biology aqa paper 1

Light microscope

* Two lense, an objective and eyepiece
* The objective lense produces a magnified image, which is then magnified an directed into the eye by the eyepiece lens
* Usually illuminated from underneath

Maximum magnification of a light microscope

They have approximately, a maximum magnification of x2000 and a resolving power (this affects resolution) of 200nm

What is a light microscope used to view

Tissues, cells and large sub-cellular structures

When was the light microscope first used

In 1665 by Robert Hooke who observed the first cells of cork

Electron microscope

* Electron are used to form an image because the electrons have a much smaller wavelength than that of light waves
* There are two types: a scanning electron microscope that creates 3d images and a transmission electron microscope which creates 2d images detailing organelles

Magnification of electron microscopes

They have a magnification of up to x2,000,000 and resolving power of 10nm (SEM) and 0.2nm(TEM)

When was the Electron microscope invented

It was developed in the 1930s and enables scientists to view deep inside sub-cellular structures, such as mitochondria, ribosomes, chloroplasts and plasmids

Magnification of a light microscope formula

Magnification of the eyepiece lens x magnification of the objective lens

Size of an object formula

Size of the image / Magnification = size of object

Differences between eukaryotic and prokaryotic cells

* Prokaryotic cells are much smaller and do not contain membrane bound organelles and a nucleus containing genetic material

What is the prokaryotic cell wall composed of?

Peptidoglycan

How is genetic information stored in a prokaryotic cell?

Found free within the cytoplasm as: Chromosomal Dna (single large loop of circular DNA) or plasmid DNA

What are plasmids

* Small circular loops of DNA found free in the cytoplasm and separate from the main DNA
* Carry genes that provide genetic advantages eg antibiotic resistance

List all the components of both animal and plant cells

* Nucleus
* Cytoplasm
* Cell Membrane
* Mitochondria
* Ribosomes

What cell components are just found in plant cells

* Chloroplasts
* Permanent Vacuole
* cell wall

Other than storing genetic information, what is the function of the nucleus?

Controls cellular activities

Describe the structure of the cytoplasm

* Fluid component of the cell
* Contains organelles, enzymes and dissolved ions and nutrients

What is the function of the cytoplasm

* Site of cellular reactions eg first stage of respiration
* Transport medium

What is the function of the cell membrane

Controls the entry and exit of materials into and out the cell

What is the function of the mitochondria

Site of later stages of aerobic respiration in which ATP is produced

What is the function of ribosomes

Joins amino acids in a specific order during translation for the synthesis of proteins

What is the plant cell wall made of

Cellulose

What is the function of the plant cell wall

* Provides strength
* Prevents the cell bursting when water enters by osmosis

What does the permanent vacuole contain?

Cell sap (a solution of salts, sugars and organic acids)

What is the function of the permanent vacuole

Supports the cell, maintaining its turgidity

What is the function of chloroplasts

site of photosynthesis

Describe how sperm cells in animals are adapted to their function

* Haploid nucleus which contains genetic information
* Tail enables movement
* Mitochondria provides energy for tail movement
* Acrosome contains enzymes that digest the egg cell membrane

Describe how nerve cells in animals are adapted to their function

* Long axon allows electric impulses to be transmitted all over the body from the central nervous system
* Dendrites from the cell body connect to and receive impulses from other nerve cells, muscles and glands
* Myelin sheath insulates the axon and specs up the transmission of impulses along the nerve cell

Describe how muscle cells in animals are adapted to their function

* Arrangement of protein filaments allows them to slide over each other to produce muscle contraction
* Mitochondria to provide energy for muscle contraction
* Merged cells in skeletal muscle allows muscle fibre contraction in unison

Describe how root hair cells in plants are adapted to their function

* Large surface area to absorb nutrients and water from surrounding soil
* Thin walls that do not restrict absorption

Describe how xylem cells in plants are adapted to their function.

* No upper or lower margins between cells to provide a continuous route for water to flow
* Thick, woody side walls strengthen their structure and prevent collapse

Describe how Phloem cells in plants are adapted to their function

* Sieve plates let dissolved amino acids and sugars be transported up and down the stem
* Companion cells provide energy needed for active transport of substances along the phloem

What is cell differentiation

The process by which cells become specialised

Why is cell differentiation important?

Allows production of different tissues and organs that perform various vital functions in the human body

At what point in their life cycle do most animal cells differentiate

Early in their life cycle

For how long do plant cells retain the ability to differentiate

Throughout their entire life cycle

What is the purpose of cell division in mature animals?

