biology topic 7

joints

structures where bones and muscles connect to allow movement

tendons

• join muscles to bone

• white fibrous tissue

• made of bundles of collagen fibres

• strong but inelastic

ligaments

• hold bones to bones in correct alignment while allowing movement

• yellow elastic tissue

• high elasticity

cartilage

• tissue at ends of bones

• hard flexible tissue

• can be compressed

• good shock absorber

• protects bones from eroding

how is movement brought about?

antagonistic pairs of muscles that work in opposite directions - flexor and extensor muscles

synovial joints

most common type of joint - have synovial fluid and a surrounding synovial capsule e.g. hip, knee and ankle

fibrous joints

bones connected by fibrous connective tissue - fixed, non-moving e.g. in skull

cartilaginous joints

bones connected by cartilage - have more movement than fibrous joints but less than synovial e.g. between vertebrae

smooth muscle

• non-striated, spindle shaped, uninuclear fibres

• in walls of internal organs

• involuntary

cardiac muscle

• striated, branched, uninuclear fibres

• walls of heart

• involuntary

skeletal muscle

• straited, tubular, multinuclear fibres

• attached to skeleton

• voluntary

myocyte

muscle cell

muscle cells

• multinucleate

• large

• cytoplasm mainly made up of myofibrils

myofibrils

bundles of myofilaments

myofilaments

long repeated chains of contractile units called sarcomeres - made of actin and myosin filaments

actin

thin filament - many monomers with myosin binding sites - covered by tropomyosin and troponin

myosin

think filament - 2 globular heads with ATP and actin binding sites with a tail

sliding filament theory

the actin filaments move between myosin filaments, shortening the length of the sarcomere

relaxed state of actin

in absence of Ca2+ tropomyosin blocks myosin binding site on actin filament

muscle contraction process

• nerve impulse causes Ca2+ release from sarcoplasmic reticulum

• Ca2+ binds to troponin which pulls tropomyosin away from myosin binding site

• myosin head attaches to actin forming a crossbridge

• powerstroke initiated - myosin head pivots and bends, pulling the actin

• ADP is released - myosin remains attached to actin

• ATP binds to myosin head - crossbridge detaches

• myosin ATPase hydrolyses ATP so myosin is ready to bind again

types of muscle fibres

fast twitch and slow twitch

twitch

a single muscle contraction that occurs in response to a single nerve impulse - all or nothing

summation

if a second nerve impulse occurs before relaxation is complete, the contraction of other muscle fibres is added, increasing overall contraction strength

slow twitch muscle fibres

• slow, sustained, can remain contracted for long time

• maintaining posture and steady movement

• mostly aerobic respiration

• precise control is possible

• rich blood supply and high myoglobin content

fast twitch muscle fibres

• fast contraction speed

• sudden and quick movement

• mostly anaerobic respiration

• low blood supply and little to no myoglobin

• no precise control

myoglobin

• present in muscle cells

• similar to haemoglobin - acts as an O2 store

• has a higher affinity for O2 - will attract away from haemoglobin

how can you change your muscle fibre composition?

• exercise - can alter the type and size of fibres

• genetics - some people born with higher proportion of slow/fast twitch muscle fibres - better at some sports

phosphorylation

adding a phosphate to a molecule

redox reactions

reactions that involve both oxidation and reduction

hydrolysis

splitting a molecule using water

metabolic pathway

a series of small reactions

active transport

process that requires ATP

respiration

process that creates ATP

eukaryotic

have a true nucleus

catabolic reactions

breaking larger molecules into smaller ones

cristae

folds in mitochondria

photolysis

splitting a molecule using light

anabolic reaction

combining smaller molecules to make bigger ones

why do we need respiration?

• muscle contraction

• active transport

• anabolism (making macromolecules)

• warmth

steps of respiration

1. glycolysis

2. link reaction

3. Krebs cycle

4. electron transport chain

substrate level phosphorylation

production of ATP by transfer of P from a phosphorylated substrate

glycolysis

splitting glucose - in cytoplasm

steps of glycolysis

• glucose —> 2x GALP using 2x ATP

• 2x GALP —> 2x pyruvate

• second part produces 4x ATP and 2x NADH

equation for glycolysis

glucose + 2 ADP + 2 P + 2 NAD+ —> 2 pyruvate + 2 ATP + 2 NADH

equation for aerobic respiration

C6H12O6 + 6O2 —> 6CO2 + 6H2O

equation for anaerobic respiration

C6H12O6 —> 2 C3H6O3

link reaction

in matrix of mitochondria

steps of link reaction

• pyruvate has CO2 removes

• NAD+ —> NADH

• pyruvate has CoA added to form acetyl CoA

equation for link reaction

2 pyruvate + 2 NAD+ —> 2 acetyl CoA + 2 NADH + 2 CO2

Krebs cycle

• in matrix of mitochondria

• also called citric acid cycle

Krebs cycle process

Krebs cycle equation

2 acetyl CoA + 6 AND+ + 2 ADP + 2 P + 2 FAD —> 4 CO2 + 6 NADH + 2 ATP + 2 FADH2

NADH

• coenzyme

• functions as a reducing agent carrying hydrogen

• reduced form - NADH

FAD

• coenzyme

• functions as a reducing agent carrying hydrogen

• reduced form - FADH2

electron transport chain

• electron transport and chemiosmosis

• on inner membrane of mitochondria

electron transport in ETC

• respiratory enzyme complexes transport electrons (in a series of redox reactions) and pump H+ out of the matrix

