2. structures and functions in living organisms Flashcards
describe cell structures, including: the nucleus cytoplasm cell membrane cell wall chloroplasts vacuole
Within a cell there are different organelles:
The nucleus, often thought as as the centre of a cell, contains all the genetic information of a cell (the cells chromosomes), it controls the activities of the cell.
Cytoplasm surrounds the nucleus within the cell walls. It is where reactions take place in the cell.
The cell membrane controls the movement of chemicals in and out of the cell.
The cell wall, which is made up of cellulose, strengthens the cell.
Chloroplasts contain chlorophyll, and are used in photosynthesis.
Vacuole keeps the cell turgid (basically keeps the cell filled with water.)
describe the levels of organisation within organisms: organelles cells tissues organs systems
Organelles are highly organised structures of molecules. They have a specific function within a cell. Mitochondria is an example, generating energy for our bodies cells.
Cells are made up of Organelles, described as a functional unit, they are the basis of living things.
Tissues are a collection of similar cells all serving a common function.
Organs are made up of several kinds of tissues together forming a functioning unit.
Systems are several organs forming an organ system. Like the cardiovascular system is made up of the heart, blood and blood vessels.
compare the structures of plant and animal cells (similarities and differences)
Differences:
Only Plant cells have a vacuole
Only Plant cells have chloroplasts
Only Plant cells have a cell wall
Similarities:
They both have a nucleus
They both have cytoplasm
They both have a cell membrane
What are the chemical elements present in…
carbohydrates
proteins
lipids (fats and oils)
Carbohydrates and lipids (fats and oils) are both made up of:
Carbon
Hydrogen
Oxygen
Proteines consist of: Carbon Hydrogen Oxygen Sulphur Phosphorous Nitrogen
What is the test for glucose?
Test for glucose:
Heat object with Benedict’s or Fehling’s Reagent.
if it turns from blue to orange then glucose is present.
What is the test for starch?
The starch test:
Apply iodine to the object you are testing,
if it turns from red to blue/black then there is starch.
Note: in an exam you are safest saying blue/black instead of blue or black.
how can the functioning of enzymes be affected by changes in temperature? (including changes due to change in active site)
High temperatures will denature enzymes, so they can’t function.
Because the energy breaks the bonds that hold the shape of the enzyme: without these the structure will be distorted, which will mean the active site won’t be able to bind with the substrate to break it down.
Note the active site is the area on an enzyme that binds with a substrate to break it down; it is the lock in the lock and key theory.
What is the role of enzymes as biological catalysts in metabolic reactions?
Enzymes lower the activation energy of a reaction- making it faster- and they are unchanged from begining to end of a reaction.
These two things mean its a catalyst.
how can the functioning of enzymes be affected by changes in active site caused by changes in pH?
Change in PH can denature enzymes by breaking the bonds that hold the structure in place. So the active site no longer fits with the the substrate it is meant to be breaking down. The PH at which this happens is different for different enzymes, but generally an extreme PH will denature any enzyme.
describe experiments to investigate how enzyme activity can be affected by changes in temperature.
Put starch into a test tube; either heat or cool it.
Add amylase
With this mixture on white tiles, add iodine
Time how long it takes for the iodine to stop being blue black
Repeat at different temperatures and compare
When the iodine stops being blue/black there is no starch present, so it must have been digested by the enzymes.
Define:
Diffusion
Osmosis
Active transport
Diffusion is when molecules move from an area of high concentration to an area of low concentration
Osmosis is the movement of water, it follows the rule that water will move from a dilute solution to a concentrated solution.
Active transport is molecules being moved from an area of low concentration to an area of high concentration. energy is needed to make this happen hence ‘active’ (it is going against the concentration gradient)
What is the importance of turgid cells in plants as a means of support?
A turgid cell is one that is, effectively, full of water; this increases the volume of the cytoplasm, which exerts pressure outwards. These cells are stronger so they support the plant- meaning that a plant grows upwards.
This is why a dehydrated plant will wilt.
What are the factors that affect the rate of movement of substances into and out of cells?
Surface area
with a larger surface area- molecules have more surfaces through which to diffuse, this increases the rate of moment
Temperature
Increased temperature means increased kinetic energy- this will mean molecules collide with the cell wall more often making movement through it more likely
Concentration gradient
This is the difference between the concentration inside and outside of the cell. The bigger the difference is the more opportunity molecules have of diffusing.
describe experiments to investigate diffusion and osmosis using living and non-living systems.
Diffusion:
Put a coloured substance (like food colouring) into a clear one (like water)
Time how long it takes for all the liquid to be the same colour.
Change the temperature of the liquid and make observations.
The higher the heat, the more kinetic energy meaning the colour moves through the liquid faster.
Osmosis:
Cut two roughly equal pieces of potato and weigh them.
Put one in distilled water and one in salt water.
After a given amount of time weigh them.
The one in salt water will have lost mass as the water in the potato moves to the less highly concentrated salt water. Where as in the pure water the potato will have gained mass as it was less dens with water.
describe the process of photosynthesis and understand its importance in the conversion of light energy to chemical energy
Photosynthesis is the process in which energy- from the sunlight- is used to create glucose.
