GCSE biology - topic 2 (B1, B2, B3)

what is a cell?

smallest unit of life which forms to make a tissue

whats an example of a cell (plant and animal)?

phloem cell, red blood cells

what is a tissue?

a group of cells with similar structure and function working together

whats an example of a tissue (plant and animal)?

epidermal tissue, muscular tissue

what is the function of the muscular tissue?

it contracts to move whatever its attached to

what does the glandular tissue do?

it makes and secretes chemicals eg. enzymes

what is an organ?

a collection of tissues working together to perform a specific function

whats an example of organs (plant and animal)?

leaf, stomach

what tissues is the stomach made of?

muscular tissue, glandular tissue, epithelial tissue

what is an organ system?

group of organs that work together to perform specific functions. The way in which one organ functions depends on other organs in the system

whats an example of an organ system (plant and animal)?

vascular system, digestive system

what is an organism?

a collection of organ systems working together

whats an example of an organism (plant and animal)?

lily, human

what is differentiation?

the process by which cells become specialised for a particular job

when does differentiation occur?

during the development of a multicellular organism

what makes chemical reactions work?

enzymes

why do chemical reactions have to be carefully controlled?

to get the right amounts of substances

how can you make a chemical reaction happen quicker?

by raising the temperature

why is there a limit to how high the temp inside a living creature can be?

because the cells could get damaged

what do enzymes do in chemical reactions?

act as biological catalysts. They reduce the need for high temps in the body and instead have enzymes to speed up the reactions

what is a catalyst?

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

what are enzymes in terms of biological makeup?

large proteins, made up of chains of amino acids. These fold into unique shapes enzymes need to do their jobs

what does every enzyme have?

an active site with a unique shape that fits onto the substance involved in a reaction

why do enzymes only usually catalyse one specific reaction?

because for the enzyme to work, the substance has to fit into its active site. If the substrate doesnt match the enzymes active site, the reaction wont be catalysed.

what does a lock and key model of an enzyme look like?

what happens if the temperature or the pH in a reaction rises or goes too low?

some of the bonds holding the enzyme together break, denaturing and changing the shape of the enzyme

what is enzymes optimal pH (usually, some exceptions, eg. pepsin)

neutral 7 (pepsin-2)

how do you do the practical of investigating the effect of pH on enzyme activity? (8)

1. put a drop of iodine on each well of a spotting tile

2. put a beaker of water over a bunsen burner until at 35°

3. add 1cm³ of amalyse solution and 1cm³ of a buffer solution to a boiling tube.

4. put the tube into a beaker of water and wait 5 mins.

5. add 5cm³ of starch solution to the boiling tube.

6. mix immediately and start a stop clock.

7. use continuous sampling (add a drop of the solution to the iodine solution every 30s until it stops turning blue/black and remains orange(this means no starch is present))

8. repeat with different pH values to see how pH affects time.

how do you calculate the rate of reaction?

rate = 1000/ time

what are starch, proteins, and fats?

big molecules (too big to pass through the walls of the digestive system, so digestive enzymes break the big molecules into smaller ones (eg. sugars, amino acids, fatty acids), which can pass through easier, allowing them to be absorbed into the bloodstream)

what is amylase an example of ?

a carbohydrase. it breaks down starch

where is amylase made in?

the salivary glands, the pancreas, the small instestine

what does proteases do?

converts proteins into amino acids

where is protease made in?

the stomach, the pancreas, the small intestine

what does lipases do?

converts lipids into glycerol and fatty acids

where is lipase made in?

the pancreas, the small intestine

what does these digestive enzymes make?

new carbohydrates, proteins, and lipids

where is bile produced and stored?

produced in the liver, stored in the gall bladder before released into the small intestine

what does bile do to the hydrochloric acid in the stomach?

it neutralises it and makes conditions alkaline so the enzymes in the stomach work properly

what does bile emulsify

fat ( it breaks the fat into tiny droplets), which gives a bigger surface area for the enzyme lipase to work on - this makes digestion faster.

what are enzymes used in the digestive system produced by?

specialised cells in glands and in the gut lining

what does the salivary glands do in the digestive system?

produces amylase enzymes in the saliva

what does the liver do in the digestive system?

produces bile

what is another word for the oesophagus?

the gullet

what does the gall bladder do in the digestive system?

where bile is stored, before being released into the small intestine

what does the large intestine do in the digestive system?

where excess water is absorbed from food

what does the rectum do in the digestive system?

where the faeces are stored before leaving through the anus

what does the small intestine do in the digestive system? (2)

1. produces protease, amylase, and lipase enzymes to complete digestion

2. where digested food is absorbed out of the digestive system into the blood

what does the pancreas do in the digestive system?

produces protease, amylase, and lipase enzymes, which are released into the small intestine

what does the stomach do in the digestive system? (3)

1. it pummels the food with its muscular walls

2. it produces pepsin

3. it produces hydrochloric acid to kill bacteria and to give the right pH for pepsin to work

what is pepsin

a protease enzyme

how do you identify what type of food molecule a sample contains?

food tests

how do you prepare a food sample?

break up a piece of food using a pestle and mortar. transfer to a beaker and add water. Stir to dissolve some of the food. Filter the solution.

what are the 2 types of sugars?

reducing and non reducing

how do you test for reducing sugars?

