Topic 7 Flashcards
1
Q
Where does movement (caused by muscles) occur?
A
At joints
2
Q
How many muscles are needed to move a bone and why?
A
At least 2
Muscles can only pull so need to work in pairs (or more)
3
Q
What are antagonistic muscles?
A
Pairs of muscles that work together to move a bone
4
Q
How does the knee move?
A
When bent, the hamstrings at the back contracts.
At the same time, the quadriceps relax so they can be stretched.
When straightened, the quads contract whilst the hamstrings relax so can be stretched
5
Q
What is an extensor?
A
A muscle that contracts to cause the extension of a joint
(e.g. quadriceps)
6
Q
What is a flexor?
A
A muscle that contracts to reverse joint movement/the action of an extensor
‘Pulls’ e.g. the hamstrings
7
Q
What are synovial joints?
Give examples
A
Joints in which the bones that move (articulate) are seperated by a cavity filled with synovial fluid
This enables them to move freely
E.g. hips, knee, ankle joint
They all have the same basic structure…
8
Q
Draw and label the structure of a synovial joint
A
See image
9
Q
What is the function of tendons?
A
Attach bones to muscles
This enables joint movement
10
Q
What property do tendons have and how does this relate to their function?
A
Non-elastic so when uscle contracts bones moves
Otherwise tendon would just stretch and bone wouldn’t be moved!
11
Q
What is the function of ligaments?
A
Connect bones to bones
12
Q
How does the structure of a ligament relate to its function?
A
Have a small amount of elasticity, allows them to gradually lengthen, increasing flexibility
Are strong + flexible
13
Q
Describe the structure of cartilage and how this relates to its function
A
Absorbs synovial fluid + acts as shock-absorber
Strong but not as tough/brittle as bone
Smooth, prevents bones rubbing
14
Q
What is the function of the synovial fluid in synovial joints?
A
Acts as a shock absorber
Is thick + viscous, enabling it to act as a lubricant
15
Q
Why do the ends of bones in joints sometimes have pads of cartilage on them?
A
To give additional protection - acts as a shock-absorber + prevents rubbing
16
Q
What is the function of the synovial membrane in joints?
A
Secretes synovial fluid
17
Q
What is the function of the fibrous capsule in joints?
A
Encloses joints
(Stops the synovial fluid leaking out…)
18
Q
What are all the types of joints found in humans?
A
Synovial joints
Ball-and-socket joints
Gliding joints
Hinge joints
Pivot joints
19
Q
Describe the structure of ball-and-socket joints and what type of movement they enable
Give an example
A
A round head fits into a cup-shaped socket
Allows movement in many directions
e.g. the hip
20
Q
Describe the structure of gliding joints and what type of movement they enable
Give an example
A
Two flat surfaces slide over one another
Allows movement in 1 plane but many combined allows many planes of movement
e.g. the articulating surfaces between vertibrae
21
Q
Describe the structure of hinge joints and what type of movement they enable
Give an example
A
A convex surface fits into a concave surface
Allows movement in 2 directions
e.g. the elbow
22
Q
Describe the structure of pivot joints and what type of movement they enable
Give an example
A
Part of one bone fits into a ring-shaped structure in
Allows movement in 2 planes/rotation
e.g. joint at the top of the spine (shake/nod head)
23
Q
Describe the structure of a muscle
A
Muscle made up of bundles of muscle fibres up to 2cm across. These are bound together with connective tissue that is continuous with tendons
Each fibre is a single muscle cell surrounded by a cell membrane
Within each fibre there are numerous myofibrils, each composed of repreated contractile units called sarcomeres
24
Q
Why are muscle fibres multinucleate?
What does this mean?
A
Each fibre/cell contains multiple nuclei
Because 1 nucleus couldn’t effectively control metabolism of such a long cell (can be up to 2cm long)
It would take too long to move proteins synthesised from mRNA to further parts of cell
25
Why are muscles described as striated?
What does this mean?
Means **striped**
Because the sarcomeres in the myofibrils are made up of **actin** + **myosin**
Where they **overlap** there is a **dark** band
Where **only actin** filaments occur there is a **light** band
26
(Briefly) describe how a muscle contracts
Within the sarcomere, the **actin filaments** move towards the **centre** of the sarcomere so they **overlap** with the **myosin** more.
This **shortens the sarcomere** and hence the muscle (so it contracts)
27
What is the sarcoplasmic reticulum?
Specialised type of **endoplasmic reticulum**
System of membrane-bound sacs around the **myofibrils** containing store of **Ca2+** needed for muscle contraction
Ca2+ only **released** when SR recieves **nerve impulse** via **neuromuscular junction**
28
What is the sarcoplasm?
The name given to the cytoplasm in a muscle cell (fibre)
29
Describe the process of muscle contraction using the sliding filament theorem
* A **nerve impulse** arrives at the **neuromuscluar junction** in the muscle fibre. This triggers the **release of Ca2+** from the **sarcoplasmic reticulum**
* The **Ca2+** ions then diffuse through the **sarcoplasm** and attach to **troponin** molecules, causing then to **move**
* This **exposes** the **myosin binding sites** on the **actin filaments**
* The **myosin**'heads' **bind** with the binding sites on the **actin**, forming **cross-bridges**
* The **myosin changes shape**, causing the myosin 'head' to 'nod' forward. This results in the **movement of the filaments** as the attached actin moves over the myosin
* An **ATP** molecule **binds** to the **myosin**, causing it to **detach** from the **actin**
* An **ATPase** on the **myosin hydrolyses ATP** to **ADP + Pi** causing the myosin 'head' to return to the **upright** position, thus allowing the cycle to begin again
* The **collective bending** of many **myosin** heads **moves** the **actin filament** in relation to the myosin filament, thus the **muscle contracts**
30
What causes a muscle to relax and what happens when it does?
