Zusammenfassung der Ressource
Biology-B2
- Cells
- Both animal and
plant cells have
similar parts. Plant
and algal cells have
additional features.
- Root hair cells have
a tiny hair like
extension to
increase the surface
area so that it can
absorb more water
and ions
- Palisade cells are
column-shaped
cells that are
packed with
chloroplasts for
photosynthesis
- Xylem cells are
long, thin, hollow
cells that contain
no cytoplasm that
transport water
through the stem
and root.
- Nerve cells have
long slender
axons that can
carry nerve
impulses over
long distances.
- The ovum or egg
cell is large so that
it can carry food
reserves for the
embryo
- The sperm cell is
mobile because of
its tail. It has to
travel from the
vagina to the ovum
- Red blood cells
have no nucleus
so that can have
lots of
haemoglobin and
carry lots of
oxygen
- White blood cells
can change their
shape to engulf
and destroy
microbes
- Bacterial cells consist
of a membrane and
cytoplasm surrounded
by a cell wall. The cell
wall isn't made of
cellulose and there
isn't a proper nucleus,
the genetic material
lies free in the
cytoplasm
- Yeast is a single-celled
organism. Yeast cells have a
nucleus, cytoplasm and a
membrane surrounded by a
cell wall.
- Dissolved
substances
pass
through cell
membranes
to get in
and out of
cells by
using
diffusion.
- Large
multicellular
organisms have
developed
systems for
exchanging
materials. Cells
differentiate
when they are
being developed
so that they can
perform different
functions.
- Tissues,
organs and
organ
systems.
- Muscle tissue
can contract
to bring
movement.
- Glandular tissue can
produce substances
such as enzymes
and hormones
- Epithelial tissue
covers all parts
of the body
(skin)
- An organ is made of different
tissues that work together to
do a certain job. The heart,
lungs, kidneys and ovaries are
all examples of organs.
- A stomach has
muscular tissue to
churn the contents
- Glandular tissue to
produce digestive
juices
- Epithelial tissue to
cover the outside
and inside of the
stomach
- An organ system is a
group of organs that
perform a particular
function.
- There are many
different systems
in the body:
circulatory system,
digestive system,
nervous system,
reproductive
system, respiratory
system, skeletal
system and urinary
system.
- The digestive system is
an example of an organ
system in which humans
and other mammals
exchange substances
with the environment.
- Glands produce
digestive juices to
break down food
(the pancreas and
salivary glands)
- The stomach
and small
intestine is
where digestion
occurs
- The small intestine
is where the
absorption of
soluble food occurs
- The large intestine
is where water is
absorbed from the
undigested food,
producing faeces
- The liver
is where
bile is
produced
- Plants also have cells that are organised into tissues and organs
- Plant organs include stems, roots, leaves and flowers
- Epidermal
tissues
cover the
plant
- Mesophyll
carries out
photosynthesis
- Xylem and phloem
transports
substances around
the plant. The xylem
transports water and
salts, whereas the
phloem transports
food substances
- Photosynthesis
- Green plants don't absorb food
from the soil, they make their own
using sunlight-This process is called
photosynthesis and it occurs in the
cells of green plants
- Photosynthesis requires:
light from the sun, CO2 from
the air, Water from the soil
and chlorophyll in the eaves
- Two things are
produced by
photosynthesis:
Glucose and oxygen
- Glucose can be used to
provide energy for
respiration, used to
produce oil or fat for
storage, used to
produce cellulose, used
to produce proteins or
converted into
insoluble starch for
storage
- Photosynthesis can
be limited by a: Low
temperature,
shortage of CO2,
shortage of light.
- At temperatures about 45
degrees, the enzymes controlling
photosynthesis are destroyed,
stopping photosynthesis
- These limiting factors
mean that plant growth
can be controlled. E.G
in greenhouses, plants
can be encouraged to
grow more quickly by
increasing the
temperature to 40
degrees, increasing CO2
levels and increasing
light intensity
- Organisms and their environment
- Organisms may be distributed
across a land, factors that affect
this distribution are:
Temperature, nutrients, amount
of light, availability of water,
oxygen or carbon dioxide
- Proteins
- Proteins have various functions
in the body, they are structural
components of tissues such as
muscle, some hormones (insulin)
are proteins, antibodies that form
part of the body's defence
system, are proteins, and
enzymes are proteins.
- Protein molecules are large
molecules made up of long chains of
amino acids, these chains are folded
to produce a specific shape, which
enables other molecules to fit into
the protein.
- Enzymes are biological
catalysts; they increase the rate
of reactions in an organism. The
amino chain is folded into a 3-D
shape which allows other
molecules to fit into the enzyme
- Different enzymes work best at different
temperatures and pH levels.
