Transport Systems in Plants and Animals

Transpiration is basically how plants move water from their roots up to their leaves, where it evaporates through tiny pores called stomata. Think of it like a plant's drinking and sweating system combined! Water enters through root hair cells by osmosis, travels up the xylem vessels (which are strengthened with lignin rings), and eventually evaporates from the leaves.

Guard cells act like bouncers at the stomata, controlling whether they're open or closed and therefore how much water the plant loses. High temperatures, wind, and large surface areas increase transpiration, whilst high humidity decreases it.

Plants have two main transport systems: xylem (dead tissue that carries water and minerals upwards) and phloem (living tissue with companion cells that transports sugars in both directions). The phloem contains sieve plates and tubes that allow sugar to move between cells.

Key Insight: Just like humans have blood vessels, plants have their own "plumbing system" - xylem and phloem work together to keep plants hydrated and fed.

Your circulatory system works similarly but uses three types of blood vessels. Arteries carry blood away from your heart with thick, muscular walls to handle high pressure. Veins bring blood back to your heart with thinner walls, valves to prevent backflow, and wider channels for lower pressure. Capillaries have walls just one cell thick, creating massive networks in your tissues for efficient material exchange.

Respiration and Energy Production

Respiration is how your cells unlock energy from glucose - it's happening in every cell right now as you read this! This enzyme-controlled process generates ATP, which is basically your body's energy currency.

Aerobic respiration (with oxygen) happens in two stages: glycolysis in the cytoplasm breaks glucose into pyruvate (making 2 ATP), then the main event occurs in the mitochondria, producing loads more ATP plus carbon dioxide and water as waste products.

When oxygen isn't available, cells switch to fermentation. In animals, this produces lactate and only 2 ATP (which is why you get muscle fatigue during intense exercise). In plants and yeast, fermentation creates ethanol and carbon dioxide - that's how bread rises and alcohol is made!

Remember: Aerobic respiration gives you way more energy (lots of ATP) than fermentation (just 2 ATP), which is why you can't sprint forever without getting tired.

Cell Structure and Transport

Every cell is like a busy factory with specific parts doing different jobs. The cell membrane controls what enters and exits, whilst the nucleus contains all your genetic information. Mitochondria are the powerhouses where respiration happens, and ribosomes are protein-making machines.

DNA is a double-stranded helix held together by complementary base pairs (Adenine with Thymine, Guanine with Cytosine). Sections called genes contain instructions for making specific proteins.

Three key transport processes move substances around cells. Diffusion moves molecules from high to low concentration (no energy needed). Osmosis is the same but specifically for water through a selectively permeable membrane. Active transport moves substances against the concentration gradient, which requires energy and special membrane proteins.

Top Tip: Think of diffusion like students leaving school - they naturally spread from crowded corridors to empty spaces without any effort needed.

Proteins are made when mRNA copies the genetic code from DNA in the nucleus and takes it to ribosomes for assembly. These proteins become enzymes (biological catalysts), hormones, antibodies, or structural components.

Cell Division, Control Systems, and Reproduction

Mitosis is how your body grows and repairs itself by creating identical diploid cells (46 chromosomes). During mitosis, chromosomes line up, spindle fibres pull chromatids apart, and the cytoplasm divides to form two identical cells.

Stem cells are special because they can both copy themselves $self-renew$ and become specialised cell types. Embryonic stem cells can become any cell type, whilst tissue stem cells are more limited but less controversial.

Your nervous system works like an incredibly fast communication network. Receptors detect stimuli, sensory neurons send messages to your brain and spinal cord (CNS), interneurons process the information, and motor neurons tell effectors (muscles and glands) how to respond.

Brain Breakdown: Your cerebrum handles conscious thoughts and memory, your cerebellum controls balance, and your medulla manages vital functions like breathing and heart rate - all automatically!

Reproduction involves male and female gametes (sex cells with 23 chromosomes each). In humans, sperm from testes meets an egg in the oviduct. Variation in offspring comes in two types: discrete (distinct groups like blood type) caused by single genes, and continuous (ranges like height) caused by multiple genes working together.