Repair and replacement of cells

What changes does a cell go through as it differentiates

Becomes specialised through acquisition of a different sub-cellular structures to enable a specific function to be performed by the cell

Disadvantages of electron microscopes

* Expensive
* large so less portable
* require training to use
* only dead specimens can be observed

How do bacteria multiply

Binary fission

How often do bacteria multiply

Once every 20 minutes if enough nutrients are available and the temperature is suitable

2 ways Bacteria can be grown

* Nutrient broth solution
* Colonies on agar gel plate

Name the two types of electron microscope

* Transmission electron microscope (TEM)
* Scanning electron microscope (SEM)

Disadvantage of light microscopes

limited resolution

How does an electron microscope work?

It uses a beam of electrons which are focused using magnets. The electrons hit a fluorescent screen which emits visible light, producing an image.

Viruses

* communicable disease
* very small
* move into cells and use the biochemistry of it to make copies of itself
* This leads to the cell bursting and releasing all the copies of it into the bloodstream
* The damage and destruction of the cell make the individual feel ill

Bacteria

* Communicable diseases
* They multiply very quickly through dividing by a process called binary fission
* small
* They produce toxins that can damage cells

Protists

* Communicable
* Some are parasitic which means they can use humans and animals as their hosts

Fungi

* communicable
* They can either be single celled or have a body made of hyphae
* They can produce spores which can be spread to other organisms

Anaerobic respiration in plants and yeast

* This is called fermentation and is used to make bread and alcoholic drinks
* Glucose → ethanol + co2

The trachea and bronchi

* secret mucus in other to trap pathogens
* Cilia best to waft mucus upwards so it can be swallowed

The stomach

* Produces hydrochloric acid that kills any pathogens in your mucus, food or drink

Tobacco mosaic virus symptoms

* discolouration of the leaves, the affected part of the leaf cannot photosynthesise
* Good field hygiene and pest control can help prevent it

Diffusion

Diffusion is the spreading of particles resulting in a net movement from an area of higher concentration to an area of lower concentration

* The higher the temperature the greater the rate of diffusion because the particles have more kinetic energy
* The larger the surface area of the cell membrane, the greater the rate of diffusion

Osmosis

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

Active transport

Active transport moves substances from a more dilute solution to a more concentrated solution which requires energy from respiration

What is the difference between diffusion and active transport?

* Diffusion: particles move down the concentrated gradient and don’t require energy from respiration
* Active transport: Particles are moved against the concentrated gradient and this requires energy from respiration

What three ways do the white blood cells destroy pathogens

* Phagocytosis
* Producing antibodies
* producing antitoxins

Phagocytosis

Engulfing and consuming pathogens which destroys them meaning they can no longer make you feel ill

Antibodies

Each pathogen has an antigen on their surface, which is structure which a specific complementary antibody can bind to. Once antibodies begin to bind to the pathogen, the pathogens start to clump together, resulting in it being easier for white blood cells to find them.

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If you become infected again with the same pathogen, the specific complementary antibodies will be produced at a faster rate.

Anti toxins

They neutralise the toxins released by the pathogen by binding

Three stages of the cell cycle

* In the first stage of the cell cycle the DNA replicates to form two copies of each chromosome. The cell also grows and copies it’s internal structures such as mitochondria and ribosomes.
* I’m the second stage, mitosis takes place. One set of each chromosome is pulled to each end of the cell and the nucleus also divides
* In the final stage the cell membrane and the cytoplasm divide to form two identical cells

Functions of mitosis

* Essential for growth and development of multicellular organisms
* Mitosis takes place when an organism repairs itself (eg when a broken bone heals)
* Mitosis happens during asexual reproduction

Blood plasma

Blood plasma transports soluble digestion products from the small intestine to other organs, Carbon dioxide from the organs to the lungs to be breathed out and the waste urea from the liver to the kidneys to be extracted in urine

Red blood cells

Red blood cells transport Oxygen from the lungs to the body cells, they contain the oxygen carrying molecule haemoglobin. Red blood cells have no nucleus and in the centre of the cell there are dimples.

White blood cells

White blood cells form part of the immune system, they contain a nucleus which contains Dna that encodes the instructions that the white blood cell needs to do their job.

