BIOLOGY: CELLS AND THEIR MOVEMENTS,

BIOLOGICAL MOVEMENTS, PLANT NUTRITION,

TRANSPORT AND REPRODUCTION
B1: CELLS
CHARACTERISTICS OF LIVING ORGANISMS
●​ Movement: Action by an organism that causes change of position
●​ Respiration: Chemical reactions that break down nutrients and release energy
●​ Sensitivity: Detect and respond to changes in the environment
●​ Growth: Increase in size
●​ Reproduction: Processes that make more of the same kind of organism
●​ Excretion: Removal of waste products in excess of requirements
●​ Nutrition: The taking in of materials for energy, growth and development

MICROSCOPES
The kind of microscope used in a laboratory is a light microscope. It uses glass lenses
to magnify and focus the image, it can magnify 1500 times. You can calculate the times
magnified, the real size of an object or the fictional size, with this formula:

CELL STRUCTURE
●​ Cell membrane: All cells have it, it's made by a bilayer of phospholipids, it controls
what goes in/out of the cell, being partially permeable.
●​ Cell wall: It's on plant cells, it's made of cellulose, It stops the cell from bursting,
and it's fully permeable.
●​ Cytoplasm: Clear jelly, nearly all water, metabolic reactions take place inside of it.
●​ Nucleus: Where the genetic information is stored. The information is kept on the
chromosomes, made of DNA. Chromosomes can’t usually be seen because they
are very thin, however, when the cell is dividing the become short and thick and can
be seen
●​ Ribosome: They form part of both cells, and they synthesise protein.
●​ Mitochondria: The powerhouse of the cell, it generates energy (ATP)
 ●​ Vacuoles: Space in a cell surrounded by a membrane containing a solution. Plant
cells have very large vacuoles which contain cell sap

PLANT CELLS VS ANIMAL CELLS

Animal Cells Plant cells

Only cell membrane Cell wall and cell membrane

Cytoplasm Cytoplasm

Nucleus Nucleus

No Chloroplasts Chloroplasts

Small vacuoles Large vacuoles with cell sap

No starch gains Often have Starch gains

Irregular shape Regular shape

Ribosomes Ribosomes

LEVELS OF ORGANIZATION

B2: MOVEMENTS IN/OUT OF THE CELL

TYPES OF MOVEMENTS
●​ Passive Transport
➢​ Diffusion
➢​ Osmosis
●​ Active transport
 DIFFUSION
It's the net movement of molecules and particles going from a region of a higher
concentration to a region of lower concentration down a concentration gradient.
Because of the random movement of molecules, moving themselves as evenly as they
can.

●​ Example: There is a higher concentration of oxygen inside a leaf, therefore oxygen

diffuses out of the leaf

Requirement: Kinetic Energy, which comes from the particles random movements

OSMOSIS
The net movement of water molecules from a region of high water potential to a region
of lower water potential, through a partially permeable membrane.

Water potential: When there is a lot of water, it has a high water potential, and a
concentrated solution, has less water potential

Cell membranes are partially permeable, so they often separate to different solutions, if
these solutions are of different concentrations osmosis will occur.

An animal cell in pure water shrinks until it bursts, while because of the cell wall, plants
cells are much stronger

●​ Turgid cell: When the cell is tight and firm

●​ Turgor pressure: Outward pressure
●​ Plasmosis: A cell which membrane tears away form the cell wall when its
immersed in concentrated solutions
 ACTIVE TRANSPORT
It's the movement of particles, from a lower concentration to a higher concentration
against a concentration gradient

Requirements: ATP (energy)

●​ Example: Na/K Pump, will pump outside the cell 3Na+ against the gradient and
pump inside the cell 2K+

B3: BIOLOGICAL MOLECULES

Most of our bodies are made up of water. We also contain carbohydrates, proteins, and
fats.

WATER
Almost 80% of our body is made up of water. Inside every living organism, chemical
reactions are going on all the time, these reactions are called metabolism reactions.
And they can only take place if the chemicals are dissolved in water. If cells dry out, the
reaction stops and the organism dies.

CARBOHYDRATES
Include starches and sugars. Their molecules contain three kinds of atoms. Carbon,
Hydrogen and Oxygen. A carbohydrate molecule has about twice as many hydrogen or
oxygen atoms.
SUGAR
Monosaccharides, Glucose is a sugar.

●​ Glucose: Glucose is made up of six carbon atoms joined together in a ring.

