Biology S2

• Cell Size and Diffusion

Cell Theory

1. All living organisms are composed of one or more cells.

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

3. All cells come from pre-existing cells.

4. The activity of an entire organism depends on the total activity of its independent cells.

Organelles:

• The cell is the basic unit of life, but is made up of many different parts called organelles. Organelles are specialized cells that perform specific functions.

Cell Membrane:

• Cell membrane separates the cell contents from its external environment and allows for selective transport of materials in and out of the cell.

• Structure:

  • Two layers of phospholipids with proteins and carbohydrates embedded.

Nucleus:

• Contains the genetic material that controls the activities of the cell. Where DNA replication and transcription occurs.

• Structure:

  • Double-layered nuclear membrane containing nucleoplasm, DNA, and a small lump called the nucleolus.

Nucleolus:

• Site of ribosome production and storage site for RNA.

Centrioles:

• During cell division, they move apart to opposite poles of the cell and each forms a daughter centriole.

• Spindle fibers form between the pairs and serve to sort and separate the chromosomes during cell division (mitosis).

Ribosomes:

• Location of protein synthesis

• Translates genetic code into a specific string of amino acids which grow into long chains to form proteins.

Endoplasmic Reticulum (ER)

• Network of membranes

• Found throughout the cell and connected to the nuclear envelope.

• 2 types of endoplasmic reticulum:

  • Rough ER - with ribosomes

  • Smooth ER - without ribosomes

• Forms canals that transport materials throughout the cell.

Golgi Bodies:

1. Takes products from the endoplasmic reticulum

2. Gathers and packages the chemicals into vesicles

3. Modifies, sorts, and distributes substances throughout the cell

Mitochondria:

• Powerhouse of the cell

  • Produces ATP (adenosine triphosphate), which is the major energy compound used for all cellular activities

  • Takes energies from food molecules to make ATP

  • Carbon dioxide is produced in this process

Cytoplasm:

• Contains cell contents and is a transport medium for substances within the cell.

• Structure:

  • Clear gel-like fluid that fills the cell

  • Contains organelles, enzymes, nutrients, waste products, cytoskeleton.

Flagella and Cilia:

• Hair-like structures that use a wave-like motion to move  the entire cell

Vacuole:

• Storage of food, waste, and other materials.

Lysosomes:

• Food vacuoles merge with lysosomes to digest food particles

  • Lysosomes can destroy invading bacteria that enter the cell

  • Lysosomes break down and release their digestive enzymes into cytoplasm, breaking down the entire cell when it gets old and starts to malfunction

Cell Wall:

• Provides structural support

• Encloses plant cells and allows the exchange of material and communication with the environment

• Allows for the development of turgor pressure

• Structure:

  • Composed of small fibers of cellulose

Chloroplasts:

• Chlorophyll in the chloroplasts traps energy from the sun and uses the energy to produce glucose (sugar)

• Contains its own DNA and ribosomes, and they undergo cell division

Animal cell:

Plant Cell:

Cell Size and Diffusion

The Cell Cycle

• Series of events cells go through as they grow and divide

• Cell grows, prepares for division, then divides to form 2 daughter cells, each of which then begins the cycle again.

Cell Cycle Checkpoints - Special proteins monitor cell activities and cells surrounding. A cell should remain in Interphase and not divide if:

1. Cell lack nutrients

2. DNA within nucleus not replicated

3. DNA is damaged

Mitosis: Division of the nucleus into 2 nuclei, each with the same number of chromosomes; Occurs in all of the somatic (body) cells.

• Why does mitosis occur? 

