Flashcards in Topic 1: Key Concepts In Biology Deck (54):
What’s a eukaryotic cell?
A complex cell. All plants + animals
What’s a prokaryotic cell?
Smaller, simpler cell. Prokaryotes are single celled organisms. Bacteria are prokaryotes.
What’s a nucleus?
Contains genetic material arranged in chromosomes, controls activities of cell
What’s a cytoplasm?
Contains enzymes which control chemical reactions that take place here
What’s a cell membrane?
Holds cell together, controls what enters and exits cell
Where reactions for respiration (transfers energy cells need to work) take place
Involved in translation of genetic material in synthesis of proteins
What’s the rigid cell wall?
Made of cellulose, supports and strengthens cell
What’s a large vacuole?
Contains cell sap (weak solution of sugar and salts) maintains internal pressure of cell
Where photosynthesis occurs, contain green chlorophyll
What’s chromosomal dna?
Controls activities and replication, floats free in cytoplasm
Rotates to move bacterium away from harmful and towards good substances
What’s plasmid dna?
Small loops of extra dna, can be passed between bacteria, contains genes
What are specialised cells?
Specialised cells have a structure adapted to their function
What’s an acrosome?
At front of sperm cell, stores enzymes to digest membrane of egg cell
How are egg cells specialised for reproduction?
Have nutrients in cytoplasm to nourish early developing embryo
Has haploid nucleus
After fertilisation membrane changes structure
What is resolution?
How well microscope distinguishes between two points thats are close together
How do light microscopes work?
Invented in 1590, they pass light through specimen
How do electron microscopes work?
Invented in 1930, use electrons. Can’t be used to view living cells
Describe the practical ‘how to view a specimen using a light microscope’
1) take things slice (lets light through) of specimen
2, pipette 1 drop of water onto clean slide (secures specimen) and tweezer specimen onto slide
3, add stain to colourless specimen (so you can see it, different stain highlights different structures within cells)
4, hold cover slip at angle using mounted needle, carefully lower onto slide over specimen (So no air bubbles)
5, clip slide onto stage + choose lowest powered objective lens
6, use coarse adjustment knob, move stage up so slide just underneath objective lens. Look down eyepiece, move stage down until specimen almost focused (avoids collision)
7, adjust focus with fine adjustment knob, until image is clear. Position clear ruler on stage, measure diameter of visible circular area
8, greater magnification > higher powered objective lens
Describe the practical ‘scientific drawing of specimen’
1, Outline main features with unbroken lines
2, keep all parts in proportion
3, label important features using straight lines that don’t cross over each other. Include magnification used and a scale.
What is magnification?
How many times bigger the image is
What’s the two equations for total magnification?
Total magnification = eyepiece lens magnification x objective lens magnification
magnification = image size / actual size
Order the units picometer, micrometer, millimetre, nanometre from largest unit of measurement to smallest. How do you convert between them?
Larger > smaller, x 1000
Smaller > larger, divide by 1000
What are enzymes?
Enzymes are biological catalysts that speed up useful chemical reactions in the body without being changed
What’s a substrate?
Molecule changed in the reaction
What’s active site?
Where enzyme joins onto substrate
What do enzymes and substrates have?
Enzymes have a high specificity for their substrate (lock and key)
Some bonds holding enzyme together break, causing shape of enzymes active site to change. Substrate will no longer fit.
Describe the practical ‘investigating effect of pH on enzyme activity’
1, put a drop of iodine solution into every well of a spotting tile
2, place Bunsen burner on heat proof mat, and tripod and gauze over it. Put beaker of water on tripod, heat water to 35* (use thermometer) and try to keep temperature constant throughout experiment
3, use syringe add 3cm^3 of amylase solution and 1cm^3 of a buffer solution with pH 5 to boiling tube. Using test tube holders, out boiling tube in beaker of water, wait 5 mins
4, using different syringe, add 3cm^3 starch solution to boiling tube
5, immediately mix contents of boiling tube and start stop clock
6, record how long it takes amylase to break down all starch using continuous sampling (use dropping pipette, take fresh sample from boiling tube every 10 seconds, put a drop into a well.) When iodine solution remains browny orange, starch no longer present
7, repeat experiment with buffer solutions of different pH values, see how pH affects time taken to break down starch
8, control any variables each time. Could use electric bath to control temperature. Could use pH metre to accurately measure pH of solutions.
What is rate?
How much something changes over time
What is equation for rate of reaction when rate given as unit of time?
Rate of reaction = 1000 / time
What is equation for rate of reaction when experiment is measuring how much something changes over time?
Rate of reaction = change / time
What do digestive enzymes do?
Break food into smaller, soluble molecules that can easily pass through walls of digestive system and be absorbed into blood stream, then pass into cells for use in the body
What do enzymes do in plants?
Break starch (a carbohydrate) into smaller molecules that can be respired to transfer energy to be used by cells
What do carbohydrase enzymes do? Give an example
Carbohydrates > simple sugars
Starch >(amylase enzyme) maltose + other sugars
What do protease enzymes do?
Proteins > amino acids
What do lipase enzymes do?
Lipids > glycerol + fatty acids
How do enzymes synthesise carbohydrates?
Join together simple sugars
How do enzymes synthesise proteins?
Join amino acids together
How do enzymes synthesise lipids?
Join fatty acids and glycerol
How do enzymes synthesise glycogen?
Chains of glucose molecules > (glycogen synthase) glycogen
Molecule used to store energy in animals
Net (overall) movement of particles from an area of higher concentration to an area of lower concentration. Moves down concentration gradient, happens in liquids and gases. Only small molecules can diffuse through cell membranes.
Net movement of water molecules across a partially permeable membrane, from a region of higher water concentration to a region of lower water concentration (water can be replaced with ‘solute’)
Solute solution will become more dilute with osmosis
What’s a partially permeable membrane?
Membrane with small holes in
What’s active transport?
Movement of particles across a membrane against a concentration gradient (lower > higher) using energy transferred during respiration
Describe the practical ‘investigating osmosis’
1, prepare sucrose solutions of different concentrations (from pure water to very concentrated sucrose solution)
2, use cork hoarder to cut 1 potato into 1cm diameter cylinders
3, divide cylinders info groups of 3, use mass balance to measure mass of each group
4, place 1 group in each solution
5, leave cylinders in solution for at least 40 minutes
6, remove cylinders. Remove excess water with paper towel (more accurate measurement of final mass)
7, weigh each group again. Record results
8, higher concentration of sucrose solution > lower water concentration. M/mol dm^-3 = Unit of concentration. 0.0M = pure water
What do you do with your results for the practical ‘investigating osmosis’?
1) Calculate percentage change in mass for each cylinder group before and after time in sucrose (positive results = cylinders gain mass)
2) Plot graph and analyse results
What’s equation for percentage chance in mass?
Percentage change = [(final mass -initial mass)/initial mass] x 100
In a graph of percentage change in mass (y axis), concentration of sucrose solution (x axis), what do the points above the x axis mean?
Water concentration of sucrose solution is higher than in cylinders, cylinders gain mass, water drawn in by osmosis
In a graph of percentage change in mass (y axis), concentration of sucrose solution (x axis), what does the point where the curve crosses the x axis represent?
Fluid inside cylinders and sucrose solution are isotonic
What does it mean for something to be isotonic?
Have same water concentration