COMBINED SCIENCE
GCSE NOTES
COMPLETE SUMMARY
INCLUDES:
● Summary notes for EVERY topic (Biology, Chemistry
and Physics)
● ALL required practicals
● 70 pages of condensed information - everything you
need to SMASH the exams
● Diagrams
Notes I made and used to get 99 (A**) in AQA Combined Science
BIOLOGY PAPER 1
,Cell Biology
Cells either eukaryotic (complex, incl. all animal + plant cells) or prokaryotic (smaller + simpler e.g.
bacteria)
Animal cells – nucleus (DNA, controls activities), cytoplasm (chemical reactions, enzymes), cell
membrane (holds together, in + out control), mitochondria (aerobic respiration) + ribosomes
(proteins made)
Plant cells – everything animal cells have + cell wall (cellulose, support), permanent vacuole (sap) +
chloroplasts (photosynthesis, chlorophyll)
Bacterial cells – much smaller, prokaryotes, no chloroplasts or mitochondria, no true nucleus but
single circular strand of DNA in cytoplasm and may have small rings of DNA (plasmids)
-
Light Microscope Electron Microscope
Use light + lenses to magnify Use electrons (higher magnification +
resolution)
See individual cells + large subcellular See smaller things in more detail + can see
structures ribosomes + plasmids
Cheaper V. expensive
magnification=image ¿ real ¿ ¿
Need to have image + real sizes in same units (1cm = 10mm, 1mm = 1000μm [micrometres], 1μm = m [micrometres], 1μm [micrometres], 1μm = m =
1000nm [nanometres])
-
Microscopy practical:
- Drop of water on clean slide
- Use tweezers to peel epidermal tissue off one of the layers
- Place into water on slide
- Add drop of iodine solution (stain)
- Lower cover slip on (avoid bubbles)
- Clip slide onto stage + select lowest-powered objective lens
- Use coarse adjustment knob to move stage up + down
- Look down eyepiece, move stage until it focuses
- Adjust focus w/ fine adjustment knob
- Swap to high-powered objective lens + refocus
- Draw observations
-
Differentiation – becoming specialised, cells develop different subcellular structures + turn into
different types of cell, usually occurs when organism develops but lots of plant cells never lose
ability.
,Sperm cell (reproduction) – long tail, streamlined head = swimming, mitochondria = energy, enzymes
= digest through egg cell membrane
Nerve cell (rapid signalling) – long = cover more distance, branched connections = connect to other
nerve cells to form network
Muscle cell (contraction) – long = space to contract, lots of mitochondria = generate energy
Root hair cell (absorb water + minerals) – long ‘hairs’ = big surface area
Phloem + xylem (transporting substances) – xylem = hollow, phloem = v. few subcellular structures
-
Chromosomes – coiled up lengths of DNA, body cells have 23 pairs
Cell Cycle:
Growth + DNA replication – Cell grows + increases amount of subcellular structures,
then duplicates its DNA forming X shaped chromosomes
Mitosis – chromosomes line up at centre of cell + cell fibres pull them apart to
opposite ends of cell, membranes form around each of the sets of chromosomes,
become nuclei of two new cells, cytoplasm + cell membrane divide
Cell has produced two new daughter cells w/ exact same DNA as each other + parent cell
-
Stem Cells – undifferentiated, found in early human embryos. Can be found in adults (mainly bone
marrow) but can only turn into some types of cells
Bone marrow transplant: replace faulty blood cells
Insulin-producing cells: diabetes
Nerve cells: people paralysed by spinal injuries
Therapeutic cloning (embryos made to have same genetic information as patient): no rejection
For Against
Help suffering people Embryos still human lives
Only use unwanted embryos from fertility Fertility clinics also immoral, both should be
clinics banned
Would follow strict guidelines (already do in Should concentrate more on finding other
UK) sources of stem cells
In plants: found in meristems, can differentiate throughout entire life, used to produce clones of rare
plants quickly + cheaply, can also grow crops of identical plants w/ identical features (e.g. disease
resistance)
-
Diffusion: spreading out of particles from an area of higher concentration to an area of lower
concentration, happens in solutions + gases
, Higher concentration gradient = faster diffusion rate, higher temp = more energy = faster diffusion,
higher surface area = more particles can pass through = faster diffusion
Cell membranes: control movement in + out of cells, small molecules (oxygen, water etc.) diffuse
through but big molecules (starch + proteins) can’t fit
-
Osmosis: movement of water molecules across a partially permeable membrane (v. small holes, so
water fits through but sucrose can’t) from a region of higher water concentration to a region of
lower water concentration
Water molecules move randomly, so pass both ways through membrane but still steady net flow to
region w/ fewer water molecules: strong sugar solution = more dilate
Osmosis practical:
- Cut potato into identical cylinders & put in beakers w/ different conc. sugar solutions
- Measure mass of cylinders & leave in beakers for 24hrs
- Take out, dry & measure mass
- If drew in water by osmosis, mall will increase & vice versa
Dependant – mass of potato
Independent – conc. of sugar solution
Possible errors – not fully dried, water evaporated
Reduce effect of errors by repeating experiment & calculation mean & change at each conc.
