AQA AS LEVEL BIOLOGY

what is RNA?

ribonucleic acid
MRNA and TRNA
single stranded
shorter
AU CG

what are biological molecules?

molecules made and used by living organisms eg. lipids, carbs, DNA, AT, water, inorganic ions

what are the functions of carbohydrates?

-energy source (respiration)
-energy store (starch and glycogen)
-structure (cellulose)

ATP structure?

1 adenosine 3 phosphates
ADP and energy= ATP
condensation reaction using ATP synthase
carries energy in bonds
hydrolysis breaks down into ADP and energy using ATP hydrolase
releases energy from phosphate group bonds

what are the building blocks of carbohydrates called?

monosaccharides

why is ATP a good source of energy?

immediate release, only need to break one bond
releases small amounts of energy at a time, manageable

examples of monosaccharides

glucose, fructose, galactose

uses of ATP?

protein synthesis
organelle synthesis
dna replication
mitosis
active transport
metabolic reactions
movement
homeostasis

formula for monosaccharides?

c6h12o6 -same formula but arranged differently

role of water in biology?

acts as a habitat for organisms
make up cytoplasm, tissue fluid, blood, xylem and phloem

water properties?

dipolar
partially positive hydrogen partially negative oxygen
so separate water molecules form hydrogen bonds with eachother

difference between alpha and beta glucose?

on carbon 1, alpha glucose has an OH group on the bottom. beta glucose has it at the top.

how are monosaccharides joined together?

condensation reaction between 2 OH groups

roles of water?

-habitat, high shc so a lot of heat needs to be applied before evaporation due to hydrogen bonds. ice is less dense than water so floats up
-solvent, dipolar so separate solutes by charge depending on partial charge. solute dissolves in water, useful for cytoplasm, diffusion and active transport ect
-hydrostatic pressure, when pressurised, water provides a strong pushing force particularly in mass flow. supports turgidity
-homeostasis, sweat on skin uses blood heat to evaporate, cooling individual. sweat is made up of hydrogen bonds,stable structure, large amount of heat to evaporate. LATENT HEAT OF EVAPORATION.

bond in carbohydrate?

glycosidic

what are inorganic ions?

salts or minerals
don't contain carbon
eg sodium and chloride ions

examples of disaccharides

sucrose, lactose (glucose + galactose), maltose (glucose + glucose)

kingdoms of biology?

animal, plant, bacteria, fungi, protocista
animal and plant multicellular
others are microorganisms
viruses aren't living
all organisms made up of cells

eukaryotic vs prokaryotic

eukaryotic - membrane bound organelles eg. nucleus
prokaryotic - no membrane bound organelles, smaller ribosomes

formula for disaccharides?

c12h22o11

what are the 2 forms of reproduction?

sexual- 2 parents each provide gamete which fuse to make zygote which develops into organism
asexual- one parent to produce genetically identical offspring

how are polymers separated?

hydrolysis (addition of water)

how does a zygote develop into an organism?

stem cell, undifferentiated
divides by mitosis to make more stem cells
each cell differentiates into specialised
each specialised divides by mitosis to make tissues
different tissues for organ, and so on

what is a polysaccharide?

many monosaccharides joined together by condensation reaction/glycosidic bonds.

structure of nucleus?

contains DNA wrapped around histones to form chromatin
double membrane called nuclear envelope with pores
nucleolus produces ribosomes and mRNA
nucleoplasm contains chromatin

examples of polysaccharides

-amylose, long chain of alpha glucose, makes starch/glycogen
-cellulose, long chain of beta glucose

properties of starch and glycogen as energy stores?

-insoluble, doesn't affect water potential, cell won't shrink or burst
-coiled, compact, fits inside cells better
-branched/chained, easy to break down, glucose removed from the end

endoplasmic reticulum?

rough- has ribosomes ,protein synthesis, process and package
smooth- makes lipids and carbs

golgi apparatus?

processes and packages proteins
into vesicles
digestive enzymes placed into lysozomes, vesicles with membranes

structure of cellulose?

