biology - topic 2 - a,b,c,d,e(human),g(plants),i,j

what is the level of organisation

cells, tissues, organs, organ system, organism

describe the cell structure of a plant cell

• nucleus
• cell membrane
• cytoplasm
• ribosomes
• mitochondria
• chloroplasts
• permanent vacuole
• cell wall

describe the cell structure of an animal cell

cytoplasm, shape is not rigid, nucleus, ribosomes, mitochondria, cell membranes.

what are the differences between plant and animal cells

plant cell has chloroplasts, cell wall and vacuole

what does the nucleus do

It contains genetic material and controls the activities of the cell

what does the cytoplasm do

Its a gel-like substance where most of the chemical reactions happpen

what does the cell membrane do

It holds the cell together and controls what goes in and out

what does the cell wall do

Protects and supports the cell

what does mitochondria do

This is where most of the reactions for respiration take place. Respiration releases energy that the cell needs to work.

what do chloroplasts do

This is where photosynthesis occurs, which makes food for the plant. They contain chlorophyll - a green pigment - which absorbs light needed for photosynthesis

what do ribosomes do

protein synthesis

what does the vacuole do

It contains cell sap and helps maintain the shape of the cell + stores food water and waste

what is the importance of cell differentiation in the development of specialised cells

allows cells to specialize and perform specific functions in an organism. This allows for the formation of tissues and organs, and is necessary for the proper functioning of the body.

advantages of using stem cells in medicine

Can be used to heal things like certain types of cancer. It could also be used to regrow organs in the future.

disadvantages of using stem cells in medicine

-Ethical issue

-Long term effects are unknown

-Adult stem cells have a fixed cell they will turn into

-Obtaining stem cells is a difficult process

-Very costly

-Limitations to research possibilities

what are the molecules in carbohydrates

made up of sugar molecules

what are the molecules in lipids

made up of glycerol and fatty acids

what are the molecules in proteins

amino acids

what are the chemical elements in proteins

carbon, hydrogen, oxygen, nitrogen

what are the chemical elements in lipids

carbon, hydrogen, oxygen

what are the chemical elements in carbohydrates

carbon, hydrogen, oxygen

how to investigate the presence of glucose

Benedict's reagent can be used to test for glucose. The test involves heating a solution of the sugar to be tested with Benedict's reagent and observing the colour change of blue to orange.

how to investigate the presence of starch

We can test for starch with the help of an iodine test. Soak any food item, namely potato, in drops of iodine for some time. If it turns blue-black afterwards, it contains starch. The liquid used for testing starch is an iodine solution.

how to investigate the presence of proteins

The biuret test is used to detect peptide bonds in proteins. Add Biuret solution A to a solution of the food being tested and mix carefully. Then trickle a little Biuret solution B down the side of the tube. Look for a purple colouration where the solutions meet.

how to investigate the presence of fat

Shake or crush the food to make it dissolve. Filter or dilute the food and ethanol mix so that you get a clear liquid (a solution of fat in ethanol). Add this to a test tube of water. A white (milk-like) emulsion indicates the presence of fats or oils.

what is the role of enzymes

they are biological catalysts that speed up the rate of a chemical reaction

how does temperature change affect enzyme function

the enzyme's active site will denature therefore cannot bind to anything

what binds with an enzyme

substrate

experiment about how temp affects enzyme activity

Set up water baths at various temperatures (e.g. 0°C, 20°C, 40°C, 60°C and 80°C).
Add starch solution to 5 test tubes.
Add amylase solution to another 5 test tubes.
Place one starch and one amylase test tube into each water bath for 5 minutes - to allow the enzyme and substrate to reach the desired temperature.
Place 1 drop of iodine into each dimple on a spotting tile.
Add the amylase to the starch in the 0°C water bath.
Start the timer.
Every minute remove a sample of the starch-amylase solution and add it to a drop of iodine on the spotting tile.
Repeat step 8 until the iodine no longer changes colour - meaning that there is no starch present, in other words the amylase has broken all starch down.
Repeat steps 6-9 for each of the temperatures.
Record results.
Draw a graph to show the time taken for starch to be digested at different temperatures.

how can enzymes be affected by pH

if the pH is too high, the enzymes will denature and the active sites will lose shape

experiment on how pH affects enzymes

Set up a Bunsen burner, heatproof mat, tripod and gauze.
Place a beaker of water on the gauze and adjust the flame to keep the water at about 35°C.
Now put two drops of iodine solution into each spot of a spotting tile.
Add 2 cm3 of amylase enzyme solution to a test tube.
Place 2 cm3 of starch solution into the same tube.
Finally add 1 cm3 of pH solution to the tube. This will keep the pH constant.
Mix the solution in the test tube and place it into the beaker of water on the Bunsen burner.
Use a pipette to remove a few drops of solution every 20 seconds from the test tube and put them into a different well of the spotting tile.
Repeat until the iodine solution stops turning black.
Record the time this takes.
Repeat with different pH solutions.

