SB1 - KEY CONCEPTS IN BIOLOGY Flashcards
all living organisms can be grouped of ‘classified’ using the classification system that consists of five kingdoms. these five kingdoms are:
- animals
- plants
- fungi
- protoctists
- prokaryotes
kingdoms containing eukaryotic organisms (4)
- animals
- plants
- fungi
- protoctists
features of eukaryotes (2)
- can be multicellular or single-celled
- made up of cells that contain a nucleus bound by a distinct membrane
features of prokaryotes (3)
- always single-celled
- do not contain a nucleus (instead, the nuclear material is found in the cytoplasm)
- prokaryotic cells are substantially smaller than eukaryotic cells
bacteria are prokaryotic organisms
main features of animals (8)
- multicellular
- cells contain a nucleus with a distinct membrane
- cells do NOT have cellulose cell walls
- cells do NOT contain chloroplasts (so unable to carry out photosynthesis)
- feed on organic substances made by other living things
- often store carbohydrates as glycogen
- usually have nervous coordination
- able to move from place to place
cell structures found in animal cells (5)
- nucleus
- cytoplasm
- cell membrane
- ribosomes
- mitochondria
function of the nucleus
- contains the genetic material (DNA) which controls the activities of the cell
function of cytoplasm
- a gel-like substance composed of water and dissolved solutes
- supports internal cell structures
- site of many chemical reactions, including anaerobic respiration
function of cell membrane
- holds the cell together, separating the inside of the cell from the outside
- controls which substance can enter and leave the cell
function of ribosomes
- found in the cytoplasm
- site of protein synthesis
function of mitochondria
- site of most of the reactions involved in aerobic respiration, where energy is released to fuel cellular processes
** energy is RELEASED not made ** - cells with high rates of metabolism (carrying out many different cell reactions) have significantly higher number of mitochondria than cells with fewer reactions taking place
main features of plants (7)
- multicellular
- cells contain a nucleus with a distinct membrane
- cells have cell walls made out of cellulose
- cells contain chloroplasts (so they can carry out photosynthesis)
- they feed by photosynthesis
- store carbohydrates as starch or sucrose
- do not have nervous coordination
cell structures found in plant cells (8)
- nucleus
- cytoplasm
- cell membrane
- ribosomes
- mitochondria
+ - cell wall
- chloroplasts
- permanent vacuole
function of cell wall
- made of cellulose (a polymer of glucose)
- gives the cell extra support, defining its shape
function of chloroplasts
- contains green chlorophyll pigments (to absorb light energy) and the enzymes needed for photosynthesis
function of permanent vacuole
- contains cell sap; a solution of sugars and salts dissolved in water
- used for storage of certain materials
- also helps support the shape of the cell
main features of fungi (9)
- usually multicellular but some (eg. yeast) are single-celled
- multicellular fungi are mainly made up of thread-like structures known as hyphae that contain many nuclei and are organised into a network known as a mycelium
- cells contain a nucleus bound by a distinct membrane
- cells have cell walls made of chitin
- cells do not contain chloroplasts (so cannot carry out photosynthesis)
- feed by secreting extracellular digestive enzymes onto the food (usually decaying organic matter) then absorbing the digested molecules
- some fungi are parasitic and feed on living material
- some fungi store carbohydrates as glycogen
- do not hav coordination
examples of fungi include: moulds, mushrooms, yeasts
cell structures found in fungi (6)
- nucleus
- cytoplasm
- cell membrane
- ribosomes
- mitochondria
+ - cell wall (containing chitin, not cellulose)
main features of protoctists (7)
- a very diverse kingdom of organisms that don’t really belong in any of the other eukaryotic kingdoms
- mainly microscopic and single-celled but some aggregate (group together) into larger forms
- cells contain a nucleus bound by a distinct membrane
- some have features making them more like animal cells, some have features making them more like plant cells
- some protoctists photosynthesis, some feed on organic substances made by other living things
- do not have nervous coordination
cell structures found in protoctists
- nucleus
- cytoplasm
- cell membrane
- ribosomes
- mitochondria
+ - food vacuole
- contractile vacuole
the nuclear material of prokaryotic cells is found in the _________
cytoplasm
prokaryotes are too small to contain __________ or ____________
chloroplasts or mitochondria
bacteria are (prokaryotic/eukaryotic) organisms
prokaryotic
features of bacteria (6)
- microscopic single-called organisms
- possess a cell wall (made of peptidoglycan, not cellulose), cell membrane, cytoplasm and ribosomes
- lack a nucleus but contain a circular chromosome of DNA that floats in the cytoplasm
- plasmids are present in prokaryotes; small rings of DNA (also floating in the cytoplasm) that contain extra genes to those found in the chromosomal DNA
- lack mitochondria, chloroplasts and other membrane-bound organelles found in eukaryotic cells
- some bacteria also have a flagellum or several flagella; long, thin, whip-like tails that allow them to move
specialised cells definition
cells that have developed certain characteristics (adaptations) in order to perform particular functions
cells specialise by undergoing _______________
differentiation
describe what happens during differentiation
