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Biology A-Level IAL Edexcel > Unit 5- Topic 7 > Flashcards

Unit 5- Topic 7 Flashcards

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1
Q

what is cellular respiration

A

the proces by which respiratory substrate is broken down to yield ATP

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2
Q

what is aerobic respiration and what does it involve

A

it is the type of cellular respiration that takes place in the presence of oxygen. it involves breaking down the respiratory substrate (glucose) to release carbon dioxide as a waste product and reuniting hydrogen with atmospheric oxygen to form water, with the release of large amounts of energy

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3
Q

equation for aerobic respiration

A

C6H12O6 + 6O2 -> 6CO2 + 6 H2O (+ ATP)
glucose + oxygen -> carbon dioxide + water

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4
Q

what is the reaction ADP + Pi called and what does it form

A

froms ATP and it is called phosphorylation

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5
Q

what is the reaction of the break down of ATP called and what does it produce

A

called hydrolysis, makes ADP and free inorganic phosphate

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6
Q

What are the stages of aerobic respiration

A

Glycolysis, Link Reaction, Krebs Cycle, Electron transport chain

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7
Q

Enzymes and respiration

A

It is a multi-step process, with each step controlled and catalysed by a specific intracellular enzyme.

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8
Q

Where does cellular respiration take place

A

The enzymes controlling glycolysis are found in the cytoplasm. All other stages in aerobic respiration occur inside the mitochondria. The matrix of the mitochondrion contains the enzymes of the Krebs Cycle, the cristae carry the stalked particles associated with protein synthesis.

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9
Q

Reactions that occur in the electron transport chain that allow ATP to be produced

A

It is produced through a series of oxidation and reduction (redox) reactions in the electron transport chain

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10
Q

How do redox reactions occur in the electron transport chain

A

Because during cellular respiration, hydrogen is removed from compounds and received by a hydrogen acceptor which is reduced several times. The hydrogen is split into a proton and an electron and the electron passes through the electron transport chain. Each redox reaction releases a small amount of energy which is used to drive the synthesis of ATP

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11
Q

Examples of hydrogen acceptors

A

NAD: coenzyme, a small molecule that assists in enzyme-catalysed reactions. When NAD accepts hydrogen atoms from a metabolic pathway, it becomes reduced to form rNAD or NADH
FAD: coenzyme, accepts hydrogen from reduced NAD and forms reduced FAD. Each time this happens, a molecule of ATP is created

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12
Q

What does a respirometer measure

A

Measures the uptake of oxygen (the quantity used) or the output of carbon dioxide (the quantity produced by whole organisms. This gives valuable information about the rate of cellular respiration

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13
Q

What does a respirometer consist of

A

A closed chamber into which no air can enter and which contains one or more living organisms (eg.germinating seeds). You can use soda lime to absorb the CO2 produced by respiration. This means that any changes in volume will be caused by the uptake of oxygen by the organisms. As the organisms use oxygen, the pressure reduces and so the fluid in the manometer moves towards the tube containing the organisms. Using the syringe you can measure the volume of gas you need to return the manometer to normal, and use this measurement to calculate the intake of oxygen per minute which gives you an approximate rate of respiration

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14
Q

How can you investigate respiration at the cellular level

A

-You can break open cells and centrifuge the contents to obtain a fraction containing just mitochondria. If these are kept supplied with glucose and oxygen, they will produce ATP
-using high-resolving electron microscopes, you can see that the surface of the inner membrane of the mitochondrion is covered in closely packed stalked particles. These provide a greatly increased surface area, which is an ideal site for enzymes to work
-you can separate the stalked particles and the small pieces of membrane associated with them from the rest of the mitochondrial structure.

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15
Q

Where does the glucose used in glycolysis come from

A

It can one directly from the blood, or by the breakdown of glycogen stores in te muscle and liver cells

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16
Q

Give a step by step of glycolysis

A

6C sugar glucose is phosphorylated into a phosphorylated 6C. This later sugar is broken down to give two molecules of a 3-carbon sugar. One hydrogen atom is removed from each 3C sugar and collected by NAD to make rNAD. A small amount of ATP is produced by substrate level phosphorylation using the phosphorus used to phosphorylate glucose at the beginning of the reaction. After all of this steps, each 3 Carbon sugar is converted to into one pyruvate ion

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17
Q

Why is glucose phosphorylated in glycolysis

A

Because it makes the sugar more reactive and makes thee molecule unable to pass through the cell membrane

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18
Q

Where does the reduced NAD travel after it has gained the electron/hydrogen

A

It passes through the outer mitochondrial membrane into the electron transport chain

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19
Q

what two types of ‘paths’ can pyruvate take after glycolysis

A

It can go to aerobic respiration or anaerobic respiration

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20
Q

What occurs to pyruvate in aerobic respiration

A

Only occurs if there is plenty of oxygen
-it occurs in the mitochondria and will be used in aerobic reactions
-complete oxidation
-waste products are: H2O and CO2
-net energy: 31 ATP

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21
Q

What occurs to pyruvate in anaerobic respiration

A

If levels of oxygen are low
-The pyruvate will remain in cytoplasm
-incomplete oxidation
-waste products: lactate (in mammals) or ethanol and CO2 (in plants and yeast)
-net energy: 2 ATP

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22
Q

Why does anaerobic respiration produce such a low number of ATPs

A

Because some of the reduced NAD is used to reduce pyruvate to lactate rather than entering the electron transport chain. The hydrogen is required to form lactate and oxidises NAD to continue the conversion of 3C sugar to pyruvate. This reduction of pyruvate to lactate is known as NAD+ regeneration.

