bio mocks Flashcards
characteristics of living organisms:
M ovement
R espiration
S ensitivity
C ontrol
G rowth
R eproduction
E xcretion
N utrition
what does a typical animal cell contain?
-nucleus: an organelle which contains the genetic material that controls the cell’s activities, it is surrounded by its own membrame
-cell membrame: this membrane forms the outer furface of the cell and controls the substances that go in and out
-cytoplasm: a gel-like substance where most of the cell’s chemical reactions happen, it contains enzymes which control these reactions
-mitochondria: small organelles where most of the reactions for aerobic respiration take place
-ribosomes: small organelles where proteins are made in the cell
what does a typical plant cell contain?
-chloroplasts: photosynthesis, which makes food for the plant happens here, they contain a green substance called chlorophyll, which is used in photosynthesis
-cell wall: a rigid structure made of cellulose, which surrounds the cell membrane, it supports the cells and strengthens it
-vacuole: a large organelle that contains cell sap which helps to support the cell
tissues:
-a tissue is a group of similar cells that work together to carry out a particular function
-a tissue can contain more than one cell type
organs:
-an organ is a group of different tissues that work together to perfom a function
-e.g: lungs in mammals and leaves on plants
organ systems:
-organs work together to form organ systems, each system does a different job
-for example, in mammals, the digestive system is made up of organs including the stomach, intestines, pancreas and liver
organelle -> cell -> tissue -> organ -> organ system
eukaryotic organisms:
-organisms that have a nucleus and organelles that are found within a plasma membrame
-plants
-animals
-fungi
plants:
e.g: cereals (maize) and herbaceous legumes (peas)
-plants are multicellular
-they have chloroplasts which means they can photosynthesise
-they have cell walls, which are made of cellulose
-plants store carbonates as sucrose or starch
animals:
e.g: mammals (humans) and insects (flies)
-animals are multicellular
-they don’t have chloroplast so they can’t photosynthesise
-don’t have cell walls
-most have nervous coordination
-animals store carbonates as glycogen
fungi:
e.g: yeast (single-cell) or mucor (multicellular)
-some are single-celled
-others have a body called mycelium made up of hyphae (thread-like structures) containing lots of nuclei
-can’t photosynthesise
-have cell walls made of chitin
-most feed by saprotrophic nutrition (they secrete extracellular enzymes into the area outside their body to dissolve their food, so they can absorb nutrients)
-fungi store carbohydrates as glycogen
prokaryotic cells:
-do not have a nucleus or membrame-bound organelles
-protoctists
-bacteria
-viruses
protoctists:
e.g: chlorella (plant-cell-like) or amoeba (animal-cell-like)-live in pond water
-these are single-celled and microscopic
-some have chloroplasts and are similar to plant cells
-other are more like animal cells
bacteria:
e.g: lactobacillus bulgaricus (used to make yoghurt) or pneumococcus (causes pneumonia)
-single-celled and microscopic
-don’t have a nucleus
-they have circular chromosomes of DNA
-some can photosynthesise
-most bacteria feed off other organisms (dead or alive)
viruses:
e.g: influenza virus (causes the ‘flu’), tobacco mosaic virus (prevents chloroplast formation) or HIV which lead AIDS
-viruses are small particles -not living organisms
-parasitics: can only reproduce within living cells, can infect every type of organisms
-they come in loads of different shapes and sizes
-do not have a cellular structure-they have a protein coat around some genetic material (either DNA or RNA)
pathogens:
-are disease-causing organisms that include some viruses, protoctists and bacterias
-protoctist: plasmodium, which causes malaria
-bacterium: pneumococcus, which causes pneumonia
-viruses: influenza virus (which cause ‘flu’) and HIV (which causes AIDS)
biological molecules:
-carbohydrates
-proteins
-lipids
carbohydrates:
-they are made of carbon, oxygen and hydrogen
-starch and glycogen are large, complex carbohydrates, which are made up of many smaller units joined together in a long chain