Light energy is absorbed by chlorophyll in plants leaves. It is then used to convert carbon dioxide (from the air) and water (from the ground) into glucose; which is used for respiration. Oxygen is a by-product of this process.
This is using light energy, from the sun, to create chemical energy (glucose); which conserves the energy from the sun. This energy is then passed through the food chain, which is why plants are called the producer (producing the chemical energy in the chain from the sun light.)
What is the word equation for Photosynthesis?
What is the symbol equation for Photosynthesis?
Carbon dioxide + water > glucose + oxygen
6CO2 + 6H2O -> C6H12O6 + 6O2
How does varying carbon dioxide concentration, light intensity and temperature affect the rate of photosynthesis?
Carbon dioxide:
If there is insufficient carbon dioxide a plant will not be able to photosynthesis to its full potential. Because there is less carbon dioxide- less reactant- there has to be less product being made.
Light intensity:
If the light is at a low intensity the rate of photosynthesis is lowered because the energy that the light provides is less, so the reaction is slowed down. A higher light intensity will enable photosynthesis to happen faster.
Temperature:
In colder temperatures the rate of photosynthesis will decrease. If the temperature is too high however, the plant will not be able to photosynthesise.
Which mineral ions do plants need for growth?
As well as water and sunlight, plants require mineral ions to grow. Different mineral ions do different things, two key examples of this are that:
magnesium ions are needed for chlorophyll.
nitrate ions are needed for amino acids.
What should a balanced diet should include?
A balanced diet should include appropriate proportions of: carbohydrate protein lipid vitamins minerals water dietary fibre
describe the structures of the human alimentary canal.
describe the functions of the: mouth oesophagus stomach small intestine large intestine pancreas
The mouth:
Mechanical digestion happens here- your jaw action.
A bolus is created; this is a ball of food covered in saliva. This is help full as the food is lubricated to enable swallowing and enzymes in the saliva can begin to break down the food. (amylase)
The oesophagus:
this tube connects you mouth and stomach. It is next to the trachea which is covered by the epiglottis when you swallow so the food only enters the oesophagus.
Peristalsis- or muscular contractions- moves the food downward.
The stomach:
Churning mechanically digests whilst enzymes do so chemically.
Chyme is the name for liquid food existing in the stomach.
The small intestine:
This absorbs digested molecules into the blood stream.
Villi cover the inside giving it a large surface area which many molecules can diffuse through into the blood.
Large intestine:
This absorbs water from undigested food, producing faeces.
Pancreas:
This produces the enzymes lipase, amylase and protease.
Describe the processes of:
ingestion digestion absorption assimilation egestion
Digestion: process in which large insoluble molecules of food are broken down into smaller ones.
Absorption: the process by which soluble molecules produced by digestion are taken from the gut (occurs mostly in the small intestine.) The soluble products of digestion are then transported to the various tissues by the circulatory system.
Assimilation: the cells of the tissues absorb the molecules for use.
Egestion: removal of waste- undigested- products as faeces.
Excretion: removal of waste products that have been in the body.
explain how and why food is moved through the gut. (What is the name of the process?)
Food is moved through the gut by peristalsis.
Muscles move food because mechanical action is needed to get food through the system.
What is the role of digestive enzymes?
( include the digestion of starch to glucose by amylase and maltase, the digestion of proteins to amino acids by proteases and the digestion of lipids to fatty acids and glycerol by lipases )
Enzymes break down food into useful things that our boddies need. Different enzymes break down different components of our food. You should learn that:
amylase and maltase convert starch to glucose
proteases convert proteins to amino acids
lipases convert lipids to fatty acids and glycerol.
Which organ produces bile?
Where is the bile stored?
What is the role of bile?
Bile is produce by the liver and stored in the gall bladder.
Enzymes in the small intestine work best in alkaline conditions but the food is acidic after being in the stomach. Bile is alkaline and so when it is released into the small intestine it enables the enzymes to work.
Bile also emulsifies fat; this gives it a larger surface area, which means that it is easier for lipases to work.
identify sources and describe functions of:
carbohydrate protein lipid (fats and oils) vitamins A, C and D the mineral ions calcium and iron water dietary fibre
(As components of the diet)
Carbohydrates:
immediate energy
bananas, brown rice, wholemeal foods and potatoes.
Protein:
Growth; repair
sea food, eggs, pork and soy.
Lipids:
long term energy store; insulation; protection
fish, eggs, milk and beef.
Vitamin A:
maintaining normal reproduction; good vision; formation and maintenance of healthy skin, teeth and soft tissues of the body; immune function (has anti-oxidant properties).
Milk, cheese, eggs, fatty fish, yellow-orange vegetables and fruits such as carrots, pumpkin, mango, apricots, and other vegetables such as spinach, broccoli.
Vitamin C:
aiding absorption of iron and copper; healthy bones; helps fight infection.