Platelets

These are tiny fragments of cells and their job is to help the blood clot

Gas exchange in lungs

Air passes into the lungs through a tube called the trachea. Rings of the cartilage prevent the trachea from collapsing during inhalation. The trachea now splits into two smaller tubes called bronchi with one passing to each lung further into into the lungs, the bronchi subdivide into many smaller tubes called bronchioles which end in tiny air sacs called Alveoli. Alveoli are where gases diffuse in and out of the blood stream

Breathing

* Breathing increases the rate of diffusion
* Millions of alveoli mean that the lungs have a huge surface area

Cancer

Cell division by mitosis occurs all over the body, especially during growth and repair. It’s extremely lightly controlled genes in the nucleus tell cells when to divide and when not. Sometimes changes take place in these genes and that leads to uncontrolled growth and mitosis which produces a tumour

Benign tumours

These are growths of abnormal cells which are found in one area and are usually contained within a membrane.

* Benign tumours do not invade other parts of the body

Malignant tumours

Their cells invade neighbouring tissues and move into the bloodstream, these cells are classed as a cancer as they spread and from secondary tumours

Cancers linked to genetic s

* Certain types of breast cancer, prostate cancer and cancer of the large intestine

Cancer linked to lifestyle

* Smoking causes lung cancer
* Ultraviolet light causes skin cancer
* Alcohol can cause mouth and throat cancer

Radon

This is a radioactive gas that increases your risk of developing lung cancer because it releases ionising radiation which damages the DNA in our cells

Risk factors for cardiovascular disease

* A diet high in fat and low in vegetables as this increases the rate that fatty materials build up in the arteries
* A diet high in salt can increase blood pressure

Risks involved with smoking

* Smokers risk cardiovascular diseases
* Smoking when pregnant increases the risk of miscarriages and premature birth or a baby being born with a low body mass

Risks of drinking alcohol

* Adults who drink increase their risk of liver cirrhosis and liver cancer
* Alcohol can also effect the brain leading to addiction and memory loss

uses of monoclonal antibodies

* In pregnancy testing they are used to detect a specific hormone. (Hormone produced by the placenta of the developing fetus)
* We can use them to measure the levels of hormones in blood and to detect pathogens in the blood
* The can be used to locate or identify specific molecules in a cell or tissue
* Sometimes they can stop cancer cells from dividing

Give one reason that cell division by mitosis is important in fully grown animals

Repair of tissues/regrowth of cells

Stems, roots and leaves

All plant organs which are made of tissue and work together to carry substances around the plant

Epidermal tissue

Covers the whole plant

Palisade mesophyll tissue

The part of the leave where the most photosynthesis happens

Why are the leaves of the rose yellow

Chlorophyll has been broken down and they grow slowly as they aren’t going through photosynthesis

Food tests

Sugar - Benedict’s solution

Starch - Iodine solution

Protein - Blurent reagent

Why is starch not absorbed into the blood

Starch is insoluble

Spongy mesophyll tissue

Part of the leaf that has big air spaces. this allows gas to move in and out of cells

Xylem and phloem

Transport water, mineral ions and food around the roots, stems and leaves

Meristem tissue

Found at the growing tip of shoots and roots

Food tests colours

Biuret solution (proteins) - Purple

Iodine test (starch) Blue black

Benedict’s solution (sugars) Red, orange, yellow green depending on how much glucose

Sudan III (fats) - stains red

What are the four main blood vessels associated with the heart

Aorta (left) - carries oxygenated blood from the heart to the body

Pulmonary vein (left) carries oxygenated blood from the lungs to the heart

Vena cava (right) Carries deoxygenated blood from the body to the heart

Pulmonary artery (right) carries deoxygenated blood from the heart to the lungs

What is the purpose of valves in the heart

Prevent the back flow of blood

What is the purpose of coronary arteries

Supple the heart muscle with oxygenated blood

How is the heart rate controlled

Heart rate is controlled by a group of cells in the right atrium which act as a pacemaker. They release waves of electrical activity which cause the heart muscle to contract

What are the three types of blood vessel in the body?

Arteries

Veins

Capillaries

How are arteries adapted for their function

Function: carry blood away from the heart

Thick muscle layer which adds strength to resist high pressure

Thick elastic layer which allows arteries to stretch and recoil in order to withstand high pressure

How are veins adapted for their function

Function:carry blood towards the heart

Wide lumen - enables lows blood pressure

Valves prevent the back flow of blood

How are capillaries adapted for their function

Function: enable transfer of substances between the blood and the tissue

Walls are one cell thick - short diffusion path

Permeable walls - substances can diffuse across

Narrow lumen - blood moves slowly so there’s more time for diffusion

How to calculate the rate of blood flow

Volume of blood/number of minutes

What tissues and organs make up the gas exchange system

Trachea

Intercostal muscles

Bronchi

Bronchioles

Alveoli

Diaphragm