Triple Science Biology revision

What is the word equation for photosynthesis?

carbon dioxide + water --light--> glucose +
oxygen

What is the symbol equation for photosynthesis?

6CO2 + 6H2O --> C6H12O6 + 6O2

What type of reaction is photosynthesis and why?

Endothermic because energy is transferred
from the environment to the chloroplasts by
light

State the four factors that affect the rate of
photosynthesis

Temperature, light intensity, carbon dioxide
concentration and amount of chlorophyll

Why does a change in temperature affect
the rate of photosynthesis?

Because photosynthesis involves enzymes
which work better at higher temperatures but
denature at extremes of temperature

Why would the line on a
graph of rate of photosynthesis against
light intensity level off?

Because at high light intensities, something
else is limiting the rate, such as carbon dioxide
concentration

How could we use the inverse square law to work out the light intensity in
the pondweed investigation?

Calculate 1/distance2

so when the distance
doubles, the light intensity is divided by 4.

Why do plant growers need to consider limiting factors when deciding how much to
spend on enhancing conditions in a greenhouse?

Increasing a limiting factor (e.g. light intensity)
can increase the rate of photosynthesis, but
only up to a point. Increasing it further
wouldn't make a difference and can also be
expensive.

Give 3 ways in which the plants use the glucose produced in photosynthesis (can you get all five?)

respiration; converted to starch; fats and oils;
cellulose to strengthen cell wall; amino acids
for protein synthesis

Why is glucose converted to starch for storage by plants and not just left as glucose?

Starch is insoluble. This means it will not move
out of the cell and will not affect osmosis.

Plants can convert glucose from photosynthesis into amino acids for protein
synthesis. What ions are added from the soil to do this?

Nitrate ions

What type of reaction is cellular respiration and why?

exothermic because energy is released

What is the purpose of respiration?

To transfer (or release, but not make!) energy
for living processes

Which type of respiration requires oxygen?

Aerobic respiration

Which type of respiration does not require
oxygen?

Anaerobic respiration

Which type of respiration (aerobic or anaerobic) releases less energy per molecule of glucose?

Anaerobic respiration

What is produced in anaerobic respiration but not in aerobic respiration?

Lactic Acid

Give 3 reasons why energy from respiration is needed in the body

For chemical reactions to build larger
molecules; for movement; for keeping warm

Write the word equation for aerobic respiration

glucose + oxygen --> carbon dioxide + water

What is the symbol equation for respiration?

C6H12O6 + 6O2 --> 6CO2 + 6H2O

Write the word equation for anaerobic respiration in muscles

glucose --> lactic acid

Write the word equation for anaerobic respiration in plant and yeast cells

glucose --> ethanol + carbon dioxide

Why is less energy transferred in anaerobic
respiration than in aerobic respiration

Oxidation (breakdown) of glucose is
incomplete, so not all the energy is released

What is the name of anaerobic respiration in yeast cells?

fermentation

Why is fermentation useful?

Produces ethanol for alcoholic drinks and
carbon dioxide to make bread rise

State 3 things that increase in the body during exercise

Heart rate, breathing rate and breath volume

Why does heart rate increase during exercise?

To supply the muscles with more oxygenated
blood for respiration

Why might a person doing exercise experience muscle pain and fatigue?

There is insufficient oxygen for aerobic
respiration, so they do anaerobic respiration
too. This causes lactic acid to build up in the
muscles.

What is meant by the 'oxygen
debt' during exercise?

The amount of extra oxygen the body needs
after exercise to react with lactic acid and
remove it from the cells.

What happens to the lactic
acid after exercise and in which organ?

Converted back into glucose in the liver

What is metabolism?

The sum of all the reactions in a cell or body

Give one example of metabolism in humans

Conversion of glucose to starch, glycogen &
cellulose; formation of lipids from glycerol & 3
fatty acids; use of glucose & nitrate ions to
form amino acids for protein synthesis;
respiration; breakdown of excess proteins to
form urea for excretion.

What type of organisms are prokaryotic cells?

Bacteria

What type of organisms have eukaryotic cells?