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23
Q

Equation for anaerobic respiration in mammals

A

C6H12O6 -> 2 C3H6O3 (+ATP)

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24
Q

How does lactic acid affect the muscles and blood

A

The movement of hydrogen ions and lactate into the blood from the acidic muscle tissue (caused by the lactic acid) lowers the pH of the blood, which as a result affects the central nervous system

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25
Q

What happens after intense exercise stops

A

When the exercise stops, the levels of lactate in te blood remain high. The lactate is toxic so it must be oxidised back to pyruvate to enter the Krebs Cycle and be respired aerobically, producing CO2, H2O and ATP. The lactate therefore is carried to te liver in the blood. Oxygen is needed to oxidise the pyruvate made from the accumulated lactate s you continue to breath heavily after exercise

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26
Q

How does training help athletes improve

A

Training allows athletes to get more oxygen to their muscles faster as better blood supply develops, and to tolerate higher levels of lactate before the muscle becomes tired.

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27
Q

Equation for anaerobic respiration in plants and fungi

A

C6H12O6 -> 2C2H5OH + 2 CO2 (+ATP)
Glucose -> ethanol + carbon dioxide

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28
Q

What is the Krebs Cycle

A

A series of biochemical steps that leads to the complete oxidation of glucose, resulting in the production of carbon dioxide, water and relatively large amounts of ATP. It occurs in the matrix of the mitochondrion

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29
Q

where is most ATP produced in a cell

A

The electron transport chain and ATP production occur on the inner membrane of the mitochondria, which is folded up to form the cristae, producing a large surface area, in the presence of oxygen. The surface of the cristae is covered with closely packed stalked particles which seem to be the site for ATPase enzymes

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30
Q

what is the link reaction

A

the reaction needed to move the products of glycolysis into the krebs cycle

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31
Q

where does the link reaction occur and how does pyruvate get there

A

occurs into the mitochondria. pyruvate crosses through the mitochondrial membrane from the cytoplasm into the mitochondria

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32
Q

what occurs in the link reaction

A

an atom of carbon and a molecule of oxygen are removed from pyruvate by decarboxylation giving a 2-Carbon molecule and CO2. 2-C molecule joins with coenzyme A (CoA) to form acetyl coenzyme A. at the same time, the pyruvate is oxidised, losing a hydrogen to NAD by dehydrogenation making reduced NAD

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33
Q

what enzymes are in charge of decarboxylation and dehydrogenation

A

-decarboxylases
-dehydrogenases

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34
Q

what happens to acetyl CoA after the link reaction

A

the energy contained in the acetyl CoA is released in the Krebs Cycle

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35
Q

steps of the krebs cycle

A

acetyl CoA combines with a 4C compound to form A 6C compound
-the 6C is broken down to a 5C releasing a CO2 by decarboxylation and reducing an NAD into rNAD by dehydrogenation.
-the 5C compound now is broken down to release IN ORDER:
-a CO2 by decarboxylation
-an ATP by substrate level phosphorylation
- an rNAD by dehydrogenation
-an rFAD by dehydrogenation
-an rNAD by dehydrogenation
- a 4C compound which combines again with acetyl CoA

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36
Q

how many times does the krebs cycle occur per one molecule of glucose

A

for each molecule of glucose that enters the glycolytic pathway, the Krebs cycle is completed twice because the 6C glucose produces two 3C pyruvate

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37
Q

what are hydrogens needed for in the electron transport chain

A

they are needed for chemiosmosis to supply energy needed to synthesise ATP. Hydrogen atoms in the end combine with oxygen atoms to form water, but it is mainly electrons that are passed along the carrier system. each electron is passed down from one enrgy level to another driving the production of ATP

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38
Q

why is ATP production in thye electron transport chain called oxidative phosphorylation

A

because ADP is phosphorylated in a process that depends on the presence of oxygen

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39
Q

what is the order of electron carriers of the electron transport chain

A

reduced NAD
reduced FAD
reduced cytochromes
reduced cytochrome oxidase
electron picked up by oxygen to make water

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40
Q

types of electron carriers

A

-the coenzymes NAD and FAD act as hydrogen acceptors for hydrogen released in the Krebs cycle
-cytochromes are protein pigments with an iron group (similar to haemoglobin), they are reduced by electrons from rFAD and rNAD
-cytochrome oxidase an enzyme that receives electrons from the cytochromes
-oxygen is the last hydrogen acceptor. when this is reduced, water is formed and the chain is at an end

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41
Q

when is ATP produced referring to electron carriers

A

when the electron carriers are oxidised and the next carrier with a lower energy level reduced, an ATP molecule is produced

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42
Q

how do hydrogen ions behave in the electron transport chain

A

there is an active transport of the hydrogen ions across the inner membrane which results in a different hydrogen ion concentration on each side of the inner membrane. the membrane space has a higher concnetration of hydrogen ions than the matrix, so there is a concentration, pH and due to their positive charge, an electrochemical gradient across the membrane. the hydrogen ions tend to move back into the matrix through pores which are on the stalked particles and contain ATPase. As hydrogen ions move along their gradients, their energy is used to drive the synthesis of ATP.

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43
Q

what is the respiratory quotient (RQ)

A

the relationship between the amount of carbon dioxide produced and the amount of oxygen used when different respiratory substrates are used in cellular respiration

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44
Q

equation for respiratory quotient

A

carbon dioxide produced
respiratory quotient=______________________________
oxygen used

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45
Q

what can RQ help you do

A

know what types of food are being oxidised in the body of an organism at a particular time.

