bio (E-H)

diffusion is a consequence of

random movement of individual particles.

-movement of substances down a conc gradient

why do living organisms require diffusion

diff. doesnt require energy and only certain substances pass through the cell membrane this way e.g. water, co2, o2

Purpose of leaf having large SA

For diffusion of co2 and absorption of light

osmosis=

diffusion of water molecules from an area of higher w.p to an area of lower w.p across a s.p.m

osmosis -gradient

goes down a water potential gradient

turgid=

in plants or animals

swollen and pushed against the cell wall

plants

plasmolysed=

in plants or animals

shrunk and pulled away from the cell wall

plants (plas.. plant)

lysis=

in plants or animals

the cell bursts because it cant resist the pressure

animals

diffusion examples

yes

crenation example

in plants or animals

cell shrivels and shrinks.

animal

why plants wilt when not enough water

• water moves in and out of plant cell through the cell wall + membrane by osmosis

• when the cell vacuole is full of water, water pressure pushes against the cell wall and the cell is turgid.

• the cell wall is inelastic so it supports the cell + plant

• when the vacuole doesnt contain enough water bcus its losing more water then its absorbing, it becomes flaccid. theres not enough water pressure so it begins to wilt

• if it loses so much water that the cell membrane pulls away from the cell wall then it is plasmolysed.

flaccid vs plasmolysed

Flaccid refers to a wilted or limp state of a plant cell due to water loss and reduced turgor pressure, while plasmolysed describes a cell that has lost water to the point where the cell membrane pulls away from the cell wall, resulting in cell shrinkage.

what factors effect rate of diff

conc gradient,

SA-vol ratio,

temp,

distance

active transport=

the movement of particles from an area of low conc to an area of high conc against a concentration gradient. thisrequires energy from respiration (ATp)

-needs a carrier protein in membrane

at transports what kind of stuff

large or charged particles

small obj have a smaller or larger SA:vol ratio

large

respiration in cell is

diffusion

Equation for photosynthesis

Carbon dioxide + water --(chlorophyll/ light energy)→ oxygen + glucose

How photosynthesis work

It transfers light energy into chemical energy in the bonds in glucose

why do animals not do photosynthesis

They get their chemical energy in the food they eat (they’re heterotrophs not autotrophs)

Why glucose stored as starch

It’s insoluble so can be stored in cells without affecting the water movement in and out of cells by osmosis

Why some glucose converted to sucrose

Soluble but not as reactive as glucose so can easily be carried around the plant in solution

Why do you need glucose

To make energy and cellular structure

Factors affecting photosynthesis

(What they lack- LACCT)

-light intensity

-availability of water

-chlorophyll concentration (leaf size)

-carbon dioxide concentration

-temperature

How to inc physis

-artificial lighting (plants continue growing at night)

-adding co2 to atmosphere around plants by burning coal on oil stoves

-heating inc temp/ ventilated to dec temp

What absorbs co2

Potassium hydroxide

What’s a hydroponic

Grow plants without soil

do plants grow from water alone?

no as the plant is reliant on the roots for water + mineral uptake. the soil provides support from the stem

why leaves green

chlorophyll absorbs green wave lengths from the sun

how sugar made in leaf

water, co2 and sunlight combine

where is excess sugar stored in plant and in what form

-in roots as starch

aquatic plant

pondweed

what is a limiting factor

prevents r.o.r increasing

component of a reaction that is in shortest supply

why leaves have veins

to support and transport of water, minerals + sugar

what happens at night for plant

respiration takes place and co2 will diffuse out, also happens in day but o2 produced is more and there is light energy

why stomata on underside of leaf

to reduce water loss by transpiration

-not directly exposed to sun and more protected from the breeze.

explain why farmers add fertilisers to their fields to inc the yield but a wild area doesnt need for plants to grow well

the minerals r taken away w the crop when its harvested.

plants in wild areas do not need fertilisers cus the minerals in them return to the soil when they die and are decomposed so they r not removed from the soil

eg of inorganic fertiliser (chemical)

ammonium nitrate

eg of organic fertiliser

farmyard manure + straw

pros and cons of inorganic fertiliser

pros:-mineral content is known- minerals r soluble and available for immediate uptake so can be applied j as the crop needs them.

cons:-needs reapplying during the growing season -soluble minerals easily washed out of the soil polluting rivers and lakes

pros and cons of organic fertiliser

pros:-doesn’t need reapplying during the growing season -improves the soil structure

cons:-minerals not available immediately as the organic matter needs to decay -mineral content is not known and is variable

eutrophication-

is the adding of nutrients to water

( can be adv unless its excess)

eutrophication due to excess nutrients us caused by

fertiliser leaching and sewage pollution

explain process of eutrophication + water pollution

-fertiliser dissolves in rainwater and washes into lakes and rivers (leaching)

-the nitrate and phosphate in the fertiliser cause the rapid growth of algae

-the blanket of algae reduces the light reaching the water plants which now can’t photosynthesis

-water plants die due to lack of photosynthesis and eventually algae die as the nutrients in the fertiliser are depleted

-bacteria multiply very quickly as they decompose the dead plants + algae

-sewage can also be released into the water and the bacteria in sewage multiply very quickly

—the conc of dissolved water falls due ti the aerobic respiration of decaying bacteria