What is diffusion?

Movement of molecules from high to low concentration

what is osmosis

Diffusion of water through a semi- permeable membrane

What is active transport?

movement of molecules into or out of a cell against a concentration gradient

which factors affect the rate of movement of substances into and out of cells and why

Surface Area to Volume Ratio:
Larger surface area allows more substances to diffuse at once, increasing the rate of movement.
Smaller cells typically have a higher surface area-to-volume ratio, enabling efficient diffusion.
Concentration Gradient:
The greater the difference in concentration between the inside and outside of the cell, the faster the movement of substances (e.g., in diffusion or osmosis).
Temperature:
Higher temperatures increase the kinetic energy of molecules, leading to faster diffusion rates.
Distance:
Shorter diffusion pathways allow substances to move more quickly.

Investigate diffusion in non-living systems

Diffusion in Non-Living Systems:
Experiment: Use agar jelly containing a pH indicator (like phenolphthalein) and immerse it in dilute acid.
Observation: Acid diffuses into the agar jelly, changing its color as it neutralizes the indicator.
Conclusion: Diffusion is the movement of particles from a region of higher concentration to lower concentration.

investigate osmosis in living systems

Osmosis in Living Systems:
Experiment: Place a piece of potato in distilled water and another in a concentrated sugar solution.
Observation: Potato in water becomes turgid (gains mass) due to water entering by osmosis, while the potato in sugar solution becomes flaccid (loses mass).
Conclusion: Osmosis is the movement of water across a semi-permeable membrane from a dilute solution to a concentrated solution.

investigate osmosis in non-living systems

Osmosis in Non-Living Systems:
Experiment: Fill a dialysis tube (semi-permeable membrane) with sugar solution, immerse it in distilled water, and observe the volume increase.
Observation: Water moves into the tube by osmosis.
Conclusion: Water moves through a semi-permeable membrane to balance solute concentrations.

Balanced diet should include?

Carbohydrates, proteins,lipids, vitamins, minerals, water and dietary fibre

Source & function of carbohydrate

Function = source of energy, from bread, cereals, pasta…

Sources and function of protein

Source - meat, fish, pulses, function - growth and repair

Sources and function Of lipids

Sources - butter,oil,nuts function - insulation and energy storage

Sources and function Of dietary fibre

Function - provides b luck for the intestine to push food through it, source - vegetables, whole grains

Sources and function Of vitamins and minerals

Function - needed in small quantities to maintain health, source - fruit and veg, meats, dairy products

Sources and function Of water

Function - needed for chemical reactions in the body, source - water, fruit, juice

vitamins and minerals + examples & uses

Examples:

• calcium - needed for strong teeth and bones and involved in blood clotting - deficiency = osteoporosis - in milk

• Vitamin D - helps body absorb calcium - in oily fish

• Vitamin A - needed to make the pigment for retina for vision - in meat

• Vitamin C - collagen protein which makes up skin, hair, gums and bones - deficiency = scurvy - found in greens and citruses

• Iron - needed to make haemoglobin - in red meat

Variation in energy requirements - age

• amount of energy young people need increases towards adulthood as this energy is needed for growth, children need a higher proportion of protein in their diet as it is required for growth - energy needs of adults decrease as they age

Variation in energy requirements - activity levels

• the more active, the more energy required for movement as muscles are contracting more and respiring faster

Variation in energy requirements - pregnancy

• during pregnancy, energy requirements increase as energy is ended to support the growth of the developing foetus as well as the larger mass that the mother needs to carry around, extra calcium and iron are needed in the diet to help build the blood, bones and teeth of the foetus

• For breastfeeding mother, energy requirements increase and extra calcium is needed to make high-quality milk

Why do men need more energy than women

They have a larger proportion of muscle compared to fat

What is digestion

A process in which large, insoluble molecules in food such as starch are broken down into smaller, soluble molecules that can be absorbed into the bloodstream and delivered to cells in the body which can be used for growth, repair and function

