Organisation And Maintenance Of Organisms

Question 1

What are the three ways of molecular movement in/out of cells?

Answer 1

Diffusion
Osmosis
Active transport

sometimes phagocytosis

Question 2

What is diffusion?

Answer 2

Diffusion is the net movement of particles within a gas or liquid, from a region of high concentration to a region of low concentration (down a concentration gradient), as a result of their random movement, until an equilibrium is reached

Question 3

How can diffusion speed be increased?

Answer 3

Short distance for diffusion to take place (thin membranes)

Maintained concentration gradients ( eg. Blood flow)

Large diffusion surfaces (membrane with a large surface area)

Question 4

What is osmosis?

Answer 4

The diffusion of water molecules, from a region of high concentration (of water) to a region of a low concentration(of water), down a water potential gradient, through a partially permeable membrane.

Question 5

What happens to plant and animals cells in high/ low water concentrations?

Answer 5

Plant:
High concentration, the cell swells, the cytoplasm expands and the cell becomes turgid but the cell does not burst due to the cell wall
Low concentration, the cell shrinks, the cytoplasm pulls in on the cell wall and the cell becomes flaccid but the cell doesn’t break

Animal:
High concentration, the cell swells and bursts due it to not having a cell wall, called cell lysis
Low concentration, the cell shrinks and the cell becomes shrivelled, called crenation

Question 6

What is active transport?

Answer 6

It is a way of moving particles against a concentration gradient but requires energy and involves protein carrier membranes.

Question 7

What are the four organic molecule groups?

Answer 7

Carbohydrates
Lipids
Proteins
Nucleic acids

Question 8

What do organic molecules do?

Answer 8

They provide energy to drive life processes, and provide raw materials for growth and repair of tissues

Question 9

What is hydrolysis

Answer 9

Large molecules being broken down by smaller ones with the addition of water

Question 10

What is condensation?

Answer 10

Large molecules being built up from smaller ones by the removal of water

Question 11

What type of reaction is hydrolysis/condensation?

Answer 11

Reversible

Question 12

What are mono/polysaccharides?

Answer 12

Monosaccharides are the simplest carbohydrates eg. Glucose

Polysaccharides are made from many monosaccharides eg. Starch.

Question 13

How are lipids formed?

Answer 13

From the condensation of three molecules of fatty acid with one molecule of glycerol

Question 14

Give the test for protein

Answer 14

A few drops of biuret added to 2cm^3 unknown solution
Mixture gently shaken
Mauve purple if protein is present

Question 15

Give the test for starch

Answer 15

A few drops of iodine added to 2cm^3 unknown solution
Mixture gently shaken
Deep blue black if starch is present

Question 16

The test for glucose

Answer 16

2cm^3 Benedict’s reagent added to 2cm^3 unknown sol.
Mixture heated in a boiling water bath for 2-3 mins
Orange / brick red if glucose is present

Question 17

Give the test for lipids

Answer 17

2cm^3 ethanol added to unknown sol
Mixture gently shaken
Mixture poured into equal volume of distilled water
Milky-white émulsion if lipid is present

Question 18

Explain the lock and key hypothesis

Answer 18

The active site of the enzyme and the substrate fit exactly together like a lock and key. Different enzymes are complimentary to different substrates (eg. Amylase is specific to starch).

Question 19

What factors effect enzyme activity?

Answer 19

pH and temperature

Question 20

Why does the temperature affect the enzyme activity?

Answer 20

Too low: the substrate and enzyme don’t have much energy and make few successful collisions
Too high: the enzyme’s active site deforms and the substrate doesn’t fit in. The enzyme is said to be denatured

Question 21

Give the equations for photosynthesis and respiration

Answer 21

Photosynthesis:
6 CO2 + 6 H2O —> C6 H12 O6 + 6 O2

Respiration:
C6 H12 O6 + 6 O2 —> 6 CO2 + 6 H2O

Question 22

What do chloroplasts do?

Answer 22

Chloroplasts are energy transducers that contain chlorophyll and convert light energy into chemical energy

Question 23

What do the layers of a leaf do?