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46
Q

what results can you get in RQ and what do they mean

A

RQ= 1 -> carbohydrates
RQ= 0.7 -> fats
RQ= 0.9-> proteins
RQ= less than 1 -> combination of carbohydrate and lipid
RQ= more than 1 -> anaerobic respiration or a photosynthetic organism since CO2 produced is being used by the organism so it cannot be measured

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47
Q

characteristics of bone

A

-strong and hard
-bone cells fixed firmly in a matrix of collagen and calcium salts
-strong against compression forces
-compact bone is dense and heavy, found in long bones
-spongy bone has a more open structure so much lighter, found in large masses of bone (pelvis)

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48
Q

characteristics of cartilage

A

-hard but flexible
-made up of chondrocytes within an organic matrix that are varying amount of collagen fibrils
-elastic and withstand compressive forces
-acts as a shock absorber
-found between bones
-hyaline cartilage is found at the end of bones
-white fibrous cartilage has bundles of densely packed collagen in the matrix. more tensile strength but less flexible. found between bones in joints

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49
Q

characteristics of tendons

A

-made almost entirely of white fibrous tissue. This consists of bundles of collagen fibres.
-strong but inelastic tissue
-joins muscle to bone
-makes a secure attachment for muscles to bone and provides shock absorption for the joint

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50
Q

characteristics of ligaments

A

-hold the bone together in correct alignment by forming a capsule around the joint and holding the bones together inside the joint.
-elastic so the bones of the joint can move if needed
-made of yellow elastic tissue which gives strength and elasticity
-different joints have more mobility depending if the capsule is tighter or loser. the difference in the properties of the ligaments comes from the varying amounts of collagen and white fibrous tissue in the mixture

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51
Q

why do you need joints

A

to allow movement and locomotion since the bones in the joint form two solid masses moving over each other while experiencing severe forces

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52
Q

state the types of joints and where they are found

A

ball and socket joint - shoulder
pivot joint - elbow
saddle joint - wrist
hinge joint - knee

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53
Q

why ia cartilage needed in joints

A

the ends of the two bones would become thinner and weaker through the rubbing together. cartilage is needed to protect the bone and so the joint to be able to articulate smoothly. the more mobile joint also release synovial fluid which acts as a lubricant and ensures a friction free movement.

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54
Q

how do we move?

A

by the action of muscles on bones. each of your skeletal muscles are attached by tendonds to two different bones. when muscles contract they pull on a bone and so it moves relative to another bone.

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55
Q

why are skeletal muscles found in pairs

A

because when muscles relax they do not push in a corresponding way, they simply stop contracting and can be pulled back to their original shape. One muscle pulls the bone in one direction, the other pulls it back to its original position

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56
Q

what are extensors

A

the muscles which extend a joint

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57
Q

what are flexors

A

the muscles that bend or flex a joint

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58
Q

what is an antagonistic pair

A

muscles which work in opposition to each other, pulling in opposite direction. they are a extensor with its corresponding flexor

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59
Q

characteristics of muscles

A

-mostly made of protein
-consist of large numbers of muscle fibres (very long cells) which are held together by connective tissue
-muscles have good blood supply to provide them with glucose and oxygen for cellular respiration (supplies ATP needed for muscle contraction) and makes it easy to remove carbon dioxide and other waste products
-muscles respond to stimulation from the nervous system and to chemical stimulation from hormones such as adrenaline

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60
Q

types of muscle

A

-skeletal muscle
-smooth muscle
-cardiac muscle

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61
Q

characteristics of the skeletal muscle

A

-the muscle attached to the skeleton
-involved in locomotion
-under the control of the voluntary nervous ystem
-under microscope it is striated
-it contracts rapidly, but also fatigues or tires relatively quickly

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62
Q

what are muscle fibrils made up of

A

many myofibrils lying parallel to each other. the cytoplasm of the myofibrils is called the sarcoplasm and it contains many mitochondria which supply the energy that the muscle needs to contract. sarcoplasmic reticulums are also found and this stores and releases calcium ions

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63
Q

what are myofibrils made up of

A

individual units of sarcomeres. the sarcomere is made of proteins called actin (active) and myosin (middle).

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64
Q

what is the Z line

A

the end of the actin filament, it determines the start and end of the sarcomere

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65
Q

what is the H zone

A

the zone where only myosin is found

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66
Q

what is the A band

A

the whole length of the myosin filament, including where actin and myosin overlap

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67
Q

what is the I band

A

the whole length of where myosin is not found. The I band includes half the actin filament of one single sarcomere with the next actin filament of the next sarcomere.

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68
Q

characteristics of smooth muscle

A

-not striped
-under the control of the involuntary nervous sytem.
-mucle found in the gut where it is involved in moving the food along and muscle found in blood vessels
-it contracts and fatigues slowly

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69
Q

characteristics of cardiac muscle

A

-only found in the heart
-striated
-fibres joined by special cross-connections
-contracts spontaneously so it is not stimulated by nerves nor hormones
-it does not fatigue

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70
Q

what can be found in muscle cells

A

-contain many mitochondria as it isthe site of cellular respiration
-contain myoglobin which is similar to haemoglobin
-> myoglobin acts as an oxygen store in muscles
->it only has one protein chain instead of the 4 in haemoglobin
->it has a higher affinity for oxygen than haemoglobin
-> it can act as an oxygen store as it will hold onto oxygen until all the oxygen in oxyhaemoglobin has been used. it will then release its oxygen so aerobic respiration can continue

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71
Q

Types of skeletal muscle fibres

A

Slow twitch muscle fibres
Fast twitch muscle fibres

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72
Q

Characteristics of slow twitch muscle fibres

A

-adapted for steady action over a period of time
-contract slowly and stay in tetanus for a long period of time
-maintain body posture and long periods of activity
-rich blood supply
-lots of mitochondria
-high levels of myoglobin

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73
Q

How does the adaptations of slow twitch muscle fibres help perform their function

A

The adaptations allow them to maintain their activity without needing to respire anaerobically for any length of time.
-rich blood supply and high levels of myoglobin means that they have a deep red colour
-the glucose needed as a fuel is supplied by their big network of blood vessels so they can continue to produce ATP for as long as oxygen is available

