bio paper 2

Nitrogen fixation

Nitrogen fixing bacteria convert atmospheric nitrogen (N2) into ammonium (NH4+)

Nitrification

Nitrifying bacteria convert ammonium (NH4+) into nitrites (NO2-), then into nitrates (NO3-)

Nitrogen fixing vs ammonification

Nitrogen fixing is atmospheric nitrogen to ammonium, by nitrogen fixing bacteria

Ammonification is nitrogen-containing compounds into ammonium, by decomposers, which break down urea, proteins, nucleic acids, and vitamins.

Denitrification

The conversion, by denitrifying bacteria, of soil nitrates into atmospheric nitrogen

Haber process

An industrial process which combines atmospheric nitrogen and hydrogen to form ammonia

Atmospheric fixation

The conversion of atmospheric nitrogen to nitrates by lightning

Why is atmospheric nitrogen inert

Because of the triple covalent bonds in nitrogen molecules

Why are legumes important in the nitrogen cycle

They have a symbiotic relationship with nitrogen-fixing bacteria that live in their root nodules, which convert atmospheric nitrogen into nitrates, to be used for the plant. The plant provides them with glucose for respiration.

function of vacuole

contains cell sap and supports shape of cell

how do plants store carbohydrates

starch or sucrose

how do animals store starch

glycogen

structure of funghi

mycelium made of hyphae with many nuclei

how do funghi store carbohydrates

glycogen

types of protoctists

amoeba = like animal cells

chlorella = chloroplasts and like plants

plasmodium = pathogenic and causes malaria

what are bacteria cell walls made of

peptidoglycan

how do bacteria store carbohydrates

glycogen

tissue definition

similar cells performing one function

test for starch

iodine turns orange-brown to blue-black

test for protein

biuret turns blue to purple

test for lipids

ethanol turns colourless to cloudy emulsion

vitamin c function

makes collagen for skin, hair, bones, gums

what happens in the oesophagus

contractions push the bolus down

what happens in the stomach

pepsin digests proteins

churning

HCl kills bacteria

what happens in the duodenum

enzymes digest food

what happens in the ileum

absorption of digested food molecules

villi increase rate of absorption

what happens in the large intestine

water absorbed from material in the colon

faeces produced and stored in rectum

what happens in the pancreas

amylase + protease + lipase produced

enzymes secreted in alkaline fluid to duodenum

muscles in peristalsis

circular muscles contract to reduce lumen of oesophagus or small intestine

longitudinal muscles contract to reduce length of section

what does the lacteal do in villi

takes fatty acids + glycerol away

adaptations of xylem

dead cells = hollow tubes

strengthened by lignin

what do receptors do

convert stimulus energy to electrical energy, act as transducers

what happens after neurotransmitters diffuse across synapses

bind to receptor molecules on the membrane of the post-synaptic neuron

what happens to the iris in dim light

circular muscles relax

radial muscles contract

pupil dilates

ureter function

Passes urine from kidneys to bladder

seminal vesicle function

Secretes alkaline fluid and nutrients (for the sperm cells), which is a major component of semen

prostate gland function

Adds more fluid and nutrients to sperm to form semen

epididymis function

large tube to store sperm

urethra function

Tube that passes semen and urine through the penis

vas deferens function

Tube to carry sperm from the epididymis to the urethra

menstrual cycle hormone order

FSH

oestrogen

LH

progesterone

mitosis phases

interphase = DNA doubles

prophase = DNA condenses + nuclear membrane begins to break down

metaphase = chromosomes line up along equator

anaphase = chromosomes split

telophase = chromosomes reach poles

cytokinesis = splits into two cells

why do plants need potassium

for growth of fruits and flowers

recombinant DNA definition

Dna created by joining the genetic material of two or more different organisms

transgenic organism definition

an organism with genetic material from an organism of a different species

define stem cell

an undifferentiated cell of an organism that can divide an unlimited number of times

what are the three types of stem cells

embryonic, adult, meristem

features of embryonic stem cell

from the inside layer of an embryo

can differentiate into any type of cell

can be cloned into almost any cell in the body

features of an adult stem cell

from bone marrow

can differentiate into many types of cell

mainly into red blood cells

features of a meristem cell

from the tips of roots and shoots of plants

can form any type of plant

advantages of stem cells

can replace damaged cells

bone marrow transplants can treat leukaemia

can grow organs for transplants

if the organ is from the patient’s own cells, there will be no rejection

you can test drugs without animal testing

issues with stem cells

ethical issues (embryonic)