-
Active transport – when substances are absorbed against conc. gradient using E from respiration
Plants: need to absorb mineral ions from soil, conc. much higher in root hair cell than soil so must
use AT
Humans: used in gut, lower conc. of nutrients in gut but higher in blood, allows nutrients to be taken
into blood & used in cells
-
How easy it is for organism to exchange substances w/ its environment depends on SA:V
Large organisms have smaller SAs compared to V
Single-celled organisms – large SA:V so enough substances can diffuse directly across cell membrane
to supply volume
Multicellular organisms – smaller SA:V so not enough substances can diffuse directly to supply entire
volume & exchange surfaces needed
Exchange surface adaptations – thin membrane = short diffusion distance, large SA = lots of
substances can diffuse at one, lot of blood vessels (animals only) = can get substances in & out of
blood quickly, ventilated = air moves in & out
-
Lungs – transfer O2 to blood & remove waste CO2, contain millions of alveoli where gas exchange
takes place. Enormous SA, moist lining (for dissolving gases), v. thin walls, v. good blood supply
GCSE NOTES
COMPLETE SUMMARY
INCLUDES:
● Summary notes for EVERY topic (Biology, Chemistry
and Physics)
● ALL required practicals
● 70 pages of condensed information - everything you
need to SMASH the exams
● Diagrams
Notes I made and used to get 99 (A**) in AQA Combined Science
BIOLOGY PAPER 1
,Cell Biology
Cells either eukaryotic (complex, incl. all animal + plant cells) or prokaryotic (smaller + simpler e.g.
bacteria)
Animal cells – nucleus (DNA, controls activities), cytoplasm (chemical reactions, enzymes), cell
membrane (holds together, in + out control), mitochondria (aerobic respiration) + ribosomes
(proteins made)
Plant cells – everything animal cells have + cell wall (cellulose, support), permanent vacuole (sap) +
chloroplasts (photosynthesis, chlorophyll)
Bacterial cells – much smaller, prokaryotes, no chloroplasts or mitochondria, no true nucleus but
single circular strand of DNA in cytoplasm and may have small rings of DNA (plasmids)
-
Light Microscope Electron Microscope
Use light + lenses to magnify Use electrons (higher magnification +
resolution)
See individual cells + large subcellular See smaller things in more detail + can see
structures ribosomes + plasmids
Cheaper V. expensive
magnification=image ¿ real ¿ ¿
Need to have image + real sizes in same units (1cm = 10mm, 1mm = 1000μm [micrometres], 1μm = m [micrometres], 1μm [micrometres], 1μm = m =
1000nm [nanometres])
-
Microscopy practical:
- Drop of water on clean slide
- Use tweezers to peel epidermal tissue off one of the layers
- Place into water on slide
- Add drop of iodine solution (stain)
- Lower cover slip on (avoid bubbles)
- Clip slide onto stage + select lowest-powered objective lens
- Use coarse adjustment knob to move stage up + down
- Look down eyepiece, move stage until it focuses
- Adjust focus w/ fine adjustment knob
- Swap to high-powered objective lens + refocus
- Draw observations
-
Differentiation – becoming specialised, cells develop different subcellular structures + turn into
different types of cell, usually occurs when organism develops but lots of plant cells never lose
ability.