Temperatures about 37 degrees destroy
most enzymes' special shape. Which is
why it is dangerous for the body to go
above 37 degrees.
- Outside living cells, digestive
enzymes are produced by specialised
cells in glands in the lining of the gut.
- Enzymes pass out of the cells
into the guy where they come
into contact with food molecules
- Three enzymes
(protease, lipase and
amylase) are
produced in four
separate regions of
the digestive system.
They digest proteins,
fats and
carbohydrates to
produce smaller
molecules that can be
absorbed.
- Bile is produced in the liver and stored in
the gall bladder before being released into
the small intestine. It can be used to
neutralise acid and emulsify fats in the body.
- Enzymes are used at home, protease is used
in washing powders to break down stains
such as food or blood. Lipase is used to
break down oil and grease stains
- In industry, protease is
used to pre-digest protein
in baby foods,
carbohydrases are used
to convert starch into
sugar syrup and
isomerase converts
glucose syrup into
fructose syrup.
- Enzymes
are also
used as
natural
catalysts
in
industry.
- Aerobic
and
Anaerobic
Respiration
- Aerobic respiration is
respiration that takes place
when oxygen is present. The
oxygen combines with
glucose molecules in cells to
produce energy, this reaction
is catalysed by enzymes.
- Aerobic
respiration takes
place inside the
mitochondria.
Aerobic respiration
takes place
constantly in a
plant and animal
cells and is
extremely efficient.
- The energy released
during respiration is used
to build larger molecules
using smaller ones. To
enable muscles to
contract. To maintain a
constant temperature in
colder surroundings and to
make proteins in plants
and animals from amino
acids.
- During
exercise, a
number of
changes take
place. The heart
rate increase,
Arteries widen
and rate and
depth of
breathing
increases.
- The supply of oxygen
and sugar is
increased and
removal of carbon
dioxide speeds up.
Glycogen stored in
muscles is broken
down to glucose to
be used in
respiration
- Anaerobic
respiration happens
if enough oxygen
can't be supplied to
the working
muscles. Anaerobic
respiration is the
incomplete
breakdown of
glucose
- A waste product of
anaerobic respiration is
lactic acid, which builds
up in the tissues and
causes muscle fatigue.
This means that the
muscles stop contracting
efficiently. Lactic acid is
removed by the blood
flowing through the
muscles
- Cell Division and Inheritance
- Chromosomes are
found in the nucleus,
they are made of
DNA and have a
double helix
structure. They
contain genetic
information in the
form of genes. A
gene is a section of
DNA.
- Like all pairs of
chromosomes, offspring
inherit one sex
chromosome from the
mother and one from the
father. The sex of an
individual is decided by
whether the ovum is
fertilised by an X carrying
sperm or a Y carrying sperm
- Mitosis is the
division of
body cells to
produce new
cells, it only
needs one
parent cell
which
produces an
offspring that
is identical to it
- Meiosis is
sexual
reproduction
and requires
two parent
cells to
produce an
offspring with
qualities from
both parents
- When gametes join at
fertilisation, one chromosome
comes from each parent and a
single body cell with new pairs
of chromosomes is formed. This
then divides by mitosis to form
a new individual.
- Some
characteristics
are controlled by
a certain gene.
Each gene has
different forms
called alleles.
E.G, the gene
that controls
whether you can
roll your tongue
or not has two
alleles, you
either can or you
can't.
- In a pair of
chromosomes, the
alleles for a gene can
be the same or
different. If they are
different, then one
allele will be dominant
and one will be
recessive.
- Genotype
refers to the
alleles
present, e.g
one brown
eye allele and
one blue eye
allele.
Phenotype
refers to the
characteristic
that shows
itself e.g
brown eyes.
- When cells develop a
specialised structure to
carry out a specific
function, this is
differentiation. Many
plant cells can
differentiate through life.
Animal cells differentiate
at an early stage so
quickly become muscle,
nerves, etc.
- Human stem cells are cells
in human embryos and
adult bone marrow, which
have yet to differentiate.
They can be made to
differentiate into many
different types of cells, e.g
nerve cells to treat
paralysis
- Some genetic disorders
are inherited. Embryos
can be screened for the
genes that cause genetic
disorders. Polydactyly is
where you have extra
fingers or toes and is
caused by a dominant
gene. Cystic fibrosis is a
disorder of cell
membranes, caused by
a recessive allele so it
must be inherited from
both parents.
- Body cells have 46 chromosomes arranged
in 23 pairs. Gametes have 23 chromosomes
(one from each pair). The fusion of gametes
produces a zygote, that has 46 chromosomes
- Of the 23 pairs of chromosomes in the human
body cells, one pair is the sex chromosomes.
In females, these are identical and are called X
chromosomes. In males one is shorter, the
shorter is called the Y chromosome, the larger
is the X