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