(C6H12O6)

If two sugar molecules are joined together a larger molecule called a complex sugar is
made.

POLYSACCHARIDES
If many simple sugars join together in a chain, a very large molecule called a
polysaccharide is made. The cellulose of a plant cell wall is a polysaccharide.

●​ Starch: Often found inside of plant cells.

●​ Glycogen: Animal cells.

They are insoluble and do not taste sweet as sugar does.

FUNCTIONS OF CARBOHYDRATES
+​ Carbohydrates are needed for energy. The energy released by respiration, which
normally uses glucose. And it’s also the way in which carbohydrates are
transported around an animal’s body.
+​ Human blood plasma contains dissolved glucose being transported to all the
cells.
+​ Plants also use glucose in respiration for energy, but they don’t transport glucose
around their bodies. Insted, sucrose, which can be changed to glucose when
needed
+​ Plants store carbohydrates as starch as it's quick and easy to be made from or
into glucose.
+​ Animals do not store starch, they store glycogen. Only small quantities can be
stored.
+​ Cellulose is used for building cell walls.

TEST FOR CARBOHYDRATES

By adding Benedict’s solution to food, and heating it. If the food contains reducing
sugar, then a brick-red colour will be produced.

The test for starch is easier, you simply add iodine solution to a sample of the food. If
there is starch present, a blue-black colour will be produced.
 FATS
Also known as lipids, they only contain Carbon, Hydrogen and Oxygen. A fat molecule is
made of four smaller molecules joined together. One of these is glycerol, and attached
to it there are three long molecules called fatty acids.

Fats are insoluble in water. Fats that are liquid at room temperature are called oils.

FUNCTIONS OF FATS
+​ To release energy, a gram gives about 39kJ of it. But are only used when cells are
out of carbohydrates.
+​ They are useful for storing and releasing energy.
+​ Inner layer of fat is useful to keep heat inside the body.
+​ Many plants store oil in their seeds. Oils provide a good store of energy for
germination.

PROTEINS
Protein molecules contain some kinds of atoms which carbohydrates and fats do not.
As well as carbo, hydrogen and oxygen, they also contain nitrogen and small amounts
of sulphur.

Protein molecules are made of long chains of smaller molecules joined end to end. The
smaller molecules are called amino acids. There are about twenty kinds of them. They
make up, in a specific order, all the molecules of proteins.

FUNCTION OF PROTEINS
+​ Some of them are soluble in water
+​ Not normally used to produce energy, but for making new cells.
+​ Reappearing damaged parts of the body.
+​ Enzymes
+​ Its chains can curl up into different shapes determined by the sequence of amino
acids in the chain. This shape will affect its function.

TESTING FOR PROTEINS

The biuret test involves mixing the food in water, and then adding dilute copper sulphate
solution. A purple colour indicates that the protein is present.

ENZYMES
Many chemical reactions can be speeded up by substances called catalysts.
 ●​ Catalyst: Alters the rate of a chemical reaction, without being changed itself.

Every metabolic reaction is controlled by catalysts called enzymes. These are proteins,
without them, the reactions would take place very slowly. They ensure that the rates of
Metabolic reactions are great enough to sustain life.+

●​ Amylase: Digest starch to sugar maltose

●​ Protease: Digest protein to amino acids
●​ Maltase: Breaks down maltose
●​ Sucrase: Breaks down sucrose

For example, large molecules are broken down to smaller ones in digestion and these
are sped up by enzymes. They are also found on plants, for instance, in germinating
seeds, where they digest the food stores, as the seed soaks up water, the amylase is
activated.

●​ Catalase: Catalase works inside the cells of most living organisms. It breaks down
hydrogen peroxide to water and oxygen, This is necessary because hydrogen
peroxide is produced by many of the chemical reactions, it must be broken down
immediately.

Not all break things down. Many help to make large molecules from small ones.

NAMING ENZYMES
Enzymes are named according to the reaction that they catalyse.

+​ If they break down carbohydrates they are called carbohydrases

+​ If they break down proteins, they are proteases
+​ If they break down fats, they are lipases

Sometimes they are given more specific names. For example, Amylase,
maltase,Protease, Catalase.

HOW THEY WORK

A chemical reaction always involves one substance changing into another. In an
enzyme-controlled one, the substance which is present at the beginning of the reaction
is called substrate and the substance made by it is named product.