mutations can occur in cultured stem cells

when do stomata open

when there is a lot of sunlight

how do stomata open

water moves through osmosis into guard cells

they become turgid

colours of hydrogen carbonate indicator

yellow = high

orange/red = atmospheric

purple = low

describe how root hair cells take up water

take in mineral ions through active transport

lowers water potential

water moves in through osmosis

adaptations of root hair cells

mitochondria release energy for active transport

increase sa of roots

define transpiration

evaporation of water from the surface of a plant

why does high wind speed increase rate of transpiration

removes water vapour from air around leaf

concentration gradient becomes steeper

increases water loss

why does high humidity decrease rate of transpiration

more water vapour in the air

weaker concentration gradient

decreases water loss

explain mass potometer

change in mass shows mass of water that has evaporated

explain bubble potometer

uptake of water by stem is the same volume of water lost by transpiration as it is being replaced

for bubble potometer, rate of transpiration =

distance moved by bubble (mm) / time (min)

explain how vaccines work

antigens in vaccine trigger an immune response

lymphocytes recognise antigens

make antibodies

memory cells and antibodies remain in the bloodstream

future antibody production occurs sooner, faster and in greater quantity

how do platelets lead to blood clots

release chemicals that cause solube fibrinogen proteins to convert into insoluble fibrin

forms an insoluble mesh across the wound

traps red blood cells

purpose of blood clots

prevents blood loss and entry of microorganisms

where is ADH released from

pituitary gland

inner part of kidney

medulla

outer part of kidney

cortex

describe the nephron

renal artery transports oxygenated blood to Bowman’s capsule at high pressure

glomerulus (collection of capillaries) increases pressure as the efferent arteriole (exiting) is narrower than the afferent arteriole (entering)

pressure causes ultrafiltration

glomerular filtrate = salts, water, urea, amino acids, glucose

red blood cells and large proteins are never filtered

selective reabsorption of glucose and amino acids at proximal convoluted tubule

as there are many mitochondria that provide energy for active transport

salts reabsorbed by loop of Henle

water reabsorbed at collecting duct

what does FSH do

secretes oestrogen

follicle development

what does oestrogen do

triggers LH

inhibits FSH

development of uterus lining

what does LH do

triggers progesterone

ovulation

corpus luteum development

what does progesterone do

inhibits LH and FSH

maintains uterus lining

describe transcription

occurs in nucleus

hydrogen bonds between complementary base pairs break

exposes the gene (from which a particular polypeptide will be produced) to be transcribed

complementary copy of code from the gene is made by creating a single stranded molecule (mRNA)

leaves nucleus via a pore in the nuclear envelope

describe translation

occurs in cytoplasm

after leaving the nucleus, mRNA attaches to a ribosome

there are free molecules of tRNA in the cytoplasm

tRNA molecules have an anticodon (triplet of unpaired bases) at one end and a region where a specific amino acid can attach at the other

there are at least 20 different tRNA molecules with specific anticodons and amino acid bonding sites

tRNA molecules bind with a specific amino acid and bring it to mRNA on the ribosome

the anticodon on each tRNA molecule pairs with the complementary codon on the mRNA molecule

two tRNA molecules fit onto the ribosome at any time

a peptide bond is formed between two amino acids

process continues until the stop codon on mRNA is reached

amino acid chain forms a polypeptide

what things increase the likelihood of mutations

ionising radiation and chemical mutagens (tar in tobacco)

define biodiversity

variety of living organisms in an ecosystem

effects of deforestation

extinction of species, soil erosion which leads to leaching, flooding, increase of CO2, disturbance to water cycle

explain soil erosion

tree roots stabilise soil

trees take in minerals from soil

minerals are not taken in so leach into rivers or lakes when it rains

how is flooding caused by deforestation

without trees, topsoil is loose and unstable

easily washed away by rain

how does deforestation cause disturbance to the water cycle

many trees together means there are high levels of transpiration

this lead to the formation of clouds, resulting in nearby rainfall

loss of these trees makes nearby areas drier

advantages of fish farms

can selectively breed fish

protects against predators

controls water quality

controls feeding

explain micropropagation

cells (explants) are scraped from parent plant

surface of explants is sterilised

transferred to a petri dish with agar

encourages explants to grow and divide into a small mass of cells (callus)

each callus is transferred to a fresh growth medium that contains plant growth regulators (hormones)

causes development of roots, stems and leaves

forms a plantlet

transferred to potting tray and develops into a plant

advantages of micropropagation

can control desired characteristics

all year round

quick

use of clones

they can produce organs for transplants