Cell Biology Concepts

• Human Biology explores the functional characteristics of life

Characteristics of Life

• Made of cells and basic nutrients (proteins, carbohydrates, lipids & nucleic acids)
• Innate order progresses from atoms to complex molecules, then to tissues, organs, and organisms
• Growth and reproduction are essential
• Living things use energy and raw materials
• Responsiveness to the environment is a key trait
• Maintenance of homeostasis is vital
• Evolution and adaptation are ongoing processes
• Death is an inevitable part of life

Levels of Biological Organization

• Organization ranges from the simplest to the most complex
• Atom: The smallest unit of matter
• Molecule: Multiple atoms forming a functional entity
• Organelle: Molecules working together within a cell for a specific function
• Cell: Organelles collaborating to form a specific cell type (e.g., skin, neuron, muscle)
• Tissue: Similar cells working together for a specific function (e.g., muscle tissue)
• Organ: Multiple tissues working together for a specific function
• Organ System: Multiple organs working together for a specific function
• Organism: The sum of all organ systems in the body

Scientific Method

• Observation: Begins with curiosity and questions (how? why? what? when? where? who?)
• Hypothesis: Forming a testable explanation, contrasted with a null hypothesis
• Experiment Design: Creating experiments to predict outcomes that either support or eliminate the hypothesis
• Result Analysis: Determining if results support the hypothesis

Statistical Significance

• P-value indicates the probability that observed differences are due to chance
• A p-value of less than 5% is generally considered acceptable in biology, supporting the hypothesis

Experimental Design

• Control Group: Used to determine if the hypothesis is correct, control group and experimental group needed
• Independent Variables: Groups should be treated the same except for the variable being tested
• Dependent Variables: This reveals the effects of the experiment
• Control Variables: Factors that could affect results other than the experimental condition must be considered to ensure accurate outcomes
• Prediction: Based on the hypothesis, predict how the experimental group will differ from the control group

Human Experimentation

• Initial Testing: Medicines and materials are first tested on laboratory animals, typically rodents
• Clinical Trials: If initial tests are favorable, human clinical trials begin, where participants provide informed consent
• Clinical Trials Structure: Experimental groups receive different dosages, and a control group receives a placebo
• Double-Blind Study: Prevents bias, neither researchers nor participants know who receives the treatment
• Epidemiological Studies: Involve looking for patterns in large populations

Molecular Bonds

• Covalent Bonds: sharing of electrons between nuclei of 2 atoms
  • Strong due to nuclei of 2 atoms sharing electrons, which are most stable in pairs
• Nonpolar Covalent Bonds: Form when electrons are evenly shared between two atoms
• Polar Covalent Bonds: Occur when one atom holds the shared electrons more tightly than the other
• Ionic Bonds: transfer of electrons from one atom to another
  • Very strong and form when electrons are completely transferred from one atom to another
  • One atom has a positive charge, and the other has a negative charge, attractions hold them tightly together
  • Break apart in the presence of polar molecules, like water
• Hydrogen Bonds: weak electrostatic attraction between polar molecules
  • Form due to weak electrostatic attraction between polar molecules from uneven charge distribution of non-polar covalent bonds

Properties of Water

• High Heat Capacity: Water moderates temperatures by absorbing or releasing heat with only slight temperature changes
• High Heat of Vaporization: Evaporation of water requires energy to break H-bonds, providing a cooling effect, such as in sweating
• Excellent Solvent: Water dissolves polar molecules and ions, but not lipids, due to hydration shells
• Digestion of Food Nutrients: Water aids in the breakdown of major macromolecules, including carbohydrates, proteins, and nucleic acids

Macromolecules

• Carbohydrates (sugars): Provide energy as ATP
• Proteins: Varied, with roles in structure, enzymes, motor functions, defense, receptors, transport, and hormones
• Nucleic Acids: Serve as information managers
• Lipids (fats): Used in membranes, cholesterol, hormones, energy storage, etc

Carbohydrates

• Composition: Always contain carbon, hydrogen, and oxygen atoms
• Energy Storage: Serve as quick or short-term energy storage
• Energy Release: Energy is produced when a bond is broken
• ATP Use: Energy, as ATP, can be used by cells for activities
• Short-Term Storage: Glycogen or starch
• Structural Carbohydrates: Dietary fibers cannot be digested

