Ficha de revisão: Cells and Body Systems

📋 Course Outline

1. Microscope Types and Purposes
2. Microscope Parts and Use
3. Cell Theory and Organisation
4. Cell Structures and Cell Types
5. Unicellular and Specialised Cells
6. Digestive and Excretory Systems
7. Nervous and Endocrine Systems
8. Organ Replacement and Ethics

📖 1. Microscope Types and Purposes

🔑 Key Concepts & Definitions

• Microscope : A scientific instrument used to make very small objects appear much larger so that cells, microorganisms and tiny structures can be studied.

📝 Essential Points

📌 A compound light microscope uses multiple lenses and allowed scientists such as Robert Hooke to see cells, whereas an electron microscope uses electrons and provides much greater magnification for viruses and tiny cell structures.

💡 Memory Hook

Light microscopes use light, whereas electron microscopes use electrons.

📖 2. Microscope Parts and Use

📝 Essential Points

• The main parts of a light microscope are:

  • the eyepiece lens
  • the objective lens
  • the stage
  • the coarse focus knob
  • the fine focus knob
  • the arm
  • the base
  • the light source
  • the stage clips

• 🔄 To set up a microscope:

  1. carry it using the arm and base
  2. place it on a flat surface
  3. turn on the light source
  4. place the slide on the stage
  5. secure the slide with stage clips

• 🔄 To focus a microscope: begin with the lowest-power objective lens, use the coarse focus to bring the image into view, use the fine focus to sharpen it, centre the specimen, switch to higher power and use only the fine focus knob

📐 Formula — Total magnification is calculated by multiplying the eyepiece magnification by the objective-lens magnification: $M = M_e \times M_o$.

📌 As magnification increases, field of view decreases and the image becomes more detailed; as magnification decreases, field of view increases and more of the specimen is visible.

💡 Memory Hook

Carry, place, light, slide, secure; then focus from low to high power.

📖 3. Cell Theory and Organisation

🔑 Key Concepts & Definitions

• Cell : The basic building block and basic unit of life, and all living organisms are made of one or more cells.
• Unicellular organism : Consists of only one cell, which performs all the functions needed for life.

📝 Essential Points

• Cell theory states that: all living things are made of one or more cells, the cell is the basic unit of life, all cells come from pre-existing cells

• 🔄 In multicellular organisms, organisation increases from:

  1. cells
  2. tissues
  3. organs
  4. organ systems
  5. the complete organism

💡 Memory Hook

Cells → tissues → organs → organ systems → organism.

📖 4. Cell Structures and Cell Types

🔑 Key Concepts & Definitions

• Plasma membrane : Controls what enters and leaves the cell and is selectively permeable, allowing only certain molecules to pass.

📝 Essential Points

• The nucleus contains genetic material and controls cell activities, while ribosomes make proteins needed for cell growth and repair.

• Mitochondria release energy through respiration, and the endoplasmic reticulum transports materials and helps make proteins and lipids.

📌 Plant cells usually have a cell wall, chloroplasts and a large vacuole; animal cells lack cell walls and chloroplasts; fungal cells have a cell wall and vacuoles but no chloroplasts.

💡 Memory Hook

Plant cells have chloroplasts and a cell wall, animal cells have neither, and fungal cells have a wall but no chloroplasts.

📖 5. Unicellular and Specialised Cells

🔑 Key Concepts & Definitions

• Specialised cell : Adapted for a specific function through its shape, organelle number or unique structures.

📝 Essential Points

📌 Skeletal muscle is voluntary and moves the body, smooth muscle is involuntary and moves substances through organs, and cardiac muscle is involuntary, found only in the heart and rich in mitochondria.

• Mature red blood cells are flexible, disc-shaped, filled with haemoglobin and lack a nucleus to provide more space for oxygen-carrying haemoglobin.

• Root hair cells absorb water and minerals using a large surface area and thin cell wall, while guard cells open and close stomata by swelling and shrinking.

• Xylem cells transport water and minerals through hollow, thick-walled tubes, whereas phloem cells transport sugars through long tubes with sieve-like ends.

💡 Memory Hook

A unicellular organism performs every life function in one cell, whereas a multicellular organism divides functions among specialised cells.

📖 6. Digestive and Excretory Systems

🔑 Key Concepts & Definitions

• Homeostasis : The maintenance of a stable internal environment, including stable temperature, water levels, blood sugar, oxygen levels and pH.

📝 Essential Points

• 🔄 The digestive tract processes food in the order:
  1. mouth
  2. oesophagus
  3. stomach
  4. small intestine
  5. large intestine
  6. rectum

📌 Physical digestion breaks food into smaller pieces and increases surface area, whereas chemical digestion uses enzymes to break large food molecules into smaller molecules.

• Amylase breaks down starch, proteases break down proteins and lipases break down fats.

• The kidneys filter blood, remove wastes, control water and salt levels and produce urine; the bladder stores urine and the urethra carries it out of the body.

💡 Memory Hook

Mouth → oesophagus → stomach → liver → small intestine → large intestine → rectum.

📖 7. Nervous and Endocrine Systems

📝 Essential Points

📌 The central nervous system consists of the brain and spinal cord, whereas the peripheral nervous system consists of all nerves outside the central nervous system.

• A neuron has:
  • dendrites
  • a cell body
  • an axon
  • axon terminals

📌 Sensory neurons carry messages from receptors to the central nervous system, whereas motor neurons carry messages from the brain or spinal cord to muscles or glands.

• 🔄 Information generally travels through the nervous system from:
  1. stimulus
  2. receptor
  3. sensory neurone
  4. central nervous system
  5. motor neurone
  6. response

📌 The nervous system uses fast electrical impulses with short-term effects, whereas the endocrine system uses slower hormones with longer-lasting effects.

💡 Memory Hook

Nervous messages are electrical, fast and short-lived, whereas endocrine messages are hormonal, slower and longer-lasting.

📖 8. Organ Replacement and Ethics

🔑 Key Concepts & Definitions

• Organ transplant : A medical procedure in which a damaged organ is replaced with a healthy donor organ for a recipient.

📝 Essential Points

📌 Organ rejection occurs when the immune system recognises a transplanted organ as foreign and attacks it, so recipients often take immunosuppressant drugs that reduce immune responses but increase infection risk and can cause side effects.

• Dialysis filters blood and removes waste products and excess water when kidneys cannot function properly, but it does not fully replace kidney function.

📌 Natural organs are highly efficient, naturally controlled and able to self-repair to some extent, whereas artificial replacements may not perform every function and may break down or require surgery and maintenance.

• Ethical issues in organ transplantation include: organ shortages and allocation, donor consent, fair access to treatment, surgical risks and complications for living donors

💡 Memory Hook

Organ damage → replacement technology → improved function, but possible rejection, limitations and ethical concerns.

📊 Synthesis Tables

Cell Type Comparison

Feature	Plant cell	Animal cell	Fungal cell
Cell wall	Yes	No	Yes
Chloroplasts	Yes	No	No
Vacuole	Large	Small	Present

Message System Comparison

Feature	Nervous system	Endocrine system
Signal	Electrical impulses	Hormones
Speed	Very fast	Slower
Effect duration	Short-term	Longer-lasting