Biology: key concepts Flashcards
What are all living things made of?
Cells
What two types can cells be?
Eukaryotic or prokaryotic
How can you tell if a cell is eukaryotic?
Has a nucleus
How can you tell if a cell is prokaryotic?
Has no nucleus
What are eukaryotes?
Organisms made up of eukaryotic cells
What is a prokaryote?
A prokaryotic cell (single-called organism)
What are the insides of a cell called?
Sub cellular structures
What is the function of a nucleus?
Contains genetic material arranged in chromosomes that controls activities of the cell
What is the function of a cytoplasm?
Gel-like substance where most chemical reactions happen. Contains enzymes which control chemical reactions.
What is the function of a cell membrane?
Holds cell together, controls what goes in and out
What is the function of a mitochondria?
Where most of the reactions for respiration take place, respiration transfers energy
What is the function of a ribosomes?
Involve in the translation of genetic material in the synthesis of proteins
Name the 5 parts of an animal cell
Nucleus, cytoplasm, cell membrane, mitochondria, ribosomes
What is the function of a rigid cell wall?
Made of cellulose, supports and strengthens cell
What is the function of a large vacuole?
Contains cell sap, a weak solution of sugar and salts. Maintains the internal pressure to support the cell
What is the function of a chloroplast?
Contains chlorophyll. Where photosynthesis occurs, makes food for he plant.
What are the 8 parts of a plant cell?
Nucleus, cytoplasm, cell membrane, mitochondria, ribosomes, cell wall, large vacuole, chloroplasts
What are the five sub cellular structures of a bacteria cell?
Ribosomes, cell membrane, plasmid DNA, chromosomal DNA, flagellum
What is the function of a chromosomal DNA?
One long circular chromosome, controls cells activities and replication, floats free in the cytoplasm
What is the function of a plasmid DNA?
Small loops of extra DNA, contains genes for things like drug resistance, can be passed between bacteria
What is the function of a flagellum?
Rotate to make bacteria move, away from harmful things, towards useful things
What does it mean if a cell is specialised?
It has adapted to a specific function
What are egg and sperm cells specialised for?
Reproduction
What type of nucleus do egg and sperm cells have?
Haploid (half the number of chromosomes in a normal body cell)
What are three main ways an egg cell is specialised?
It contains nutrients in the cytoplasm to feed the embryoIt has a haploid nucleus
Straight after fertilisation membrane hardens to stop more sperm getting in
What are four main ways an sperm cell is specialised?
Has long tail to swim to the egg
Has lots of mitochondria to provide energy (from respiration)
Has an acrosome at front of ‘head’, where it stores enzymes to ‘digest’ through egg cell membrane
Contains haploid nucleus
What is the function of Epithelial cells?
Line the surface of organs
How are ciliated epithelial cells specialised?
Specialised for moving materials. Have cilia (hair like structures) on top surface of cell. Cilia beat to move substance in one direction, along surface if the tissue.
Give an example of ciliated epithelial cells being used
Lining of airways contains lots of ciliated epithelial cells, help move mucus up throat away from the lungs
What do microscopes use to magnify images?
Lenses
What do microscopes do to an image?
Magnify + increase resolution
What does resolution mean?
How well a microscope distinguishes between two points that are close together
If a resolution is high, what does this mean for the image?
It can be seen clearly, in more detail
When we’re light microscopes invented?
1590s
How do light microscopes work?
By passing light through the specimen.
When were electron microscopes invented?
1930s
How do electron microscopes work?
Passing electrons through the specimen
What can light microscopes do that electron microscopes can’t?
View living cells
What can electron microscopes do that light microscopes can’t?
See the internal structure of sub cellular structures
What are the 8 steps for viewing a specimen using a light microscope? (Practical)
1) take a thin slice of specimen (to let light through)
2) take clean slide, add one drop of water using Pipette, use tweezers to place specimen on slide (water secures in place)
3) add drop of stain to specimen (if specimen is transparent/colourless) - makes specimen easier to see
4) place cover slip at one end of specimen, hold at angle with mounted needle, carefully lower onto slide. Press down gently (to avoid air bubbles), clip slide to stage
5) select lowest-powered objective lens
6) use coarse adjustment knob to move stage up so slide is just underneath objective lens. Look down eyepiece, move stage downwards until specimen nearly focused
7) adjust focus with fine adjustment knob, until image clear. Position clear ruler on stage and use it to measure diameter of circular visible area - field of view
8) if need to see specimen with greater magnification, swap to high powered objective lens, refocus,recalculate FOV accordingly
What are the three steps to creating a scientific drawing of a specimen
Draw outlines of main features using clear, unbroken lines. No colouring/shading.
