SB1: key concepts in biology Flashcards
what are microscopes used for?
to produce magnified images
facts about light microscopes
-used to study living cells
-for regular use when low magnification & resolution is enough
-can magnify ×1500
-specimen can be living
-2D images only
-existed for 100s of years
facts about electron microscopes
-higher magnifications & resolutions
-can’t be used to see living cells
-can magnify ×2000000
-3D images can be given out
-recently made
total magnification (equation)
eyepiece × objective lens
image size equation
magnification × actual size
triangle = IAM
units
-metre (m) multiplied by 1000 = millimetre
-millimetre multiplied by 1000 = micrometer
-micrometer multiplied by 1000 = nanometer
-nanometer multiplied by 1000 = picometer
1mm
1000 micro metres
what types of cells are animal & plant cells?
-eukaryotic cell
-multicellular
-has cell membrane
what parts of an animal cell are visible under a light microscope?
-nucleus
-cell membrane
-cytoplasm
(also mitochondria but not in detail
what is in an animal cell?
nucleus
-contains genetic material, controls cell activities
cytoplasm
-jelly like, contains organelles, where chemical reactions al occur
cell membrane
-semi permeable, controls movement of substances in sound out of cell
mitochondria
-contains enzymes for respiration
-where most energy is released in respiration
ribosomes
-tiny structures where protein-synthesis occurs
what is in a plant cell?
chloroplast
-contains chlorophyll (green pigment), absorbs light energy for photosynthesis, contains enzymes needed for photosynthesis
cell wall
-provides structure & protection
-made from cellulose
permanent vacuole
-filled with cell sap, keeps cell swollen
microscope core practical steps:
- put a small drop of water
on the microscope slide - peal some onion skin from inside one of the leaves of the onion bulb
- use forceps to put the onion skin into the slide, lay it flat & make sure there are no trapped air bubbles
- stain the cells with iodine (make the internal structures more visible)
- place a coverslip over the specimen (prevents the slide from drying out when it’s being examined)
what does each resolution/ power show in the microscope core practical?
low power = shows arrangement
high power = detailed with individual cells
measuring cell size (microscope core practical)
- place micrometer on stage
- line up one of the divisions of the graticule with a fixed point on the stage micrometer
- count the number of divisions on the graticule that correspond with the stage micrometer
- calculate the distance in micrometers on division on eyepiece graticule
what type of cell is a bacterial cell?
prokaryotic (no nucleus, single-celled)
what is in a bacterial cell?
chromosomal DNA
-found loose in cytoplasm
plasmid DNA
-small, closed circles of DNA
flagella
-rotate in whip like motion to move cell
-can be one or more on a cell
how do bacterial cells copy?
binary fission
what is a specialised cell?
a cell which has adapted unique features to perform its function
how is a sperm cell specialised?
acrosome
-enzyme to break down egg
tail
-for swimming
mitochondria
-carry energy for the journey
sperm cell facts
-haploid
-carries genetic info to egg in conception
how is an egg cell specialised?
cell membrane
-(jelly coat) when the sperm cell enters, the cell membrane becomes hard to stop other sperm from entering
cytoplasm
-contains nutrients for energy & growth of embryo
facts about egg cell
-contains genetic info from mother, fuses with sperm in conception
-haploid nucleus
how is a ciliated epithelial cell specified?
cilia
-covered in cell membrane, contains strands of a substance that causes wavy movement
-moves backwards and forwards to move egg cells
mitochondria
-provides energy for movement of cilia
facts about ciliated epithelial
cells
-in oviducts of female reproductive system
-transports fertilised eggs to uterus
what are enzymes?