●​ Active site: A dent where the substrate will fit

The substrate of a product is like a key that fits perfectly into the enzyme. Then the
enzyme breaks the key (substrate) and turns it into products.
PROPERTIES
+​ are proteins
+​ are made inactive by high temperature
+​ work best at a particular temperature
+​ work best at a particular pH
+​ are catalysts
+​ are specific (unique)

TEMPERATURE AND PH REGARDING ENZYME ACTIVITY

At a higher temperature, there is more kinetic energy, so an enzyme is likely going to
bump into its substrate more quickly and with more energy. However, enzymes are
actually damaged by high temperatures. As the temperature increases and passes a
limit, the enzymes start to lose their shape, and the active site starts to no longer fit
perfectly. The enzyme is said to be denatured.

●​ Optimum temperature: Temperature at which the enzyme works the fastest. Each
enzyme has a different one.

The pH of a solution also affects the shape of an enzyme. Most are their correct shape
at about 7. And is called neutral. Although some enzymes have an optimum pH that is
not neutral.

B4: PLANT NUTRITION

TYPES OF NUTRITION
Animals feed on organic substances

●​ Organic Substances: That have originally been made by plants.

Some animals eat other animals, all the substances passing from one organism to the
other were firstly made by plants.

●​ Inorganic substances: Carbon dioxide, water and minerals from the air and soil.
Plants use them to make more complex substances like carbohydrates.

PHOTOSYNTHESIS
It is the process by which plants manufacture carbohydrates from raw materials using
energy from light.
CHLOROPHYLL
Sunlight alone won't make CO2 and water react, they have chlorophyll.

●​ Chlorophyll: The pigment which makes plants look green. When sunlight falls on a
chlorophyll molecule, some of the energy in the light is absorbed. The chlorophyll
molecule then releases the energy.

THE PHOTOSYNTHESIS EQUATION

LEAVES
Photosynthesis happens inside chloroplasts. This is where enzymes and chlorophyll are
that catalyse and supply energy for the reaction. Most chloroplasts in the plant are in
the leaves.

LEAF STRUCTURE
A leaf consists of a board. The flat part is called the lamina. Which is joined to the rest
of the plant by a leaf stalk. Running through the leaf there are vascular bundles. The leaf
is made up of several layers of cells.

●​ Epidermis: The top and bottom layers. Do not contain chloroplasts so sunlight can
pass through. They protect the cells in the leaf.
●​ Cuticle: The substance that secretes a waxy substance from the upper epidermis.
It helps to stop water from evaporating from the leaf.
●​ Stomata: Small opening in the lower epidermis.
●​ Guard Cells: Surround the stomata, can open it or close it and contain chloroplasts.

The middle layers are called mesophyll. They all contain chloroplasts

●​ Palisade Mesophyll: Top mesophyll. Arranged like a fence, in various parts

separated from each other so sunlight passes through.
●​ Spongy Mesophyll: They have holes, so that CO2 can enter and O2 can get out.

Running through the mesophyll there are vascular bundles. Each contains xylem
vessels.

●​ Xylem: It is from where H2O can enter. It is the transport system too.
 ●​ Phoem: Conduct system that will transport sucrose and other nutrients the leaf has
made.

LEAF ADAPTATIONS
●​ Carbon dioxide: Obtained from the air. The leaf is held out into the air by the stem
and the leaf stalk, and its large surface area helps to expose it to as much air as
possible.The carbon dioxide can get into the leaf through the stomata by diffusion
●​ Water: Obtained from the soil and carried by the xylem vessels
●​ Sunlight: The position of a leaf and its broad, flat surface help it to obtain as much
sunlight as possible. In the mesophyll cells, the chloroplasts are arranged to get as
much sunlight as possible, particularly those in the palisade cells.

USES OF GLUCOSE
USED FOR ENERGY
Some of the glucose which a leaf makes will be broken down by respiration, to release
energy.

STORED AS STARCH
As glucose is soluble in water and very reactive (and might be involved in chemical
reactions), it is not a very good storage molecule. The glucose is therefore converted
into starch to be stored.
MAKE PROTEINS AND OTHER SUBSTANCES
Plants make carbohydrates, sucrose and cellulose. Plants also make fats and oils.
Plants can also use the sugars they have made in photosynthesis to make amino acids

Plants have to be supplied with nitrogen in a more reactive form, usually as nitrate ions
absorbed from the root hairs by diffusion or active transport. If they don’t get these, they
will have weak growth and their leaves will turn yellowish.

