B1 - Key Concepts in Biology

difference between electron and light microscopes

electron microscopes use beams of electrons, light microscopes use beams of light

electron microscopes can magnify up to x2000000

difference between plant and animal cells

both contain a nucleus, mitochondria, cytoplasm, ribosomes and cell membrane. plant cells also contain a cell wall (provides structure), chloroplast (absorbs light energy for photosynthesis), and a vacuole (filled with sap to help cell stay swolen)

difference of (human) diploid and haploid cells

in humans, diploid cells contain 23 pairs of chromosomes - these are normal body cells. haploid cells contain one set of 23 chromosomes, and are used during sexual reproduction

what is an epithelial cell, and what do cilia do

epithelial cells line structures, and cilia are small cells which sweep substacnes. cells with cilia on there inner are called cilited epithelial cells

how are sperm cells adapted for function

tip of head contains vacuole. vacuole contains enzymes which breakdown substances in an egg cells coat, allowing sperm to enter egg. mitochondria are arranged around tail, releasing energy allowing sperm to swim

how are egg cells adapted for function

jelly coat protects the egg cell and only hardens after fertilisation (ensures only one sperm cell enters), cytoplasm is packed with nutrients to supply the egg with energy (allows for embryo to grow and develop)

what does a bacterial cell include

flagella - allows bacteria to move

chromosonal DNA - no nucleus, so DNA is loose in cytoplasm

plasmid DNA - some DNA is in closed circles called plasmids

what is an enzyme

enzymes are biological catalysts

what does iodine test for?

tests for starch: drop iodine on food, if it turns blue-black, starch is present

what is the benedicts test

test for reducing sugars: add water and benedicts solution with food samply in 1:1:1 ratio, heat solution - if turrns brick red, reducing sugars are present

what is the biurets test

test for protein - add water and potassium hydroxide, add two drops of copper sulfate. if turns purple, protein is present

what is emulsion test

test for lipids - mix with ethanol and water, if a milky white emulsion forms, lipids are present

what is diffusion

the movement of particle from a higher concentration to a lower concentration, creating a concentration gradient. In cells, this allows small molecules such as oxygen or carbon dioxide to move in and out of cells.

what is osmosis

the diffusion of water molecules from an area of higher concentration to an area of lower concentration through a partially permeable membrane

what is active transport

a process that is required to move molecules against a concentration gradient. it requires energy