Biology Ultimate Review

Plant and Animal Cells

Cell Theory

  • 1. All living things are composed of one or more cells.

  • 2. Cells are the basic units of structure and function in living organisms.

  • 3. All cells arise from pre-existing cells.

Cell Types

Prokaryotic Cells:

  • Lack a nucleus and membrane-bound organelles.

  • Genetic material floats in the cytoplasm.

  • Example: Bacteria.

Eukaryotic Cells:

  • Contain a nucleus and organelles enclosed by membranes.

  • Example: Plant and animal cells.

Cell Structures and Their Functions

  1. Nucleus:

    • Contains genetic material (DNA) organized into chromosomes.

    • Controls all cell activities and functions.

  2. Cytoplasm:

    • Jelly-like substance in which organelles are suspended.

    • Composed mostly of water but also stores nutrients and waste.

  3. Cell Membrane:

    • Flexible double-layered structure surrounding the cell.

    • Semi-permeable: Allows certain substances to pass in and out while blocking others.

  4. Mitochondria:

    • The "power plants" of the cell; convert glucose and oxygen into usable energy (ATP).

    • Equation: Glucose + Oxygen → Carbon Dioxide + Water + Energy.

    • Active cells (e.g., muscle cells) have more mitochondria than less active cells (e.g., fat-storage cells).

  5. Endoplasmic Reticulum (ER):

    • Network of branching tubes and pockets connected to the nuclear membrane.

    • Rough ER: Studded with ribosomes; synthesizes proteins.

    • Smooth ER: Produces lipids; involved in detoxification.

  6. Golgi Apparatus:

    • Collects, processes, and packages materials to be transported or excreted.

    • Produces mucus (abundant in cells lining the intestines).

  7. Vacuoles:

    • Plants: One large vacuole that maintains internal pressure (turgor) and stores substances.

    • Animals: Many small vacuoles that store nutrients and waste.

  8. Chloroplasts (Plant Cells Only):

    • Contain chlorophyll for photosynthesis.

    • Equation: Carbon Dioxide + Water + Sunlight → Glucose + Oxygen.

  9. Cell Wall (Plant Cells Only):

    • Rigid, porous structure made of cellulose.

    • Provides support and protection from physical injury.

Key Differences Between Plant and Animal Cells

Feature

Plant Cells

Animal Cells

Outer Layer

Cell wall + cell membrane

Cell membrane only

Chloroplasts

Present (photosynthesis)

Absent

Vacuoles

One large central vacuole

Many small vacuoles

Shape

Rigid, rectangular

Flexible, rounded

The Importance of Cell Division

Why is Cell Division Important?

  1. Reproduction:

    • Asexual Reproduction:

      • Offspring arise from a single parent.

      • Genetically identical to the parent.

      • Examples: Bacteria, houseleek plants.

    • Sexual Reproduction:

      • Involves fusion of two gametes from different parents.

      • Produces genetically diverse offspring.

      • Examples: Humans, horses.

  2. Growth:

    • Multicellular organisms grow by increasing the number of cells.

    • Old cells die and are replaced by new ones.

  3. Repair:

    • Essential for healing injuries and replacing dead cells.

    • Example: Skin cells regenerate daily; red blood cells are replaced every 120 days.

Mechanisms of Material Transport

  • Diffusion:

    • Movement of substances from areas of higher concentration to lower concentration.

    • Passive; does not require energy.

  • Osmosis:

    • Movement of water across a semi-permeable membrane toward an area with higher solute concentration.

  • Limiting Factors:

    • The efficiency of diffusion and osmosis decreases as the cell size increases, necessitating division.

The Cell Cycle Overview

  • The cell cycle consists of three main stages:

  1. Interphase:

    • The cell performs normal functions and prepares for division.

    • DNA replication occurs.

    • Sub-phases:

      • G1: Growth phase; preparation for DNA synthesis.

      • S (Synthesis): DNA replication.

      • G2: Preparation for mitosis.

  2. Mitosis:

    • Division of the nucleus.

    • Produces two genetically identical nuclei.

  3. Cytokinesis:

    • Division of the cytoplasm to form two distinct daughter cells.

Mitosis Stages

  1. Prophase:

    • Chromatin condenses into visible chromosomes.

    • Nuclear membrane dissolves.

