1: Key Concepts - YK Flashcards
(15 cards)
What is resolution?
The resolution of a microscope is the smallest distance between two points that can still be seen as two separate points.
What formula links magnification, image size, and actual size?
Actual size = image size / magnification
What is the order of the 4 SI units below cm?
milli (mm), micro (μm), nano (nm), pico (pm)
What is the difference between eukaryotic and prokaryotic cells?
Eukaryotic cells have a membrane-bound nucleus and membrane-bound organelles
What organelles are found in animal and plant cells and what are their functions?
Nucleus (both) - controls all cell functions, stores DNA in chromosomes
Cytoplasm (both) - watery jelly where most of the cell’s activities occur
Cell membrane (both) - controls what enters and leaves the cell through its semi-permeable membrane, separates one cell from another
Mitochondria (both) - site of aerobic respiration
Ribosomes (both) - make new proteins for the cell
Cell wall (plant) - made of cellulose, supports and protects the cell
Chloroplast (plant) - site of photosynthesis (contains chlorophyll which traps energy from sun used in photosynthesis)
Vacuole (plant) - stores cell sap to keep cell firm and rigid
What adaptations do specialised cells for digestion have?
Outer membranes has many small folds (microvilli) to increase surface area (increases absorption of nutrient molecules); cells in the pancreas make enzymes (proteins) so cells have many ribosomes; wall of the small intestines has muscles to squeeze food along, muscle contractions take lots of energy so cells have many mitochondria
What adaptations do specialised cells for reproduction have?
Ovum: haploid, membrane becomes hard after fertilisation to stop other sperm cells entering, cytoplasm has nutrients to supply fertilised egg cell with energy and raw materials for growth and development of embryo, jelly coat protects the cell
Sperm: haploid, streamlined shape, flagella allows movement, acrosome (in tip of head) contains enzymes to break down jelly coat to burrow into egg, lots of mitochondria in section at top of ‘tail’ to release energy
Ciliated epithelial cell (also moves mucus): cilia covered with substance which can contract to move egg towards the uterus
What form of DNA does bacteria contain?
A large loop of chromosomal DNA and smaller plasmids (makes them prokaryotic)
What do enzymes do?
Enzymes are biological catalysts (made of protein) which speed up reactions in the body, each enzyme being specific to one substrate. Digestive enzymes break down large molecules in food so they can be absorbed by the small intestine. Some enzymes can also speed up synthesis reactions.
What are some enzymes and their reactions catalysed?
Amylase: breaks down starch into small sugars
Starch synthase: creates starch from glucose (in plants)
Protease: breaks protein molecules into amino acids
Lipase: breaks lipids down into fatty acids and glycerol
Catalase: breaks down hydrogen peroxide into water and oxygen
DNA polymerase: creates DNA from its monomers
What is the lock and key model of enzyme activity?
Substrate molecules bind to their specific enzyme in the active site, they are held in place for bonds to form to make a product molecule, product doesn’t fit perfectly in the active site so it is released
How do environmental conditions affect enzyme activity?
Temp: enzyme activity increases as molecules move faster (increasing chance of collision) up to optimum temperature, after which the active site starts to deform until the substrate can’t fit at all (enzyme is denatured)
pH: shape of active site is affected above and below optimum so enzyme can become denatured in both ways
Substrate concentration: reaction rate increases as more enzymes can fill their active sites, until rate plateaus because all enzymes are working
What is diffusion?
Diffusion is the movement of particles from an area of high concentration to an area of low concentration, or down a concentration gradient. If the concentration gradient is steeper (difference in concentration is greater) diffusion will be faster. Small molecules (e.g. carbon dioxide and oxygen) can move into and out of cells through diffusion.
What is osmosis?
Osmosis is the passive process allowing water to pass through a semi-permeable membrane down a concentration gradient (from a more dilute to a less dilute solution).
What is active transport?
Active transport is the active process which moves molecules against a concentration gradient or molecules too large to diffuse through a cell membrane. A molecule sticks to a transporter protein, energy changes the protein’s shape, and the molecule is released on the other side of the membrane.
