1.1.2 Magnification = the degree to which the
size of an image is larger than the object
1.1.3 Resolution = the degree to which you can distinguish
between 2 objects that are very close together. the
higher the resolution the more detailed it is.
1.1.4 Electron Microscopes
184.108.40.206 Scanning Electron
220.127.116.11.1 Resolution 0.2nm
18.104.22.168.2 Magnification x100000
22.214.171.124.3 3D image of
surface of sample
bounce of the
126.96.36.199 Transmission Electron
188.8.131.52.1 Resolution 0.2nm
184.108.40.206.2 Magnification x500000
sample to produce
220.127.116.11.3.1 Denser parts of the
cell will take up less
electrons so it gives
18.104.22.168 Need to put it in a vaccum
bind to the organelles to
22.214.171.124 Sectioning...cutting up the sample really thin
and embed them in wax.
126.96.36.199 Needs a high degree of skill
1.2.2 Endoplasmic Reticulum
1.2.3 Golgi Apperatus
1.2.7 Plasma membrane
1.2.8 Chloroplast...they have a double membrane
with a layer of fluid inbetween. They have
thylakoids that look like piles of plates. A stack
of thylakoids are called a granum. Used in
photosynthesis in plant cells.
1.2.10 Cilia and Flagella...they are both structurally
the same. They are hair like extension. They
are made up of a cylinder containing 9
microtubules in central bundle. Can make
the whole cell move and can help move
things within the cell. Cilia less than 10
1.2.11 Cytoskeleton refers to the
network of protein fibres found
within a cell that give structure
and shape to the cell and also
moves organells around inside
the cell. provides mechanical strength
188.8.131.52 REMEMBER - provides mechanical strength to cells
-aiding transport within cells and enabling cell
1.2.12 Plant Cell vs Animal Cell
184.108.40.206 Have got,
220.127.116.11 Have got
RER and SER,
18.104.22.168 Both have nucleus,
SER and RER,
1.3 PROKARYOTES VS EUKARYOTES
1.3.1 Eukaryotes - have a
complicated internal structure
- they have a nucleus
1.3.2 Prokaryotes - 1-5 micrometers,
smaller than eukaryotes - they show all
characteristics of living organisms
(they respire, they produce waste)
22.214.171.124 One plasma membrane
126.96.36.199 Do not contain membrane bound
organelles like mitochondria and
188.8.131.52 Surrounded by cell wall not
made up of cellulose, made up of
184.108.40.206 Slippery layer
outside cell wall
220.127.116.11 Contain ribosomes
(simple things) they are
much smaller 20nm in
18.104.22.168 No cytoskeleton
22.214.171.124 DNA is circular
1.4 CELL MEMBRANES
1.4.1 Role is to separate cell content from
outside cell, separates cell components
from cytoplasm, cell recognition and
cell signalling, holding components of
metabolic paths in place, regulate the
transport of materials in and out of cell.
1.4.2 Partially permeable
1.4.3 Fluid Mosaic Model -
molecular arrangement in
membrane. There is a bilayer of
Various proteins floating around
in the phospholipid bilayer.
Some exintric proteins sticking
out of bilayer.
1.4.4 Cholesterol - gives
stability. Fit between fatty
acid tails to help make
barrier more complete so
substances like water
molecules and ions can't
pass through easily.
1.4.5 Glycolipids and
molecules with small
1.4.6 Channel proteins - allow
movement of some substances
across membrane that are too
large and to hydrophilic to pass
1.4.7 Carrier proteins - move
substances across membrane. e.g.
magnesium ions activly pumped
through into root hair cells from soil
using ATP. Nitrate ions are actively
transported into xylum vessel to lower
water potential gradient.
1.4.8 Temperature - Increase temp
molecules get more kinetic
energy. Move faster. Membrane
is leaky so molecules enter and
leave the cells when they
1.4.9 Cell Signaling - cells communicate via signals.
126.96.36.199 Any cell with
called a target
188.8.131.52 Hormone molecule
binds to receptor,
184.108.40.206 E.g Insulin receptor
220.127.116.11 Medical Drugs - Drugs
complementary shapes to
receptor molecule. They block
1.4.10 Passive Transport
18.104.22.168 Diffusion...net movement of ions or molecules down their concentration gradient
22.214.171.124 Facilitated Diffusion...Ions passing through membrane by diffusion down concentration gradient
but through channels e.g chloride ions
1.4.11 Active transport...moving ions through transported proteins using ATP (energy) up their concentration
gradient e.g. sodium potassium pump
1.4.12 Bulk Transport
126.96.36.199 Exocytosis..moving substances out, in vessicle via microtubules.
fuses with membrane substance emptied outside cell
188.8.131.52 Endocytosis...moving substances in (e.g. phagocyte engulfs
bacterium). Fingers around substance. Ring around it. contained in
vacuole. enzymes secrete into vacuole to digest it. Use energy
1.4.13 Osmosis...net movement of
of water down the water
potential gradient because
of random motion, no
184.108.40.206 Animal Cell...become
crenated when water is lost.
when too much water is taken
in it bursts.
