organisation biology gcse aqa

excluding anything about cancer or The effect of lifestyle on some non-communicable diseases

what are xylem and phloem

transport tissues

what is epidermal tissue in plants

covers surfaces and protects them. sometimes have a waxy cuticle which waterproofs it

diagram of the inside of a leaf (really good diagram, everything you need to know)

palisade mesophyll

• tightly packed cells

• lots of chloroplasts to absorb light for photosynthesis

spongy mesophyll

• spherical cells

• lots of air spaces to allow gases to diffuse quickly

• large surface area to volume ratio to increase gas exchange

gaurd cells

control the opening and closing of the stomata

stomata

tiny openings on the lower surface of the leaf that allow gases to move into and out of the leaf

diagram of tissues in a root (must be able to draw)

cross section diagram of a leaf (must be able to draw)

diagram of tissues in a stem (must be able to draw)

remember: xylem is always on the inside, phloem is always on the outside

vascular bundles in the leaf

network of vessels to support the soft tissue

vascular bundles in the stem

located around the outer edge to provide support and resist bending

vascular bundles in the root

centrally located allowing root to anchor the plant

xylem

Xylem tissue transports water and mineral ions from the roots to the stems and leaves.

It is composed of hollow tubes strengthened by lignin adapted for the transport of water in the transpiration stream.

phloem

Phloem tissue transports dissolved sugars (e.g. glucose) from the leaves to the rest of the plant for immediate use or storage. The movement of food molecules through phloem tissue is called translocation

Phloem is composed of tubes of elongated cells. Cell sap can move from one phloem cell to the next through pores in the end walls.

transport in the xylem

• water and mineral ions move in one direction only

• in woody trees the dead xylem makes up most of the wood and the phloem is just under the bark

transport in the phloem

root hair cells adaptation

Root hair cells are adapted for the efficient uptake of water by osmosis, and mineral ions by active transport

role of stoma and gaurd cells

The role of stomata and guard cells are to control gas exchange and water loss.

what is transpiration

the evaporative loss of water vapour through the stomata

what are stomata

• pores located on the underside of leaves (lower epidermis)

• allow carbon dioxide to enter for photosynthesis

• this also allows oxygen to be lost by diffusion

• they shut at night to reduce water vapour loss by transpiration

what is the transpiration stream

• water evaporates off the spongy mesophyll cells and diffuses into the air spaces and out through the stomata

• this loss pulls more water up the xylem from the roots to maintain a continuous column of water in the xylem

• this is called the transpiration stream

how exactly do the stoma open

• when a plant has plenty of water, the gaurd cells become turgid

• the cell wall on the inner surface is very thick, so it cannot stretch as much as the outer surface

• so, as the gaurd cells swell up, they curve away from each other, opening the stoma

importance of transpiration

• provides water to cells to keep them turgid -As water leaves the leaf, it pulls on the water around it, and this creates a continuous column of water

• provides water to cells for photosynthesis

• transports mineral ions to leaves

importance of translocation

• moves dissolved sugars made in the leaves during photosynthesis to other parts of the plant

• this allows for respiration, growth, and glucose storage

• occurs in phloem

what does a xylem vessel look like?

what does a phloem vessel look like?

factors affecting rate of transpiration

• temperature

• humidity

• wind speed

• light intensity

effect of temperature on rate of transpiration

• higher temperatures increase the rate of transpiration

• because water evaporates faster in higher temperatures

effect of humidity on rate of transpiration

• lower humidity increases the rate of transpiration

• because the drier the air, the steeper the concentration gradient of water molecules between air and leaf

effect of wind speed on rate of transpiration

• more wind increases rate of transpiration

• because wind removes water vapour quickly, maintaining a steeper concentration gradient

effect of light intensity on rate of transpiration

• higher light intensity increases rate of transpiration

• becasue stomata open wider to let more carbon dioxide into the leaf for photosynthesis.

what do you use to measure the rate of transpiration

a potometer.

it measures rate of water uptake which is equivalent to the amount of water lost through transpiration.

which adaptation of xylem helps prevent water leaving the xylem vessels

lignin in the walls of the xylem

how is sugar transported around a plant

upwards in the xylem

what is blood made of?

plasma, red blood cells, white blood cells, platelets

plasma

• yellow liquid that makes up 55% of volume of blood

• mostly water

• transports blood and other substances like glucose and amino acids around the body

where is urea from break down of amino acids transported to and where from, via plasma?

transported from:

the liver

transported to:

kidneys

where is lactic acid from anaerobic respiration transported to and where from, via plasma?

from:

muscles

to:

liver

where is carbon dioxide from aerobic respiration transported to and where from, via plasma?

from:

every living cell

to:

alveoli in lungs

where are small soluble products of digestion transported to and where from, via plasma?

from:

small intestine

to:

liver

4 examples of substances transported in plasma

• urea from break down of amino acids

• lactic acid from anaerobic respiration

• carbon dioxide from aerobic respiration

• small soluble products of digestion

cells in the blood diagram

red blood cells

• most common type of blood cell

• made in the bone marrow+ live for about 4 months

• function: to carry oxygen from the lungs to the respiring cells

adaptations of red blood cells

• biconcave disk-greater surface area

• no nucleus- more space for haemoglobin= more oxygen can be carried

• have haemoglobin- red pigment that binds o2

white blood cells

• larger but fewer than red ones

• have a nucleus

• form part of bodys defence system against harmful microorganisms

3 ways white blood cells can protect against microorganisms

• engulfing and digesting them

• producing antibodies to them

• producing antitoxins to poisons released by them

platelets

• small fragments of cells

• no nucleus

• help blood clot at the site of a wound

describe how blood clots at the site of a wound/ how a scab forms

• blood clots by a series of enzyme controlled reactions stimulated by platelets

• this forms a fibrous mesh of fibrin over the wound and traps cells to form a clot