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74
Q

Characteristics of fast twitch muscle fibres

A

-contract very rapidly so used for rapid brief activity
-function anaerobically using glycolysis so fatigue quickly
-few blood vessels
-low levels of myoglobin so much paler in colour
-contain a small number of mitochondria
-rich glycogen stores - can convert to glucose
-high levels of creating phosphate - used to form ATP from ADP
-many more myofibrils than in slow twitch since space is not occupied by mitochondria

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75
Q

What changes in the muscle fibres in training

A

The number stays the same but the size and type of the muscle fibre may change.
Genetics may also affect the basic components of our muscles giving a natural advantage and higher sporting potential to those athletes that perform the sport appropriate to their genetics

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76
Q

What bands in a muscle fibre change when a muscle contacts

A

The A band (length of myosin filament) stays the same whether the muscle is contracted or relaxed
The I bands and H zone become shorter when a muscle fibre contracts.
This suggests that the two types of filaments Slide over each other during contraction- sliding filament theory

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77
Q

What is myosin filament made out of

A

It is made out of many myosin molecules held together. The myosin molecule is made up of two long polypeptide chains twisted together, each one ends in a large, globular head which has ADP and inorganic phosphate molecules attached to it. The head can act as an ATPase enzyme

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78
Q

What is the actin filament

A

Made up of two chains of actin monomers joined together. The shape of actin molecules produces binding sites for myosin. But tropomyosin wraps around the double actin chains covering the myosin binding sites

79
Q

What is tropomyosin made out of

A

It is a long chain protein molecule which in a relaxed state, it wraps around the double actin chains covering the myosin binding sites.
It has molecules of troponin (another protein) which are attached at regular intervals along the chain. Troponin has 3 subunits: 1 binds actin, 1 binds tropomyosin and 1 binds calcium ions

80
Q

How do muscles contract

A

-in a relaxed state: myosin head contain ADP + Pi and is pulled back (original state) and the tropomyosin is covering the myosin binding sites in actin filament
-calcium ions are released from stores in sarcoplasmic reticulum and attach to binding sites in troponin, changing their shape, so troponin molecules pull on the tropomyosin molecules they are attached to. This moves the tropomyosin away from the myosin binding sites, exposing them ready for action
-the myosin head binds to the actin, forming an actomyosin bridge
-ADP and Pi are released from the myosin head. The myosin head changes shape, power stroke
-free ATP binds to the head, causing another shape change in the myosin, so the binding of the head to acting is broken. Activates ATPase in the myosin head which also needs calcium ion to work, atp is hydrolysed and head returns to its original position

81
Q

what happens when there is no longer a continued stimulation during muscle contraction

A

calcium ions in the sarcoplasm are pumped back into the sarcoplasmic reticulum using ATP. troponin and tropomyosin return to their original positions and the contraction is complete.

82
Q

why does the heart beat increase during exercise

A

to transport blood faster since the blood brings glucose and oxygen which are needed by the rapidly respiring cells and removes the increased waste products

83
Q

characteristics of cardiac cells

A
  • they are myogenic - they contract without an external stimulus
  • they intrinsic rhythmity
84
Q

how is the intrinsic rhythm of the heart maintained

A

by a wave of electrical excitation similar to nerve impulses which spreads through special tissue in the heart muscle

85
Q

what is the sinoatrial node (SAN)

A

a group of cells in the right atrium with the fastest intrinsic rhythm. they act as the heart’s natural pacemaker which keeps the heart beating regularly

86
Q

description of the steps in the heart beat refering to electrical impulses

A

-The SAN establishes a wave of electrical excitation (depolarisation) which causes the atria to start contracting. This initiates the heartbeat.
-excitation spreads to other areas of similar tissue called the atrioventricular node (AVN)
-AVN is excited due to SAN but produces a delay before the wave of depolarisation passes into the bundle of His. This makes sure the atria have stopped contracting before the ventricles start.
-bundle of His splits into two branches and carries the wave of excitation on into the Purkyne tissue
-as the depolarisation travels through the tissue it starts the contraction of the ventricles, starting at the apex and so squeezing blood upwards out of the heart

87
Q

what is the bundle of His

A

a group of conducting fibres in the septum of the heart.

88
Q

what is the Purkyne tissue

A

conducting fibres that penetrate down through the septum, spreading around the ventricles

89
Q

what is special about the speed at which the excitation spreads through the heart

A

it makes sure that the atria have stopped contracting before the ventricles start. the changes in the electrical excitation of the heart that causes the repeating cardiac cycle

90
Q

what does an ECG measure

A

it produces a record of the electrical activity of the heart

91
Q

how does an ECG measure the electrical activity of the heart

A

the wave of depolarisation that causes the rhythm of the jeart causes a tiny electrical changes on the surface of your skin. 12 electrodes and leads are attached to your body. your skin is wiped with ethanol prior to remove any grease or sweat so the electrodes can make good contact with your skin

92
Q

What does dynamic equilibrium involve

A

Matching the supply of oxygen and glucose to the continually changing demands of the body. At the same , carbon dioxide must be removed and an even temperature and pH maintained

93
Q

What is homeostasis

A

Maintaining a state of dynamic equilibrium through the responses of the body to external and internal stimuli

94
Q

Why does pH have to be maintained in the body

A

So that the structures of protein molecules remain stable. This allows enzymes to function at their optimum activity and the structure of cell membranes to be maintained

95
Q

Why does the core temperature of the body

A

Need to stable to maintain the optimum activity of the enzymes that control the rate of cellular reactions, to maintain the structure and function of the cell membranes.