the benedicts test

how do you do the benedicts food test?

prepare a food sample and transfer some to a test tube. prepare a water bath to about 75 degrees. add roughly 10 drops of benedicts solution to your test tube. place in water bath and leave for 5 minutes.

what colour will your food test be if it has sugars?

yellow, green, or brick red.

what colour will your food test be if it doesnt have sugars?

it will remain the same

how do you check for the presence of starch?

make a food sample and transfer to test tube. Add a few drops of iodine solution and gently shake.

what colour will your food test be if it doesnt have starch?

remain the same

what colour will your food test be if it does have starch?

black / blue

what test do you use to check for the presence of proteins?

the biuret test

how do you do the biuret test?

prepare a food sample and add to test tube. add 2cm³ of biuret solution and shake gently

what colour will your food test be if it doesnt have proteins?

will stay blue

what colour will your food test be if it does have proteins?

go pink/ purple

what test do you use to check for the presence of lipids?

the sudan 111 test

how do you do the sudan 111 test?

prepare a food sample ( dont filter), and add to test tube. add 3 drops of sudan 111 stain solution and gently shake

what will happen if your food test doesnt have lipids?

it will remain the same

what will happen if your food test does have lipids?

the mixture will separate into 2 layers, with the top layer bright red.

what is the thorax?

the top part of your body, separated from the lower part of the body by the diaphragm

what are the lungs like?

big pink sponges which are protected by the ribcage, while being surrounded by pleural membranes

what does the air you breathe go through?

the trachea

What does the trachea split into?

2 tubes called bronchi, one going to each lung, which split into smaller tubes called bronchioles, which split into small air sacs called alveoli

what happens in the alveoli?

gas exchange

what is the alveoli surrounded by?

a network of blood capillaries

what does the blood near the alveoli contain?

lots of CO2 and very little oxygen. more oxygen diffuses out of the alveoli (high conc) to the blood (low conc) and CO2 diffuses out of the blood (high conc) into the alveoli (low conc) to be breathed out

what happens when the blood reaches body cells?

oxygen is released from the red blood cells (high conc) and diffuses into the body cells (low conc). at the same time, CO2 diffuses out of the body cells (high conc) into the blood (low conc)

how do you work out breaths per minute?

number of breaths / number of minutes

what is the circulatory system made up of?

the heart, blood vessels, and blood

how many circulatory systems do humans have?

2 circuits joined together

what is in the first circulatory system?

the right ventricle pumps deoxygenated blood to the lungs to take in oxygen. the blood then returns to the heart

what happens in the second circulatory system?

the left ventricle pumps oxygenated blood around all the other organs of the body. the blood gives up its oxygen at the body cells and the deoxygenated blood returns to the heart to be pumped out to the lungs again

what are the walls of the heart mostly made of?

muscle tissue

what is the heart?

a pumping organ that keeps the blood flowing around the body

what do the valves in the heart do?

make sure that blood flows in the right direction- they prevent it from flowing backwards

how does the heart use four chambers to pump blood around? (5)

1. blood flows into 2 atria from the vena cava and the pulmonary vein.

2. the atria contract, pushing the blood into the ventricles.

3. the ventricles contract, forcing the blood into pulmonary artery, and the aorta, and out of the heart.

4. the blood then flows to the organs through arteries and returns through veins.

5. the atria fill again and the cycle starts over

what does the heart need?

its own supply of oxygenated blood.

what branch off the aorta?

coronary arteries which surround the heart, making sure the heart gets all the oxygenated blood it needs

what is your resting heart rate controlled by?

a group of cells in the right atrium wall that act as a pace maker

what do the pacemaker cells in the heart do?

produce a small electric impulse which spreads to the surrounding muscle cells, causing them to contract

what is an artificial pacemaker?

a small device that is implanted under the skin and has a wire going to the heart. it produces an electric current to keep the heart beating regularly

when is an artificial pacemaker used?

if the natural pacemaker cells dont work properly

what are the 3 different types of blood vessel?

arteries (carry blood away from the heart), capillaries (involved in the exchange of materials at the tissues), and veins (carries the blood to the heart)

what are the artery adaptions? 4

1. the heart pumps the blood out at high pressure so the walls are strong and elastic

2. the walls are thick compared to the size of the lumen

3. they contain thick layers of muscle to make them strong

4. they have elastic fibres to allow them to stretch and spring back

what are the capillary adaptions? 4

1. arteries branch into capillaries which are really tiny. they carry the blood really close to every cell in the body to exchange substances with them

2. they have permeable walls, so substances can diffuse in and out

3. they supply food and oxygen, and take away wastes like CO2

4. their walls are usually only one cell thick, this increases the rate of diffusion by decreasing the distance over which it occurs

what are the vein adaptions? 3

1. the blood is at the lowest pressure in the veins so the walls dont need to be as thick as artery walls

2. they have a bigger lumen than arteries to help the blood flow despite the lower pressure

3. they also have valves to help keep the blood flowing in the right direction

rate of blood flow = ?

volume of blood / number of minutes

what type of cell organisation is blood?

a tissue

what is the job of the red blood cells?

to carry oxygen from the lungs to all the cells in the body

what is the shape of red blood cells?

a biconcave disc (like contact lenses), which gives a large SA for absorbing oxygen. they dont have a nucleus, which allows more room to carry oxygen