b2 cell specialisation

red blood cells

• 🔴 1. Red Blood Cell (Erythrocyte)

  Function: Transport oxygen from the lungs to the body’s tissues and carbon dioxide back to the lungs.

  Adaptations:

  • Biconcave shape → Increases surface area for faster diffusion of gases.

  • and short distance for gases to move across

  • No nucleus → More space for haemoglobin, the protein that binds to oxygen.

  • Flexible membrane → Allows the cell to squeeze through tiny capillaries.

  • packed with haemoglobin - Haemoglobin binds with oxygen to form oxyhaemoglobin in the lungs.

  • thin cell membrane - gases liek carbon dioxide and oxygen can easily pass through

  • No mitochondria or organelles:

    • More internal space for haemoglobin.

    • Red blood cells don’t need to use the oxygen they carry — all of it is for body tissues.

  Structure–Function Match:

  • Packed with haemoglobin: each molecule can carry 4 oxygen molecules.

  • Thin outer membrane: short diffusion path for gases

white blood cells

• Function: Protect the body by engulfing and digesting pathogens (bacteria/viruses).

  Adaptations:

  • Flexible membrane → To surround and engulf pathogens (called phagocytosis).

  • Lobed nucleus → Easier movement through tissues and squeezing through capillary walls.

  • Lysosomes → Contain digestive enzymes to destroy the pathogens.

  Structure–Function Match:

  • Irregular shape helps them adapt to attacking different types of pathogens.

  • Travel through blood and tissues to infection sites.

nerve cell

3. Nerve Cell (Neuron)

Function: Transmit electrical impulses quickly from one part of the body to another.

Adaptations:

• Long axon → Carries impulses over long distances (e.g., from spine to foot).

• Dendrites → Branch-like extensions that receive signals from other nerve cells.

• Myelin sheath → Fatty layer that insulates the axon and speeds up the impulse.

Structure–Function Match:

• Long, thin shape enables fast communication.

• Synaptic endings release neurotransmitters to pass signal to next neuron or muscle.

muscle cell

Function: Contract and relax to move bones or organs.

Adaptations:

• Long cells with protein filaments (actin and myosin) that slide to cause contraction.

• Multiple nuclei → Controls large amounts of protein synthesis.

• Lots of mitochondria → Release energy for movement via respiration.

Structure–Function Match:

• Strong, fibrous structure helps generate force.

• Found in biceps, triceps, and other muscles.

root hair cell

Function: Absorb water and mineral ions from soil.

Adaptations:

• Long root hair extension → Increases surface area for absorption.

• Thin cell wall → Shorter distance for water to travel into the cell.

• No chloroplasts → Not exposed to light; focuses energy on absorption.

Structure–Function Match:

• Vacuole stores ions and helps draw water in by osmosis.

• Positioned on outer layer of root for maximum contact with soil.

palisade mesophyll cell

Function: Absorb water and mineral ions from the soil.

Adaptations:

• Long root hair extension → Increases surface area for absorption.

• Thin cell wall → Shorter distance for water to travel into the cell and for gas exchange

• No chloroplasts → Not exposed to light; focuses energy on absorption.

• acts as a rigid exoskeleton allowing the cell to withstand osmotic pressure and environmental stresses while preventing the over-expansion of cell

• cells arranged close together to allow for maximum light absorption

• packed with chloroplast near the edge to absorb more light to make glucose

• chloroplast can be moved around the cytoplasm by cytoskeleton in order to maximise the amount of light absorbed - they can move to where the light is in dark conditions and away from light in intense conditions

• large vacuole in centre - helps keep the pressure up and prevents cell from becoming flaccid

Structure–Function Match:

• Vacuole stores ions and helps draw water in by osmosis.

• Positioned on outer layer of root for maximum contact with soil.

sperm cell

Function: Fertilise the female egg cell.

Adaptations:

• Tail (flagellum) → For swimming to reach the egg.

• Acrosome → Enzyme-filled cap to break through egg membrane.

• Streamlined head → Helps move quickly.

• Mitochondria in midpiece → Provide energy for tail movement.

Structure–Function Match:

• Carries half the genetic material (haploid).

