GCSE Biology (Full Specification)

What is the structure eukaryotic cell?

Have a cell membrane, cytoplasm and genetic material enclosed in a nucleus

What types of organisms contain eukaryotic cells?

Animal and plant cells

What is the structure of a prokaryotic cell?

Contain cytoplasm, cell membrane, cell wall, genetic material not enclosed in a nucleus, rings of DNA called plasmids

What types of organisms contain prokaryotic cells?

Bacteria

What is a sub-cellular structure?

Structures within the cell

What sub-cellular structures do animals cells have?

nucleus, cytoplasm, cell membrane, mitochondria, ribosomes

What additional sub-cellular structures do plants cells have that animal cells don't?

cell wall, chloroplasts, permanent vacuole

What is the function of the nucleus?

Contains genetic material (DNA) which controls the cell's activities

What is the function of the cytoplasm?

Jelly-like substance where most chemical reactions happen

What is the function of the cell membrane?

Surrounds the cell and controls movement of substances in and out

What is the function of the mitochondria?

Part of the cell where energy is released from glucose

What is the function of the ribosomes?

Makes proteins

What is the cell wall made of?

Cellulose

What is the function of the cell wall?

Provides structure and support

What is the function of the chloroplasts?

Where photosynthesis occurs

What substance is contained in the chloroplasts that absorbs light?

Chlorophyll

What is the function of the vacuole?

Contain cell sap, a solution of sugar and salts

How do we observe cells?

Using a microscope

What is a light microscope?

A microscope that uses visible light and lenses

What are the key features of a light microscope?

Stage, objective lens, eye piece lens, focus adjustment, light source

What is an electron microscope?

A microscope that uses electrons and electron lenses

What is magnification?

How many times bigger than it actually is

What is resolution?

Minimum distance apart that two objects can be in order for them to be seen as separate objects

Compare light microscopes and electron microscopes.

-Light uses light rays whereas electron uses electron beams

-electron microscopes have a much higher magnification

-electron microscopes have a much higher resolving power

-Light are small+ portable, but elec is large + not portable

-electron are much more expensive

What are the advantages of using an electron microscope compared to a light microscope?

Higher magnification and resolution

How is magnification calculated?

magnification = image size / actual size

What does the prefix milli mean?

Thousandth of a metre (x 10-3m)

What does the prefix micro mean?

Millionth of a metre (x 10-6m)

What does the prefix nano mean?

Billionth of a metre (x 10-9m)

What is the relationship between the prefixes milli, micro and nano?

1000 times smaller each time

Why do cells differentiate?

The process by which a cell changes to become specialised for a particular job

When does most cell differentiation happen in animals?

At an early stage of development (as a foetus)

What is cell division mainly used for in mature animals?

Repair and replace cells

When does cell differentiation occur in plants?

Most plant cells retain the ability to differentiate throughout the life of the plant

Why is cell differentiation important?

carry out this function in the most efficient way

what is a drawback about cell differentiation?

differentiated cells often lose the ability to make new copies of themselves

What is a specialised cell?

A cell that has a structural adaptation to perform a particular function

What are 3 examples of specialised cells in animals?

Sperm cells, nerve cells & muscle cells

How is a sperm cell specialised to carry out its function?

Long tail and streamlined head to swim; lots of mitochondria to provide it with energy

How is a nerve cell specialised to carry out its function?

They a very long with branched connections to connect to other nerve cells and form a network it the body

How are muscle cells specialised?

They are long and contain a lot of mitochondria for contraction

What are 3 examples of specialised cells in plants?

Root hair cells, xylem and phloem cells

How are root hair cells specialised?

Has a large surface area from root hair to absorb more water and mineral ions

Do not contain chloroplasts as they are underground - more space

How are xylem cells specialised?

(transport water and minerals up the plant.)

They are hollow in the centre and have very few sub-cellular structures so that stuff can flow through them

How are phloem cells specialised?

(transport dissolved sugars in a plant.)

-few sub cellular structures so sugars flow through easily

-pores in end walls to let sugars through

Compare xylem and phloem

- mature xylem cells are dead, phloem are living

- xylem transports water, dissolved minerals and nutrients needed for growth from the roots to the leaves in one direction, phloem transports sugars in both directions

- xylem cell walls are tubular and elongated

- substances that xylem transport are absorbed via osmosis from the soil via root hair cells, substances that phloem transports are from photosynthetic cells or storage tissues

How do bacteria divide? (Triple only)

By binary fission

How often can bacteria divide through binary fission? (Triple only)

Up to once every 20 minutes

How are bacteria grown in a lab? (Triple only)

On a nutrient broth solution or as colonies on an agar gel plate

What is the definition of 'aseptic'? (Triple only)

'Free from contamination'

Why is it important we can grow uncontaminated cultures of microorganisms? (Triple only)

To investigate the action of disinfectants and antibiotics

Why is it important equipment is sterilised before and during aseptic technique? (Triple only)

To prevent contamination of unwanted microorganisms

Why is the lid of the petri dish secured with adhesive tape? (Triple only)

To prevent microorganisms entering or leaving the petri dish

Why are petri dishes stored upside down? (Triple only)

To stop condensation dripping on the agar

At what temperature should bacterial cultures be stored in school laboratories? (Triple only)

25°C

Why do schools use a maximum temperature of 25°C when incubating cultures? (Triple only)

To avoid harmful bacteria growing

What is a chromosome?