96
Q

Why does the water potential has to be maintained

A

To avoid osmotic effects that could damage or destroy cells

97
Q

What do the sensors/ receptors do

A

They detect changes in the body. They then send messages to effectors

98
Q

What do effectors do

A

They either wok to reverse the change or to increase it using a number of different feedback systems. Effectors are usually muscles or glands

99
Q

What is the communication in a homeostatic feedback system

A

By hormones (chemical messengers) or by nerve impulses (electrical messengers). There is often a small overshoot or undershoot so the levels of most body systems fluctuate slightly around the ideal level in a dynamic equilibrium

100
Q

What does a negative feedback system provide

A

A way to maintain a condition, such as the concentration of a substance, within a narrow range. The receptors detect a change in conditions; this results in effectors being simulated to restore the equilibrium

101
Q

What occurs in a positive feedback system

A

Effectors work to increase the effect that has triggered the response.
Eg: the uterus contracting in labor

102
Q

What does the control of the heart rate emphasise the importance of having receptors for

A

-detect internal changes
-the ways in which the parasympathetic and sympathetic nervous system work together in a complementary way
-the interactions between nervous and hormonal control

103
Q

Why does the heart need baroreceptors, chemoreceptors… to accelerate or slow the heart down

A

Because the intrinsic rhythm cannot cope with changes in demand. The response of the heart to these changes in demand is the result of a number of negative feedback systems

104
Q

How can the heart respond when there is an increased demand of glucose and oxygen

A

The reate at which the heart beat increases
The cardiac volume increases by a more efficient contraction of the ventricles

105
Q

Equation for cardiac output

A

Cardiac output (dm3 min -1) = cardiac volume (dm3) x heart rate (beatsmin -1)

106
Q

Describe the nervous control of the heart

A

Most of the nervous control of the heart is by the autonomic nervous system. The cardiovascular control centre is situated in the medulla oblongata of the brain which plays a major part in controlling changes in the heart rate and the volume of blood pumped with each heartbeat in response to changes in the internal environment

107
Q

How does the blood vessels and chambers of the heart have a nervous control of the heart rate

A

Chemical, stretch and pressure receptors in the lining of blood vessels and the chambers of the heart send nerve impulses to the cardiovascular control centre. It responds by sending impulses to the heart along the sympathetic or parasympathetic nerves. The heart responds to these impulses so controlling the rate at which it beats. Most of the body organs are supplied by both types of nerves, giving a level of fine control

108
Q

How does the sympathetic nerve increase the force and rate of contraction of the heart (nerve)

A

Nerve impulses that travel down the sympathetic nerve from the cardiovascular control centre to heart release noradrenaline to stimulate the SAN. This increases the frequency of the signals from the pacemaker region, so that the heart beats more quickly. Branches of this sympathetic nerve also pass into the ventricles, so they also increase the force of contraction

109
Q

How does the parasympathetic nerve decreases the force and rate of contraction of the heart (nerve)

A

Parasympathetic nerve releases acetylcholine (ACh), inhibiting the SAN and slowing the heart down.

110
Q

What are baroreceptors

A

Are mechanoreceptors in the carotid arteries in the neck and on the aorta that are sensitive to pressure changes. At rest, they send a steady stream of signals back through sensory neurones to the cardiovascular control centre in the brain.

111
Q

what is the balance of impulses that pass to the heart from the cardiovascular control centre affected by

A

by inputs from a number of different sensory receptors in the main arteries and in the heart itself

112
Q

what are chemoreceptors

A

found in the walls of the aorta and carotid arteries. they are sensitive to the levels of carbon dioxide in the blood. As CO2 level in the blood go up, pH of blood goes down. this is detected and and they send impulses along sensory neurones to the cardiovascular control centre, which increases the number of impulses travelling down the sympathetic nerve to their heart. this results in an increased heart rate, increasing blood flow to the lungs and therefore more CO2 removed. So chemoreceptors also play a role in the control of the breathing rate

113
Q

what happens at the baroreceptors at the start of exercise

A

At the beginning of exercise, the blood vessels dilate becoming wider in response to adrenaline. As a result, blood pressure falls, this reduces stretch on baroreceptors and this stop responding. the reduced stimulation of the baroreceptors causes the cardiovascular control centre to send signals along the sympathetic nerve to stimulate the heart rate and increase the blood pressure again by cpnstricting the blood vessels

114
Q

what does having a small concious control over our heart rate mean

A

that there are nerves from the concious areas of our brains that can also stimulate or inhibit the SAN

115
Q

reasons to which your heart might beat faster (no exercise)

A

you are nervous, frightened, excited and if anticipating exercise

116
Q

how does the hormonal control of your heart work

A

when you are stressed, the sympathetic nerve stimulates the adrenal medulla to release the hromone adrenaline. it is carried around the body in the blood and binds to receptors in the target organs, including the SAN. Adrenaline stimulates the cardiovascular control centre in the brain, increasing the impulses in the sympathetic neurones which supply the heart. it has a direct effect on the SAN by increasing the frequency of excitation and so heart rate increases

117
Q

Additional responses in the body as a result of exercise (not including hormones, baroreceptors or chemoreceptors)

A

During exercise, impulses from the cardiovascular control centre travel to other effectors as well as the heart. at the same time that the sympathetic system sends many impulses to the heart to speed it up, it send fewer impulses to many blood vessels. this results in the contraction of the smooth muscles lining the vessels. in this way the blood flow is diverted from areas which are temporarily less important, to provide more blood for the heart and the muscles to use.

118
Q

what is tidal volume (VT)

A

the volume of air that enters and leaves the lungs at each natural resting breath

119
Q

what is inspiratory reserve volume (IRV)

A

the volume of air that you can take in above the normal inspired tidal volume.

120
Q

what is expiratory reserve volume (ERV)

A

the volume of air that you can force out above the normal expired tidal volume

121
Q

what is vital capacity (VC)

A

the total of the tidal volume and the inspiratory and expiratory reserves.