Plants and animals (& fungi)

What is the function (job) of the nucleus in
a cell?

To control the cell. Contains DNA.

What is the function of the mitochondria?

To release energy in respiration

What is the function (job) of the cell membrane?

To control what substances can enter or leave
the cell

What process takes place at the ribosomes?

Protein synthesis / making proteins

What is the role of chloroplasts?

Absorb sunlight for photosynthesis. Contain
chlorophyll

What is inside the permanent vacuole of a
plant cell?

Cell sap

Name three cell parts (organelles) found in
plant cells but not animal cells

Cell wall, permanent vacuole, chloroplasts

Name one structure you might find in the cytoplasm of a prokaryotic cell but not in a eukaryotic cell

DNA or plasmid

Name one structure found in eukaryotic cells but not prokaryotic cells

A nucleus surrounding the genetic material (or
accept mitochondria)

Which are the smallest, prokaryotic or eukaryotic cells?

Prokaryotic cells are much smaller

What is the cell wall made of in plant and algal cells?

Cellulose

Give one adaptation of a sperm cell

Tail to swim towards the egg, acrosome to
digest egg cell membrane, lots of mitochondria
to supply energy for swimming, haploid
nucleus

Give one adaptation of a nerve cell

Long axon to transmit nerve impulses,
branched nerve endings/dendrites to
send/receive impulses from other neurones,
fatty sheath/insulating layer to speed up nerve
impulses

Give one adaptation of a muscle cell

Proteins filaments that slide to cause muscle
contraction, lots of mitochondria to release
energy, many nuclei because cells have
merged to form a stronger structure

Give one adaptation of a root hair cell

Long projection of the cell membrane to
increase surface area for water to move in

Give one adaptation of xylem cells

Dead hollow cells to form a tube for water
transport; thickened with lignin

Give one adaptation of phloem cells

Perforated end walls to act as a sieve for sugar
solution to pass through

What is cell 'differentiation'?

The process of cells becoming specialised by
acquiring different sub-cellular structures to
enable it to carry out a certain function

Give a reason why cell division is necessary
in mature animals

For repair (of tissues) and replacement (of
damaged cells), NOT "repair of cells".

How have developments in microscopy allowed us to understand more about sub-
cellular structures such as ribosomes and mitochondria?

We have electron microscopes which have a
much higher magnification and resolution, so
can see finer details inside cells.

State two advantages of an electron microscope over a light microscope

Higher magnification, greater resolving power
(resolution)

What is the formula for magnification (Hint:
The triangle is not the formula, but it can
help you work it out)?

Magnification = size of image / size of real
object

How do bacteria divide?

By binary fission

How often do bacteria divide?

Once every 20 minutes if they have enough
nutrients and a suitable temperature

Name two types of growth
medium for bacteria

Agar gel plate or nutrient broth solution

What is the purpose of aseptic technique?

To prepare an uncontaminated culture of
microorganisms

In aseptic technique, why must petri dishes and culture media be sterilised
before use?

To kill any bacteria or other microorganisms
that could multiply and contaminate the
experiment

In aseptic technique, how can inoculating loops be sterilised?

By passing through a Bunsen flame

In aseptic technique, why are
Petri dishes stored upside down?

To prevent condensation affecting bacterial
growth

When growing bacteria in a
school laboratories, why are cultures generally incubated at temperatures no
higher than 25 degrees celsius?

To prevent the growth of microorganisms that
are harmful to humans (which are likely to
multiply at temperatures close to body
temperature)

What formula would you use to calculate the cross-sectional area of a
bacterial colony or the clear area around it?

πr2

What is found in the nucleus of cells?

Chromosomes made of DNA molecules

During the cell cycle, what happens to the
genetic material (DNA) before mitosis?

It replicates (doubles)

During the cell cycle, aside from the
doubling (replication) of the DNA, what else
happens within the cell?

The cell grows and increases the number of
sub-cellular structures (organelles) e.g.
ribosomes, mitochondria

What happens to the chromosomes during
mitosis?

They are pulled to opposite ends of the cell
(NB. DNA replication/doubling is NOT part of
mitosis)