid gametes from each parent fuse (fertilization) to create a diploid zygote
• The zygote goes through mitosis to develop into a multicellular organism

Sexual Reproduction in Animals

• Diploid zygotes go through meiosis to produce haploid gametes
• Diploid offspring go through mitosis to develop into a new organism

Sexual Reproduction in Plants

• Zygotes go through mitosis to produce a haploid, multicellular organism
• The haploid organism produces gametes through meiosis
• Gametes fuse through fertilization to create a new diploid organism

Genetics

• Character (trait): A potentially variable quality or quantity in an organism
• True-breeding variety: When new generations after reproduction have the same phenotype
• Hybrid offspring: Offspring of two different varieties
• Monohybrid cross: Studying the inheritance of a single character in a hybridization experiment

Genetics Terms

• Parental (P) generation: The original parents
• First filial (F1) generation: Offspring of the P generation
• Second filial (F2) generation: Offspring of the F1 generation
• Gene: A sequence of DNA that codes for a specific trait
• Locus: The specific location of a gene on a chromosome
• Allele: An alternative form of a gene
• Genotype: The genetic makeup of an organism
• Phenotype: The observable characteristics of an organism
• Homozygous: Two identical alleles at a particular locus
• Heterozygous: Two different alleles at a particular locus
• Dominant allele: An allele that is fully expressed in a heterozygote
• Recessive allele: An allele that is not fully expressed in a heterozygote
• Pleiotropy: One gene affects multiple traits
• Dihybrid cross: Studying the inheritance of two traits in a hybridization experiment
• Independent assortment: Alleles at different loci are inherited independently of each other
• Dependent assortment: Alleles at different loci are inherited together
• Polygenic traits: Traits influenced by multiple genes (e.g., skin color)