    • Spindle fibers form.

  2. Metaphase:

    • Chromosomes align in the middle of the cell (equatorial plate).

    • Spindle fibers attach to centromeres.

  3. Anaphase:

    • Sister chromatids separate and move to opposite poles.

    • Now referred to as daughter chromosomes.

  4. Telophase:

    • Chromosomes decondense into chromatin.

    • Nuclear membranes reform around the two sets of chromosomes.

Cytokinesis

  • Animal Cells: A cleavage furrow forms, pinching the cell in two.

  • Plant Cells: A cell plate forms, eventually developing into a new cell wall.

Checkpoints in the Cell Cycle

  • Purpose: Ensure proper division and prevent errors.

  • Key Checks:

    • DNA is fully replicated.

    • DNA is undamaged.

    • There are sufficient nutrients for division.

Cancer: Uncontrolled Cell Division

What is Cancer?

  • Definition: A group of diseases resulting from uncontrolled cell division.

  • Cause: Failure of cell cycle checkpoints.

  • Impact: Unchecked growth leads to tumor formation and potential spread (metastasis).

Tumors

  1. Benign Tumors:

    • Non-cancerous.

    • Do not invade surrounding tissues.

    • Can still cause issues by physically crowding nearby organs.

  2. Malignant Tumors:

    • Cancerous and harmful.

    • Invade surrounding tissues, disrupting their function.

Metastasis

  • Cancer cells break away from the primary tumor.

  • Travel through the bloodstream or lymphatic system.

  • Establish secondary tumors in other parts of the body.

Causes of Cancer

  1. Genetic Factors:

    • Family history of cancer increases susceptibility.

    • Examples: BRCA gene mutations in breast cancer.

  2. Environmental Factors (Carcinogens):

    • Smoking: Leads to lung, throat, and mouth cancer.

    • UV Radiation: Causes skin cancer by damaging DNA.

    • Viruses: HPV can lead to cervical cancer.

  3. Random Mutations:

    • Errors during DNA replication.

Cancer Detection and Screening

  • Self-Examinations:

    • Check for abnormal growths or lumps (e.g., breast or testicular exams).

  • Diagnostic Tools:

    • Imaging: X-rays, CT scans, MRIs.

    • Biopsies: Sampling of tumor tissue for examination.

    • Blood Tests: Detect specific markers (e.g., PSA for prostate cancer).

  • Pap Test: Detects abnormal cervical cells (early sign of cervical cancer).

Cancer Treatments

  1. Surgery:

    • Physical removal of tumors.

    • Effective if cancer is localized.

  2. Chemotherapy:

    • Drugs target rapidly dividing cells.

    • Side effects: Hair loss, nausea, fatigue.

  3. Radiation Therapy:

    • Uses ionizing radiation to damage DNA in cancer cells.

    • Kills rapidly dividing cells.

  4. Biophotonics:

    • Light-based technology to diagnose and treat cancer.

    • Fewer side effects due to precise targeting.

Prevention and Risk Reduction

  • Lifestyle Changes:

    • Quit smoking.

    • Use sunscreen to block UV radiation.

    • Maintain a healthy diet rich in fruits, vegetables, and low-fat protein.

  • Early Detection:

    • Routine screenings for high-risk individuals.

Specialized Cells

What Are Specialized Cells?

  • Specialized cells perform specific functions.

  • Differ in structure and chemical composition to optimize their roles.

Examples of Specialized Animal Cells

  1. Red Blood Cells (RBCs):

    • Contain hemoglobin to transport oxygen.

    • Biconcave shape increases surface area for gas exchange.

  2. White Blood Cells (WBCs):

    • Defend against pathogens.

    • Can engulf bacteria (phagocytosis) or destroy infected cells.

  3. Nerve Cells (Neurons):

    • Transmit electrical signals across the body.

    • Long axons and dendrites facilitate communication between cells.

  4. Muscle Cells:

    • Contain actin and myosin for contraction.

    • Work in antagonistic pairs (e.g., biceps and triceps).

  5. Sperm Cells:

    • Motile cells carrying male DNA for fertilization.

    • Tail structure (flagellum) enables swimming.

  6. Fat Cells:

    • Store energy in the form of lipids.

Examples of Specialized Plant Cells

  1. Xylem Cells:

    • Transport water and dissolved minerals.