Structure of alimentary canal

Function of mouth/salivary gland

Mechanical digestion: teeth chew food to break it into smaller pieces and increase its surface area to volume ratio

Chemical digestion: amylase enzymes in saliva start digesting starch into maltose

The food is shaped into a bolus (ball) and lubricated by saliva so it can be swallowed easily

Function of oesophagus

The tube that connects the mouth to the stomach

Wave-like contractions take place to push the food bolus down without relying on gravity

Function of stomach

Food is mechanically digested by churning actions while protease enzymes start to chemically digest proteins.

Hydrochloric acid is present to kill bacteria in food and provide the optimum pH for protease enzymes to work.

Function of small intestine

The first section is called the duodenum; this is where digestion of the food exiting the stomach is completed by enzymes that are present in the duodenum lining and secreted by the pancreas

The pH of the small intestine is slightly alkaline; around pH 8-9.

The second section is called the ileum and is where the absorption of water and digested food molecules takes place; the ileum is long and lined with villi to increase the surface area over which absorption can take place

Function of large intestine

Water is absorbed from the remaining material in the colon to produce faeces

Faeces are stored in the rectum and exit the body via the anus

Function of pancreas

Produces all three types of digestive enzymes: amylase, protease and lipase

Secretes enzymes in an alkaline fluid into the duodenum for digestion; this raises the pH of fluid coming out of the stomach

Function of liver

Amino acids that are not used to make proteins are broken down here (deamination), producing urea

Produces bile to emulsify fats (break large droplets into smaller droplets), an example of mechanical digestion

Function of gall bladder

Stores bile to release into the duodenum

Explain peristalsis

• Peristalsis is a mechanism that helps moves food along the alimentary canal

• Firstly, muscles in the walls of the oesophagus createwaves of contractions which force the bolus along

• Once the bolus has reached the stomach, it is churned into a less solid form, called chyme, which continues on to the small intestine

• Peristalsis is controlled by circular and longitudinalmuscles

  • Circular muscles contract to reduce the diameter of the lumen of the oesophagus or small intestine

  • Longitudinal muscles contract to reduce the lengthof that section the oesophagus or the small intestine

• Mucus is produced to continually lubricate the food mass and reduce friction

• Dietary fibre provides the roughage required for the muscles to push against during peristalsis

Stages of food breakdown

• Food taken into the body goes through six different stages during its passage through the alimentary canal(the gut):

  • Ingestion - the taking in of substances, e.g. food and drink, into the body through the mouth

  • Mechanical digestion - the breakdown of food into smaller pieces without chemical change to the food molecules

  • Chemical digestion - the breakdown of large, insoluble molecules into small, soluble molecules

  • Absorption - the movement of small food molecules and ions through the wall of the intestine into the blood

  • Assimilation - the movement of digested food molecules into the cells of the body where they are used, becoming part of the cells

  • Egestion - the passing out of food that has not been digested or absorbed (as faeces) through the anus

Overall purpose of digestive enzymes

• The purpose of digestion is to break down large, insoluble molecules into smaller, soluble molecules that can be absorbed into the bloodstream

What do lipids, proteins and carbohydrates all go through as first stage of break down

Mechanical digestion in the mouth, chewed with teeth and tongue, moistened by saliva.

Stages of carbohydrates breakdown steps 2-7

Amylase is produced in the saliva to start breaking down starch into maltose.

Hydrochloric acid in the stomach breaks food down further.

Muscular churning of stomach.

Bile is released into the duodenum to neutralise the acidic chyme to provide the optimum pH for enzymes in the small intestine.

Amylase from the pancreas enters the duodenum and continues to break down starch into maltose.

Amylase and maltase are released from the small intestine to break down maltose into glucose.

Stages of proteins breakdown

Hydrochloric acid in the stomach breaks food down further.

Muscular churning of stomach.

Protease released from the stomach to break protein down into amino acids.

Bile is released into the duodenum to neutralise the acidic chyme to provide the optimum pH for enzymes in the small intestine.

Protease from the pancreas enters the duodenum and continues to break down protein into amino acids.

Protease is released from the small intestine to continue break down of protein into amino acids.

Stages of lipids breakdown

Hydrochloric acid in the stomach breaks food down further.

Muscular churning of stomach.