a process where cells develop the structure and characteristics needed to be able to carry out their functions
examples of specialised cells in animals (3)
- sperm cells
- egg cells
- ciliated epithelial cells
function of a sperm cell
reproduction: to carry the DNA of the male to the egg cell (ovum) of the female
adaptations of a sperm cell (4)
- head contains the genetic material for fertilisation in a haploid nucleus (containing half the normal number of chromosomes)
- the acrosome in the head contains digestive enzymes so that a sperm can penetrate an egg
- the mid-piece is packed with mitochondria to release energy needed to swim and fertilise the egg
- the tail enables the sperm to swim
function of an egg cell
reproduction: to be fertilised by a single sperm and develop into an embryo
adaptations of an egg cell (3)
- contains a lot of cytoplasm which has nutrients for the growth of the early embryo
- haploid nucleus contains half the genetic material for fertilisation
- cell membrane changes after fertilisation by a single sperm so that no more sperm can enter
function of ciliated epithelial cells
wafting bacteria and other particles (trapped by mucus) up to the throat (to be coughed out) or down to the stomach (to be digested)
adaptations of a ciliated epithelial cell (1)
- extensions of the cytoplasm at the surface of the cell form hair-like structures called cilia which beat to move mucus and trapped particles up to the throat
the first microscopes were discovered in the __th century
17th century
the first cells were observed by ______ _____ in 1665 using a _____ _________
Robert Hooke, light microscope
with a modern light microscope, it is possible to see images of _____
cells and large sub cellular structures (like nuclei and vacuoles)
______ are often required to highlight certain parts of cells when using a light microscope
stains
maximum magnification of light microscopes
approximately 1000-2000x
the first electron microscopes were developed in the 19__s
1930s
electron microscopes use ______ __ _________, rather than light, to visualise specimens
beams of electrons
electron microscopes have a (higher/lower) resolution and magnification than a light microscope
higher
with an electron microscope, it is possible to see images of _____
many more sub cellular structures such as mitochondria, chloroplasts and ribosomes
maximum magnification of an electron microscope
2,000,000x
magnification formulas (2)
magnification = image size / actual size
magnification = magnification of eyepiece lens x magnification of objective lens
components of a microscope
- eyepiece lens (where you put your eye)
- objective lens (closest to the specimen, have low/medium/high power)
- stage (microscope slide is placed here)
- light source (mirror underneath specimen)
- coarse focus (focuses the low and medium power objective lenses) and fine focus (focuses the high power objective lens)
commonly used stains
- methylene blue to stain cheek cells
- iodine to stain onion cells
[microscopy] to prevent cells from being damaged by dehydration you can
add a drop of water to the specimen (beneath the coverslip)
limitations of optical microscopes (3)
- size of cells may appear inconsistent; cell structures are 3d and different tissue samples have been cut at different planes)
- optical microscopes have lower magnification power than other types of microscopes; there are some structures that cannot be seen
- treatment of specimens when preparing slides could alter the structure of cells
1m = _mm
1m = 1000mm
1mm = _μm
1mm = 1000μm
1μm = _nm
1μm = 1000nm
enzymes are _______
- proteins that act as biological catalysts to speed up the rate of a chemical reaction without being changed or used up
- they are made in living cells
- enzymes are necessary to all living organisms as they allow all metabolic reactions to occur at a rate that can sustain life
enzymes are ________ to one particular substrate
specific
the active site of the enzyme is where _______
the substrate attaches
active sites are a _____________ shape to the substrate
complementary
steps of an enzyme catalysed reaction
- enzyme and substrates randomly move about in solution
- when an enzyme and its complementary substrate randomly collide, an enzyme-substrate complex forms and the reaction occurs
- a product forms from the substrate and is then released from the active site. the enzyme is unchanged and will go on to catalyse further reactions
if the bonds that hold the enzyme together are disrupted or broken the enzyme is _________
denatured; the active site loses its shape
enzyme denaturation is (reversible/irreversible)
irreversible; once enzymes are denatured they cannot regain their proper shape and the reaction they are catalysing will stop
conditions that cause enzymes to denature (2)
- high temperatures
- extremes of pH
enzymes work fastest at their _______ temperature
optimum
in the human body, the optimum temperature is about __°C
37°C
low temperatures (do/do not) denature enzymes
low temperatures do not denature enzymes
- they just make them work more slowly due to a lack of kinetic energy
as temperature increases (towards the optimum), activity of enzymes _________
increases (more kinetic energy -> more collisions)
as temperature increases (beyond the optimum), enzymes ________
denature
factors affecting enzyme action (3)
- temperature
- pH
- substrate concentration
as substrate concentration increases, activity of enzymes _________
- increases to a point; likelihood of enzyme-substrate complex formation increases
- however all available active sites eventually become saturated and enzyme activity will PLATEAU