    • Hollow and dead at maturity; reinforced with lignin for strength.

  2. Phloem Cells:

    • Transport sugars produced in photosynthesis.

    • Composed of sieve-tube elements and companion cells.

  3. Photosynthetic Cells:

    • Contain chloroplasts to capture sunlight.

    • Found in leaves and other green parts of the plant.

  4. Guard Cells:

    • Regulate the opening and closing of stomata.

    • Control water loss and gas exchange.

The Respiratory System

Components

  1. Air Pathway:

    • Nose/mouth → Pharynx → Larynx → Trachea → Bronchi → Lungs → Alveoli.

  2. Lungs:

    • Contain millions of alveoli (tiny air sacs).

    • Alveoli are surrounded by capillaries for efficient gas exchange.

  3. Diaphragm:

    • Dome-shaped muscle under the lungs.

    • Contracts during inhalation (expanding lungs) and relaxes during exhalation.

Gas Exchange Process

  • Inhalation:

    • Air enters alveoli; oxygen diffuses into capillaries.

    • Oxygen binds to hemoglobin in red blood cells.

  • Exhalation:

    • Carbon dioxide (produced by cellular respiration) diffuses from blood into alveoli and is expelled.

Respiratory Disorders

  1. Tuberculosis (TB):

    • Bacterial infection affecting lungs.

    • Symptoms: Persistent cough, fever, chest pain.

    • Diagnosed using chest X-rays.

  2. SARS (Severe Acute Respiratory Syndrome):

    • Viral infection causing respiratory distress.

    • Symptoms: Fever, shortness of breath, dry cough.

    • Highly contagious; caused global outbreaks.

The Circulatory System

Components

  1. Heart:

    • Four chambers: Two atria (receive blood) and two ventricles (pump blood).

    • Made of cardiac muscle tissue that contracts rhythmically.

  2. Blood Vessels:

    • Arteries: Thick walls; carry oxygen-rich blood away from the heart.

    • Veins: Thinner walls; carry deoxygenated blood to the heart.

    • Capillaries: Thin-walled vessels; facilitate exchange of gases, nutrients, and waste.

  3. Blood:

    • Red Blood Cells: Transport oxygen.

    • White Blood Cells: Fight infections.

    • Platelets: Aid in blood clotting.

    • Plasma: Liquid portion; carries nutrients, hormones, and waste.

Key Circulatory Processes

  • Oxygen Transport:

    • Oxygenated blood flows from lungs to heart and is pumped to body tissues.

  • Waste Removal:

    • Deoxygenated blood returns to the heart and is sent to the lungs to expel CO2.

Circulatory Diseases

  1. Coronary Artery Disease (CAD):

    • Caused by plaque buildup in arteries.

    • Symptoms: Chest pain, shortness of breath.

    • Diagnosed using angiograms.

  2. Heart Attack:

    • Occurs when blood flow to the heart muscle is blocked.

    • Symptoms: Severe chest pain, nausea, sweating.

The Musculoskeletal System

What is the Musculoskeletal System?

  • Composed of bones and skeletal muscles.

  • Provides structural support, protects vital organs, and enables movement.

Components

  1. Bones:

    • Hard, dense tissue containing bone cells within a matrix of calcium, phosphorus, and collagen fibers.

    • Functions:

      • Structural support.

      • Protection (e.g., skull protects the brain).

      • Storage of minerals like calcium.

    • Internal canals carry nerves and blood vessels.

  2. Cartilage:

    • Dense, flexible connective tissue.

    • Found in joints, nose, ears, and between vertebrae.

    • Reduces friction and acts as a cushion in joints.

  3. Ligaments:

    • Tough, elastic tissue connecting bones at joints.

    • Provide stability during movement.

  4. Tendons:

    • Connect muscles to bones.

    • Less elastic than ligaments; transfer force from muscle contraction to bones.

  5. Skeletal Muscle:

    • Bundles of long cells (muscle fibers) containing proteins that contract.

    • Work in opposing pairs:

      • Flexor: Contracts to bend a joint.

      • Extensor: Contracts to straighten a joint.

How Bones and Muscles Work Together

  • Muscles contract to pull on bones via tendons.

  • Movements are enabled by joints:

    • Ball-and-Socket Joints: Shoulder, hip (wide range of motion).