Proteins

• Structure: Chains of amino acids (AAs), also known as polypeptides
• Variety: Different structures due to the different atoms in amino acids
• Catalytic: Enzymatic reactions
• Structural: Support
• Antibodies: Body defense
• Transport: Transport other things through membranes or body
• Hormonal: Coordination of bodily functions

Lipids

• Hydrophobic: All are hydrophobic and insoluble in water
• Structure: Most have 2 to 3 fatty acid chains linked to a glycerol molecule
• Fats (oil, animal fat): Primary stored energy is body fat
• Fat-Soluble Vitamins: Carry fat-soluble vitamins (A, D, E, K)
• Cell Membranes: Component of cell membranes
• Hormones and Vitamin D: Help in the production of hormones and Vitamin D
• Organ Protection: Provide protection to internal organs and insulation against temperature extremes
• Cholesterol: Basic precursor molecule
• Cell Walls: Very important in the structure of cell walls and in secondary sexual characteristics

Phospholipids

• Structure: Have a hydrophilic "head" containing a phosphate group and two hydrophobic "tails" derived from fatty acids, joined by an alcohol residue
• Cell Membrane: Main component of the cell membrane

Nucleic Acids (DNA and RNA)

• DNA: Codes for all genes
• RNA: When protein is needed, the right gene is copied into mRNA
• Protein Synthesis: mRNA goes out of the nucleus into the cytoplasm to ribosomes where a particular protein is made from the code
• Protein Determination: Which genes are copied determines which proteins are made

Cell Theory

• Basic Unit: Structural and functional unit of life
• Body Function: Dependent both on individual and collective cell functions
• Complementarity: Is the biochemical activities of cells dictated by their shapes or forms, and specific subcellular structures

Basic Cell Components

• All cells have four basic components
• Plasma Membrane: Flexible outer boundary
• Cytoplasm: Intracellular fluid containing organelles for different functions
• Nucleic acids
• Genetic Infomation
• Ribosomes: Where proteins are made

Cell Types

• Prokaryotic cell: Plasma membrane, DNA region (or nucleoid region), cytoplasm, ribosome and cell wall
• Eukaryotic cell: will be focused on
• Plasma Membrane Separation of Inside and Outside: Separates the inside from the outside of the cell
• Lipid and Protein Structure: Composed of lipids (phospholipids) and proteins for controlling what goes in and out
• Protein Communication: Proteins allow communication with the environment

Cross Cell Transport

• Size and Movement: Small molecules move in and out freely
• Diffusion: Movement from high to low concentration (no energy required)
• Pores or Proteins: Movement through pores or via proteins (no energy required)

Vesicular Transport

• Large Molecules: Moving very large things in and out of the cell using transport vesicles, requires energy

Exocytosis

• Material in vesicles is expelled from a cell
• Indigestible materials are expelled

Endocytosis

• Transport Into Cell: Macromolecules (proteins, polysaccharides, nucleic acids) are often too large to cross the membrane, so vesicles are used
• Pinocytosis: Most common form of endocytosis
• Phagocytosis: Large molecules or entire cells can be engulfed by pseudopods (parts of the cell that move like arms); humans use white blood cells (WBCs) to engulf foreign substances

Nucleus

• Largest Organelle: Distinguishing feature of eukaryotes
• Genetic Protection: Protects and stores genetic info, DNA

Ribosomes

• mRNA Sequence: Where all proteins are made according to mRNA sequence
• Location: Large numbers are free in cytoplasm, while others are attached to the endoplasmic reticulum

Endoplasmic Reticulum

• Rough Endoplasmic Reticulum (rER): Contains ribosomes that guide the production of proteins for export out of the cell
• Smooth Endoplasmic Reticulum (sER): Is involved in the production of membranes and for detoxification

Golgi Complex

• Vesicle Transfer: Proteins are transferred to the Golgi complex for processing and packaging
• Protein Destination: Proteins made in rER -> Golgi -> to cytoplasm OR to PM & outside of cell

Lysosomes:

• Bud off Golgi
• Hydrolytic Enzymes: Filled with hydrolytic enzymes and an acidic interior (pH 5.0)
• Macromolecule Digestion: Function to digest macromolecules down to their monomers

Mitochondria

• Cellular Respiration: Sites of cellular respiration
• Energy Production: Provide cell with energy through breakdown of glucose to produce ATP using oxygen

Cytoskeleton

• Cell Shape: Gives cell its shape
• Organelle Position: Helps position organelles
• Cell Movement: Aids in cell movement (ex. Flagella and cilia)
• Internal Transport: Aids in internal transport system (via vesicle movement)

Cell Division

• Process: chromosomes determine cell division
• Mitosis and Meiosis: Two types of cell division

Mitosis

• Role for growth, repair & replacement of cells
• Creates genetically identical diploid cells
• Occurs in somatic cells (all cells except germ cells)

Meiosis

• Role for creation of haploid gametes (eggs & sperm)
• Reduce # of chromosomes by 1/2 (haploid) & mix DNA of original parents
• Occurs in ovaries (oogenesis) = eggs and testes (spermatogenesis) = sperm
• Somatic Cells = Diploid
• Gamete Cells = Haploid

Fertilization

• An egg fertilized by a sperm re-establishes a diploid state

Chromosomes

• Composition: A linear strand of DNA
• Sister Chromatids: After replication, a chromosome is two sister chromatids

Chromosome Traits

• Homologous Pairs: Each diploid cell has two sets of similar (but not identical) chromosomes (homologous pairs) (2n)
• Determined by size and shape
• Haploid Set Contribution: Each parent has a haploid set (n.)
• Determine expressions

Human Genetics

• Each cell contains two chromosomes with genes for the same traits
• Chromosomes Pairs: Of the 23 pairs of chromosomes, one is sex chromosomes, and the rest are autosomes

Sex Chromosomes

• Sex chromosomes determine biological sex
  • XX = genetic female
  • XY = genetic male (Y chromosome smaller than X)

Check Points

• How's our DNA?= Did the chromosomes get replicated correctly and is the DNA damage
• Are we ready to divide? Is the cell big enough? Are there enough energy and other reserves? Is the DNA damaged?

Meiosis

• Meiosis = sexual reproduction
• Allows gene mixing and matching from 2+ individuals
• The number of chromosomes = 1/2 the originals and original DNA is mixed

Genetic Diversity

• Sexual reproduction results in genetic informational shuffling; no 2 individuals have the same genes
• Achieved by crossing over & independent assortment of chromosomes

Crossing Over

• Segments Exchange: occurs when corresponding pieces of chromatids of maternal and paternal homologues are exchanged
• Random Pole Orientation: the relative positioning of homologous maternal and paternal chromosomes with respect to poles of the cell is random

Non-disjunction

• Homologous Failure: failure of homologous chromosomes to separate results in few or too many chromosomes
• Development: can lead to abnormalities in development or miscarriages

Cell Cycles in Humans

• Developing Embryo and Fetus: body cells divide continually (by mitosis)
• Children: body cells divide for growth and repair (by mitosis)
• Adults:
  • Some cells lose ability to divide (ex most neurons)
  • Some cells stop dividing but retain ability to divide should the need arise (ex liver cells)
  • Some cells actively divide throughout life (ex skin cells)
  • Germ cells divide for eggs or sperm. (by meiosis)

Cell Death

• Dying (Necrotic) cells are damaged and starve for oxygen/nutrients, content is released, and inflammation can occur
• Apoctosis is gentically programmed, from a cell no longer needed or old cells are prone to genetic dmage

Uncontrolled Cell Division

• Benign tumor = abnormal mass of tissue surrounded by tissues - removable by surgery
• Malignant = invades surrounding tissues, often cancerous and life threatening

Cancers

• Multi-step process involving alleles
• Can be inherited = speeding up process

Explore cell biology with questions on protein production, cell membrane function, eukaryotic structures, and steroid roles. Questions cover shared features of cells, the impact of malfunctioning flagella, chromosome reduction, and cell division. This set also tests knowledge of chromosome numbers in diploid and haploid cells.