  • So, each new daughter cell has a nucleus with a complete set of chromosomes

Interphase:

• Period of cell growth and development

• DNA replication occurs during Interphase

• During Interphase the cell also grows, carries out normal cell activities, replicates all other organelles

• The cell spends most of its life cycle in Interphase

• G0-phase:

  • Resting phase for cells

• G1-phase:

  • Cell grows physically, copies organelles, and makes the molecular building blocks needed for later on. Proactively synthesizing proteins and performing its normal functions

• S-phase:

  • Cell replicates DNA, each chromosome duplicates into 2 sister chromatids

• G2-phase:

  • Cell continues to grow and prepares for mitosis, synthesizing proteins and organelles needed for the division process

4 phases of nuclear division (mitosis), directed by the cell’s DNA (P-M-A-T)

1. Prophase

2. Metaphase, Middle formation

3. Anaphase, Apart

4. Telophase, Two

(1) Prophase:

• Chromosomes coil up

• Nuclear envelope disappears

• Spindle fibers form

(2) Metaphase:

• Chromosomes line up in middle of cell

• Spindle fibers connect to chromosomes

(3) Anaphase:

• Chromosome copies divide

• Spindle fibers pull chromosomes to opposite poles

(4) Telophase/Cytokinesis:

• Chromosomes uncoil

• Nuclear envelopes form

• 2 new nuclei are formed

• Spindle fibers disappear

• Nucleus divides

  • In animal cells the cytoplasm pinches in

  • In plant cells a cell plate forms

*After mitosis and cytokinesis, the cell returns to Interphase to continue to grow and perform regular cell activities.

Cell division - process by which a cell divides into 2 new cells

• Why?

1. Living things grow by producing more cells, NOT because each cell increases in size

2. Repair of damaged tissue

3. If cell gets too big, it cannot get enough nutrients into the cell and wastes out of cell

• The original cell is called the parent cell; the 2 new cells are called daughter cells

• Each daughter cell is exactly like the parent cell – same kind and number of chromosomes as the original cell

• Types:

  • Asexual

    • Unicellular included organisms reproduce by means of asexual cell division, Ex: bateria

    • Involves only 1 parent

    • Exact genetic copies of the parent

  • Sexual

    • Multicellular organisms pass on their genetic information, some produce by asexual and some sexual reproduction

    • Involves genetic material from 2 parents, each pass along cells with “half” the DNA (known as gametes)

    • When 2 gametes combine, the offspring inherits characteristics from both parents

DNA

• DNA is found in the nucleus and controls all cell activities including cell division

• Long and thread-like DNA in a non-dividing cell is called chromatin

• Doubled, coiled, short DNA in a dividing cell is called chromosome

  • Chromatid and centromere

All somatic (body) cells in an organism have the same kind and number of chromosomes

• Examples:

  • Human = 46 chromosomes

  • Human skin cell = 46 chromosomes

  • Human heart cell = 46 chromosomes

  • Human muscle cell = 46 chromosomes

Plants

Plant cells have 2 extra organelles compared to animal cells

• Specialized Cells in your Body and Cancer

Specialized Cells in your Body

Unicellular organisms:

• Includes bacteria and protists, Ex: amoeba

• A single cellular organism performs all required functions in one cell.

• Benefits over multicellular organisms:

  • Need fewer resources

  • Can live in harsher conditions

Multicellular organisms:

• Made up of many more cells

• Much more complex

• The body needs to supply food and nutrients, transport materials, remove wastes and fight infection

• Cells in multicellular organisms are specialized to perform one task

• They work together to keep the organism healthy

Specialized Cells – cells that are designed and built to perform one

function very well. Have physical and chemical differences.

Humans have 50 – 75 trillion cells in your body

~ 220 Specialized cells have been identified

Each cell has a specific job.

Cells have specific shapes and structures that relate to their

function – look differently internally and externally 

I.e. Red Blood Cells

- function is to carry oxygen and other cells.

- shape is small and smooth

- allows it move through small blood vessels

- also shaped like a flat disc – allows surface area for carrying oxygen

All body cells come from one zygote that divides by mitosis.

As the embryo grows, its cells change in form and function through cellular differentiation, guided by DNA.

Stem cells:

• Cells that can differentiate into many different cell types.