    • Hinge Joints: Elbow, knee (movement in one plane).

Disorders of the Musculoskeletal System

  1. Osteoporosis:

    • Loss of bone density, leading to brittle bones.

    • Common in older adults, especially women.

    • Prevented by calcium and vitamin D intake, weight-bearing exercise.

  2. Arthritis:

    • Inflammation of joints causing pain and stiffness.

    • Types:

      • Osteoarthritis: Wear-and-tear damage.

      • Rheumatoid arthritis: Autoimmune condition.

The Nervous System

What is the Nervous System?

  • Detects stimuli, processes information, and coordinates responses.

  • Composed of the Central Nervous System (CNS) and Peripheral Nervous System (PNS).

Components

  1. Central Nervous System (CNS):

    • Brain: Processes and interprets sensory information.

      • Divided into regions: Cerebrum, cerebellum, brainstem.

    • Spinal Cord: Transmits signals between the brain and the rest of the body.

      • Protected by the skull, vertebrae, and cerebrospinal fluid (cushions and removes waste).

  2. Peripheral Nervous System (PNS):

    • Nerves connecting the CNS to the body.

    • Divided into:

      • Sensory Nerves: Carry information to the CNS.

      • Motor Nerves: Send signals from the CNS to muscles and glands.

Nerve Tissue

  • Made of neurons (nerve cells).

  • Each neuron transmits electrical signals in one direction:

    • Dendrites: Receive signals.

    • Axon: Sends signals to other neurons or muscles.

  • Bundles of neurons form nerves.

Sensory Receptors

  • Specialized cells that detect stimuli:

    • Eyes: (light), Ears: (sound), Skin: (pressure, temperature, pain).

    • Relay signals to the CNS for processing.

Diseases and Disorders

  1. Multiple Sclerosis (MS):

    • Autoimmune disorder where the immune system damages the myelin sheath covering neurons.

    • Symptoms: Muscle weakness, vision problems, loss of coordination.

  2. Spinal Cord Injury:

    • Damage to the spinal cord disrupts signal transmission, often resulting in paralysis.

Organ Transplantation

What is Organ Transplantation?

  • Surgical procedure where an organ or tissue is replaced to restore function.

Transplantable Organs and Tissues

  1. Organs: Heart, lungs, liver, kidneys, pancreas, intestines.

  2. Tissues: Corneas, skin, bone, bone marrow, tendons, blood vessels.

Types of Donations

  1. Living Donor:

    • Donors can give one kidney, a lobe of a lung, or part of their liver.

    • The liver can regenerate itself, allowing partial donation.

  2. Deceased Donor:

    • Most organs come from deceased donors.

    • Consent for donation is typically provided in advance via a donor card.

Xenotransplantation

  • Transplanting animal organs into humans.

  • Example: Pig heart valves used in humans.

  • Controversial due to ethical and immune rejection concerns.

Risks of Organ Transplantation

  • Rejection: Recipient’s immune system may attack the transplanted organ.

  • Managed with immunosuppressive drugs, which reduce immunity but increase infection risk.

Benefits

  • Restores organ function, significantly improving or saving lives.

  • Provides a chance for recipients to lead normal, healthy lives.

Interactions of Systems

Digestive + Circulatory Systems

  • The digestive system breaks down food into small molecules.

  • Nutrients are absorbed into the bloodstream via capillaries in the small intestine.

  • The circulatory system transports nutrients to all body tissues.

Circulatory + Respiratory Systems

  • Oxygen from the respiratory system diffuses into blood at the alveoli.

  • Carbon dioxide in the blood diffuses into alveoli for exhalation.

  • Blood carries oxygen to tissues and removes waste gases.

Circulatory + Musculoskeletal Systems

  • Muscles use oxygen and glucose delivered by blood to produce energy.

  • During muscle activity, the circulatory system removes waste like lactic acid and carbon dioxide.

Excretory + Circulatory Systems

  • Blood carries metabolic waste (e.g., urea) to the kidneys.

  • The kidneys filter waste from the blood and excrete it as urine.

System Interdependence

  • Each organ system depends on others to maintain homeostasis:

    • The nervous system coordinates functions.

    • The circulatory system ensures nutrient and oxygen delivery.

    • The digestive system provides energy for all bodily processes.