-animals with high oxygen demands suffocate and die e.g. fish

pests=

organisms that reduce yield of crop plants

pros and cons of pesticides

pros:-immediate effect

-increases yield by reducing crop eaten/ reducing competitor weeds

cons:- non-biodegradable

-kill non-pests species

-pests/insects become resistant

-can enter non target organisms and move it up food chains

pros and cons of biological control

pros:- doesn’t affect food chain

-use of a natural enemy to kill a specific pest

cons:- doesn’t kill 100% of the pests

-can cause a new pest problem

-might not be a natural enemy at that climate/ wont work as well at that climate

bio-accumlation=

inc in conc of a pollutant in an organism

bio-magnification=

inc in conc of a pollutant in a food chain

biological control=

+ e.g.

use of a natural enemy to kill a specific pest and so protect the crops

-pathogens, predators, parasites

adv of polythene tunnels

-prevent the entry of pests that can damage plants or diseases that can kill plants

-protect from weather

-slightly inc temp

nucleus=

organelle containing the genetic materialg

genome=

the entire DNA of an organism

chromosome=

very long threads of DNA found in the nucleus. only visible when the cell prepares to divide.

gene=

a section of DNA that codes for a particular protein

protein=

molecule made from a chain of amino acids which are vital for a cell to function

when is dna visible

when the cell is dividing: dna twists and coils up to form visible chromosomes

what form is dna normally found in

dna is uncoiled so the genes are accessible for protein sunthesis

dna structure

made up of two strands coiled into a double helix. each strand has a series of organic bases on the inside. the bases from each side pair up in a specific way. the chain/strand is made up of smaller units called nucleotides

what nucleotides consist

phosphate, sugar and a base

bases for DNA

(AT City Ground) adenine + thymine, Cytosine + guanine

sugar is … in dna

deoxyribose

complementary pairing=

the bases always pair in the same way

DNA vs RNA

rna: single stranded, uracil instead of thymine, has ribose sugar, shorter

genes are the code to make …

proteins

protein synthesis process:

TRANSCRIPTION:

-occurs in nucleus

-the DNA double helix unwinds, and one strand is used as a template which allows single RNA bases to attach in order to create a strand of mRNA.

-once complete, the mRNA strand leaves the nucleus to enter the cytoplasm via the nuclear pore

TRANSLATION:

-occurs in cytoplasm

-the mRNA attaches to the ribosome. The ribosome moves along the mRNA strand decoding it into base triplets, codons.

-each codon codes for a particular amino acid

-tRNA found free in the cytoplasm

-each tRNA codon has an amino acid attached to it which they bring to the ribosome. the tRNA bonds r complementary to the mRNA.

-once the amino acids have linked up, the tRNA then leaves to collect another amino acid.

-once polypeptide chain is complete, it will fold and twist or join other polypeptide chains to form a protein

RNA bases

Are U The Angel God C’s (chocolate?)

Adenine + uracil,

Thymine + adenine,

Guanine + cytosine

codon=

mRNA bases are read in groups of 3

purpose of tRNA

carries the amino acids to the ribosomes, each tRNA has a anticodon which is complimentary to the mRNA codon

a codon is made of 3 bases. there r 4 diff bases. how many diff codons can be produced?

4³ = 64nuc

nucleus cell contains

chromosomes which carry the genes

mutation=

rare random changes in the DNA

what happens if dna code changes (mutates)

the mRNA base sequence will change

-so a diff amino acid may be coded for changing the amino acid sequence

-so the function/ appearance of the protein changes

OR

-the amino acid sequence is the same + so the protein would have the same shape

alleles=

diff forms of the same genes

humans have how many chromosomes

23 -haploid

what cells dont hv pairs of chromosomes

gametes

gamete=

contains only 1 copy of each chromosome from each pair

fertilisation=

fusion of the m+f gametes forming a zygote w 2 copies of each chromosome

locus=

the specific position of a gene on a specific chromosome

dominant=

allele expressed even when only 1 copy present

recessive=

allele expressed only if 2 copies are present

heterozygous=

an individual with 2 diff alleles for a gene

homozygous=

an idividula with 2 identical alleles for a gene

genotype=

the allele each cell has for a certain feature (genetic makeup)

phenotype=

a feature that results from the genotypes (physical feature)

co-dominance=

e.g.

when neither of the alleles are dominant or recessive + so both alleles (r expressed) contribute to the phenotype

-blood groups combine so u hv both

purpose of a test cross

allows you to find out if the organism showing a dominant characterstic is homo/hetero for the fominant allele.

polygenic inheritence=

when several genes can cause a single characteristic

→therefore sm variation in features of ppl

purpose of pedigree charts

used to trace family history + work out the genotypes + risks in the case of inherited gene-related disorders

→ looks for carriers

how many alleles found in a:

zygote

gamete

2

1

monohybrid=

inheritance of characteristics controlled by a single gene

purpose of punetts square

shows possible combination of alleles that could be produced in the offspring

variation=

differences between members of the same species due to diff alleles

species=

a group of organisms that can reproduce to produce fertile offspring

discontinuos variation

-a characteristic that has discrete categories with no intermediates

-monogenic: one gene controls the characteristic

-the gene may also have 2 or more alleles

e.g. blood groups

continuous variation

-a characteristic with a range of values from the smallest to the largest

-polygenic: several genes control the same characteristic

-each gene contributes a little towards the overall pheno.

e.g. height

what factors is variation due to

genes, environment, combination of both

mutations are a source of variation due to the formation of new alleles

yes

when will a mutation be passed on in a sexually reproducing organism

if it occurs in a gamete

mutagens=

e.g.

increase the rate of mutation

ionising radiation (gamma rays), some chemical mutagens (tobacco)