AQA biology separate science higher tier paper 1

what are 2 types of eukaryotic cells

animal cells and plant cells

what type of cell is bacteria

prokaryotic cell

where is the DNA found in animal and plant cells

in the nucleus

what is the function of the cell membrane

controls movement of substances in and out of the cell

what is the function of mitochondria

site of respiration to transfer energy for the cells

what is the function of chloroplasts

contain chlorophyll to absorb light energy for photosynthesis

what is the function of ribosomes

enable production of protein

what is the function of the cell wall

strengthens and supports the cell

what is the structure of the main genetic material in a prokaryotic cell

single loop of DNA

how are electron microscopes different to light microscopes

electron microscopes use beams of electrons instead of light ,cannot be used to view samples, are much more expensive and have a much higher magnification and resolution

what is the function of a red blood cell

carries oxygen around the body

give three adaptations of a red blood cell

no nucleus, contains a red pigment called haemoglobin ,has a bi-concave disc shape

what is the function of a nerve cell

carries electrical impulses around the body

give two adaptations of a nerve cell

branched endings, myelin sheath insulates the axon

what is the function of a sperm cell

fertilises an egg

give two adaptations of a sperm cell

tail, contains lots of mitochondria

what is the function of a palisade cell

carries out photosynthesis in a leaf

give two adaptations of a palisade cell

lots of chloroplasts, located at the top surface of the leaf

what is the function of a root hair cell

absorbs mineral ions and water from the soil

give two adaptations of a root hair cell

long projection, lots of mitochondria

what is diffusion

net movement of particles from an area of high concentration to an area of low concentration along a concentration gradient-this is a passive process

name three factors that effect the rate of diffusion

concentration gradient, temperature ,membrane surface area

how are the villi adapted for exchanging substances

long and thin -increases surface area

one cell thick membrane -short diffusion pathway

good blood supply -maintains a steep concentration gradient

how are the lungs adapted for efficient gas exchange

alveoli-large surface area

moist membrane -increases rate of diffusion

one cell thick membrane-short diffusion pathway

good blood supply-maintains a steep concentration gradient

how are fish gills adapted to efficient gas exchange

large surface area for gases to diffuse across

thin layer of cells-short diffusion pathway

good blood supply -maintains a steep concentration gradient

what is osmosis

diffusion of water from a Diute solution to a concentrated solution through a partially permeable membrane

give one example of osmosis in a plant

water moves from the soil into the root hair cell

what is active transport

movement of particles against a concentration gradient -from a dilute solution to a more concentrated solution -using energy from respiration

what is active transport needed in plant roots

concentration of mineral ions in the soil is lower than inside the root hair cell-the mineral ions must move against a concentration gradient to enter the root hair cells

what is the purpose of active transport in the small intestines

sugars can be absorbed when the concentration of sugar in the small intestines is lower than the concentration of sugars in the blood

what is a stem cell

undifferentiated cell that can differentiate into one or more specialised cell

what are adult stem cells

stem cells from adults that can only differentiate into certain specialised cells

where are adult stem cells found

bone marrow

what are embryonic stem cells

stem cells from embryos than can differentiate into any specialised cell

where are embryonic stem cells found

early human embryo (usually spare embryos from fertility clinics)

what is therapeutic cloning

patients cells are used to create early embryo clones of themselves -stem cells from embryo can then be used to treat the patients medical conditions

give one advantage of using therapeutic cloning

stem cells from the embryo are not rejected when transplanted because they have the same genes as the patient

give one advantage of using adult stem cells

fewer ethical issues as obtained from adults who can consent to their use

give two disadvantages of using adult stem cells

can take a long time for a suitable donor to be found

can only differentiate into some specialised cell types -can only treat fewer diseases

give two advantages of using embryonic stem cells

can differentiate into any specialised cell ,so can be used to treat many diseases

easier to obtain as they are found in spare embryos from the fertility Clinique

give two disadvantages of using embryonic stem cells

ethical issues surrounding their use ,as every embryo is a potential life

potential risks involved with treatment such as transfer of of viral infections

what are plant meristems

areas where rapid cell division occurs in the tips of the roots and shoots

give two advantages of using plant meristems to clone plants

rare species can be clones to protect them from extinction

plants with special features such as disease resistance can be clones to produce many copies

give one disadvantage of using plant meristems to clone plants

no genetic variation -s an entire cloned crop could be destroyed by disease

what is cell division by mitosis

body cells divide to form two identical daughter cells

what is the purpose of mitosis

growth ,repair of cells and asexual reproduction

what happens during the first stage of the cell cycle

cell grows bigger ;chromosomes duplicate; subcellular structures increase

what happens during mitosis

one set of chromosomes is pulled to each end of the cell and the nucleus divides

what happens during the third stage of cell cycle

the cytoplasm and cell membrane divide forming two identical daughter cells

name the 5 levels of organisation

cells-tissues-organs-organ system-organism

what is a tissue

group of cells with similar structures and functions

what is an organ

group of tissues working together to perform a specific function

what is the function of liver in digestion

produced bile which neutralises hydrochloric acid from the stomach and emulsifies fats to form small droplets with a large surface area