122
Q

what is residual volume (RV)

A

the volume of air left in the lungs after the strongest possible expiration

123
Q

what is total lung capacity (TLC)

A

the sum of the vital capacity and the residual volume

124
Q

what is inspiratory capacity (IC)

A

the volume that can be inspired from the end of a normal expiration
IC = VT + IRV

125
Q

how is the ventilation rate measured

A

ventilation rate is a measure of the volume of air breathed in a minute.
ventilation rate (dm 3 min-1) = tidal volume (dm3) x frequency of inpiration (min-1)

126
Q

How does the ventilation rate adjust to your activity levels

A

Both the tidal volume and the frequency of inspiration change to keep thee concentration of gases in your blood as close to the ideal as possible

127
Q

What is the ventilation centre

A

An area of the medulla where the basic stimulus to inhale and exhale come from. It involves a feedback system based on the stretching of the bronchi during breathing

128
Q

How does the inspiratory centre control

A

Breathing in

129
Q

What does the expiratory centre control

A

Forced exhalation

130
Q

Describe relationship between the ventilation centre and breathing
How does it control it

A

Impulses from the ventilation centre travel along sympathetic nerves and cause the intercostal muscles and the diaphragm to contract. This makes us inhale. As lungs inflate, stretch receptors in the walls of the bronchi send nerve impulses to the ventilation centre. The more these receptors are stretched, the more rapidly they send impulses. Eventually, these impulses inhibit the ventilation centre and it stops stimulating the breathing muscles. You stop breathing in and as muscles relax, you exhale.

131
Q

How does the level of carbon dioxide in the blood affect the breathing rate

A

An increase in carbon dioxide concentration and the consequent fall in pH leads to an increase in both the rate and depth of breathing. This is because the diaphragm and the Inter coastal muscles contract harder and more frequently.

132
Q

Describe how breathing rate and levels of co2 change as soon as exercise starts and why

A

As soon as exercise starts, your brain sends impulses to stimulate the ventilation centre in the medulla. This stimulates the respiratory muscles and increases the rate and depth of ventilation. Chemoreceptors sensitive to the level of carbon dioxide and the pH of the blood send impulses back to the main ventilation centre following rises in carbon dioxide levels. Impulses are then sent out to the breathing muscles so the breathing rate changes

133
Q

What are hormones

A

They are organic chemicals produced in endocrine glands and released into the blood. They travel through the transport system to parts of the body where they cause changes, which may be extended or highly targeted. Hormones are usually proteins/peptides or steroids. They are responsible for chemical control in animals

134
Q

How do hormones work generally

A

Once a hormone enters the blood stream, its carried around in the blood until it reaches its target organ or organs. The cells of the target organs have specific receptor molecules on the surface of their membranes that bind to the hormone molecules. This leads to a change in the membrane and produces a response.

135
Q

Differences between exocrine and endocrine glands

A

Both: they both have a rich blood supply, with plenty of capillaries within the glandular tissue itself
Exocrine: consists on groups of cells that release a substance (enzyme) into a duct that carries it to where it is needed
Endocrine: have no duct and release hormone directly into the blood

136
Q

Examples of endocrine glands

A

Pituitary gland
Hypothalamus
thyroid glands
Parathyroid glands
Pancreas
Adrenal glands
Kidneys

137
Q

States the different hormone release systems

A

-control of hormone release by nervous system
-hormones released in response to another hormone in blood
-changes in chemicals in the blood: stimulate the release of hormones, acts to regulate the levels of those chemicals
-hormones released as a response to chemical stimulus

138
Q

Describe the nervous system as a hormone release system

A

If the gland is stimulated, hormone is released. If it is not stimulated, no hormone is released. The level of stimulation determines the level of response

139
Q

Describe hormone release as a response to chemical stimuli as a hormone release system

A

It consists in a negative feedback loop which controls their secretion. The presence of the appropriate chemical in the blood stimulates the release of the hormone. As a result of the rise in the hormone levels, the amount of stimulating chemical in the blood drops. The endocrine gland then receives less stimulation and so the hormone levels drop

140
Q

Function of the hypothalamus

A

To monitors the levels of a number of metabolites and hormones in the blood. It controls the activity of the pituitary gland in response to the concentrations of these chemicals

141
Q

What are neurosecretory cells

A

They are found in the hypothalamus and are nerve cells that produce secretions from the ends of the axons.
There are two types of neurosecretory cell: releasing factors/release-inhibiting factors and what we are going to call neurosecretory cells 2

142
Q

Describe function of neurosecretory cells 2

A

Produce secretions that are stored in the posterior pituitary and are released later as hormones

143
Q

Describe function of neurosecretory cell: releasing factors/releasing-inhibiting factors

A

Produces substances that stimulate or inhibit the release of the hormones from the anterior pituitary

144
Q

Does the anterior of posterior pituitary produces more hormones

A

The anterior pituitary produces six hormones while two from the posterior lobe

145
Q

What is the function of the antidiuretic hormone (ADH)

A

It’s homeostatic role in controlling the concentration of the mammalian blood plasma concentration and blood volume

146
Q

State the two ways in which hormones have their effect when they reach a target cell

A

-the release of a second messenger
-the hormone enters the cell

147
Q

Describe how the release of a second messenger allows a hormone to have its effect on a target cell

A

Peptides and protein hormones are not soluble in lipids and therefore cannot cross the cell membrane. To have an effect, these hormones have to make changes inside the cell. The hormone molecules bind to a receptor in the cell membrane. This begins a series of membrane-bound reactions that result in the formation of a second chemical messenger inside the cell. This then activates different enzymes in the cell, altering the metabolism.

148
Q

What is cyclic AMP

A

It is a second messenger which is formed from ATP. Cyclic AMP binds to other chemicals which pass into the nucleus and act as a DNA transcription factor allowing to switch the genes on and off.

