Cell Biology, Digestion, and Body Systems

Cell Theory

  • The cell theory consists of three main principles:
    • All living things are composed of one or more cells and their products.
    • The cell is the most basic unit capable of carrying out all life processes.
    • All cells arise from pre-existing cells and not from non-living matter.
  • Prokaryotes are the simplest single-celled organisms (e.g., bacteria).
  • Eukaryotes are more complex organisms, including multicellular organisms.

Cell Structure

  • Cytoplasm:
    • The cytoplasm is where all organelles are suspended.
    • It is mainly water but contains stored substances.
    • Many chemical reactions occur in the cytoplasm.
    • Its consistency can vary from jelly-like to liquid, facilitating organelle movement.
  • Cell Membrane:
    • A flexible double-layered membrane surrounds the cell.
    • It supports the cell and controls the entry and exit of substances.
    • It is semi-permeable, allowing small molecules like water and oxygen to pass through easily, but restricting larger molecules like proteins.
    • A similar membrane encloses most organelles in eukaryotic cells.
  • Nucleus:
    • A roughly spherical structure that contains genetic information (DNA).
    • It controls all cell activities.
    • Genetic information is stored on chromosomes made of DNA (deoxyribonucleic acid).
    • During cell division, DNA is copied to ensure each new cell has a complete set.
  • Mitochondria:
    • Often called the "power plants" of the cell.
    • They produce energy for the cell through cellular respiration.
    • glucose + oxygen \rightarrow carbon dioxide + water + usable energy
    • Active cells (e.g., muscle cells) have more mitochondria than less active cells.
    • Mitochondria contain enzymes that convert stored energy into usable forms.
  • Endoplasmic Reticulum:
    • A three-dimensional network of branching tubes and pockets.
    • It extends throughout the cytoplasm, continuous with the nuclear and cell membranes.
    • It transports materials (e.g., proteins) throughout the cell.
    • It is involved in hormone production in the brain and muscle contraction in muscles.
  • Golgi Bodies:
    • They collect and process materials to be removed from the cell.
    • They also produce and secrete mucus.
    • Cells that secrete a lot of mucus (e.g., cells lining the intestine) have many Golgi bodies.
  • Vacuoles:
    • Single-layered membrane enclosing fluid in a sac.
    • Functions include containing substances, removing unwanted substances, and maintaining internal fluid pressure (turgor).
    • Animal cells may have many small, often invisible vacuoles.
    • Mature plant cells usually have one large central vacuole.
    • Some animal cells, like amoeba and white blood cells, use vacuoles to engulf food or bacteria.
  • Cell Walls (Plant Cells Only):
    • Found outside the cell membrane of plant cells.
    • A rigid but porous structure made of cellulose.
    • Provides support and protection.
  • Large Vacuole (Plant Cells Only):
    • Plant cells usually have one large vacuole, occupying most of the cell's volume.
    • Maintains turgor pressure, keeping the cells plump, and the plant firm.
    • Loss of water leads to loss of turgor pressure, causing the plant to wilt.
  • Chloroplasts (Plant Cells Only):
    • Found in plant cells exposed to light, such as leaf cells.
    • Contain chlorophyll, giving leaves their green color.
    • Absorb light energy for photosynthesis.
    • carbon dioxide + water + energy (sunlight) \rightarrow glucose + oxygen
    • Plants use mitochondria to metabolize glucose, similar to animal cells.

Cell Cycle and Mitosis

  • Interphase: Cell grows, replicates chromosomes, and prepares for mitosis.
  • Mitosis: Cell division for growth, reproduction, and repair.
    • Uncontrolled cell division leads to cancer.
  • Process of Mitosis (PMAT):
    1. Prophase:
      • DNA is copied.
      • Chromosomes condense into sister chromatids.
      • The nuclear membrane dissolves.
      • Spindle fibers form between centrioles.
    2. Metaphase:
      • Chromosomes align along the middle of the cell ("equator").
      • Centromeres attach to spindle fibers.
    3. Anaphase:
      • Centromeres split, and sister chromatids are pulled apart to opposite sides of the cell (poles).
      • Sister chromatids are now called "daughter chromosomes."
    4. Telophase:
      • Daughter chromosomes uncoil and become invisible.
      • New nuclear membranes form around each group of daughter chromosomes.
      • Two identical nuclei are formed.
  • Cytokinesis: The cell divides into two "daughter" cells.
  • Cell Cycle Phases:
    • G1: Cell grows and increases in size.
    • S: DNA is copied.
    • G2: Cell prepares to divide during mitosis.