rate of reaction formula
rate = change / time
OR
rate = amount of substrates used or product formed / time
rate of reaction formula IF not told how much something has changed
rate = 1 / time
the purpose of digestion is _______
to break down large, insoluble food molecules into smaller, soluble molecules that can be absorbed into the bloodstream
carbohydrases are a group of enzymes that break down ______ into _______
carbohydrates -> simple sugars eg. glucose
example of a carbohydrase (1)
amylase
amylase is made in the _______ (3)
- salivary glands
- pancreas
- small intestine
amylase breaks down ______ into _______
starch -> glucose
proteases are a group of enzymes that break down ________ into _____ _____
proteins -> amino acids
example of a protease (1)
pepsin
pepsin is made in the _______ (1)
stomach
lipases are enzymes that break down ______ to ________ and _____ _____
lipids (fats) -> glycerol and fatty acids
lipase enzymes are produced in the ________ and secreted into the _____ _________
pancreas, secreted into small intestine
carbohydrates are synthesised by joining ______ ______ together
simple sugars
proteins are synthesised by joining _____ _____ together
amino acids
lipids are synthesised by joining _____ _____ or ________
fatty acids or glycerol
describe the food test for glucose/reducing sugars
- add benedict’s solution to the sample solution in a test tube
- heat in a boiling water bath for 5 minutes
- a positive test will show a colour change from blue -> orange or brick red
describe the food test for starch
- add drops of iodine solution to the food sample
- a positive test will show a colour change from orange-brown -> blue-black
describe the food test for protein
- add drops of biuret solution to the food sample
- a positive test will show a colour change from blue -> violet/purple
describe the food test for lipids
- mix the food sample with ethanol and shake
- allow time for the sample to dissolve in the ethanol
- strain the ethanol solution into another test tube
- add the ethanol solution to an equal volume of cold distilled water
- a positive test will show a cloudy emulsion forming
describe a simple calorimetry experiment
- pour water into a boiling tube and record it’s starting temperature
- weigh the initial mass of the food sample
- set fire to the sample of food using a bunsen burner and hold the sample 2cm from the boiling tube u tik it has completely burned
- record the final temperature of the water
- weigh the mass of any remaining food
limitations of a calorimetry experiment
- incomplete burning of the food sample
- heat energy is lost to the surroundings
ways for substances to move in and out of cells (3)
- diffusion
- osmosis
- active transport
diffusion is ______
- the movement of molecules from a region of higher concentration to a region of lower concentration
- molecules move down a concentration gradient
in diffusion, molecules move (up/down) a concentration gradient
down
describe cell membrane permeability
partially permeable:
smaller molecules can diffuse across the membrane but larger molecules cannot
examples of diffusion in living organisms (6)
- small intestine: digested food products diffuse from small intestine to blood
- leaf: oxygen diffuses from air spaces between mesophyll cells to mitochondria in all cells
- leaf: carbon dioxide diffuses from air spaces between mesophyll cells to chloroplasts in mesophyll cells
- leaf: water vapour diffuses from stomata to air outside stomata
- lungs: oxygen diffuses from alveolar air space to blood in capillaries around alveoli
- lungs: carbon dioxide diffuses from blood in capillaries around alveoli to alveolar air space
factors that influence diffusion
- surface area : volume ratio
- diffusion distance
- temperature
- concentration gradient
diffusion is a form of (active/passive) transport
PASSIVE transport
osmosis definition
the movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution) through a partially permeable membrane
osmosis is a form of (active/passive) transport
PASSIVE transport
water can move in and out of cells by _______
osmosis
osmosis occurs (up/down) a concentration gradient
down
a concentrated solution has a ___ water potential
low
a dilute solution has a ____ water potential
high
describe red blood cells in a hypertonic solution
- red blood cells have HIGHER water potential than solution
- water moves out of cells
- cells shrivel up
describe red blood cells in an isotonic solution
- water potential EQUAL between red blood cell and solution
- no net movement of water
- normal cells
describe red blood cells in a hypotonic solution
- red blood cells have LOWER water potential than solution
- water moves into cells
- cells swell, may lose (burst)
why are plant cells protected from cell lysis?
they have a supporting cell wall whereas animal cells don’t
percentage change in mass formula
(final mass-initial mass) / initial mass
active transport definition
the movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration using energy from respiration
energy is needed for active transport because ______
cells are moving against a concentration gradient, in the opposite direction from which they would naturally move (by diffusion)
examples of active transport
- allows glucose to be transported into the blood stream from the small intestine when the concentration of sugar molecules in the blood is higher
- allows root hair cells in plants to move minerals such as magnesium ions from a region of lower concentration (the soil) to a region of higher concentration ( the cytoplasm of the cell)