149
Q

Describe how the hormone entering the cell allows a hormone to have its effect on a target cell

A

Steroid hormones such as oestrogen are lipid soluble. They can pass through the membrane. Inside the cell, the hormone binds to a receptor and the hormone-receptor complex passes through the pores of the nuclear membrane into the nucleus. The hormone attached to the receptor acts as a DNA transcription factor, regulating gene expression and switching sections of the DNA on and off

150
Q

What is osmoregulation

A

The maintenance of the osmotic potential in the tissues of a living organism within narrow limits by controlling water and salt concentrations

151
Q

Why does the body need to control the water potential of the blood

A

To protect the cells from osmotic damage

152
Q

What is the role of the liver

A

It allows de Ami nation of excess amino acids in protein metabolism to occur. This is needed because your body cannot store protein or amino acid and therefore the body would have to secrete them if the liver didnt exist.

153
Q

What are hepatocytes and what is their function

A

They are liver cells that delaminate excess amino acids. They remove the amino group and convert it first into ammonia, which is very toxic and then to urea which can be excreted by the kidneys. It is converted to urea by a series of enzyme-controlled reactions known as thee ornithine cycle. The remainder of the amino acid can enter the Krebs cycle or stored as lipids

154
Q

How does osmoregulation occur in mammals

A

It is thanks to the kidneys which are capable of producing urine, which can be hypertonic to body fluids, making it possible to conserve water. The kidneys are surrounded by a thick layer of fat, which helps to protect them from mechanical damage. They control the water potential of blood plasma, remove urea and substances that would affect the water balance.

155
Q

Where is urine stored

A

Urine is stored in the bladder and released from the body at intervals

156
Q

State the two roles of the kidney

A

-Excretion: removal of urea from body
-Osmoregulation

157
Q

State the three main functions of the kidney in its osmoregulatory role

A

-ultrafiltration
-selective reabsorption
-tubular secretion

158
Q

What is the kidney made up of

A

Nephrons. There are two types:
-cortical nephrons: found mainly in the renal cortex, have a loop of Henle that only just reaches into the medulla
-juxtamedullary nephrons: have long loops of Henle that penetrate right through the medulla. They are particularly efficient at producing concentrated urine

159
Q

Why does ultrafiltration occur

A

It is the first stage in the osmoregulation of the blood. It occurs because of aa combination of very high blood pressure in the glomerular capillaries and the structure of the Bowman’s capsule and glomerulus. It is a passive process

160
Q

Why is high blood pressure needed in ultrafiltration

A

The capillaries have high blood because the diameter of the blood vessel coming into the glomerulus is greater than that of the blood vessel leaving. The hbp. Squeezes the blood out through the pores in the capillary wall. The size of pores means that almost all the contents of the plasma can pass out of the capillary and blood cells and largest plasma proteins left behind

161
Q

What does the filtrate that enter the bowman’s capsule contain

A

Glucose, salt, urea and many other substances in the same concentrations as they are in the blood plasma. Most of the filtrate is reabsorbed into the blood later.

162
Q

What occurs in selective reabsorption

A

Glucose is absorbed since it is needed for cellular respiration. Most of the water, salt and other inorganic ions passed into the tubule during ultrafiltration are also needed by the body. The main function of the kidney tubule is to return most of what has been removed during ultrafiltration back into the blood

163
Q

How is the proximal tubule specialised for its function

A

The cells lining this tubule contain microvilli which increases the surface area through which substances are absorbed. The cells have large amounts of mitochondria, showing they take part in an active process

164
Q

How does selective reabsorption occur in the proximal tubule

A

Active transport results in all the glucose, amino acids, vitamins and most hormones being returned to the blood. The sodium ions are actively transported, and the chloride ions and water follow passively down concentration gradients. Once these substances are removed from the tubule cells into the intracellulr spaces, they then pass by diffusion into the extensive capillary network that surrounds the tubules. The movement of blood maintains a concentration gradient for diffusion. The amount of reabsorption in the proximal tubule is always the same

165
Q

What is the main function of the loop of Henle

A

In charge of the adjustment of the water balance to the needs of the body

166
Q

Describe the filtrate at the end of the proximal tubule

A

The filtrate is isotonic with the tissue fluid that surrounds the tubule

167
Q

Where is the loop of Henle found

A

In the medulla of the kidney

168
Q

What makes it possible for water to be reabsorbed from the distal tubule and collecting duct

A

Because the loop of henle and the capillaries create a water potential gradient between the filtrate and the medullary tissue fluid

169
Q

how is the high concentration of sodium and chloride ions in the tissue fluid of the medulla created

A

by the flow of fluid in opposite directions in the adjacent limbs of the loop of Henle.

170
Q

what is a countercurrent multiplier

A

the combination of the flow of fluid in opposite directions in the adjacent limbs of the loop of Henle, different permeabilities to water of different sections and regions of active transport which all uses active transport to establish and maintain concentration gradients

171
Q

what happens in the descending limb of the kidney

A

it is freely permeable to water but it is not very permeable to sodium and chloride ions. no active transport occurs. fluid entering is isotonic with the blood, as fluid travels down the external conc. of sodium and chloride ions becomes higher and higher so water moves out of the descending limb by osmosis down a concentration gradient. By the time the fluid reaches the U-bend at the bottom of the loop it is very concentrated and hypertonic to arterial blood

172
Q

what happens in the first section of the ascending limb

A

very permeable to sodium and chloride ions but not permeable to water. No active transport occurs in this section. Sodium and chloride ions move down concentration gradients out of the very concentrated fluid in the loop of Henle into the tissue fluid of the medulla

173
Q

what happens in the second section of the ascending limb

A

thicker section, impermeable to water but sodium and chloride ions are actively pumped out of the tubule. the tissues of the medulla have a very high sodium and chloride concentration. since it is impermeable to water, water cannot follow the chloride and sodium ions out down the concentration gradient. the fluid left in the aascending limb becomes less concentrated