maltose (and other simple sugars) -> starch
proteins:
-proteins are made up of long chains of amino acids
-they all contain carbon, nitrogen, hydrogen and oxygen atoms
amino acids -> proteins
lipids:
-lipids (fats and oils) are built from fatty acids and glycerol
-lipids contain carbon, hydrogen and oxygen atoms
glycerol & fatty acids -> lipid
how to make a food sample:
1) get a piece of food and break it up using pestle and mortar
2) transfer the ground up food to a beaker and add some distilled water
3) give the mixture a good stir with a glass rod to dissolve some of the food
4) filter the solution using a funnel lined with filter paper to get rid of the solid bits of food
testing for glucose:
use the Benedict’s Test to test for glucose:
-if the food sample contains glucose, the solution in the test tube will change from its normal blue colour
-it will become green or yellow in low concentrations of glucose
-it will become brick-red in high concentrations of glucose
testing for starch:
use Iodine solution to test for starch:
-if the sample contains starch, the colour of the solution will change from browny-orange to black or blue-black
testing for proteins:
use the Biuret Test to test for proteins:
-if the food sample contains protein, the solution will change from blue to pink or purple
-if no protein is present, the solution will stay blue
testing for lipids:
use the Sudan III Test to test for lipids:
-if the sample contains lipids, a milky white emulsion will form
-if the sample doesn’t contain lipids, it will remain colourless
what are biological catalysts?
-a catalyst is a substance which increases the speed of a reaction, without being changed or used up in the reaction
enzymes:
-they are protein molecules and the shape of the enzyme is vital to its function
-this is because each enzyme has its uniquely shaped active site where the substrate binds (joins)
-a simplified way to look at it is the Lock and Key Hypothesis:
-a substrate is a molecule that is changed in a reaction, it must have the correct shape to fit into the active site
how does temperature affect enzyme function?
-the optimum is around 37ºC (body temperature)
-the rate of reaction increases with an increase in temperature up to this optinum, but above this temperature it rapidly decreases and eventually the reaction stops
-when the temperature becomes too hot, the bonds in the structure will break
-this changes the shape of the active site, so the substrate can no longer fit in, which means it is denatured
practical: investigate how enzyme activity can be affected by changes in temperature
1) Starch solution is heated to set temperature
2) Amylase is added
3) Iodine is added to each well after a minute
4) Measure the time it takes until the iodine stops turning blue-black (meaning starch is present)
5) Repeat the test with different temperature
how does pH affect enzyme function?
-the optinum pH for most enzymes is 7, but some that are produced in acidic conditions, such as the stomach, have a lower optinum pH
-if the pH is too high or too low, the forces that hold the amino acids chains will be affected
-this will change the shape of the active site, so the substrate can no longer fit in
-the enzyme is said to be denatured and can no longer work
diffusion:
-diffusion is the spreading out of particles resulting in a net movement from an area of higher concentration to an area of lower concentration
-it is a passive process as no energy is required
-the molecules have to be small in order to be able to move accross, for example oxygen, glucose, amino acids and water, but larger molecules such as starch and proteins cannot
osmosis:
-> the movement of water from a less concentrated solution to a more concentrated one through a partially permeable membrame
-water moves from a dilute solution to a concentrated solution because it moves from ana area with high water potential to low water potential- down a concentration gradient
-it is a passive process
What is an Isotonic solution?
If the concentration of sugar in a external solution is the same as the internal, there will be no movement and the solution is said to be isotonic to the cell
What is a Hypertonic solution?