Vocabulary

  • Chromosome: A structure in the cell nucleus made of DNA.
  • Chromatid: One of the two identical strands of DNA that make up a chromosome.
  • Centromere: The structure that holds chromatids together as chromosomes.

Importance of Cell Division

  • Growth:
    • Multicellular organisms increase in cell number as they grow.
  • Reproduction:
    • Cells divide to reproduce.
    • Each new cell has a complete set of genetic information.
    • Asexual reproduction: Offspring from ONE parent, genetically identical
  • Repair:
    • Replaces injured or dead cells.
    • Examples: healing cuts, broken bones, replacing shed skin cells, and blood cells.

Cell Size and Diffusion

  • Diffusion moves chemicals across the cell membrane.
  • Osmosis moves water across the cell membrane.
  • Movement of nutrients, gases, waste, and water depends on cell size.
  • Large cells have inefficient diffusion and osmosis.

Cell Death

  • Apoptosis: Programmed cell death.
  • Necrosis: Cell death due to lack of blood flow (ischaemia).
  • Dead cells are removed by:
    • Sloughing off (surface cells).
    • Phagocytes (white blood cells that ingest other cells).

Digestive System

  • Mechanical and chemical breakdown of organic molecules into smaller units for absorption.
  • Mechanical Digestion: Physical breakdown of food (e.g., chewing).
  • Chemical Digestion: Breaking down chemical bonds using stomach acid, bile, and enzymes.
  • Four Stages of Food Processing:
    1. Ingestion: Eating.
    2. Digestion: Breaking down food.
    3. Absorption: Absorbing molecules into the bloodstream.
    4. Elimination: Eliminating undigested materials.
  • Digestive Tract in Humans: mouth, esophagus, stomach, small intestine, large intestine, and anus.
  • Mouth:
    • Teeth and saliva break down food mechanically and chemically into BOLUS.
  • Pharynx:
    • Throat.
    • Epiglottis: Prevents food from entering the lungs.
  • Esophagus:
    • Peristalsis pushes the bolus to the stomach.
  • Stomach:
    • Mixes food and releases hydrochloric acid (HCl) to break down food.
    • pH of 2.
  • Small Intestine:
    • Absorbs nutrients into the bloodstream.
    • 6 m long.
  • Large Intestine:
    • Absorbs water and vitamins into the bloodstream.
    • Passes undigested material to the rectum.
  • Rectum:
    • Stores feces.
  • Epithelial Tissue:
    • Lines the digestive tract.
    • Creates mucus: Protects digestive tube and allows material to pass smoothly.
  • Steps of Digestion:
    • Begins in the mouth with mechanical and chemical breakdown.
    • Passes through the esophagus to the stomach.
    • Smooth muscle mixes food with enzymes and acids in the stomach.
  • Accessory Organs:
    • Liver, gallbladder, and pancreas.
    • Aid in digestion by supplying enzymes and other fluids.
  • Liver:
    • Produces bile to help break down fat.
  • Pancreas:
    • Produces insulin to regulate blood glucose.
    • Secretes enzymes to break down food.
  • Gallbladder:
    • Stores bile.

How Plants Eat

  • Plants are autotrophs and make their own food through photosynthesis.
  • Carbon dioxide + water = glucose + oxygen
  • Leaves perform photosynthesis.
  • Process:
    • Guard cells open to allow carbon dioxide in the leaf.
    • Xylem brings water to the leaf.
    • Chloroplasts in mesophyll cells use carbon dioxide and water to make sugar and oxygen.
    • Phloem transports sugar to other plant parts.

Respiratory System

  • Provides oxygen to cells and removes carbon dioxide.
  • Works with the circulatory system.
  • Organs: nose, mouth, trachea, bronchi, and lungs.
  • Pathway of Air:
    • Air enters through the mouth and nose.
    • Travels through the trachea to the lungs.
    • Trachea separates into bronchi.
    • Cilia filter out foreign materials e.g dust.
  • Gas Exchange:
    • Inhaling: brings oxygen into the lungs.
    • Exhaling: allows carbon dioxide to leave the body.
    • Gas exchange occurs in alveoli, which are surrounded by capillary networks.
    • Oxygen diffuses from the lungs to the blood and then to the cells.
    • Carbon dioxide leaves the cells and enters the blood, then the lungs.
  • Breathing:
    • Inhaling: Rib cage expands, diaphragm contracts.
    • Exhaling: Rib cage contracts, diaphragm relaxes.
  • Diseases:
    • TB (Tuberculosis): Bacterial infection in the lungs.
      *Symptoms include fever, cough, weight loss, tiredness, and chest pain.
    • Cancer: Caused by carcinogens in tobacco smoke.
    • Coronavirus: Viral infection with flu-like symptoms.

