bilogy paper 1

eukaryotic and prokaryotic cells simulates and differences

eukaryotic (animal + plant cells) - larger + more complex, contain nucleus

prokaryotic (bacteria cells) - smaller + simpler, no nucleus

animal cells organelles

mitochondria - site of respiration

nucleus - contains DNA + controls activities of cell

cell membrane - contains what goes in and out of the cell

cytoplasm - site of chemical reactions

ribosomes - where protein synthesis occurs

what do plant cells contain that animal cell do not?

cell wall - made of cellulose to provide support to the cells

permanent vacuole - contains cell sap to provide structure

chloroplast - site of photosynthesis

what does a bacteria cell contain

cell membrane

ribosomes

cytoplasm

cell wall

circular strand of DNA + plasmids

what is differentiation?

when an unspecialised cell transforming to a specialised cell which has a specific function

how are sperm cells specialised?

specialised to deliver male to DNA to female DNA during reproduction

• many mitochondria for energy

• streamlined head to swim

• long tail for movement

• enzymes in head to digest through egg membrane

how are nerve cells specialised?

to carry electrical impulses throughout the body

• long to cover more distance

• branched connections (dendrites) to form a large network around the body

how are muscle cells specialised?

specialised to contract

• long to have space to contract

• many mitochondria to release more energy

how are root hair cells specialised?

absorb water + mineral ions

• long hairs to increase surface area

• thin cell wall for faster absorption

• many mitochondria for active transport of mineral ions

how are phloem cells specialised?

specialised to transport food substances in plant

• no nucleus - more space for transporting sugars

• sieve plates to allow substances to flow between cells

• companion cells with many mitochondria to provide energy for transport

how are xylem cells specialised?

specialised to transport water and minerals up the plant

• hollow to allow water to flow easily

• no end walls to form a continuous tube for transport

explain the cell cycle

• cell grows

• increases subcellular structures e.g mitochondria and ribosomes

• replicates DNA

• mitosis - chromosomes pulled to opposite ends of cell

• nucleus divides

• cytoplasm and cell membrane divide

• form two identical daughter cells

what is a stem cell?

undifferentiated cell with no job that can differentiate into a cell with a function

e.g embryonic stem cells found in embryos which can turn into any cell

adult stem cells found in bone marrow which can only turn into blood cells

uses of stem cells

treat diseases

adult stem cells can replace blood cells + treat blood cancers e.g leukaemia

embryonic stem cells can be used to replace body cells e.g diabetes + paralysis

why are people against using embryonic stem cells to treat disease?

destroys potential human life

where are plant stem cells found?

meristem tissue (found in tips of plants shoots and roots)

can turn into any type of plant cell

used to produce identical plants to preserve rare plant species + produce crops with desired characteristics

define diffusion

process of particular spreading from an area of high to low concentration

how to increase rate of diffusion?

increase temp

Increase concentration gradient

increase surface area to volume ratio

four exchange surfaces

• alveoli in lungs used for gas exchange

• leaves adapted for gas exchange in plants

• villi which absorb nutrients in small intestine

• gills which fish use for gas exchange

how do these exchange surfaces perform more effectively?

thin membranes - short diffusion pathway

large surface area - maximise diffusion

some are ventilated - maintain a diffusion gradient

define osmosis

net movement of water particles from an area of high to low low concentration across a partially permeable membrane

where does osmosis occur

root hair cells - absorb water from high water concentration in soil to low water concentration in cell

define active transport

net movement of particles from an area of low to high concentration against a concentration gradient (process requires energy from respiration)

when is active transport used in root hair cells?

when mineral ions are absorbed from the soil

mineral in concentration is lower in the soil than than in the cell

energy is needed to move against the concentration gradient

explain hair active transport is used in the human body?

when glucose is absorbed from the gut

what are cells?

building blocks of organisms

what are tissues?

group of similar cells

what are organs?

group of different tissues performing a specific function

what are enzymes?