Coiled up lengths of DNA that contain genes

Why do cells divide by mitosis?

For growth and repair

what are the 3 stages of the cell cycle?

stage 1: growth

stage 2: DNA synthesis

stage 3: Mitosis

what happens during stage 1 of the cell cycle?

growth- increase number of sub cellular structures e.g ribosomes, mitochondria

what happens during stage 2 of the cell cycle?

DNA synthesis- DNA replicates to form 2 copies of each chromosome

what happens during stage 3 of the cell cycle (mitosis)?

one set of chromosomes is pulled to each end of the cell and the nucleus divides. Then the cytoplasm and cell membrane divide to form two cells identical to the arent cell. Mitosis happens asexually.

What is a stem cell?

An undifferentiated cell capable of giving rise to more cells of the same type

What can stem cells be used to treat?

Diabetes and paralysis

What can stem cells from human embryos be turned into?

Any kind of cell because they haven't become specialised yet

Where are stem cells found in adults?

Bone marrow

Why are bone marrow stem cells not as good as embryo stem cells?

They can't turn into any type of cell, only certain ones, like blood cell

What is therapeutic cloning?

Procedure where by an embryo is produced with the same genes as the patient.

Why is therapeutic cloning advantageous?

Any cells produced by it, wouldn't be rejected by the patient because it contains their own genes

What are the risks associated with stem cells?

If they are contaminated, viral infections may transfer to the patient

Why are some people opposed to using stem cells from embryos?

They have ethical or religious objections about destroying a potential human life

What can stem cells from meristems be used for?

Protect rare species from extinction.

Produce crops with disease resistance.

What is diffusion?

The net movement of particles from an area of high concentration to an area of lower concentration

What do particles do during diffusion?

Spread out until their concentration is even

What factors affect the rate of diffusion?

Temperature, concentration gradient, the surface area of the membrane

What are two specialist exchange surfaces in mammals?

Villi in the small intestine; alveoli in the lungs

What specialist exchange surface does a fish have to exchange gases?

Gills

How are Small intestines, lungs (in mammals), gills in fish, roots and leaves in plants adapted for exchanging materials?

as its exchange surface is increased by:

-Having a large surface area

-A membrane that is thin, to provide a short diffusion path

-(in animals) Having an ef cient blood supply

-(in animals, for gaseous exchange) Being ventilated

What is osmosis?

Osmosis is the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane

What is active transport?

Active transport moves substances from a more dilute solution to a more concentrated solution (against a concentration gradient). This requires energy from respiration.

Where and how does active transport take place in plants?

Root hairs; mineral ions are absorbed into the root hair cells from very dilute solutions in the soil

Why do plants require ions?

For healthy growth

Where does active transport take place in animals?

Sugar molecules are absorbed from lower concentrations in the gut to higher concentrations into the blood in the small intestine

What are sugar molecules used for?

Respiration

What are cells?

The basic building blocks of all living organisms

What is a tissue?

A group of cells with a similar structure and function

What is an organ?

Aggregations of tissues performing specific functions

What is an organ system?

A group of organs, which work together to form organisms

What is a muscular tissue?

A tissue that contracts to move whatever it's attached to

What is a glandular tissue?

A tissue which makes and secrete chemicals like enzymes and hormones

What is an epithelial tissue?

A tissue which covers some parts of the body

What is a catalyst?

A substance which increases the speed of a reaction, without being changed or used up in the reaction

What is an enzyme?

A biological catalyst

What is the structure of an enzyme?

Large proteins made of chains of amino acids

What is the 'active site' on an enzyme?

A uniquely shaped section of the enzyme that only certain molecules will fit into

What is a 'substrate'?

The substance involved with the chemical reaction that fits into the enzyme

What is the 'lock and key' theory?

A specific substrate (the key) fits into the active site (lock) of the enzyme, breaking the bonds in the substrate

What two conditions can affect how an enzyme works?

Temperature and pH

What happens as the temperature of an enzyme controlled reaction increases?

The rate of reaction will also increase, but only until a certain temperature

Why does the enzyme stop working past a certain temperature?

The enzyme has become 'denatured'