Blackcurrants, orange, grapefruit, guava, kiwi fruit, raspberries, sweet peppers (Capsicum), broccoli, sprouts
Vitamin D:
immune function; healthy skin; muscle strength
Sunlight on skin allows the body to produce Vitamin D. Few foods contain significant amounts however main dietary sources are fortified margarine, salmon, herring, mackerel, and eggs.
Calcium:
development and maintenance of bones and teeth; good functioning muscles and nerves; heart function
Milk, cheese, yoghurt, bony fish, legumes, fortified soy beverages and fortified breakfast cereals.
Iron:
Haemoglobin in red blood cells (important for transport of oxygen to tissues); component of myoglobin (muscle protein).
Red meats – beef, lamb, veal, pork, fish, chicken and wholegrain cereals
Dietary fibre:
Keeping the bowels functioning well; reduces the risk of bowl cancer
Cereals, bread, rice, beans and nuts.
Water:
Chemical reactions in cells need water; respiration
water.
How do energy requirements vary with activity levels, age and pregnancy?
As a young person a lot of energy is used because: activity levels tend to be high; energy is being used for growth. As a person ages they no longer use energy for growth and tend to have a less active lifestyle: thus having lower energy requirements.
Having a less or more active lifestyle has an effect because the more you do- the more energy you use- the more you need- the higher energy requirements. For example, an athlete has a more active lifestyle so has to eat more.
When pregnant a woman is not only supporting her own body but also that of her baby, this mean she requires the energy for both of them, increasing her energy requirements.
describe experiments to investigate photosynthesis, showing:
the evolution of oxygen from a water plant
the production of starch
the requirements of light, carbon dioxide and chlorophyll
The most common experiment for this is using pond weed, which is placed under water then factors are varied:
A lamp is moved further from the plant;
Baking powder is added to the water (increasing CO2);
A white leaved plant is tested against a green leaved plant (green has more chlorophyll).
The gas it gives off- being the products of photosynthesis- is counted as bubbles or measured by downwards displacement. This shows the speed of photosynthesis under different conditions.
Iodine can be used to test the production of starch.
What is respiration? What does the process break down and produce?
Respiration is a reaction that occurs in living things to create energy. It breaks down glucose to release energy.
describe the differences between aerobic and anaerobic respiration
Aerobic respiration:
Glucose + oxygen > carbon dioxide + water + energy
In this form of respiration all of the energy is released from the glucose as it is fully broken down. It is used for day to day life processes- like movement and reproduction- and keeping warm.
Anaerobic respiration:
Glucose > lactic acid + energy
Anaerobic respiration takes place when the heart and lungs cannot work fast enough to provide to oxygen needed for aerobic respiration: for example when exercising The energy released is less in anaerobic respiration because the glucose cannot be fully broken down.
The lactic acid produced accumulates in muscles; often making them feel soar. After this process ‘excess post-exercise oxygen consumption’ takes place. This process involves heavy breathing and fast heart rate to transport oxygen around the body so it can help break down lactic acid into carbon dioxide and water. Note that the time taken for the lactic acid to be removed and for the breathing and heart rate to return to normal is called the recovery period.
write the word equation and the balanced chemical symbol equation for aerobic respiration in living organisms
Glucose + Oxygen > Carbon dioxide + Water + Energy
C6H12O6 + 6O2 → 6CO2 + 6H2O (+ energy)
write the word/symbol equation for anaerobic respiration in plants
write the word/symbol equation for anaerobic respiration in animals
In animals:
Glucose > Lactic acid + Energy
C6H12O6 > 2C3H6O3 + energy
In plants:
Glucose > ethanol + carbon dioxide + energy
C6H12O6 > 2C2H5OH + 2CO2
What is the role of diffusion in gas exchange?
Diffusion is the movement of particles from an area of high density to an area of low density. In this way gasses will move from an area dense with gas to an area of low density.
In the circulatory system oxygen enters the blood and carbon dioxide leaves the blood via gaseous exchange. Gasses move across the walls of alveoli to an area of lower density than they are in: Oxygen moves into the blood as there is a low density of oxygen in the blood; Carbon dioxide moves into the lungs as it is an area of lower density.
how is the structure of the leaf adapted for gas exchange?
Leaves are thin which allows gasses to diffuse quickly through them. In addition the stomata at the bottom of the leaf allow the diffusion of gasses in to the leaf- when a guard cell is shrunk gasses can enter the leaf.
describe the role of stomata in gas exchange
Stomata are small wholes in the lower epidermis of the leaf. Guard cells regulate the opening and closing of the stomata; allowing carbon dioxide and oxygen to be exchanged between the leaf and the atmosphere. The guard cells absorb water and become turgid- opening the stomata- during the day. At night the guard cells are flaccid and so close the stomata.
describe experiments to investigate the effect of light on net gas exchange from a leaf, using hydrogen-carbonate indicator
hydrogen-carbonate indicator is an indicator for carbon dioxide: under normal levels (atmospheric) of carbon it is orange; an increase turns it yellow; a decrease turns it purple.
Fill a test tube quarter full with HCIS, attach a leaf to a bung and put in the test tube; observe the indicator colour in different light intensities.