220.127.116.11 Plant cells...water moves in, cell wall resists
expansion force called pressure potential.
water out means plasma membrane comes
away from cell wall, it tears, cell dies.
1.5 Cell Division
1.5.1 Mitosis takes up
tiny amount of
cell cycle most
of it is in copying
1.5.2 Interphase.. DNA replicated
and proteins and organelles
18.104.22.168.22.214.171.124 Two new nuclei are formed
126.96.36.199.1.1.2 Replicas pulled apart by
centromere to opposite
ends of cell
line up at equator
188.8.131.52 Needed for growth,
repair and asexual
animals and plants
the cell splits
1.5.5 Meristem cells...only
cells that are capable
of mitosis and
184.108.40.206 In plant cells a cell
plate is formed at the
start of cytokinesis.
New cell membrane is
laid along this cell plate.
that have the same genes at
the same loci. Pair up in
meiosis. Diploid organisms,
produce by sexual
homologous pairs - one
member of each pairs from
the male and the other from
1.5.7 Budding...when a yeast
cell produced new cells
off the side of an existing
one. genetically identical.
220.127.116.11 Cells called gametes must be
produced with half the number
of chromosomes to be used in
18.104.22.168 Fusion of 2 gametes is called a zygotes.
22.214.171.124 Happens in
126.96.36.199 Normal adult cells of most eukaryotes are diploid.
188.8.131.52 Their genome consists of pairs of
homologous chromosomes , they contain
the same genes but not necessarily the
same versions (alleles) of each gene.
184.108.40.206 During meiosis, one
member of each
goes into each
220.127.116.11 Daughter cells
1.5.9 Stem cell...can divide and
develop into any other type of
cell. Can be in young
embryos, they are totipotent.
Can be in adult tissues, they
are pluripotent. Can be in
bone marrow to make blood
and bone cell types.
1.6 Cell Diversity
1.6.1 Differentiation...the changes
occurring in cells of a multicellular
organism so that each different
type of cell become specialised to
perform a specific funcition.
18.104.22.168 Erythrocytes and neutrophils -
human cells that each begin with the
same set of chromosomes so each
is potentially capable of carrying out
the same functions. All blood cells
are produced from undifferentiated
stem cells in the bone marrow.
22.214.171.124 Xylem Tissue - come from dividing meristem
cells such as cambium. Consists of xylem
vessels with parenchyma cells and fibres.
meristem cells produce small cells that
elongate. Walls become waterproofed and
reinforced by deposits of lignin. This kills cell
content. Ends of cells break down so it
become continuous long tubes with a wide
lumen. Helps support plant as well as taking
water and minerals up plant.
126.96.36.199 Phloem tissue - consists of sieve
tubes and companion cells. Meristem
tissue produces cell that elongate and
line up end to end to form a long tube.
Sieve plates form between cells.
These allow movement of minerals up
or down the tubes. Next to sieve plates
there are companion cells they are
metabolically active, they help get the
produces of photosynthesis up and
down the plant in the sieve tubes.
1.6.2 Epithelial cells
1.6.3 Sperm Cells
1.6.4 Palisade cells - packed
1.6.5 Root hair cells
1.6.6 Guard Cells - can become turgid so its
bulges and lets the stomata open
1.7 Cellular orangisation
1.7.1 A tissue - a
collection of cells
that work together to
perform a common
function e.g xylem
1.7.2 An organ - A
collection of tissues
working together to
perform a particular
function e.g leaves
and the liver.
1.7.3 An organ system - Made
up of a number of organs
working together to perform
an overall function e.g
excretory system and the
1.7.4 Squamous Epithelial cells - very thin, cells
together form thin flat smooth surface, ideal
for lining blood vessel walls, also in alveoli
it provides a short diffusion pathways. Held
together by basement membrane, this is
secreted by epithelial cells. its made of
collagen and glycoproteins. Attaches
epithelial cells to tissues.
1.7.5 Ciliated Epithelial cells - column
shaped cells, lining of tubes, e.g
trachea and bronchi and bronchioles,
and uterus and oviducts. Tiny
projections of cilia, Cilia waves mucus
in the breathing tract goes up to throat
to be swallowed. Cilia moves the egg
along the oviduct from the ovary.
1.7.6 Cooperation between cells, tissues, organs and organ systems
188.8.131.52 Harvesting light - transparent
upper surface layer, layer of
palisade cells, loosely packed
spongy mesophyll (allows
circulation of gases), pores
called stomata, vein system
(xylem and phloem)
184.108.40.206 Muscular and skeletal system
work together for movement. Nerve
system instruct muscles. They
need energy to work so you need to
circulatory system to be involved.
Which needs chemicals from the
digestive and ventilation system.