biological catalysts which speed up reactions

folded into unique shapes with a gap known as active site

active site fits particles known as substrates

only one type of substrate fits into the enzyme

(Lock and key model)

digestive enzymes

carbohydrase- break carbohydrates into simple sugars

protease - break proteins into amino acids

lipase- break lipids into glycerol and fatty acids

digestive system

mouth - chew food + saliva produce amylase

amylase breaks down carbohydrates into simple sugars

food goes down oesophagus into stomach

stomach produces protease enzymes to break proteins into amino acids + stomach also produces hydrochloric acid which provides optimum pH for enzymes to work best

liver produces bile to neutralise stomach acid + emulsifies fat into smaller droplets

pancreas produces carbohydrase, protease, lipase to further break down food

when food then enters small intensifying all 3 enzymes produced again and broken down food particles are absorbed into blood

whatever is left over will be past to large intestine where excess water is absorbed

leftover forces stored in rectum

red blood cells

• red blood cells - specialised to carry oxygen (contain haemoglobin which binds to oxygen, no nucleus + biconcave shape which higher surface area to be able to carry more oxygen

function of white blood cells

used to fight infection

platelets

used to clot blood to prevent excessive bleeding + infection

plasma

liquid part of blood which carries red blood cells, white blood cells, platelets, food molecules and hormones

where is the heart’s natural pacemaker

right atrium

why is the left side of the heart thicker than the right?

it needs more muscle to pump blood at a higher pressure to rest of body whereas right only needs to pump blood to the lungs

3 blood vessels in circulatory system + function

Arteries - carry blood away from the heart under high pressure +have walls that are thick and muscular +small lumen (hole in middle)

Veins - carry blood towards the heart under low pressure + thin walls + large lumen + contain valves to prevent back flow of blood

Capilares - connect arteries to veins where gas and nutrient exchange takes place + one cell thick to help with diffusion of substances

What happens when are person has CHD

A persons arteries become blocked because of a build up of fatty material

Stents

A device made of metal that keep coronary arteries open

Statins

Drugs that lower cholesterol in blood to decrease fatty build up

Disadvantages + advantages of statins

Need to be taken regularly without interruption + can cause side effects

Artificial hearts

Can be used for heart failure when waiting for a transplant

• reduced risk of infection as they are manmade

• increased risk of rejection though

Non communicable disease

Disease that cannot be spread between organisms

Cancer

Uncontrolled cell growth and division that can lead to the formation of tumours

• tumours can be benign(not cancerous as don’t spread to other parts of body) or malignant (cancerous as they spread to different parts of the body in the blood + form secondary tumours).

Plant tissues

Upper epidermis - transparent to low light + sunlight through

Palisade mesophyll tissue - closely packed cells that contain many chloroplasts for light absorption for photosynthesis

Spongy mesophyll tissue - loosely arranged cells with air spaces to increase efficiency of diffusion of gases

Xylem - transports water + minerals up the plant

Phloem - transports sugar + other food substances up + down plant (translocation)

Lower epidermis - contain stomata + guard cells

Stomata

Job - gas exchange

• during day time they become turgid + open up to allow gas exchange

• during night there is less light intensity therefore they lose water + become more flaccid which causes them to close (less gas exchange occurs).

Meristem tissue

Found in tips of shoots + roots

Rate of transpiration increase due to what?

Light intensity up

Temperature up

Air flow rate up

Humidity down

How can you measure rate of transpiration

By using a potometer and measure how long it takes an air bubble across a certain distance

Bacteria

Loving cells that can produce poisons known as toxins which can cause illness

Virus

Smaller than bacteria + reproduce inside cells which cause cells to burst causing illness

Protist

Single celled eukaryotes that can spread through vectors like mosquitoes

Types of viruses

Measles - red skin, rash fever spread through air born droplets. Prevented + treated via MMR vaccination

HIV - flu like symptoms, spread via sex, treated by taking antiretroviral drugs, prevented by safe sex practices

Tobacco mosaic virus - discoloured leaves + stunted growth, spread via plant contact ,no cure but prevention through plant sterilisation

Bacteria diseases

Salmonella - vomiting + diarrhoea, spread through contaminated food/water, treated using antibiotics, prevented with food hygiene + handwashing.

Gonorrhoea -