-beta glucose arranged in straight chain (each alternative beta glucose rotated 180°)
-many cellulose chains are cross linked by hydrogen bonds, form microfibrils
-microfibrils crosslinked to make macrofibrils
-hydrogen bonds are strong together, hard to break,makes cellulose strong
-forms cell wall structure

mitochondria?

site of respiration, produces ATP which releases energy
cristae- inner membrane has large surface area so more metabolic enzymes can attach
matrix- middle liquid

test for starch?

iodine brown to blue/black

chloroplast structure?

absorbs light energy for photosynthesis to produce glucose
double membrane
thylakoid disks stack into granum
thylakoid surrounded by stroma fluid
large surface area

test for reducing sugars

heat with benedicts, turns brick red

vacuole

surrounded by membrane called tonoplast
contains cell sap
keeps cell turgid
pushes chloroplasts to surface

test for non reducing sugar?

-heat with benedicts, no change
-add dilute hcl (hydrolyses glycosidic bond)
-add sodium hydrogen carbonate to neutralise
-heat with benedicts, will turn brick red

structure of bacteria?

circular DNA and plasmids
no membrane bound organelles
smaller ribosomes
cell wall made of murein
some have slime capsule (protect from phagocytosis) and flagella (movement)

types of proteins?

globular and fibrous

structure of virus?

DNA or RNA
if RNA, contains reverse transcriptase enzyme to convert it into DNA
capsid
phospholipid membrane
attachment proteins to identify and attach to host

what are globular proteins?

have a specific 3d shape, soluble eg. haemoglobin

how does a virus infect their host cell?

uses attachment protein to attach
send in DNA capsid which uses cell to make virus components
producing copies and destroying host cell

what are fibrous proteins?

insoluble, inflexible and strong eg. keratin

how do amino acids differ?

have different r groups

what is a chromosome?

coiled DNA
formed during interphase
made of 2 sister chromatids joined by centromere
2 copies of same DNA molecule

what is a homologous pair of chromosomes?

1 maternal 1 paternal
same genes but different alleles

how are amino acids joined?

condensation reaction between carboxyl group and amine group. leaves bond between carbon and nitrogen, DIPEPTIDE

primary structure of a protein?

sequence of AA, polypeptide chain. change in sequence, bonds will be formed in different places in secondary.

secondary structure?

primary structure coils to form an alpha helix, hydrogen bonds form between amino acids

tertiary structure?

secondary structure folds again to form final 3d shape, held by ionic/hydrogen/disulfide bonds

quarternary structure?

more than one polypeptide chain, non protein can be involved

quarternary structure examples?

haemoglobin, antibodies, collagen

collagen structure?

-strong
-primary structure glycine
-secondary tight coil
-tertiary coils again
-quarternary three chains wrapped like rope

protein test?

biruet reagent, turns purple

what is an enzyme?

biological catalyst
speeds up reaction without being used up
lowers activation energy

what makes an enzyme specific?

specific active site, only complimentary substrates can bind and form enzyme substrate complexes

lock and key model?

active site is rigid, only exactly complimentary substrates fit

induced fit model?

shape of active site changes slightly so substrate fits exactly forming ES complex

affect of substrate concentration on enzyme activity?

more substrate, more chance of successful collisions, ES complex, increase rate
increases until all enzymes are saturated

affect of enzyme concentration on enzyme activity?

more enzymes, more successful reactions, ES complexes
continues until all the substrates are used up

affect of temperature on enzyme activity?

as temp increases, kinetic energy increases, molecules move faster
more collisions, more ES complexes
carries on until optimum
after optimum, tertiary bonds break
lose active site shape
no longer complimentary
denatured

affect of ph on enzyme activity?

if ph is changed away from optimum, bonds in tertiary structure break, enzyme denatured

competitive inbibitor?

similar shape to substrate
fits in active site
blocks ESCS from forming

non competitive inhibitor

binds on somewhere other than active site, changes the enzymes shape, prevents substrate from binding

3 types of lipids?

triglycerides
phospholipids
cholesterol

triglyceride structure

1 glycerol 3 fatty acids
joined by ester bonds in condensation reaction
COOC bond
either saturated or unsaturated

phospholipid stucture?