SUCROSE FOR TRANSPORT

As, again, glucose is reactive, it has to be transformed into the complex sugar sucrose
to be transported to other parts of the plant. They dissolve in the sap in phloem vessels
and can be distributed to any part.

B6: TRANSPORT IN PLANTS

PLANT TRANSPORT SYSTEMS
Plants have branching shapes that give them a large surface area in relation to their
volume. Water must be transported up to the leaves, this system is called xylem. Plants
also have a secondary transport system, made up of phloem, which transports sucrose
and amino acids to other parts of the plant.

XYLEM
Is like a long drainpipe made of hollow dead cells joined together. They run from the
roots of the plant right up through the stem. They do not contain cytoplasm. They are
strong.

PHLOEM
Are made of many cells (sieve tubes) whose end walls have not completely broken
down. They contain cytoplasm. The cells in the phloem are still alive.

VASCULAR BUNDLES
A group of xylem and phloem. In the root vascular tissue is found at the centre whereas
in a shoot vascular bundles are arranged in a ring near the outside edge
 WATER UPTAKE
Plants have root hairs that absorb water and mineral ions from the soil. The many root
hairs are tiny long epidermal cells that do not live for long.

Same thing happens to xylem vessels. The pressure at the top of the vessels is lowered
and the pressure at the bottom stays high because of transpiration. Water therefore
flows up the xylem vessels

TRANSPIRATION
●​ Transpiration: Loss of water vapour from plant leaves by evaporation of water at
the surfaces of the mesophyll cells followed by diffusion of water vapour through
the stomata.

The mesophyll cells inside the leaf are each covered with a thin film of moisture that
evaporates and this water vapour diffuses out the leaf through the stomata. Water from
the xylem vessel in the leaf will travel by osmosis to replace it. This is called the
transpiration stream.

WATER POTENTIAL GRADIENT

The constant loss of water from the leaves reduces the effective pressure at the top of
the xylem vessels, so water flows up them. The highest water potential is the solution in
the soil, and the lowest water potential is in the air. Low water potential being caused by
transpiration, that produces a “pull” from above.

Water molecules have a tendency to stick together. This is called cohesion. When it is
pulled through the xylem vessels it stays together.

MEASURING TRANSPIRATION RATES

The rate at which a plant takes up water depends on the rate of transpiration. There are
potometers to measure this.

●​ Potometer: Apparatus used to compare the rate of transpiration in different

conditions by recording how fast air/water meniscus move along the capillary tube
in different conditions

CONDITIONS THAT AFFECT TRANSPIRATION

●​ Temperature: Water will evaporate quickly from the leaves of a plant at a high
temperature.
 ●​ Humidity: The higher the humidity, the less water will evaporate from the leaves
because there is not much of a diffusion gradient between the air spaces inside the
leaf.

TRANSPORT OF MANUFACTURED FOOD

Some of the organic food material that the plant makes is transported in phloem tubes.
From the leaves to any part of the leaf. This is translocation.

●​ Translocation: The movement of sucrose and amino acids in phloem from

regions of production (source) to regions of storage or to regions of utilisation in
respiration or growth (sink)

SOURCES AND SINKS

The part of a plant where sucrose and amino acids are being translocated is called a
source and the part where they go is called a sink.

Phloem can transform in either direction, up or down the plant. While xylem vessels can
only go upwards because transpiration happens at the leaf surface.

B10: REPRODUCTION IN PLANTS

ASEXUAL AND SEXUAL REPRODUCTION
Each organism obtains a set of chromosomes from its parent/s.

●​ Chromosomes: Long threads made of DNA found in the nucleus of every cell, they
contain genes (“instructions”).

All reproduction methods fit under these two categories:

●​ Asexual reproduction: Process resulting in the production of genetically identical

offspring from one parent.
●​ Sexual reproduction: Process involving the fusion of the nuclei of two gametes to
form a zygote, genetically different.

ASEXUAL REPRODUCTION
+​ Only one parent.
+​ Offspring genetically identical.
+​ Miosis
SEXUAL REPRODUCTION
+​ Two parents.
+​ The parent organism produces sex cells called gametes (ex. Eggs and sperm)
●​ Fertilisation: Two gambets join and their nuclei fuse and form a zygote.
+​ The zygote divides again and again and eventually grows into a new organism.