• The daughter cells have the same DNA, but different genes may be turned on or off.

• Embryonic Stem Cells

  • Differentiates into any cell type.

• Adult Stem Cells

  • Found in certain tissues, they can become only specific cell types (e.g., bone marrow stem cells make blood cells).

  • They may help treat conditions like broken bones, type 1 diabetes, and heart damage after a heart attack.

Orders of cells to organism:

1. Cell

2. Tissue

3. Organ

4. System

5. Organism

4 types of tissues:

1. Epithelial - skin, for protection

2. Muscular - proteins, enable movements

3. Connective - storage and transport of materials

4. Nervous - neurons, coordinates body actions and sensory

Cancer

Cell Death

• Necrosis:

  • Cells may die due to external factors, ex: toxins, infections, trauma

• Apoptosis:

  • The controlled death of old cells, ex: white blood cells when they’re no longer required

Cancer is when genetic mutations can cause cells to mutate and undergo abnormal cell division, instead of undergoing apoptosis, these cells divide uncontrollably.

Cancer cell cycle:

• Results in change in DNA that controls the cell cycle

• Prevents the cells from staying in Interphase

• One or more of the checkpoints fails – so cell and subsequent daughter cells continue to divide uncontrollably

• A cancer cell can continue to divide without limit, compared to a normal healthy cell which has an upper limit of 50 - 60 divisions. Cell division occurs so fast that cells pile up on top of one another, forming a tumor. This reduces the effectiveness of the surrounding tissue.

Tumor Types:

Benign: non-cancerous tumors

• Well defined boundaries (don’t spread)

• Grow at relatively slow pace

• Limited growth

Malignant: cancerous tumors

• Faster growing - can be fatal

• Irregular boundaries

• Invading the surrounding tissue

Metastasis: primary tumor sheds cells that travel through the bloodstream and lymphatic system.

• Starts new tumor growth at other locations around the body

Appearance of Cancer:

• Organ systems

Hierarchy of Structures

Respiratory System

Respiratory System – Study Notes

Primary Functions

1. Gas exchange (O₂ in, CO₂ out)
   
   

2. Vocal sound production
   
   

3. Sense of smell
   
   

4. Regulate blood pH
   
   

Types of Respiration

• External Respiration:
  Gas exchange between air in lungs and blood
  
  

• Internal Respiration:
  Gas exchange between blood and body tissues
  
  

• Cellular Respiration:
  Cells use O₂ to make ATP (energy)
  
  
  

  • Occurs in: Mitochondria
    
    

Cystic Fibrosis (CF)

• Affects both external and internal respiration
  
  

• Problem: CFTR protein is faulty → thick mucus builds up → restricted airflow
  
  

• FEV1: Measures lung function decline in CF over time
  
  

Organs of the Respiratory System

Upper Respiratory Tract:

• Nose, sinuses, pharynx
  
  

Lower Respiratory Tract:

• Larynx, trachea, bronchial tubes, lungs
  
  

Structures and Functions

• Nasal Conchae:
  Increases surface area in nasal cavity
  
  

• Mucus Membrane:
  Warms/moistens air, traps dust
  
  

• Paranasal Sinuses:
  Lighten skull, enhance voice resonance
  
  
  

  • Named after bones: Maxillary, Frontal, Ethmoid, Sphenoid
    
    

• Pharynx:
  Behind oral cavity; 3 sections
  
  

• Epiglottis:
  Prevents food from entering airway during swallowing
  
  

• Heimlich Maneuver:
  Emergency action to clear airway when choking
  
  

• Larynx:
  Top of trachea; made of cartilage and muscles
  
  
  

  • Glottis: Contains vocal cords
    
    
    

    • True vocal folds: Produce sound
      
      

    • False folds: Close airway during swallowing
      
      

  • Laryngitis: Inflammation = hoarse voice
    
    

  • Otolaryngologist: ENT doctor
    
    