proteins that function as biological catalysts
enzyme and substrate steps
- substrate collides with active site of enzyme & attaches
- enzyme catalyses breakdown of sUbstrate
- products are released from active site
denaturing enzymes
-if enzymes are exposed to extremes of pH or high temps, their active site changes, the substrate no longer fits into the enzyme and is denatured
rate of reaction equation
amount of product formed or substrate/ time taken
how temperature affects enzyme activity
-rate increases as temperature increases due to high energy
-at high temps, rate decreases again as enzyme denatures and can’t function
how pH affects enzyme activity
-each enzyme works best at a specific pH
-after the optimum pH, the enzyme denatures
how substrate concentration affects enzyme activity
-enzymes work best with lots of substrate
-as concentration increases, so does the rate of reaction, however rate can’t increases forever, so as enzymes become more saturated, no more substrates can fit at once & the rate reaches its optimum
what is the aim of the core practical: effects of pH on enzyme activity
to determine the optimum pH of enzymes
steps of core practical: effects of pH on enzyme activity
- set up a bunsen burner, heatproof may, tripod & gauze
- place a beaker of water on the gauze and adiust the flame to keep water at 35 degrees
- add 2 drops of iodine into each spot of the sporting tile
- add 2cm^3 of amylase into the test tube & add 2cm^3 of starch into the same tube
- add 1cm^3 of pH solution into the tube to keep the pH constant
- mix the test tube solution & put into beaker of water on gauze
- use pipette to remove solution every 20 seconds & put into different spitting tiles
- repeat until iodine stops turning black and record the time this takes
- repeat this with different pH solutions
results of effects of pH on enzyme activity
pH 5 = 240seconds
pH 6 = 120seconds
pH 7 = 60seconds
pH 8 = 140seconds
-amylase (breaks down starch) has optimum ph 7 as it takes the least time to break down starch at this pH (iodine isn’t black anymore
enzymes and food
-carbs (for energy) , proteins (growth & repair) and lipids are too large to pass from the intestines into the blood so digestive enzymes are needed to break them into smaller molecules
carbohydrates
examples: starch & glucose
structure: monosaccharide
broken down by: amylase
proteins
examples: collagen, keratin
structure: large molecules made from chains of amino acids
broken down by: protease
lipids
examples: fats & oils
structure: large molecules made from smaller units of fatty acids & glycerol broken down by: lipase
test for starch
- put spatula of food on dish
- put a few drops of iodine onto it
- of the food turns blue-black, starch is present
test for reducing sugar
- put 2 spatulas of food into test tube 2. add 1cm^3 of water to the tube and stir
- add benedicts solution & place in a water bath
- food turns from blue to cloud orange/ brick red if reducing sugar is present
test for lipids
- add ethanol to food sample and shake (dissolves lipids)
- allow contents to settle
- add to test tube with water
- milky/ loudy white emulsion = lipids
test for proteins
- add 1cm^3 of water to food sample & stir
- add biuret and stir for 2 minutes
- purple = protein
calorimeter
measures the energy involved in a chemical process (joules/calories)
-small samples of food are put on it & they burn, energy is given off when the material burns
how can a simple calorimeter be made?
arrange a beaker of water above a burning sample, the change in temp shows the energy of the sample
what is diffusion?
when particles in a gas move from a high to a low concentration, the particles will move in both directions but there will be a net (overall) movement from high to low & the particles end up evenly spread
what is a concentration gradient?
the difference in concentration between two areas
what does a greater concentration gradient lead to?
(diffusion)
quicker diffusion
what does a higher temperature lead to? (diffusion)
more kinetic energy & faster diffusion
what does a greater surface area lead to? (diffusion)
faster diffusion
does diffusion require energy?
no, it is passive transport
what is osmosis?
diffusion of water across a partially permeable membrane
plant osmosis
-in a concentrated solution, the cell content loses water by osmosis & the cell shrinks (flaccid), in a highly concentrated solution the membrane pulls away from cell walls and plasmolysis occurs
animal cells & osmosis
-animal cells have no cell wall & change size and shape when put into solutions that are at different concentration to cell contents
-the concentration of contents should be within strict limits or cells don’t function properly
red blood cells & osmosis
red blood cells in concentrated solutions
-lose water and shrink
red blood cells in normal solutions
-nothing
red blood cells in dilute solutions/distilled water
-swell and burst
what is active transport?
moves molecules against a concentration gradient, requires energy
active transport in plants
-for plants to take up mineral ions, ions are moved into root hairs, where they are in a higher concentration than in the dilute solutions in the soil
-active transport then occurs across the root so that the plant takes in the ions it needs from the soil around it.
active transport in animals
in animals, glucose molecules have to be moved across the gut wall into the blood.
-glucose molecules in the intestine might be in a higher concentration than in the intestinal cells & blood
- there will be times when glucose concentration in the intestine might be lower, movement of glucose involves active transport
-the process requires energy produced by respiration
core practical: osmosis in potatoes
- cut equal-sized pieces of potato
- blot with tissue paper and weigh
- put pieces into different concentrations of sucrose solution for a few hours
- remove, blot with tissue paper and reweigh
- use the 0% sucrose as a control measure
water uptake in one hour
change in mass × 60 minutes/length of experiment (mins)
ordered rank when results are in order
percentile/100 × number told entries
what makes diffusion faster?
-greater concentration gradient
-higher temperature (more kinetic energy)
-greater surface area
