Edexcel igcse biology paper 2

(Most of the notes on paper 2, this set is unfinished)

What characteristics do all living organisms share?

Movement respiration sensitivity nutrition excretion reproduction growth

Organelles in both animal and plant cells?

Cell membrane, cytoplasm, nucleus. ribosomes, mitochondria

What are the organelles that plant cells have that animal cells dont have?

Chloroplast, vacuole, cell wall

What does the nucleus do?

Controls activity of the cell

What does the cell membrane d

Controls entry and exist of substances into the cell like oxygen, water, carbon dioxide but do not allow larger molecules like glucose, sucrose, proteins, and starch to enter

What does the cytoplasm do?

It is where chemical reactions take place

What does mitochondria do?

Where aerobic respiration takes place to release energy

What do ribosomes do?

Protein synthesis (where proteins are made)

What is the role of vacuoles?

Filled with cell sap contains dissolved sugars and mineral ions

What is the role of chloroplasts?

To carry out photosynthesis

What is the role of cell wall?

To protect and support the cell which is made out of cellulose in plant cells

What are the 2 types of cells

Eukaryotic and prokaryotic

What does eukaryotic mean

It has membrane bound organelles e.g. animal cells have mitochondria, chloroplasts, nucleus

What does prokaryotic mean?

No membrane bout organelles, e.g. bacteria and viruses

What features does a bacterial cell have?

Cytoplasm, cell membrane, cell wall made of peptidoglycan, cell capsule, mitochondria, nucleoid (circular strand of DNA/Chromosome), plasmid (rings of DNA) , flagellum

What is a pathogen?

A microorganism that causes disease

Some bacteria are pathogenic, which?

Pneumococcus (responsible for pneumonia), tuberculosis (coughing up blood)

What bacteria are useful?

Lactobacillus (yoghurt)

Are viruses bigger or smaller than bacteria?

Smaller and made of DNA or RNA, envelope, Protein coat

What do viruses not do?

Excrete respire grow, eg flue cold hiv

What does tobacco mosaic virus do in plants?

Causes discolouration in plant leaves due to prevention of chloroplast formations

Examples of protoctists?

Chlorella and algae (both have chloroplasts), amoeba (dont have cell wall or chloroplasts), plasmodium (pathogenic because it causes malaria via mosquitos)

Are protoctists unicellular or multicellular?

Both

What is cell wall in fungi made of?

Chitin

Examples of fungi?

Mucor, mushrooms

What do fungi have?

Thread like structures called hyphae that form a network called mycelium

What nutrition to fungi carry out?

Saprotrophic nutrition which is the extracellular secretion of enzymes onto dead matter to break down and absorb as food

What fungi is used in yeast and bread making?

Yeast, for anaerobic respiration o break down glucose into ethanol and CO2 (ethanol is needed for beer, CO2 is needed for bread rising)

What are the 5 kingdoms?

Plants, animals protoctists, bacteria, fungi

How are carbohydrates stored in animals fungi plants

glycogen, glycogen starch

What is a cell?

A group of organelles working together to perform the same function

What is a tissue?

A group of cells working together to perform the same function

What is an organ?

A group of tissues working together to perform the same function

What is an organ system?

a group of organs working together to perform the same function

What are all the organ systems in the body named?

Digestive system, endocrine system, reproductive system, circulatory system, respiratory system, nervous system, excretory system

What organs make up the digestive system?

Stomach, oesophagus, pancreas, large intestine, small intestine,

What is a zygote?

When the sperm and egg meet at fertilisation you form 1 cell called a zygote which has to divide to form the embryo. It divides by mitosis 2 cells —>3—>8—>16….

What is differentiation?

The process by which cells become specialised, e.g nerve cells

What is a stem cell?

A cell that has the ability to divide many times without becoming differentiated.

What are the 2 types of stem cells?

Embryonic stem cells and adult stem cells

What can embryonic stem cells do?

Embryonic stem cells can differentiate into any type of cell, e.g. if you have a damaged liver, they can make you a new liver. This means it can treat many diseases

What can an adult stem cell do?

It doe snot have the ability to differentiate or specialise into any type of cell, it’s stuck to only making 1 type of cell so it has limited use such as making bone marrow

What does leukaemia do?

It affects the blood by destroys white blood cells?

How do you fix leukemia?

Chemotherapy, which uses chemicals do destroy cancer cells but an issue is that it can also affect healthy cells and kill them, But the thing that stem cell therapy then does is that it can replace those damaged cells with new cells

What is the disadvantage of stem cell therapy?

The ethics because they come form aborted fetuses, miscarried fetuses

What elements are found in carbohydrates?

Carbon hydrogen oxygen

What elements are found in proteins?

carbon hydrogen oxygen nitrogen

what elements are found in lipids

3 fatty acids and 1 glycerol

What is an enzyme?

It is a biological catalyst which means it speeds up the rate of a reaction without being used up

Enzymes and the active site image?

this

What do enzymes usually end in?

ase

Amylase is an enzyme, what is it made in?