Air Pathway

Trachea → Primary Bronchi → Secondary Bronchi → Tertiary Bronchi → Bronchioles → Alveoli

• Alveoli:
  Tiny air sacs for gas exchange
  
  
  

  • Surrounded by capillaries (blood vessels)
    
    

  • In CF: mucus blocks airflow to alveoli
    
    

Lungs

• In Pleural cavity, covered in serous fluid
  
  

• Right Lung = 3 lobes
  
  

• Left Lung = 2 lobes (+ Cardiac Notch for heart)
  
  

Breathing Mechanism

1. Diaphragm contracts (moves down) – air enters lungs
   
   

2. Intercostals contract – chest cavity expands
   
   

3. Surfactant & surface tension keep alveoli open
   
   

4. Other muscles = deeper breath
   
   

5. Diaphragm relaxes – Elastic recoil (exhalation)
   
   

• Newborn’s first breath is hardest due to low surfactant
  
  

Respiratory Cycle

• 1 inhale + 1 exhale
  
  

• Lowering diaphragm = inspiration
  
  

Respiratory Volumes (Measured by Spirometry)

• Resting Tidal Volume: Normal breath
  
  

• Vital Capacity: Max air in/out (deep breath)
  
  

• FEV1: Volume exhaled in 1 sec – used in CF monitoring
  
  

Factors Affecting Breathing

• Increased CO₂
  
  

• Emotions (fear, pain, stress)
  
  

• Hyperventilation: Fast breathing → lowers CO₂
  
  

Gas Exchange

• Happens through simple squamous epithelium
  
  

• O₂ diffuses into blood
  
  

Conditions

• Hypoxia: Low oxygen in tissues
  
  

• Asphyxia: Blocked breathing → causes hypoxia
  
  

Circulatory System

🫀 Circulatory System – Study Notes

Key Vocabulary

• Artery, Vein, Capillary, Heart, Atrium, Ventricle
  
  

• Pulmonary artery/vein, Heart valves, Red/White blood cells
  
  

• Platelet, Urea, Blood vessel, Circulatory system
  
  

Why Do We Need Blood?

• Delivers oxygen and nutrients
  
  

• Removes waste (e.g., CO₂, urea)
  
  

• Fights infection
  
  

• Regulates body temperature
  
  

Heart Basics

• Organ that pumps blood throughout the body
  
  

• 4 chambers:
  
  
  

  • Right atrium → Right ventricle
    
    

  • Left atrium → Left ventricle
    
    

• Heart valves prevent backflow
  
  
  

  • “Lub” = atrioventricular valves close
    
    

  • “Dub” = semilunar valves close
    
    

• Anatomical position explains diagram layout (left/right reversed for the observer)
  
  

Blood Flow Through the Heart

1. Right atrium
   
   

2. Right ventricle → Lungs (via pulmonary artery)
   
   

3. Left atrium ← Lungs (via pulmonary vein)
   
   

4. Left ventricle → Body (via aorta)
   
   

Gas Exchange

• Right ventricle blood (deoxygenated):
  
  
  

  • O₂: 36.1 mmHg
    
    

  • CO₂: 46.8 mmHg
    
    

• Left atrium blood (oxygenated):
  
  
  

  • O₂: 95.1 mmHg
    
    

  • CO₂: 38.7 mmHg
    
    

• Lungs add oxygen, remove CO₂
  
  

Blood Vessels

• Arteries: Carry oxygen-rich blood away from heart
  
  

• Veins: Carry oxygen-poor blood to heart
  
  

• Capillaries: Exchange O₂/CO₂ with body cells
  
  

Pulmonary Circulation

• Pulmonary arteries: Carry deoxygenated blood → lungs
  
  

• Pulmonary veins: Carry oxygenated blood ← lungs
  (Opposite of normal arteries/veins)
  
  

Circulatory System Analogy

Like a road system:

• Arteries/veins = roads
  
  

• Blood = cars delivering goods (oxygen, nutrients) and picking up waste
  
  

What’s in Your Blood?