2) are sure drawing takes at least half of space available. All parts in proportion
3) label important features with straight lines not overlapping. Include magnification used + scale
What is calculation for total magnification?
Eyepiece lens magnification x objective lens magnification
What is the equation for working out magnification without knowing lenses used?
Magnification = image size/ actual size
What can we say about the units for image size and actual size?
Need to be the same units
Real size of specimen is 21.5nano meters. Image size is 9800nanometers. Estimate the magnification
Round to 1 significant figure
10000/20=x500
Order from largest to smallest: Millimeter, Nanometer, picometre, micrometer
Millimetre, micrometer, Nanometer, picometre
How do we convert one of the four mini measurements to the next one down?
x1000
Millimeter in Standard Form?
X10^-3m
Micrometer in Standard Form?
x10^-6m
Nanometer in Standard Form?
X10-9m
Picometer in Standard Form?
10^-12m
What little letter symbol is Millimeter represented by?
mm
What little letter symbol is micrometer represented by?
um
What little letter symbol is Nanometer represented by?
nm
What little letter symbol is picometer represented by?
pm
A specimen is 5x10^-6m wide. Calculate the width of the image of the specimen under a magnification of x100. Give your answer in standard form.
Rearrange magnification formula Image size=magnification x real size Fill in values you know Image size = 100 x (5x10^-6m) Write out values in full =100x0.000005m Carry our calculation then convert back to standard form =0.0005m =5x10^-4m
What are enzymes?
Biological Catalysts produced by living things
Why are enzymes so useful?
Reduce the need to raise temperatures to speed up reactions, which would speed up unwanted reactions.
What two things do chemical reactions usually involve?
Things either being split apart or joined together
What is the active site?
The part where the enzyme joins on to its substrate to catalyse the reaction
What do enzymes have in relation to substrate
High specificity for their substrate
What is a substrate?
The Molecule changed in the reaction
Describe the lock and key mechanism
The substrate has to fit into the active site for the enzyme to work. If substrate doesn’t match the active sites shape, then the reaction won’t be catalysed
Enzyme|. 2 -
Activity |. 1 /. \3
|. /. \
|\_\_\_\_\_\_\_\_\_\_\_\_\_\_
Temperature
Describe what is happening at 1,2 and 3
1) rate of reaction increases as the temperature increases. As kinetic energy increases more collisions occur.
2) optimum temperature (best/highest rate of reaction)
3) enzyme denatured - active site has changed shape
Enzyme|. 2 -
Activity |. 1 /. \3
|. /. \
|\_\_\_\_\_\_\_\_\_\_\_\_\_\_
pH
Describe what is happening at 1,2 and 3
1) rate of reaction increases as pH increases
2) optimum pH: highest rate of reaction. Varies depending on enzyme.
3) enzyme denatured as pH is too high
Enzyme|. 2 --------
Activity |. 1 /.
|. /.
|\_\_\_\_\_\_\_\_\_\_\_\_\_\_
Substrate concentration
Describe what is happening at 1 and 2
1) rate of reaction increases as the enzyme concentration increases
2) rate of reaction stays constant - too much substrate, not enough enzyme
8 steps of a practical to investigate how pH affects amylase activity
1) put a drop of iodine solution into every well or a spotting tile
2) place Bunsen burner on heat proof mat, and tripod and gauze over Bunsen. Put beaker of water on top of tripod and heat water to 35*C. Keep temp constant through experiment, use thermometer to measure
3) use syringe to add 3cm^3 amylase solution to 1cm^3 of buffer solution with ph5 in boiling tube. Use test tube holders and put boiling tube into beaker of water. Wait for 5 minutes.
4) use new syringe to add 3cm^3 of starch solution to boiling tube
5) mix contents of boiling tube and start Stop clock
6) use continuous sampling to record how long it takes for amylase to break down all the starch. Use dropping Pipette to take fresh sample from boiling tube every ten seconds and put a drop into a well. When iodine solution remains browny-orange, starch is not present.
7) repeat whole experiment with buffer solutions of different pH values to see how pH affects time taken for starch to be broken down
8) control and variables each time (e.g. Concentration and volume of amylase solution) for fair test
What is rate?
A measure of how much something changes over time
An experiment measures how much something changes over time. How do you calculate the rate of reaction?