Bile is released into the duodenum to neutralise the acidic chyme to provide the optimum pH for enzymes in the small intestine.

Bile is released from the gall bladder and it emulsifies lipids into smaller droplets over which lipase can act. Lipase from the pancreas enters the duodenum and breaks down lipids into fatty acids and glycerol.

Lipase is released from small intestine to continue break down of lipids in FAs and glycerol.

2 things bile does

Neutralises and emulsifies

Adaptations of small intestine for absorption

• very log and has a highly folded surface with millions of villi = increase the surface area = faster and more absorption

  • Villi: increase surface area - microvilli on surface of villi

  • A short diffusion distance = villi have one cell thick walls

  • Well supplied with a network of blood capillaries = steep concentration gradient e.g lacteals runs through the centre of the villus to transport fatty acids and glycerol + enzymes produced in the walls of the villi assist with chemical digestion + villi waft

Practical : testing the energy content in a food sample - method + results

Method : Use the measuring cylinder to measure out 25 cm³ of water and pour it into the boiling tube

• Record the starting temperature of the water using the thermometer

• Record the mass of the food sample

• Set fire to the sample of food using the bunsen burner and hold the sample 2 cm from the boiling tube until it has completely burned

• Record the final temperature of the water

• Repeat the process with different food samples

  • E.g. popcorn, nuts, crisps

• Results:

  • The larger the increase in water temperature, the more energy is stored in the sample

  • We can calculate the energy in each food sample using the following equation:

        

Practical - investigating respiration - method + results

Method

• Measure out 10 cm³ of hydrogencarbonate indicator into 3 boiling tubes

• Put in a layer of cotton wool

• Place 10 germinating seeds in tube A

• Place 10 boiled/dead seeds in tube B

• Place 10 glass beads in tube C

• Seal each tube with a rubber bung

• After 3 hours, observe the colour of the indicator

Results

• In this investigation, we would expect to note the following

  • Tube A should turn yellow as the seeds are respiringand producing carbon dioxide

  • Tube B should remain red as the dead seeds produce no carbon dioxide

  • Tube C should remain red as there is no living material in there

Corms evaluation :

• Change - We will change the content of the boiling tube (germinating seeds, dead seeds or glass beads)

• Organisms - The seeds used should all be of the same age, size and species

• Repeat - We will repeat the investigation several times to ensure our results are reliable

• Measurement 1 - We will observe the change in the hydrogen carbonate indicator

• Measurement 2 - ...after 3 hours

• Same - We will control the volume of hydrogen carbonate indicator, the number of seeds/beads, the temperature of the environment

Practical - demonstrating the production of heat in respiration - method + results + evaluation

Method

• Set up the flasks as shown in the diagram

  • Flask A with the dead seeds

  • Flask B with the germinating seeds

• Make sure the cotton wool is plugging the top of each flask

• Hold the thermometer in place with the cotton wool

• Invert the flask

• Record the initial temperature

• After 4 days, record the final temperature

Results

• The thermometer in the flask with the germinating seeds(Flask B) should show an increase in temperature

• Flask A should remain at room temperature

• This is because the seeds in flask B are respiring and producing heat energy in the process

• This shows that respiration is an exothermic reaction

• The seeds in flask A are not respiring because they are dead, so the temperature remains the same

Evaluation :

• Change - We will change the content of the flasks (germinating seeds or dead seeds)

• Organisms - The seeds used should all be of the same age, size and species

• Repeat - We will repeat the investigation several times to ensure our results are reliable

• Measurement 1 - We will observe the change in the temperature on the thermometer

• Measurement 2 - ...after 4 days

• Same - We will control the number of seeds, the starting temperature of the flasks, the material and size of the flasks

What is the role of diffusion in plants

Drives the process of gas exchange

Equation for photosynthesis

Carbon dioxide + water → glucose + oxygen

In order for plants to photosynthesise and respire..

