Transcript B2 Topics - Burton Borough School

B2 Topics- What do you want to
revise?
• Plant and Animal Cells
• Specialised Cells
• Bacterial and Fungal
Cells
• Diffusion
• Animal Tissues, Organs
and Organ Systems
• Photosynthesis
• Plant Tissues and
Organs
• Sampling Techniques
• Mean, mode median
• Enzymes
Respiration
Mitosis
Meiosis
Inheritance
Mendel
Genetic diseases
Embryo Screening, Stem
Cells and DNA
Fingerprinting
• Fossil record
• Extinction
• Forming a New Species
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Animal and Plant Cells
In Both Animal and Plant Cells
Part
Function
contains genetic material, which controls the activities of
nucleus
the cell
most chemical processes take place here, controlled by
cytoplasm
enzymes
cell membrane controls the movement of substances into and out of the cell
mitochondria most energy is released by respiration here
ribosomes
protein synthesis happens here
Part
cell wall
Plant Cells Only
chloroplasts
permanent vacuole
Function
strengthens the cell
contain chlorophyll, which absorbs
light energy for photosynthesis
filled with cell sap to help keep the
cell turgid
Specialised Cells
• You are likely to be given information,
perhaps in a diagram, to help you to
explain the adaptations of a particular
cell type to its function.
• You should be able to name specialised
cells, state their function and explain
how they are adapted to carry out their
function
Red Blood Cells
Carry Oxygen to the
Cells
Adaptations
- Thin outer membrane,
to allow quick
diffusion of oxygen
- Large surface area, to
allow diffusion quicker
- No nucleus, so whole
cell is full of
haemoglobin
Sperm Cell
• Fertilises the female egg cell
Adaptations
• The head contains genetic
information and an enzyme to
help penetrate the egg cell
membrane.
• The middle section is packed
with mitochondria for energy.
• The tail moves the sperm to
the egg.
Root Hair Cell
• Absorbs water and mineral
ions from the soil
Adaptations
• Long 'finger-like' process
with very thin wall, which
gives a large surface area.
Palisade Cell
• Absorbs light energy for
photosynthesis
Adaptations
• Packed with chloroplasts.
• Regular shaped, closely
packed cells form a
continuous layer for
efficient absorption of
sunlight.
Bacterial and Fungal Cells
Bacteria
• A bacterium is a
single-celled organism.
• It has cytoplasm, a
membrane and a
surrounding cell wall,
but the genetic
material in a bacterial
cell is not in a distinct
nucleus.
Fungi
• Yeast is a single-celled organism.
• Like bacterial cells, yeast cells have
cytoplasm and a membrane
surrounded by a cell wall.
• Unlike bacterial cells, yeast cells have
a nucleus.
Diffusion
Key Points
• From a high concentration to a low
concentration
• If answering about movement through
cells, you must say “through a cell
membrane” or “through a partially
permeable membrane”
Two examples of diffusion down
concentration gradients
Location
Particles move
From
To
Small intestine
Digested food
products
Small intestine
Blood in capillary
of villus
Lungs
Oxygen
Alveolar air space
Blood circulating
around the lungs
Animal Tissues and Organs
Cells are
the basic
units of
life.
Groups of cells
work together
to form
tissues.
Groups of
tissues work
together to
form organs.
Digestive System
The pancreas
secretes
enzymes but
food does not
travel through
the pancreas so
don’t state it as
a “site of
digestion”
The liver produces bile. The bile is
stored in the gall bladder.
After the stomach, food travels to
the small intestine.
in the
small intestine work best in alkaline
conditions, but the food is acidic
after being in the stomach. Bile is
an alkaline it is secreted into the
small intestine, where it emulsifies
fats. This is important, because it
provides a larger surface area in
which the lipases can work.
Plant Tissues
Tissue
Epidermal tissue
Palisade Mesophyll
Xylem and phloem
Stomata
Function
Covers the plant
Carries out photosynthesis
Transport of substances around
the plant
To allow CO2 to diffuse into the
leaf
Photosynthesis
• Examples of plant organs include:
– Roots
– Stems
– Leaves- site of photosynthesis
• Factors that can limit the rate of
photosynthesis;
–
–
–
–
CO2 concentration
Light intensity
Water availability
Temperature
Light Intensity
• Without enough
light, a plant cannot
photosynthesise
very quickly, even if
there is plenty of
water and carbon
dioxide. Increasing
the light intensity
will boost the speed
of photosynthesis.