Divide the ankh that it has changed by the time taken
The enzyme catalase catalysed the breakdown of hydrogen peroxide into water and oxygen. During an investigation into the activity of catalase, 24cm^3 of oxygen was released in 50 seconds. Calculate the rate of the reaction. Write your answer in cm^3 s^-1
Amount of product formed = change = 24cm^3
Rate of reaction = change / time = 24cm^3 / 50s = 0.48cm^3 s^-1
What is the si unit for rate?
s^-1
What type of molecules are proteins, lipids and some carbohydrates?
Big molecules
Why do some big molecules need to be broken down into their smaller components?
So they can be digested and used for growth and other life processes
What happens to molecules in food we eat once they’re broken down by digestive enzymes?
They are broken into smaller, soluble molecules. These pass easily through the walls of the digestive system, allowing them to be absorbed into the bloodstream. They then pass into cells to be used in the body
Plants store energy in the form of starch, a carbohydrate. How does a plant use this energy?
The enzymes break down the starch into smaller molecules (sugars) that can then be respired to transfer energy to be used by the cells
What enzyme breaks down carbohydrates? Into what? Give an example of a carbohydrase, and state what it breaks down and what it’s broken down into
Carbohydrases convert carbohydrates into simple sugars.
Amylase is breaks down starch, into simple sugars
What breaks down proteins? What are they broken down into?
Proteases break down proteins into amino acids
What breaks down lipids? What are they broken down into?
Lipases break down lipids into glycerol and fatty acids
What are enzymes used to synthesise?
Carbohydrates, proteins and lipids from their smaller components
How is carbohydrate synthesised?
By joining together simple sugars
What is glycogen synthase
An enzyme that joins together lots of chains for glucose molecules to make glycogen (a molecule used to store energy in animals)
What is glycogen made of? Which enzyme is used to synthesise it?
Many glucose molecules. Glycogen synthase joins these chains of molecules together.
How is proteins synthesised?
Joining amino acids together
How is lipids synthesised?
From fatty acids and glycerol
What is diffusion?
Net movement of particles from an area of higher concentration to an area of lower concentration
Is diffusion moving up or down the concentration gradient?
Down
What substances does diffusion happen in?
Liquids and gases
What types of molecules can diffuse through a cell membrane?
Very small molecules, like glucose, amino acids, water and oxygen. Big molecules (starch, proteins) can’t fit through
What is osmosis?
The net movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration
What is a partially permeabel membrane?
Membrane with small holes in it.
How does osmosis effect a solute solution?
It makes it more dilute
What is active transport?
The movement of particles across a membrane against a concentration gradient (from area of lower to an area of higher concentration) using energy transferred during respiration
Give an example of how active transport works in the digestive system
Lower concentration of nutrients in the gut than in the blood, active transport allows nutrients to be taken into the blood to stop us starving.
Give the 10 steps of Investigating Osmosis experiment/practical
1) prepare sucrose solutions of different concentrations ranging from pure water to very concentrated
2) .use cork borer to cut potato in same size pieces (about 1cm diameter)
3) divide potato cylinders into forums of three, use mass balance to measure mass of each group
4) place one group in each solution
5) leave cylinders in solution for 40 mins
6) remove cylinders and pat dry gently with paper towel, removing excess water, so measure of final masses is accurate
7) weigh each group again and record results
8) in experiment, you change concentration of of sucrose solution. Volume of solution, size of potato cylinders, type of potato use, amount of drying etc must be kept the same
9) calculate percentage change in mass for each group of cylinders before and after their time in sucrose
10) plot a graph and analyse results
(Investigating Osmosis experiment) A group of cylinders weighed 13.2g at the start of the experiment. At the end they weighed 15.1g. Calculate percentage change in mass.
Percentage change = ((final mass - initial mass) / initial mass) x 100
15.1-13.2/13.2x100=14.4%
Positive result = potato cylinder gained mass
Formula for percentage change in mass
Percentage change = ((final mass - initial mass) / initial mass) x 100
You have a graph of results from the Investigating Osmosis practical. What can you say about water concentration in points above x axis?
Water concentration of sucrose solution is higher than in the cylinders.
You have a graph of results from the Investigating Osmosis practical. What can you say about water concentration in point where curve crosses x axis?
Fluid inside cylinders and the sucrose solution are isotonic (have same water concentration?)
What does isotonic mean?
Same water concentration
What Will a graph showing results from Investigating Osmosis practical look like
X axis = concentration of sucrose solution. Starts at 0 on y axis
Y axis = % change in mass
Gentle curve, shallower at bottom of y axis
You have a graph of results from the Investigating Osmosis practical. What can you say about water concentration in points below x axis?
Wate concentration of sucrose solutions is lower than in the cylinders