1 glycerol 2 fatty acids 1 phosphate group
phosphate forms hydrophilic head
fatty acid hydrophobic tail
forms phospholipid bilayer

what are nucleic acids?

polymers made from nucleotides
eg DNA and RNA

what is DNA?

deoxyribonucleic acid
in all organisms
carries genes, section of DNA coding for a protein

building block of DNA?

nucleotide (made of phosphate, deoxyribonucleic sugar, nitrogenous base)
AT
CG

DNA structure?

double helix
sugar and phosphate condensation reaction
hydrogen bonds between bases
AT CG
double strand coiled in double helix

properties of DNA structure?

double stranded, one strand acts as template for semi con replication
helix, more compact
sugar phosphate backbone protects bases
hydrogen bonds weak, easy to break for replication
complimentary Base pairing, ensures identical DNA copies made

describe semi conservative replication?

DNA double strand separated by DNA helicase, breaks h bonds
one strand acts as template
free nucleotides match up and bind to complimentary bases
DNA polymerase joins sugar phosphate back of new strand

scr evidence?

bacteria DNA has 2 isotopes 14n and 15n
15n heavy
14n light
nitrogen found in bases

what does mitosis produce?

two genetically identical diploids which have a full set of chromosomes

what happens in interphase?

dna replication
protein and organelle synthesis

what happens during prophase?

chromatin condenses to make chromatids
nuclear envelope breaks down
spindle fibres form

what happens during metaphase?

chromosomes line up on cell equator
attach to spindle fibres by centromere

what happens during anaphase?

spindle fibres pull sister chromatids by centromere to opposite poles
sister chromatids make a v shape

what happens during teleophase?

chromatids uncoil to make chromatin again
nuclear envelopes reform
2 identical nuclei formed in one cell

what happens during cytokinesis?

cytoplasm splits into 2 creating 2 identical sister cells

what happens to chromosome number during mitosis?

stays the same
diploid

what is cancer?

formation of tumour due to uncontrolled mitosis/ cell division

how does uncontrolled cell division occur?

mutation of dna/ genes that regulate mitosis
cell mutations
can occur randomly or due to mutagens eg. radiation
cancer cells are rapidly dividing
spend less time in interphase and more time in mitosis

treatments for cancer?

surgery to remove tumour
chemotherapy, drugs that inhibit mitosis in rapidly dividing cells
radiotherapy, radiation used to kill cancer cells

disadvantages of chemotherapy?

kills off normal healthy cells eg hair skin rbcs
causing hair loss,dry skin and tiredness
needs to be given as regular doses to allow time for healthy cells to recover

how do bacteria reproduce?

binary fission (roughly splits cell into two parts)
copy DNA and separate by asexual reproduction

formula for magnification

image/actual

unit conversions?

1mm=1000 micrometers
1mm=1,000,000 nanometers

why do mitochondria appear different shapes in images?

viewed from different angles at different levels
some cut transversely others cut through the middle of the cell

why do electron microscopes have a higher resolution?

electron beams have a shorter wavelength

TEM and SEM differences?

tem- electrons absorbed
sem- electrons bounce off specimen

advantages and disadvantages of TEM?

good- highest magnification and resolution
bad- artefacts made, only dead specimens, need to be thin, black and white, 2d image

why do electron microscopes need to be in a vacuum?

in air, oxygen molecules could collide with electrons and prevent electrons from reaching specimen

advantages and disadvantages of SEM?

good- 3d image
bad- only dead specimens, black and white image, artefacts

why does cell solution need to be cold, isotonic and ph buffered before homogenisation?

cold- reduce enzyme activity which could damage organelles
isotonic- no osmosis occurs so cells don't shrink or burst
ph buffered- mantain constant ph

why do cells need to be homogenised during cell fractionation?

to break open cell membrane and release organelles so organelles can be studied in isolation

why do cells need to be filtered during fractionation?

remove membrane and whole cells

what is cell ultra centrifugation?

spun at low centrifugal force at first
nucleus is largest so forms the first pellet at bottom
pellet decanted and supernatant recentrifuged at higher speed
next heaviest organelle leaves and so on

organelles by size?

nucleus
chloroplast
mitochondria
er/golgi/lysozomes
ribosomes

factors affecting diffusion?

surface area
concentration gradient
thickness
temperature
size of molecules