• the clot dries to form a scab

• this stops blood leaving and microorganisms entering

double circulatory stystem

• consists of heart, blood vessels and blood

• double circulatory system = in one full circuit of the body, blood will pass through the heart twice

3 types of blood vessel

arteries, capillaries, veins

deoxygenated blood enters which side of the heart?

the right side

oxygenated blood enters which side of the heart?

the left side

2 circulatory stytems

• pulmonary

• systemic

pulmonary circulatory system

deoxygenated blood is transported from the right side of the heart to the lungs to become oxygenated and returned to the left side of the heart

systemic circulatory system

oxygenated blood leaves the left side of the heart and is transported to the tissues and organs of the body and returns deoxygenated to the right side of the heart

function of veins

carry blood back to the heart (low pressure)

function of a capillary

• carries blood to tissues and cells

• connects arteries and veins

function of an artery

to carry blood away from the heart (high pressure)

structure of capillaries

• one cell thick- short diffusion distance for substances to move between blood and tissues

• very narrow lumen

structure of veins

• veins have valves to stop blood flowing the wrong way

• relatively thin walls

• large lumen

• low pressure

which artery does not carry oxygenated blood

pulmonary artery

in which vessels can a pulse be felt

arteries

why do veins contain valves

to prevent backflow

why are capillary walls so thin

to allow exchange

what happens to the speed of blood as it flows through capillaries and why

it slows down due to a larger network of capillaries (being spread out)

the heart

• the heart pumps blood around the circulatory stytems

• made of cardiac muscle

• the muscle contracts to push blood out and then relaxes to allow the heart to refill with blood

heart diagram with all the labels you actually need to know (as stated in spec)

heart rate

heart rate is calculated as the number of beats per minute

can be measures by feeling the pulse where an artery passes close to the skin

which parts of the heart actually pump blood

left and right ventricle

natural pacemaker of the heart

a cluster of cells in the right atrium causing it to contract at about 70 bpm

problems you can have:

• if the heart beats too slowly not enough oxygen reaches the cells of the tissues

• if the heart beats too quickly the blood is not pumped properly

• artificial pacemakers can be used to control irregular heartbeats

artificial pacemakers

electrical devices implanted under the skin of the chest

send a regular electrical stimulus to the heart to make it beat regularly

artificial hearts

• if you suffer complete heart failure you may be fitted with one

• usually only effective for short periods of time until a heart transplant can be performed

• sometimes used to allow the heart to rest as an aid to recovery

artificial heart valves

• heart valves can become sticky or leaky so can be replaced w artificial ones

• these may be biological- e.g. pig, cow or human

• they can be mechanical. these last a long time but drugs must be taken to stop blood clotting

what is coronary heart disease

• coronary heart disease is when fatty deposits build up in the lining of the coronary arteries, narrowing the lumen

• this reduces blood flow to the heart muscle, reducing oxygen supply and can cause a heart attack

• treatment can be surgical or with drugs

what are stents? (used for problems with blood flow)

• tubes which can be placed within arteries

• they hold the arteries open so that the blood can flow through them easily

what is bypass (used for problems with blood flow)?

when blocked arteries are replaced with other veins under general anesthetic

what are statins

• statins are drugs that lower blood cholesterol levels , reducing the chance of coronary heart disease developing by slowing the rate at which fatty materials are deposited into the artery linings.

advantages and disadvantages of stents

advantages:

no anesthetic required, relatively cheap, effective

disadvantages:

ineffective against severely blocked or narrowed arteries

advantages and disadvantages of bypass

advantages:

very effective against severe blockages

disadvantages:

general anesthetic required, expensive

advantages and disadvantages of heart transplants

advantages:

could be a lifelong treatment

disadvantages:

expensive, requires a donor, requires a lifetime of immunosuppressant drugs to prevent rejection

advantages and disadvantages of statins

advantages:

cheap, effective, readily avaliable

disadvantages:

patients may not change their unhealthy diets, people might not take them

ventilation/ breathing- by the respiratory stytem

how breathing occurs to move air in and out of lungs

gas exchange- in the alveoli

when o2 from the air diffuses into the bloodstream and co2 diffuses out of the blood

respiration- in the cells

a chemical reaction that happens in the mitochondria of cells using glucose and oxygen to release energy (ATP)

ciliated epithelium

line the trachea to waft mucus to the throat, away from the lungs

diagram of lungs, windpipe and ribs

rib movement when you inhale/exhale

inhale- move up and out

exhale- move down and in

diaphragm movement when you inhale/exhale

inhale- flattens and contracts

exhale- curves and relaxes

chest volume when you inhale/exhale

inhale- increases

exhale- decreases

chest pressure when you inhale/exhale

inhale- decreases

exhale- increases

compare inhaled and exhaled air

Inhaled air contains about 21% oxygen, 0.04% carbon dioxide, and 78% nitrogen, while exhaled air contains about 16% oxygen, 4% carbon dioxide, and 78% nitrogen

features of a good exchange surface

• large surface area

• short diffusion path

• steep concentration gradient

which blood vessel transports blood from the lungs to the heart

pulmonary vein

which chamber in the human heart contracts with the greatest force

left ventricle

blood flow through a double circulatory system (start at left side of heart)

left side of heart- body organs- right side of heart- lungs

why does the left ventricle have more muscle than the right ventricle

because it must pump blood to the entire body, while the right ventricle only pumps blood a short distance to the lungs.

which structure in the heart controls the direction of blood flow between the left atrium and right ventricle

bicuspid (or AV valve)

which tissue of the wall of the heart contracts to pump the blood

cardiac muscle

what supplies the cardiac muscle tissue (not the heart) with oxygen

coronary arteries