biology sigma

What is passive transport?

Movement of substances across a membrane without using ATP (energy), down the concentration gradient.

What is active transport?

Movement of substances against the concentration gradient, requiring energy (ATP).

What is diffusion?

The movement of particles from an area of high concentration to an area of low concentration.

What is osmosis?

diffusion of water across a selectively permeable membrane

What are the three main tenets of Cell Theory?

All living things are made of cells, cells are the smallest unit of life, all cells come from pre-existing cells.

What are the advantages of compartmentalisation?

Efficient reactions, different simultaneous processes, and protection from external changes.

What is a key difference between prokaryotic and eukaryotic cells?

Prokaryotes lack membrane-bound organelles and a true nucleus; eukaryotes have them.

What structures are found in plant cells but not animal cells?

Cell walls, chloroplasts, and a large central vacuole.

What is the function of the rough Endoplasmic Reticulum (ER)?

To build and process proteins using attached ribosomes.

How is total magnification calculated?

Objective lens magnification multiplied by ocular lens magnification.

What is the Fluid Mosaic Model of the cell membrane?

A lipid bilayer with embedded proteins that move laterally, providing flexibility.

What occurs to a cell in a hypertonic solution?

Water moves out of the cell, causing it to shrink.

What is the role of the sodium-potassium pump?

Pumps Na+ out and K+ in against the concentration gradient using ATP.

What are the levels of organisation in multicellular organisms?

Cells to tissues to organs to systems to organism.

What is the function of xylem tissue in plants?

Transporting water and dissolved minerals upward from roots in dead, hollow tubes.

What is the difference between Lock & Key and Induced Fit enzyme models?

Lock & key has an exact fit; induced fit involves the enzyme changing shape slightly.

What are the stages of mitosis in order?

Prophase, metaphase, anaphase, telophase (followed by cytokinesis).

What is the difference between embryonic and adult stem cells?

Embryonic stem cells are pluripotent; adult stem cells are multipotent.

Where do the light-dependent and light-independent reactions occur?

Light-dependent in thylakoids; light-independent (Calvin Cycle) in the stroma.

What are the three main stages of aerobic cellular respiration?

Glycolysis, Krebs Cycle, and the Electron Transport Chain (ETC).

What is transpiration?

The loss of water vapour through stomata, driving water uptake from roots.

What is the difference between open and closed circulatory systems?

Closed systems keep blood entirely within vessels; open systems release fluid directly into cavities.

How does counter-current exchange in fish gills work?

Water flows opposite to blood flow, maintaining a constant concentration gradient for high oxygen absorption.

What are the four main steps of urine formation in nephrons?

Filtration, reabsorption, secretion, and excretion.