• Small and fast – adapted for fertilisation.

egg cell

Function: Receive sperm and provide nutrients for early development.

Adaptations:

• Large size → Contains nutrients to support embryo.

• Jelly coat → Hardens after fertilisation to prevent more sperm entering.

• Haploid nucleus → Has half the number of chromosomes.

• zona pellucida - contains many glycoproteins that sperm cells recognise and are drawn to

• corona radiata - protein heavy layer than provides nutrients for the egg and early embryo

Structure–Function Match:

• Organelles and cytoplasm support early embryo until implantation.

• Combines with sperm cell to form a full set of chromosomes.

white blood cells extra

• White blood cells are part of the immune system.

• Their job is to defend the body against infection from bacteria, viruses, and other harmful microbes.

• Unlike red blood cells, white blood cells do have a nucleus and come in several types with different roles.

types of white blood cells - neutrophils

Function:

• Neutrophils detect, engulf, and digest invading pathogens like bacteria.

Key Features:

• Lobed nucleus → helps squeeze through small spaces (like capillary walls).

• Contain lots of lysosomes → filled with enzymes to break down microbes.

• cytoplasm contains a large number of lysosomes that contain hyrochloric enzymes used to digest pathogens that are injested by neutrophills via phagocytosis.

• Short-lived, but fast-acting – they’re the first to arrive at infection sites.

• highly mobile - will move to where they are needed

process of phagocytosis - neutrophils

• Phagocytosis is the process where phagocytes (a type of white blood cell) engulf and destroy pathogens such as bacteria.

  It is a non-specific immune response, meaning it works against any pathogen — not a specific one.

• 1. Detection

  • The phagocyte detects chemicals or antigens on the surface of a pathogen.

  • The pathogen is attracted to the phagocyte (chemotaxis).

  2. Engulfing

  • The phagocyte’s cell membrane surrounds the pathogen.

  • The pathogen is trapped in a bubble-like structure called a phagosome (a vesicle inside the cell).

  3. Digestion

  • Lysosomes (small organelles inside the phagocyte) move toward the phagosome.

  • They fuse with the phagosome and release enzymes.

  4. Destruction

  • The enzymes break down and digest the pathogen inside the phagosome.

  5. Exocytosis (optional for extra detail)

  • The waste from the digested pathogen may be released out of the phagocyte.

    summary - "Phagocytosis is when a white blood cell, like a neutrophil, detects a pathogen, engulfs it into a vesicle (phagosome), then uses enzymes from lysosomes to break it down."

lymphocytes - type of wbc

• Lymphocytes are a type of white blood cell involved in the specific immune response.

• They help the body recognize and target particular pathogens.

• Types of Lymphocytes:

  • B Cells:

    • Produce antibodies that bind to antigens on pathogens.

    • Help neutralize and destroy invading organisms.

  • T Cells:

    • Include killer T cells that destroy cells infected by viruses and other pathogens.

    • Also have helper T cells that activate B cells and other immune system components.

  • Natural Killer (NK) Cells:

    • Target and destroy virus-infected and cancerous cells.

    • Operate without the need for antibodies, allowing for rapid response.

• Key Points to Remember:

  • B cells are the antibody builders.

  • T cells are the targeted cell destroyers and activators of the immune response.

  • NK cells provide quick responses by eliminating harmful cells without prior activation.

simularities and differences between neutrophills and lymphocytes

✅ Similarities:

• Both are white blood cells (WBCs).

• Both help defend the body against infections.

• Both are found in the blood and tissues.

• Both are part of the immune system.

Differences:

• Neutrophils are granulocytes (they have granules); lymphocytes are agranulocytes (no granules).

• Neutrophils are larger and have a multi-lobed nucleus; lymphocytes are smaller with a large round nucleus.

• Neutrophils respond quickly and are part of the non-specific (innate) immune response.

• Lymphocytes respond more slowly but are part of the specific (adaptive) immune response.

• Neutrophils kill pathogens by engulfing them (phagocytosis).

• Lymphocytes either produce antibodies (B cells) or kill infected cells (T cells).

• Neutrophils live for a short time (hours to days), while lymphocytes can live much longer (even years in some cases).