Gas exchange of oxygen and carbon dioxide are needed and this requires diffusion of gases

Adaptations of leaf for gas exchange - spongy mesophyll

Have lots of air spaces to allow gases to diffuse in and out of cells faster, as it increases the surface area to volume ratio

Adaptations of leaf for gas exchange - Guard cells

Kidney- shaped cells that open and close the stomata by absorbing or losing water. When lots of water is available, the cells fill and open stomata

Adaptations of leaf for gas exchange - Stomata

Where gas exchange and loss of water by evaporation takes place - opens during the day and closes at night

Adaptations of leaf for gas exchange - Thin leaves

Short distance of diffusion for carbon dioxide to diffuse into the leaf and oxygen to diffuse out

Adaptations of leaf for gas exchange - Flattened shape

Increases surface area for absorption of light and carbon dioxide

… occurs at night and day as plants require energy at all times

Respiration

Why can photosynthesis only occur when light

It requires light

Why is there a net balance of gases during the day

As respiration generally occurs at the same rate as photosynthesis - but at night since there is no photosynthesis, more oxygen is taken into the plants and more carbon dioxide is released

Practical - investigate the effect of light on net gas exchange from a leaf, using hydrogen carbonate indicator - method + results

Results = closer lamp is to plant = stronger light intensity = more photosynthesis = more CO2 taken into the plants by plant = low CO2 concentration = hydrogen carbonate indicator turns purple + if there is more CO2 present - indicator = yellow

Why do simple, unicellular organisms rely on diffusion for movement of substances

Bcs they have a relatively large surface area to volume ratio and so due to low metabolic demands, this diffusion across the surface of organisms is enough

Why do multicellular organisms rely on a transport system

They have a small surface area to volume ratio so instead need adaptations that allow molecules to be transported in and out of cells faster e.g root hair cells, alveoli, villi

Practical - investigate the role of environmental factors in determine the rate of transpiration from a leafy shoot

• Set up potometer underwater to remove air bubbles in xylem so there is a continuous stream of water and the system is made airtight

• Measure distance moved by air bubbles in xylem over time

• Change a limiting factor

• if air bubbles move faster = greater rate of water uptake and therefore higher rate of transportation

What is plasma important for

The transport of CO2, digested food, urea and hormones & heat energy

Adaptations of red blood cells

• biconcave shapes = maximises SA for O2 to be absorbed

• Flexible = fit into narrow blood vessels

• No nucleus = creates more space for haemoglobin

• Contains haemoglobin which is a red protein that combines with oxygen to allow oxygen transport

How does the immune systems respond to disease using white blood cells - phagocytosis

• type of white blood cells which can undergo phagocytosis (phagocyte), where the pathogen is engulfed and killed and they have a non-specific function

How does the immune systems respond to disease using white blood cells - lymphocytes

• produces antibodies (lymphocytes)

• Each pathogen has an antigen on their surface and this antigen has a specific structure which is complementary to an antibody

• Once antibodies begin to bind to pathogen, the pathogens start to clumps together, making it easier for white blood cells to find them

• If you become infected again with the same pathogen, the specific complementary antibodies will be produced at a faster rate and the individual will not feel the symptoms of the illness, they are said to be immune

How does the immune systems respond to disease using white blood cells - antitoxins

• producing antitoxins

• WBCs can bind to the toxins released by the pathogen to neutralise them

What happens in vaccinations

Contain either a dead or inactivated form of the pathogen and when injected, they stimulate the white blood cells to produce the correct complementary antibody to combat it. Since the antigen is dead or inactivated, it doesn’t cause any symptoms to the individual

• Some of these white blood cells remain int eh body as memory cells and if this person is exposed to real pathogen in future the memory cells procured antibodies much faster and lots more so it can be destroyed before any symptoms are felt

How are platelets involved in blood clotting

• wound = platelets arrive to stop bleeding

• Clotting cascade occurs within blood plasma

• Platelets release chemicals that cause fibrinogen proteins to form a mesh of insoluble fibrin across wound = trapping red blood cells = clot

• Clot develops into scab to protect wound from bacteria

Structure of arteries

Arteries carry blood AWAY from the heart = layers of muscle in the walls make them strong + contain elastic fibres which allow them to stretch + this helps the vessels withstand high pressure created by pumping of heart

Structure of veins

Carry blood TOWARDS the heart → lumen (tube which blood flows through) is wide to allow the low pressure blood to flow through + they have valves to ensure blood flows in right one way direction

Structure of capillaries

Allow blood to flow very close to cells to enable exchange of substances, capillary walls are one cell thick to create short diffusion pathway + permeable walls so substances can move across them

General structure of circulation system

How does blood flow through heart

• From vena cava, then RA

• From pulmonary vein, then LA

• Atria contract, forcing the blood into ventricles

• Ventricles contract, pushing blood in RV to pulmonary artery (to go to lungs) and blood in LV into aorta (to be taken around body)

• As this happens valves close