Respiration in Plants

  • Pores in stems allow diffusion of CO2 and O2.
  • Pores are stomata in herbaceous stems.

Circulatory System

  • Transports oxygen and nutrients and carries away waste.
  • Consists of blood, the heart, and blood vessels.
  • Blood:
    • Components: water (92%), dissolved protein (8%), glucose, amino acids, vitamins, minerals (mainly NaCl), urea, CO_2, hormones, antibodies.
    • Red blood cells: Transport oxygen (hemoglobin).
    • White blood cells: Destroy bacteria and viruses (contain a nucleus).
    • Platelets: Help clot blood.
    • Plasma: Carries blood cells.
  • The Heart:
    • Made of cardiac muscle tissue, epithelial tissue, nerve tissue, and connective tissue.
    • Contracts to move blood.
    • Factors affecting heart rate: stress, temperature, general health.
  • Blood Flow:
    • Veins carry deoxygenated blood to the right atrium.
    • Right ventricle pumps blood to the lungs for oxygenation.
    • Oxygenated blood returns to the left atrium.
    • Left ventricle pumps oxygenated blood to the body.
  • Blood Vessels:
    • Arteries: Carry blood away from the heart (thick).
    • Veins: Carry blood toward the heart (not as thick).
    • Capillaries: Connect arteries and veins; allow diffusion of oxygen and nutrients.
  • Coronary Artery Disease:
    • Plaque buildup (fat, cholesterol, calcium) in coronary arteries.
    • Caused by genetics or lifestyle choices (high-fat diet, smoking, lack of exercise).
  • Heart Attack:
    • Coronary arteries become completely blocked, stopping the heart.

Cancer

  • Cell division gone wrong due to changes in DNA.
  • Checkpoints in the Cell Cycle:
    • Controlled by proteins that monitor cell activities and surroundings.
    • If not enough nutrients to provide for cell growth, no division can occur.
    • If signals from surrounding cells tell the cell not to divide, it remains in interphase
    • If there is too much damage to the DNA, the cell is usually destroyed.
  • Cancer:
    • Uncontrolled cell division due to changes in DNA that controls the cell cycle.
    • Cells divide uncontrollably, forming tumors.
  • Tumors:
    • Mass of cells that grow and divide without any function.
    • Benign tumors: Stay together and don't affect surrounding tissue.
    • Malignant tumors: Interfere with the function of neighboring cells and tissues (cancerous).
  • Metastasis:
    • Cancer cells break away from the primary tumor and form secondary tumors elsewhere.
  • Causes of Cancer:
    • Random changes (mutations) in DNA.
    • Carcinogens: Environmental factors that cause cancers (chemicals in tobacco, radiation, toxins, poor diet, viruses).
    • Heredity: Genetic link that increases the likelihood of developing cancer.
  • Cancer prevention : Cancer prevention and increase chances of survival.
    • Giving up smoking
    • Never starting in the first place.
    • Staying away from second-hand smoke.
  • Cancer Screening:
    • Breast Cancer: regular self-examination
    • Cervical Cancer: regular pap smears
    • Colon Cancer—colonoscopy
    • Testicular Cancer—testicular self exam
    • Prostate Cancer—blood test
    • Skin Cancer: check moles for "ABCD."
      • Asymmetry: one half of the mole doesn't match the other
      • Border irregularity
      • Color that is not uniform
      • Diameter greater than 6 mm (about the size of a pencil eraser)
  • Diagnosing Cancer:
    • Imaging Technology.
      • Endoscopy: camera, cable sent into the body to look at tissue and remove tissue samples.
      • X-ray: to view bones/lungs.
      • Mammogram: to view breast tissue.
      • Ultrasound: sound waves create a digital image.
  • Cancer Treatments:
    • Surgery: Removal of cancerous tissue.
    • Chemotherapy: Drugs to slow/stop cancer division.
    • Radiation: High-energy radiation to shrink tumors and kill cancer cells.
    • Biophotonics: Light energy to diagnose and treat cancer cells.

Hierarchy of Structure in Animals

  • Organ Systems within Animals.
    • Nervous System.
    • Respiratory System.
    • Circulatory System.
    • Integumentary System (skin).
    • Digestive System.
    • Endocrine System.
    • Reproductive System.
    • Immune System.
    • Excretory System.
    • Skeletal system.
    • Muscular System.

Microscopes

  • Specimen Size = Diagram Size / Magnification
  • Micrometers (\mum) = Multiply by 10,000