Can you explain what
is happening here?
CO2
• Sometimes
photosynthesis is
limited by the
concentration of
carbon dioxide in
the air. Even if
there is plenty of
light, a plant cannot
photosynthesise if
there is insufficient
carbon dioxide.
Something other than CO2
concentration is acting as a
limiting factor
Temperature
• If it gets too cold,
the rate of
photosynthesis will
decrease. Plants
cannot
photosynthesise if
it gets too hot.
Why?
Respiration
• Site of respiration- mitochondria
Aerobic- “in the presence of
oxygen”
Glucose + oxygen  Carbon Dioxide +
water (+Energy)
C6H12O6+O2  CO2 + H2O (+energy)
The energy made is used to make larger
molecules from smaller molecules.
It is also used in muscle contraction and
maintaining body temperature.
Good for long distance.
Anaerobic Respiration- no oxygen
Glucose →Remember
Lactic acidin(+yeast
energy)
anaerobic respiration
produces ethanol and
This type of respiration may be used
carbon dioxide (which
when, for example, an animal is being
is why we used it to
chased by a predator (short bursts).
make beer and bread)
Less energy is produced less than from
aerobic respiration.
Sampling Techniques- Quadrats
• A square made of wire. It may contain
further wires to mark off smaller areas
inside. The organisms underneath,
usually plants, can be identified and
counted.
Quadrat Key Points
Random
sampling
canso that a
• It should
be placed
randomly
be achieved
representative
sample isby
taken
assigning numbers to
the
area
being
• The validity
and
reproducibility
of the
using
a from
results sampled
increases and
as the
results
random
more quadrats
are number
analysed
generator
Transects
• A transect is a line across a habitat or
part of a habitat. It can be as simple as
Transects can
a string
or
rope
placed
in
a
line
on
the
be used
ground.
together with
quadrats
to
• The
number
of organisms of each
create a belt
species
transect.can be observed and recorded
at regular intervals along the transect.
Mean
• Add the numbers together and divide
the total by the amount of numbers
Example
Mean = (2 + 4 + 5 + 3 + 4) ÷ 5 = 18 ÷ 5 =
3.6
Quadrat sample
1
2
3
4
5
Number of dandelion plants
2
4
5
3
5
Mode
• The median is the middle number. To calculate
a median:
• Put all the numbers in numerical order
• If there is an odd number of results, the
median is the middle number
• If there is an even number of results, the
median will be the mean of the two middle
numbers
• Example :
23455
The median is 4.
Median
• The mode is the number which occurs
most often in a set of data.
• Example :
• 2345 5
• The number 5 occurs twice, so it is the
mode.
(Note that you can have more than one
mode.)
Enzymes- biological catalysts
(speed up reactions)
When the enzyme and substrate are
together this is called an enzymesubstrate complex
Key Points
• Enzymes are reusable
• They are affected by pH and
temperature- these can cause them to
denature
• They are proteins (made by ribosomes)
• Enzymes have an optimum temperature
and pH (faster rate of reaction)
Enzymes and Temperature
Describing the
changes;
The rate of reaction
increases up to 40°c.
The optimum is
40°c.
After 40°c the rate
of reaction
decreases to 0 at
approximately 63°c.
Explaining the changes;
At 0°c the rate of reaction
is slow, this is because
there is a small amount of
kinetic energy and the
number of successful
collisions between the
enzymes active site and the
substrate are low.
After 40°c the enzymes
start to denature and are
no longer complimentary to
the substrate.
pH and enzymes
• Different enzymes
have different
optimum
temperatures.
• Above or below the
optimum the
enzymes denature.