what is the function of saliva in digestion

lubrication to help swallowing-contains amylase to break starch down

name three enzymes produced in the pancreases

amylase, protease, lipase

name the four main components of blood

red blood cells ,white blood cells ,plasma ,platelets

for is the function of the platelets

form blood clots-prevent the loss of blood and stop wounds from being infected

describe three adaptations of red blood cells

bi-concave disc shape -large surface area to volume ratio for diffusion of oxygen

contains haemoglobin-binds to oxygen

no nucleus-more space of oxygen

how do white blood cells protect the body

engulfs pathogens

produces antitoxins to neutralise toxins or antibodies

name the substances transported in the blood plasma

hormones, proteins, urea, carbon dioxide, glucose

why is the human circulatory system a double circulatory system

blood passes through the heart twice for every circuit around the body -deoxygenated blood is pumped from the right side of the heart to the lungs and the oxygenated blood that returns is pumped from the left side of the heart to the body

what does the structure of an artery relate to its function

carried blood away from the heart under high pressure -has a small lumen and thick elasticated walls that can stretch

how does the structure of a vein relate to its function

carried blood back to the heart at low pressure- doesn’t need thick walls but has valves to prevent the backflow of blood

how does the structure of a capillary relate to its function

carries blood to cells and tissues-has a one cell thick wall to provide a short diffusion distance

list the structures air passes through when breathing in

mouth-trachea-bronchi-bronchioles-alveoli

what are enzymes

protein molecules that catalyse specific reactions in an organism

why are enzymes described as specific

each enzyme only catalyses a specific reaction because the active site only fits together with certain substates

describe the function of amylase

to break down starch into glucose

where is amylase produced

salivary glands ,small intestines .pancreas

describe the function of proteases

break down proteins into amino acids

where are proteases produced

stomach pancreas and small intestines

describe the function of lipases

to break down lipids into fatty acids and glycerol

where are lipases produced

pancreas and small intestines

what are two factors that affect the rate of activity of an enzyme

temperature and ph

what does denature mean

shape of an enzymes active site has changed by high temperatures or extreme ph so it can no longer bind with the substrate

describe the effect of temperature on enzyme activity

as temperature increases the rate of reaction increases until it reaches the optimum for the enzyme activity -above this temperature enzyme activity decreases and eventually stops

describe the effect of ph on enzyme activity

different enzymes have a different optimum ph at which their activity is greatest a ph much lower or higher than this enzyme activity decreases and stops

why do different digestive enzymes have different optimum phs

different parts of the digestive system have very different PHs the stomach is strongly acidic and the ph in the small intestines is close to neutral

why is a leaf an organ

there are many tissues inside the leaf the work together to preform photosynthesis

how is the upper epidermis adapted for its function

single layer of transparent cells allow light to pass through

cells secrete a waxy substance that makes leaves waterproof

how is the palisade mesophyll adapted for its function

tightly packed cells with lots of chloroplasts to absorb as much light as possible for photosynthesis

how is the spongy mesophyll adapted for its function

air spaces increase the surface area and allow gasses to diffuse quickly

what is the function of the guard cells

controls the opening and closing of the stomata

what is the function of a xylem

transport water and mineral ions from the roots to the rest of the plant

give three adaptations of the xylem

made of dead cells

no end wall between cells

walls strengthened by a chemical called lignin to withstand the pressure of water

what is the function of the phloem

transport dissolved sugars from the leaves to the rest of the plant

what is the purpose of translocation

transport dissolved sugars from the leaves to the other parts of a plant for respiration, growth and storage

define the term transpiration

movement of water from the roots to the leaves through the xylem

what is the purpose of transpiration

provide water to keep cells turgid

provide water to cells for photosynthesis

transport mineral ions to leaves

name four factors that effect the rate of transpiration

temperature ,light intensity ,humidity ,wind speed

what effect does temperature have on the rate of transpiration

higher temperatures increase the rate of transpiration

what effect does humidity have on the rate of transpiration

higher levels of humidity decrease the rate of transpiration

why does increased light intensity increase the rate of transpiration

stomata open wider to let more carbon dioxide into the leaf for photosynthesis

what is the function of stomata

allows diffusion of gasses in and out of the plant

where are most stomata found

underside the leaves

what is the advantage to the plant of having a high number of stomata in the location

reduces the amount of water loss through evaporation

what is a communicable disease

a disease that can be transmitted from one organism to another

what is a pathogen

a microorganism that causes disease

name the four types of pathogens

bacteria ,fungi, protists, viruses

how can pathogen spread

air, water ,direct contact