174
Q

what happens in the distal tubule

A

it is permeable to water but the permeability varies with the levels of antidiuretic hormone (ADH). If there is not enough salt in the body, sodium can be actively pumped out of the tubule with chloride ions down an electrochemical gradient. Water leaves by diffusion if walls are permeable at that time

175
Q

what happens in the collecting duct

A

it is strongly affected by ADH. Water moves out down a water potential gradient as it passes through the medulla. As water leaves the collecting duct, the urine becomes steadily more concentrated. Concentration of sodium ions in the surrounding fluid increases through the medulla towards the pelvis of the kidney, so water can be removed along the whole length of the collecting duct

176
Q

what is urine

A

the fluid that the kidney tubules produce. it is collected in the central chamber of each kidney. It then passes along the ureters to the bladder and is stored there until the bladder is sufficiently stretched to stimulate urination. it passes out of the body through the urethra

177
Q

how is the osmotic potential of the blood maintained

A

within a narrow range by balancing the water and salts taken in by eating and drinking with the water and salts lost by sweating, defaecation and in the urine. The amount of water lost in urine is controlled by a negative feedback system involving antidiuretic hormone (ADH)

178
Q

how does ADH affect the kidney

A

ADH increases the permeability to water of the distal tubule and the collecting duct

179
Q

Mechanism of ADH Action

A

ADH cannot cross the membrane of the tubule cells. It binds to specific receptors, which triggers reactions that result in the formation of cAMP as the second messenger. The cAMP starts a series of reactions that cause vesicles within the cells lining the tubules to move to and fuse with the cell membrane. The vesicles contain water channels which are inserted into the membrane and make it permeable to water. Water then moves out of the tubules and into the surrounding blood capillaries by osmosis

180
Q

Why does the mechanism of ADH Action provide a close control to match water demands

A

because the amount of ADH released controls the number of channels that are inserted so permeability can be very closely controlled

181
Q

what does the negative feedback of ADH prevent

A

when water potential becomes too negative due to a large amount of inorganic ions in blood, the osmotic balance of the tissue fluids would become disturbed, causing cell damage

182
Q

how does the negative feedback system of ADH work with reference to inorganic ions

A

osmoreceptors in the hypothalamus detect an incresing plasma concentration of inorganic ions. They send nerve impulses to the posterior pituitary, releasing stored ADH. The ADH is accepted by receptors in the cells of the kidney tubules. ADH increases the permeability so water leaves the tubules by osmosis into the surrounding capillary network. So blood plasma receives more water from the filtrate, small volume of urine produced.

183
Q

how can baroreceptors assist osmoregulation

A

Changes in blood pressure can stimulate or inhibit the release of ADH. These changes are detected by the baroreceptors in the aortic and carotid arteries. A rise in blood pressure will suppress the release of ADH and so increase the volume of water lost in the urine so blood pressure falls as blood volume falls.

184
Q

why can small animals regulate their temperature easier than large animals

A

because small animals have a large surface area- o-volume ratio so they transfer energy more rapidly

185
Q

ways in which organisms warm up

A

-as a by-product of metabolism. Chemical inefficiency means energy is wasted, which warms the centre of the organism
-energy might be transferred from the environment by radiation. Infrared radiation is the most common form of energy absorbed or radiated by animals
-energy transferred from the environment by convection. Convection currents are set up around hot objects so adaptations to prevent cooling by these currents are common in animals
-energy transferred from the environment by conduction. Air and fatty tissue do not conduct well so they are valuable insulators, preventing energy exchanges with the environment

186
Q

ways in which organisms cool down

A

-by evaporation of water from the body surfaces. Sweating and wallowing can increase this cooling.
-energy might be transferred to the environment by radiation.
-energy transferred to the environment by convection.
-energy transferred to the environment by conduction.

187
Q

what are endotherms

A

organism that relies on its own metabolic processes to provide at least some warming and has a body temperature higher than the ambient temperature. Their metabolic rate has to be high, so have to eat a lot of food to supply their metabolic needs, they need adaptations to thermoregulate.

188
Q

what is the main source of warming in humans

A

our metabolism

189
Q

how does the skin allow cooling

A

it has a rich supply of capillaries near to the surface of the skin. Cooling by radiation, conduction and convection to environment from blood flowing through the skin. This is controlled by the arteriovenous shunt which in high temps closes so vasodilation occurs. Allowing more blood to flow through the capillaries at the surface of the skin. The erector pili muscles are relaxed, rate of sweat production in the sweat glands increases with inses in core temperature. -Subcutaneous fat acts as insulation reducing cooling

190
Q

how does the skin allow warming

A

the arteriovenous shunt in blood supply to the skin opens, reducing blood flow through capillaries- vasoconstriction, reduces energy lost from the surface of the skin.
People sweat less, cooling by evaporation reduced, erector pili muscles contracted pulling hairs upright. Metabolic rate speeds up, warming the body, shivering occurs which with the energy released raises the body temp. Animals living in cold areas develop thick layers of subcutaneous fat

191
Q

what receptors control the core temperature

A

there are two types, located in the brain which directly monitor the temperature of the blood and receptors in the skin which detect changes in the external temperature. The receptors in the brain are in the hypothalamus and act as a thermostat to keep it at the right temperature

192
Q

what happens when the temperature of the blood flowing through the hypothalamus increases

A

the thermoregulatory centre is activated which sends out impulses along autonomic motor nerves to effectors that increase the blood flow through the skin and increase sweating. The erector pili muslces are relaxed and shivering stops. Metabolic rate is reduced to lower the amount of warming in the body

193
Q

what happens when the temperature of the blood flowing through the hypothalamus drops

A

thermoregulatory centre sends impulses through the autonomic nervous system to the skin causing a reduction in the blood flowing through the capillaries in the skin, as well as a reduction in production of sweat and contraction of erector pili muscles. the impulses also stimulate involuntary contractions of muscles and raise metabolic warming

Biology A-Level IAL Edexcel (4 decks)

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