Answer 23

Waxy cuticle: reduces water loss especially on the upper surface (more exposed to the sun)
Upper epidermis: transparent layer that prevents the entry of disease causing organisms
Palisade mesophyll: densely packed cells full of chloroplasts to gain highest rate of photosynthesis.
Veins: transport system in / out of the leaf. Xylem = water and mineral salts/// phloem = organic products (eg. Glucose)
Spongy mesophyll: loosely packed Cally with air spaces to allow gases to diffuse through the leaf.
Stomata: pores that control the amount of water lost/carbon dioxide gained. (Is proportional though so if a lot of water is lost then a lot of CO2 is gained).

Question 24

What affects the light energy absorbed by a plant?

Answer 24

The intensity of light ( bright or dim )
The wavelength of the light ( ie. colour )
The duration of light exposure.

Question 25

What does the deficiency of magnesium do to a plant?

Answer 25

Chlorosis- the leaves turn yellow from bottom to top

Question 26

What does the deficiency of nitrogen do to a plant?

Answer 26

Plant growth is stunted (because nitrogen is important in many nutrients), the stem becomes weak and the leaves turn yellow and die.

Question 27

What problems can fertilisers cause to habitats?

Answer 27

If fertilisers flow into a river or lake, they promote growth of algae. The algae die and are decomposed by bacteria that use the oxygen in the water for aerobic respiration. This
Leads to oxygen deficient water and larger animals die

Question 28

What does food give to organisms?

Answer 28

• molecules that are the raw materials for repair, growth and development of body tissues
• molecules that can be oxidised in respiration and act as a source of energy
• elements and compounds that enable the raw materials and energy to be used efficiently

Question 29

Give examples of foods from carbohydrates, lipids and proteins and state why they are necessary.

Answer 29

Carbs - rice, potatoes, wheat - main source of energy. Glucose is used to make energy, make molecules in the body and aid cell division. Excess is stored as glycogen

Lipids - eggs, milk, cheese - vital energy store because they are insoluble in water. They provide insulation on nerves and under the skin, and are used in the making of hormones (eg. steroid)

Proteins - meat, fish, eggs - used for catalysts, transport molecules, structural materials (eg. Muscles), hormones (eg. Insulin), and defence against disease.

Question 30

Give sources and symptoms of vitamins C and D

Answer 30

C:
Cherries, citrus fruits, and green leafy veg.
Deficiency leads to scurvy (affected production of fibres in the body) and cell ageing

D:
Liver, dairy products, eggs.
Deficiency leads to rickets (bones become soft and may bend because vitamin D is needed for the absorption of calcium

Question 31

Give sources and symptoms of deficiency of Iron and Calcium.

Answer 31

Iron:
Red meat, liver, leafy veg.
Deficiency leads to anaemia (a shortage of haemoglobin)

Calcium:
Milk cheese, fish.
Deficiency leads to weak bones and teeth, poor blood clotting, and uncontrolled muscle spasms.

Question 32

Why is fibre necessary in the diet?

Answer 32

Fibre is indigestible, and it provides bulk in faeces. Shortage in fibre can lead to constipation and eventually could cause bowel cancer.

Question 33

What is kwashiorkor and how can it be cured?

Answer 33

It is when a person has an insufficient protein intake and therefore their mental and physical development is impaired.
It can be cured by intake of the right nutrients.

Question 34

What is marasmus and how can it be cured?

Answer 34

It is when a person has symptoms of general starvation. There is not enough protein or energy. The body’s tissues waste away and the person becomes very thin.
It can be cured by intake of the right nutrients

Question 35

List the order of the digestive organs and what they do

Answer 35

Mouth- food converted to a bolts (ball) produced by teeth and saliva during mastication
Salivary glands- produce saliva through the salivary ducts
Oesophagus- muscular tube which helps food move to the stomach by peristalsis
Liver- produces bile, which neutralises acidic chyme and emulsifies fats.
Stomach - muscular bag which mixes food with acids to form chyme
Gall bladder- stores nile before pouring it into the duodenum through the bile duct
Pancreas- produces enzymes, mucus and hydrogencarbonate which neutralises acidic chyme and is poured into the small intestine through the pancreatic duct
Duodenum- first part of the S.I. where food is mixed with pancreatic juices
Ileum- second part of the S.I. where digested food is absorbed into the blood and the lymphatic system
Rectum- where faeces is stored
Anus- ring of muscle that controls defaecation

Question 36

How does diarrhoea occur and how can it be treated?