If the concentration of sugar in an external solution is higher than the internal, water moves out, and the solution is said to be hypertonic to the cell
What is a Hypotonic solution?
if the concentration of sugar in external solution is lower than the internal, water moves in, and the solution is said to be hypotonic to the cell
active transport:
-active transport is the movement of particles from an area of lower concentration to an area of higher concentration, i.e: against a concentration gradient
-this requires energy from respiration as it is working against the gradient, which is why its called active
concentration gradient: affecting rate of movement
the greater the difference in concentration, the faster the rate of diffusion because more particles are randomly moving down the gradient than are moving against it
temperature: affecting rate of movement
the greater the temperature, the greater the movement of particles, resulting in more collisions and therefore a faster rate of diffusion
surface area:volume ratio: affecting rate of movement
the greater the surface area, the more space for particles to move through, resulting in a faster rate of diffusion
distance: affecting rate of movement
the further the particles have to travel the longer it will take
practical: investigate diffusion in non-living systems
1) cut a 1cm^3 cube of agar made of sodium hydroxide and phenolphthalein
2) place cube in solution with hydrochloric acid
3) remove the cube and wash with water to stop further reaction
4) cut the cube in half and measure the distance that the acid has caused agar to become colourless from outside inwards
5) repeat the experiment two more times and calculate the mean
6) repeat with different concentrations of hydrochloric acid
practical: investigating osmosis in potatoes
1) place different sucrose solutions including 0% for a control, in different boiling tubes
2) dry potato strips on a paper towel and measure the masses
3) place each potato strip into each surcrose solution for 20 mins and record how the mass changed
4) repeat tests at each solution several times with potato strips of similar masses
photosynthesis:
-photosynthesis is the process of making glucose from sunlight in the leaves of the plant
-it is an endothermic reaction in which light energy is converted into chemical energy within the chloroplasts
word equation for photosynthesis:
carbon dioxide + water (light)-> glucose + oxygen
CO2 + H20 -> C6H12O6 + O2
balanced: 6CO2 + 6H02 -> C6H12O6 + 602
factors affecting photosynthesis: temperature
-with an increase in temperature, the rate of photosynthesis increases
-however, as the reaction is controlled by enzymes, this trend only continues up to certain temperature until the enzymes begin to denature and the rate of reaction decreases
factors affecting photosynthesis: light intensity
-for most plants, the higher the light intensity, the rate of photosynthesis increases
-as the distance between the light source and the plant increases, the light intensity decreases, i.e. it is inversely proportional to the square of the distance: light intensity∝ 1/distance^2
-this means that if a lamp is 2 metres away from a plant, then light intensity of the lamp is a 1/4 of its original value -> 1/2^2 = 1/4
factors affecting photosynthesis: carbon dioxide concentration
-carbon dioxide is also needed to make glucose
-as the concentration of carbon dioxide increases, the rate of reaction increases
structure of a leaf:
-waxy cuticle: helps to reduce water loss by evaporation and is a protective layer found at the top of a leaf
-upper epidermis: very thin and transparent in order to let light in to the palisade mesphyll
-palisade mesophyll: contain lots of chloroplasts so that photosynthesis can happen rapidly
-spongy mesophyll: have lots of air spaces to allow gases to diffuse in and out of cells faster
-lower epidermis: contains guard cells and stomata (gaps)
-guard cell: kidney-shaped cells that open and close the stomata by absorbing or losing water(when lots of water is available, the cells fill and open stomata)
-stomata: where gas exchange and loss of water by evaporation takes place- opens during the day and closes at night
plants require 2 main types of mineral ions:
-mineral ions: for growth
-magnesium: required for chlorophyll production, deficiency -> causes leaves to turn yellow
-nitrate: required to produce amino acids, deficiency
-> causes stunted growth and turns leaves yellow
practicals investigating photosynthesis:
-use water plants, such as Elodea which release bubbles of oxygen when photosynthesising
-a lamp with an LED bulb is set up beside the beaker of water containing the water plant. An LED is best as it will not raise the temperature of the water
-sodium hydrogen carbonate (NaHCO3) is added to the water to supply carbon dioxide
-this can set up can be used to investigate the evolution of oxygen from a water plant
structure of the heart:
-muscular walls to provide a strong heartbeat
-the muscular wall of the left ventricle is thicker because blood needs to be pumped all around the body rather than just to the lung like the right ventricle
-4 chambers that seperate the oxygenated blood from the deoxygenated blood: 2 atria above and 2 ventricles below
-valves to make sure blood does not flow backwards
-coronary arteries cover the heart to provide its own oxygenated blood supply