It is made in salivary glands and small intestines and pancreas, what it does it catalyses the breakdown of starch into glucose, in this case, starch is the substrate (the thing entering the amylase enzyme) and the product is glucose, amylase has been broken down into a small simpler sugar named glucose

What does protease do?

It breaks down proteins into amino acids, it is found in your stomach, small intestine, pancreas

What is lipase?

It breaks down lipids into fatty acids and glycerol and is made in small inestine and pancreas

What happens as you increase temperature of enzymes?

enzyme activity increases because enzymes are colliding more often, when it reaches its peak, the enzymes and substrates are coming together more frequently, after this temperature of 37 degrees usually, there is a massive decrease in enzyme activity because they have become denatured (pH also does this)

What are the 3 types of transport?

Diffusion, osmosis and active transport

What is the definition of diffusion?

The net movement of particles from an area of high concentration to low concentration, diffusion doesn’t require energy

Definition of osmosis?

The net movement of water molecules from an area of high water potential to an area of low water potential across a partially permeable membrane, it doesnt require energy

What is active transport?

It requires energy, the net movement of particles from an area of low concentration to high concentration

Wht is diffusion quick in amoeba (small organism)?

They are single celled and have a high surface area to volume ration so diffusion occurs quickly

Why is diffusion too slow in multicellular organisms (large organisms)?

Because they have a small surface area to volume ration so diffusion is too slow whhich is why they have a circulatoiry system

What is photosynthesis?

It is carried out in chloroplasts of the plant which absorb light to carry it out

What is the photosynthesis equation?

Carbon dioxide + water—> glucose + oxygen, this is good because lots of O2 is created

What are the limiting factors of photosynthesis?

CO2, light intensity, temperature

Definition of limiting factor?

A factor in a reaction which is in the shortest supply and a lack of this factor is why the rate of reaction no longer increases

In the morning, why is a temperature and light intensity a limiting factor?

It means enzymes have little kinetic energy

What is the limiting factor of photosynthesis at midday?

CO2 levels

At night what do plants do?

Because they can’t photosynthesise due to lack of sunlight, it will just be respiring so more Oxygen enters the leaf than exit

What are the adaptions of leaf?

large surface area, thin (so gases don’t need to diffuse too far), flat

Structure of a leaf image?

this

What is waxy cuticle for?

Prevent transpiration (loss of water form the leaf)

What is the upper epidermis for?

Transparent to allow light to enter the leaf

What is palisade mesophyll for?

Contains lots of chloroplasts which absorb light in photosynthesis

What is spongy mesophyll for?

it has air spaces to allow gases to diffuse (Co2 and O2)

What is the vein containing xylem and phloem for?

the xylem brings water to the leaf, the phloem removes sugar

What is guard cells for?

Controlling opening and closure of stomata

What is stomata for?

Allowing CO2 into the leaf and oxygen out

What is glucose in photosynthesis used to make

Proteins, fats, cellulose for cell wall, starch for storage

What are mineral ions absorbed for the soil by?

Active transport into the root hair cell (magnesium and nitrates)

What is magnesium used to makee?

Chloroplasts

What does magnesium deficiency look like?

Yellow leaves

What does nitrate defficiency look like?

Stunted growth in plants

What is the definition of digestion?

The break down of large insoluble molecules into smaller soluble ones (so that it can be absorbed through the walls of the small intestine)

What is mechanical digestion?

It takes place in the mouth teeth when food is broken into smaller chunks, (chemical digestion is when amylase digests starch into glucose), The food then passes through the osoeephagus through peristalsis (muscular contractoins push the bolus of food down the oesophagus) down into your stomach, in stomach the muscular linings of the stomach help churn the food, in stomach HCl is also secreted o break down he food and kill pathogens

What is a pathogen?

A microorganism which causes disease

What is bile?

A greeen liquid made in liver, stored in gall bladder, released into small intestines to emulsify large fat droplets into smaller droplets to create a much larger surface area so that lipase can work more easily on the lipd molecules, bile also neutralises the stomach acid (HCl)

How is the small intestine adapted for its role?

It has large SA provided by villi and microvilli, lots of capillaries, thin wall for short diffusion distance, lacteals for absorptions of fats

After food passes the small intestine what does it do in th large intestine?

Water is reabsorbed into the blood

Where are faeces stored?

Rectum before the leave the body via the anus (this is named egestion)

Do you extrete or egest faeces?

You egest them

What is excretion definition?

The removal of waste products of metabolism

What is ingestion definition?

The process of taking in food to the mouth

What is metabolism definition?

The rate at which chemical reactions take place

What is the definition of assimilation?

The build up of large molecules from small ones

What does a balanced diet contain?

carbohydrates, fats, proteins, vitamins, minerals, fibre, water

What are carbs an important source of?

Energy

What is protein good for?

The growth and repair of muscles

What is the disease form lack of protein?

Kwashiorkor (stomach comes out very far)

What are fats?

A very concentrated source of energy, also used for insulation

Where is vitamin C found and what is it food for?

Citrus fruits, important for repair of tissues