Answer 36

Cholera releases a toxin which increases loss of water and chloride ions into the small intestine. It prevents the uptake of water and chloride ions.
Oral rehydration therapy is the best treatment (drinking a mixture of water and mineral salts.

Question 37

List the different parts of the tooth and what they do

Answer 37

Enamel- the hardest tissue in the body. Produced by tooth forming cells. Made of calcium salts. Enamel cannot be renewed or extended.
Dentine-forms a major part of the tooth. Harder than bone and made of calcium salts deposited on a framework of collagen fibres. The dentine contains a series of fine canals which extend to the pulp cavity.
Gum- covers the junction between the enamel and the cement.
Periodontal membrane- bundles of collagen fibres anchoring the cement to the jawbone. It is held firmly but not rigidly. The periodontal membrane has many nerve endings which detect pressures during chewing and biting.
Cement- similar to the dentine, but no canals. It helps anchor the tooth to the jaw.
Pulp cavity- contains: tooth producing cells, blood vessels, and nerve endings.

Question 38

What effect does vitamin C deficiency have on teeth?

Answer 38

Impairs the production of collagen fibres, including those in the periodontal membrane, so teeth may become loose and fall out (symptom scurvy).

Question 39

How does peristalsis occur?

Answer 39

Waves of (circular) muscle contractions occur behind the gut contents, squeezing it forward. Without fibre, the guts contents would be very liquid, so the circular muscles wouldn’t be able to squeeze them efficiently.

Question 40

What does bile do in digestion?

Answer 40

Bile emulsifies fats by breaking them down from large globules into small smaller droplets, giving the lipase a larger surface to work on.
Bile also neutralises acidic chyme from the stomach.

Question 41

How is the small intestine adapted to increase the rate of digestion?

Answer 41

The small intestine has villi which are small finger like structures that give the small intestine a larger area.
The villi have a one cell thick epithelial cell layer to give a short distance for active transport.
They are covered in mucus (secreted by the goblet cells).
They have a rich blood supply that allows them to keep a constant concentration gradient and transports absorbed products to the liver via the hepatic portal vein.
It also has has a lacteal which transports fatty acids and glycerol.

Question 42

What does the liver do?

Answer 42

Manufactures bile, important for the digestion of fats.
Stores glucose as glycogen.
Interconversion of glucose and glycogen, which keeps the glucose concentration constant for working tissues of the body.
Interconversion of amino acids- the live can convert some into others that may be required in a process called transamination. The acids can be built up to proteins, including plasma proteins (eg.Fibrinogen).
Excretion of excess amino acids. The amino part of amino acids is removed in a process called deamination and is excreted the the urea.
Removes old red blood cells from the circulation and storage of the iron they contain.
Breakdown of alcohol and other toxins, called detoxification.

Question 43

Why are plant transport tissues arranged in the way they are?

Answer 43

To allow the most efficient transport of materials from sources (where they are made) to sinks (where they are used).
To allow the most effective support in air (for the stem) and in soil (for the root).

Question 44

List the sequence of transpiration

Answer 44

Water evaporates from the leaves and lowers the water potential in the leaf tissues.
Water moves from the xylem to the leaf tissues down a water potential gradient.
Water moves up the stem through the xylem as a column of water due to the tension caused by water los from the leaves and the cohesion of the water molecules.
Water uptake occurs by osmosis from the soil solution (high water potential) to the root (low water potential).

Question 45

How may atmospheric conditions affect transpiration?

Answer 45

Wind moves the humid air away from the leaf surface, keeping a concentration gradient.
High temperatures increase the water holding capacity of the air and increase transpiration.
Low humidity increases the water potential gradient between the leaf (high) and the air (low) and increases transpiration.
High light intensity causes stomata to open (to allow photosynthesis) and allows transpiration to occur.

Question 46

How does leaf structures affect transpiration?

Answer 46

Thick, waxy cuticle reduces evaporation from epidermis.
Stomata may be sunk into pits which trap a pocket of humid air.
Leaves may be rolled with the stomata on the inner surface close to a trapped layer of humid air.
Leaves may be needle shaped to reduce their surface area.