• Red blood cells – carry oxygen
  
  

• White blood cells – fight infection
  
  

• Platelets – help clotting
  
  

• Plasma – carries dissolved substances
  
  

Substance Entry & Exit Points

• Sugar enters: Liver
  
  
  

  • Highest concentration there
    
    

• Sugar removed: Kidneys
  
  
  

  • Lowest concentration found there
    
    

• Urea enters: Liver
  
  

• Urea removed: Kidneys
  
  

Digestive System

Study Notes: Digestive System - Gizmo Exploration

Key Vocabulary

• Digestion: Breaking down food into nutrients.
  
  

• Absorption: Nutrients entering the bloodstream.
  
  

• Elimination: Removal of waste.
  
  

• Mechanical digestion: Physical breakdown (e.g., chewing, churning).
  
  

• Chemical digestion: Breakdown via enzymes and acids.
  
  

• Peristalsis: Muscle contractions that push food through the system.
  
  

• Nutrients: Carbs, proteins, fats, vitamins, water, minerals.
  
  

• Enzymes: Proteins that speed up digestion (e.g., amylase, pepsin, lipase).
  
  

• Bile: Emulsifies fats, produced by the liver and stored in gallbladder.
  
  

• Villus: Small intestine structures that absorb nutrients.
  
  

Digestive System Functions

• Why eat? Provides energy and nutrients for body functions.
  
  

• Breakdown Process: Mouth (mechanical) → Stomach (chemical/mechanical) → Small Intestine (enzymatic + absorption) → Large Intestine (water absorption) → Elimination (rectum/anus).
  
  

• Main Digestive Organs:
  
  
  

  • Mouth & Stomach: Start mechanical and chemical digestion.
    
    

  • Small Intestine: Primary nutrient absorption.
    
    

  • Large Intestine: Absorbs water and some vitamins.
    
    

  • Pancreas: Secretes enzymes.
    
    

  • Liver/Gallbladder: Produces/stores bile for fat digestion.
    
    

  • Rectum: Waste compaction and elimination.
    
    

Activity C: Nutrient Absorption

• Capillaries: Absorb sugars, amino acids, water (especially in small intestine).
  
  

• Lymphatic Vessels: Absorb fatty acids (only effective in the small intestine).
  
  

• Large Intestine: Absorbs some water and a small amount of sugar (via fiber digestion).
  
  

• Efficient Absorption System Includes:
  
  
  

  • Capillaries in small & large intestine
    
    

  • Lymphatic vessels in small intestine
    
    

• Apple Challenge System: 71.5% Cal absorbed with 5 organs (mouth, salivary gland, jejunum/ileum, pancreas, capillaries)
  
  

• Poop Consistency: Less water absorbed = more liquid stool
  
  

Activity D: Human Digestive System Summary

• Why start with the mouth/stomach?
  
  
  

  • Prepares food physically/chemically for absorption.
    
    

  • Smaller pieces & chyme make nutrient extraction easier.
    
    

• Key Structure Matches:
  
  
  

  • Amylase: Breaks down starches
    
    

  • Pepsin: Protein digestion
    
    

  • Bile: Fat emulsifier
    
    

  • Peristalsis: Moves food
    
    

  • Capillaries & Lymph Vessels: Nutrient absorption
    
    

  • Parietal Cells: Secrete stomach acid
    
    

• Villus Function: Maximizes surface area for absorption
  
  

• Why Small Intestine is Long: Allows more time and surface area for nutrient absorption
  
  

Core Takeaways

• Digestion is a teamwork process between mechanical actions and chemical reactions.
  
  

• Absorption depends on having the right structures (villi, capillaries, lymph vessels) in the right locations.
  
  

• Efficient systems mimic human anatomy: mouth → stomach → small intestine (duodenum, jejunum, ileum) → large intestine → anus.