Enzymes are specific and
complimentary to their substrates
Enzyme
Amylase
Reaction catalysed
Starch
Protease Proteins
Lipase
Lipids
→
→
Where the enzyme is
produced
Glucose
salivary glands, pancreas,
small intestine
Amino acids
stomach, pancreas, small
intestine
→ Fatty acids +
Glycerol
pancreas, small intestine
Enzymes in Industry
Enzyme
Use
Pre-digest proteins during the manufacture
Protease
Remember when talking
of babyabout
foods
Together
with protease
- in biological
enzymes you
should
describe
detergents to break down - digest - the
the reactants
and the
Lipase
substances in stains into smaller, water
products.
soluble substances
Convert starch syrup, which is relatively
cheap, into sugar syrup, which is more
Carbohydrase
When lipase
down
valuable -breaks
for example,
as an ingredient in
sportslower
drinks
fats, fatty acids will
Convert glucose syrup into fructose syrup the pH
Isomerase
fructose is sweeter than glucose, so it can be
used in smaller amounts in slimming foods
Mitosis
1. Parent cell
2. Chromosomes make
identical copies of
themselves
3. They line up along the
centre
4. They move apart
5. Two daughter cells form
with identical chromosomes
to the parent cell (46
chromosomes)
Meiosis
• Creates 4
daughter cells
• Genetically
unique
• Gametes (sperm
and egg cell)
• 23 chromosomes
Inheritance Vocabulary
• Alleles -different forms of the same gene
• Homozygous- 2 of the same allele e.g. bb
• Heterozygous- 2 different versions of the
same gene e.g. Bb
• Genotype- the genes present
• Phenotype- the genes that are expressed e.g.
Bb, brown eyes
• Recessive- only expressed when homozygous
• Dominant- expressed when either heterozygous
or homozygous
Mendel
• Gregor Mendel (1822-1884) studied the
inheritance of different characteristics
in pea plants
• He was the first person to come up with
the idea that “factors” are passed on
through generations and sometimes
they skip a generation (recessive genes)
Generation 1
Generation 2
Cystic Fibrosis
• Affects the cell membranes, causing
the production of thick and sticky
mucus. It is caused by a recessive allele.
Punnett Square
Polydactyly
• Polydactyly is an dominant inherited
condition in which a person has extra
fingers or toes.
• This means it can be passed on by just
one parent if they have the disorder.
DNA fingerprinting
By cutting a sample of DNA into fragments
and comparing it with other samples it's
possible to work out if the DNA has come
from the same person.
Embryo Screening
• Embryos can be screened for the alleles
that cause polydactyly, cystic fibrosis
and other genetic disorders.
• Note that you do not need to know or
understand how embryo screening works
for the examination but your need to be
able to discuss the pros and cons
Discussing Ethical Issues
• Science can answer the question, 'What are the
chances of my child having cystic fibrosis?'.
However, it cannot answer the question,
'Should I have my pregnancy terminated?‘
• Clearly state the issue
• Summarise the different views
• Identify arguments that are based on the
right decision, ie a decision that produces the
best outcome for most of the people involved.
• Identify when certain actions are very hard to
justify because they are considered unnatural
or wrong.
Stem Cells
• Human stem cells can come from human embryos or
from adult bone marrow.
• They are able to develop into any kind of human cell.
• Note that you do not need to know any details of how
this happens for the examination.
• They have the potential to be used in new treatments
for conditions such as Parkinson's disease and
paralysis.
• There are social and ethical issues concerning the use
of human embryonic stem cells in medical research
and treatments.
Fossil Record
Fossil remains have been found in
rocks of all ages. Fossils of the
simplest organisms are found in
the oldest rocks, and fossils of
more complex organisms in the
newest rocks. This supports the
theory of evolution.
Many early forms of life were
soft-bodied - and have left few
traces behind.
Forming a New Species
• New species can arise as a result of isolation.
This is where two populations of a species
become geographically separated.
• Genetic variation - where each population has a
wide range of alleles that control their
characteristics
• Natural selection - where the alleles which help
an organism to survive are selected in each
population
• Speciation - where the populations become so
different that successful interbreeding cannot
happen anymore
Extinction
• Some of the factors that can cause a
species to become extinct:
• New diseases
• New predators
• New, more successful competitors
• Changes to the environment over geological
time - such as a change in climate
• A single catastrophic event - such as a
massive volcanic eruption or a collision
between an asteroid and the Earth