• the final electron acceptor in O2 leading to the production of H2O

chemiosmosis and oxidative phosphorylation in ETC

the resulting electrochemical H+ gradient is used by ATP synthase to make ATP

electron transport chain diagram

chemiosmosis

movement of H+ across a selectively permeable membrane during respiration down their electrochemical gradient

oxidative phosphorylation

production of ATP in a process where energy is released in the ETC, the energy is used to establish the H+ gradient which power ATP synthase

ETC equation

10 NADH + 10 H+ + 2 FADH2 + 34 ADP + 34 P + 6 O2 —> 10 NAD+ + 2 FAD + 34 ATP + 6 H2O

why is the maximum yield of ATP not achieved?

• leaky membranes

• energy cost for transporting pyruvate and ADP into mitochondria

what factors affect the rate of respiration?

• pH

• temperature

• enzyme concentration

• substrate concentration

what are the advantages of respiration being enzyme controlled?

• controlled release of energy

• prevents cell form overheating

respirometer

used to measure the rate of respiration by measuring the rate of oxygen consumption

equation of anaerobic respiration

C6H12O6 —> 2 lactate(lactic acid) + 2ATP

stage 1 of anaerobic respiration

glycolysis to form 2 pyruvate

stage 2 of anaerobic respiration

lactic fermentation - pyruvate is reduced to lactic acid by oxidising NADH + H+ , happens in cytoplasm

what are the downsides of anaerobic respiration?

• low energy yield

• build up of lactic acid

what is the problem with lactic acid?

low pH - affects enzym activity

how do cells get rid of lactic acid?

resynthesized to pyruvate, then transported through Krebs cycle etc.

Excessive post-exercise oxygen consumption (EPOC)

oxygen uptake greater than normal in recovery period after exercise to break down lactic acid - oxygen debt

what is oxygen needed for in oxygen debt?

• breakdown of lactic acid via Krebs cycle

• transport of lactic acid to liver to resynthesise glucose

• reoxygenation of myoglobin

• increased metabolism

• energy to allow increased breathing and heart rate

gluconeogenesis

synthesis of glucose

where does energy come from at the beginning of exercise?

as ATP is used, it is immediately regenerated from phosphocreatine stored in muscles which give Pi to ADP

how long does the PC store last?

can generate ATP for about 6-10 seconds

how are PC levels restored?

creatine gets Pi from ATP when we are at rest

what are the three energy systems?

1. aerobic respiration

2. anaerobic respiration

3. ATP-PC

what does the ability to do prolonged strenuous exercise depend on?

• genetics

• gender

• fitness

• ratio of fast to slow twitch muscle fibres

aerobic capacity

ability to consume oxygen

factors that affect aerobic capacity

• breathing efficiency

• cardiac output

• efficiency of oxygen use in muscles

VO2

aerobic capacity - volume O2 consumption per minute

VO2 max

maximal aerobic capacity during intense exercise

effect of training on aerobic capacity

• increased vital capacity

• increased capillarisation of lungs

• increased stroke volume of heart

• increased cardiac output

• increased red blood cell production

• increased capillarisation of muscles

• lower fat : muscle ratio

• increased number and size of mitochondria

cardiac output

the volume of blood pumped by the heart in one minute

equation for cardiac output

cardiac output = stroke volume x heart rate

why does cardiac output increase during exercise?

to deliver oxygen to muscles and remove carbon dioxide at a higher rate

stroke volume

volume of blood pumped out of the left ventricle per contraction

why does stroke volume increase during exercise?

greater force of contraction and larger venous return

venous return

the volume of blood returning to heart in vena cava

heart rate

the number of left ventricle contraction per minute

ECG

graphic record of electrical activity during the cardiac cycle

control of heart rate

• cardiovascular control centre in medulla receives impulses

• impulses form CO2 chemoreceptors and baroreceptors in vena cava, aorta and carotid artery

• sends impulses down sympathetic(accelerator) or parasympathetic(decelerator) nerves

tidal volume

volume of air breathed in and out at each breath at rest

vital capacity

maximum volume of air that can be breathed in and out

inspiratory reserve volume

maximum volume of air that can be inhaled beyond tidal

expiratory reserve volume

maximum volume of air that can be exhaled beyond tidal

reserve volume

volume of air remaining in lungs after maximal exhalation

total lung capacity

volume of lungs at maximal inhalation

minute ventilation

volume of air taken into lungs in one minute