,Sperm cell (reproduction) – long tail, streamlined head = swimming, mitochondria = energy, enzymes
= digest through egg cell membrane
Nerve cell (rapid signalling) – long = cover more distance, branched connections = connect to other
nerve cells to form network
Muscle cell (contraction) – long = space to contract, lots of mitochondria = generate energy
Root hair cell (absorb water + minerals) – long ‘hairs’ = big surface area
Phloem + xylem (transporting substances) – xylem = hollow, phloem = v. few subcellular structures
-
Chromosomes – coiled up lengths of DNA, body cells have 23 pairs
Cell Cycle:
Growth + DNA replication – Cell grows + increases amount of subcellular structures,
then duplicates its DNA forming X shaped chromosomes
Mitosis – chromosomes line up at centre of cell + cell fibres pull them apart to
opposite ends of cell, membranes form around each of the sets of chromosomes,
become nuclei of two new cells, cytoplasm + cell membrane divide
Cell has produced two new daughter cells w/ exact same DNA as each other + parent cell
-
Stem Cells – undifferentiated, found in early human embryos. Can be found in adults (mainly bone
marrow) but can only turn into some types of cells
Bone marrow transplant: replace faulty blood cells
Insulin-producing cells: diabetes
Nerve cells: people paralysed by spinal injuries
Therapeutic cloning (embryos made to have same genetic information as patient): no rejection
For Against
Help suffering people Embryos still human lives
Only use unwanted embryos from fertility Fertility clinics also immoral, both should be
clinics banned
Would follow strict guidelines (already do in Should concentrate more on finding other
UK) sources of stem cells
In plants: found in meristems, can differentiate throughout entire life, used to produce clones of rare
plants quickly + cheaply, can also grow crops of identical plants w/ identical features (e.g. disease
resistance)
-
Diffusion: spreading out of particles from an area of higher concentration to an area of lower
concentration, happens in solutions + gases
, Higher concentration gradient = faster diffusion rate, higher temp = more energy = faster diffusion,
higher surface area = more particles can pass through = faster diffusion
Cell membranes: control movement in + out of cells, small molecules (oxygen, water etc.) diffuse
through but big molecules (starch + proteins) can’t fit
-
Osmosis: movement of water molecules across a partially permeable membrane (v. small holes, so
water fits through but sucrose can’t) from a region of higher water concentration to a region of
lower water concentration
Water molecules move randomly, so pass both ways through membrane but still steady net flow to
region w/ fewer water molecules: strong sugar solution = more dilate
Osmosis practical:
- Cut potato into identical cylinders & put in beakers w/ different conc. sugar solutions
- Measure mass of cylinders & leave in beakers for 24hrs
- Take out, dry & measure mass
- If drew in water by osmosis, mall will increase & vice versa
Dependant – mass of potato
Independent – conc. of sugar solution
Possible errors – not fully dried, water evaporated
Reduce effect of errors by repeating experiment & calculation mean & change at each conc.
-
Active transport – when substances are absorbed against conc. gradient using E from respiration
Plants: need to absorb mineral ions from soil, conc. much higher in root hair cell than soil so must
use AT
Humans: used in gut, lower conc. of nutrients in gut but higher in blood, allows nutrients to be taken
into blood & used in cells
-
How easy it is for organism to exchange substances w/ its environment depends on SA:V
Large organisms have smaller SAs compared to V
Single-celled organisms – large SA:V so enough substances can diffuse directly across cell membrane
to supply volume
Multicellular organisms – smaller SA:V so not enough substances can diffuse directly to supply entire
volume & exchange surfaces needed
Exchange surface adaptations – thin membrane = short diffusion distance, large SA = lots of
substances can diffuse at one, lot of blood vessels (animals only) = can get substances in & out of
blood quickly, ventilated = air moves in & out
-
Lungs – transfer O2 to blood & remove waste CO2, contain millions of alveoli where gas exchange
takes place. Enormous SA, moist lining (for dissolving gases), v. thin walls, v. good blood supply