GAMETES
They contain half as many chromosomes as usual so that when two of them fuse the
zygote will have the correct number of chromosomes. (Each egg or sperm has 23, and
later the zygote 46). The 46 are of 23 different kinds, two of each kind as there are two
sets of chromosomes (23 and 23) in the cell. Gametes are haploid.

●​ Diploid: When a cell has two sets of chromosomes (46 in total)

●​ Haploid: Single set of chromosomes (23), ex. Egg or sperm.

MALE GAMETES AND FEMALE GAMETES

There are two different kinds of gametes.

●​ Female: Large and does not move much. In humans, the egg. In flowers, the
nucleus inside the ovule.
●​ Male: Smaller, actively moves searching for the female gamete. In humans, the
sperm. In flowers, inside the pollen grain.

FLOWERS
Many flowering plants reproduce in more than one way. Sexually and asexually.

FLOWER STRUCTURE
The function of a flower is to make gametes, and ensure that fertilisation will take
place.
 ●​ Sepals: On the outside of the flower. They protect it. Often green.
●​ Petals: Inside the sepals. Often brightly coloured, they attract insects to the flower.
Some have guidelines to guide insects to the base.
●​ Nectary: On the base of the Petal. Makes sugary liquid called nectar which insects
feed from.
●​ Stamens: Inside the petals, male parts of the flower. Made up of a long filament
with an anther on top. In this anther, there are pollen grains containing the male
gametes.
●​ Carpels: The female part of a flower. It varies in the arrangement of the ovules. It
contains:
➢​ Ovary with ovules containing female gametes
➢​ Style at the top with a stigma at the tip, which functions to catch pollen
grains.

POLLEN GRAINS AND OVULES

The male gametes are inside the pollen grains and made in the anthers. The anther has
four spaces or pollen sacs inside it. Some on the edge of the pollen sacs divide to make
pollen grains. When the flower bud opens, the anthers split open and the pollen is on the
outside of the anthers.

Pollen is yellow. Pollen grains of different flowers have different shapes, each
surrounded by a hard coat so it can survive. The coat protects the male gametes inside
the grains, as the pollen is carried from one flower to another.
Female gametes are inside ovules. Each ovule contains a nucleus. Fertilisation happens
when a pollen grain nucleus fuses with an ovule nucleus.

POLLINATION
For fertilisation, the male gametes must travel to the female gametes. First, pollen is
taken from the anther to a stigma. This is pollination.

●​ Pollination: The transfer of pollen grains from the male part of the plant (anther) to
the female part of the plant (stigma).
➢​ Insect pollination: It is carried out by insects which are attracted by pollen’s
colour and scent. They follow the guide-lines to the nectaries; some of the
pollen sticks to its body. The insect then goes to another flower looking for
more nectar and the pollen it picked up at the first flower sticks onto the
stigma of the second flower. If the second flower is from the same species
of plant as the first, pollination takes place.
+​ Large petals with guide-lines
+​ Strongly scented
+​ Nectaries
+​ Anthers inside flowers; insects has to brush past to reach nectar
+​ Stigma inside flowers; insects has to brush past to reach nectar
+​ Sticky or spiky pollen, to stick to insects
+​ Large quantities of pollen are made because some will be eaten or
delivered wrongly.
➢​ Wind pollination: When the wind carries the pollen between flowers.
+​ Small or no petals
+​ No scent
+​ No nectaries
+​ Anthers dangling outside the flower catching the wind
+​ Stigmas large and feathery outside the flower waiting for pollen in the
air
+​ Smooth, light pollen, blown by the wind.
+​ Large quantities of pollen are made because most will be blown away
and lost.

FERTILISATION
After pollination the male gamete inside the pollen grain on the stigma still has not
reached the female gamete, inside the ovule in the ovary. If the pollen grain has landed
on the right stigma it begins to grow a tube, which grows down through the style
secreting enzymes digesting this way through towards the ovary and ovule. It then fuses
with the ovule nucleus and fertilisation takes place. One pollen grain per ovule.

SEEDS
After the fertilisation of ovules, parts of the flower are not needed anymore. The sepals,
petals and stamens have done their job, they wither and fall off. The ovule starts to
grow now containing a zygote. The ovule now is called a seed.

The seed contains a tiny embryo plant and food for it. It contains hardly any water, as it
has drawn out when formed. What happened without water? The metabolic reactions
cannot occur, so the seed is inactive or dormant. The seed must be in certain conditions
before it will begin to germinate.