A muscle relaxes when it is **no longer stimulated by nerve impulses**
**Ca2+** ions are actively **pumped out of sarcoplasm** using **ATP**
The **troponin + tropomyosin move** back, **blocking myosin-binding sites** on actin again
31
What happens when there is a lack of both nerve stimulation and ATP in a muscle fibre?
The muscle stops contracting/relaxes
The lack of ATP means actin-myosin **cross-bridges remain**, hence the muscle remains contracted/unmoves
This is what happens in **rigor mortis**
32
What are T tubulues?
What does the T stand for?
**Transverse** tubules
Used to **transport**/bathe muscle in **Ca2+ **
This results in the spread the nervous impulse throughout the muscle fibre + allows the muscle to contract
33
What is BMR?
Basal metabolic rate
The minimum energy requirement of the body at rest to fuel basic metabolic processes
Measured in **kJg-1h-1**
34
How is BMR measured?
By **recording oxygen consumption** under strict conditions:
**No food** consumed 12hrs before
Body is **totally at rest** in a **thermostatically** controlled room
35
What factors affect BMR?
It's roughly **proportional to the body's surface area**
Varies depending on **age** + **gender**
**Body fat** seems to be important in accounting for these differences
36
What must happen to phosphate ions before they can be combines with ADP to make ATP?
They must be **dehydrated** - must be seperated from the water molecules bound to them when they are in solution
This requires energy
37
How can ATP stored in water be used as a way of storing chemical potential energy in the body?
**ATP in water** is **higher in energy** than **ADP + Pi in water**
**ATP** keeps the **Pi seperated from water**, however when one is removed by **hydrolysis**, the **Pi is hydrated**, releasing a lot of **energy**
This is because the energy released by the **bonds formed** between **H2O + Pi** is **greater** than the small amound needed to **hydrolyse** the **Pi**
**ADP** is also formed as a result of the hydrolysis of ATP
38
What is the overall equation for the hydrolysis of ATP?
ATP in water → ADP in water + hydrated Pi + energy transfered
39
Why are glucose and oxygen not brought together directly during respiration?
Because this **would release large amounts of energy quickly** which would **damage** **the cell**
Releasing the energy quickly would mean some would be wasted/unused
40
How is the energy used to generate ATP produced?
What is the main/principle reaction underpinning aerobic respiration?
The **H stored in glucose** is brought together with **oxgen** to form **water**
The **bonds** between **O + H** in **water** are **stronger** than those between **C + H** in **glucose**
Therefore the **output of energy is greater** than the input needed to break bonds
41
What happens to glucose during aerobic respiration?
What controls this?
What is released as a waste product?
**Glucose is split apart** (oxidised) in a series of smaller steps
Each of these is controlled by a **specific intracellular enzyme**
**CO2** is released as a waste product
42
What is the first step of respiration (aerobic and anaerobic)?
Glycolysis
43
What is glycolysis?
What does it literally mean?
The 'splitting of sugar'
The 1st stage of respiration - glucose is broken down into pyruvate
44
What must happen before glycolysis can take place?
Stores of **glycogen** in **muscle/liver cells** must be converted into **glucose**
To do this they are **hydrolysed**
45
Where does glycolysis occur?
In the **cytoplasm**/**sarcoplasm** of the cell
46
What type of molecule is coenzyme NAD?
What does NAD stand for?
A non-protein organic molecule (and coenzyme!)
## Footnote
**Nicotinamide adenine dinucleotide**
47
Describe the process of glycolysis
1. **2 Pi** groups are **added to glucose** from 2ATP to **increase its reactivity**
2. It's then split into **2** molecules of **phosphorylated 3C compounds**
3. Each intermediate **3C compound oxidised**, producing **3C pyruvate**
During this reaction **2H atoms removed** + taken up by coenzyme **NAD** to form **NADH**
4. **Glucose** is at a **higher energy** level than pyruvate so **energy is released**
5. This is used to **transfer Pi** from the **intermediate phosphorylated compounds** to ADP to form **2ATP**
48
What are the overall products of glycolysis?
**2ATP**
**2 pairs of H** atoms (4H total)
**2 pyruvate** (3C)
49
What does the fate of pyruvate depend upon?
The availability of oxygen
50
What happens to pyruvate if oxygen is present?
What happens if it is not?
If oxygen present undergoes the **link reaction** to form **acetyl coenzyme A** which is used in **Krebs cycle**
If not it is converted into **lactate** by the addition of 2H from NADH
51
Describe the steps of the link reaction
Pyruvate is:
**decarboxylated** - **CO2** released as waste product
**dehydrogenated** - **2H** taken up by 2x coenzyme **NAD**
**Acetyl coenzyme A** is formed as a result
This carries the **2C acetyl groups** to Krebs cycle
52
What are the four important types of reaction that occur in Krebs cycle?
**Phosphorylation** - when **Pi added** e.g. ADP + Pi → ATP
**Deecarboxylation** - which **break off CO2** e.g. pyruvate → acetyl CoA + CO2
**Reduction** - **H added** e.g. oxidied NAD + 2H → NADH
**Oxidation** - **dehydration**/H removed e.g. pyruvate → acteyl CoA + 2H
53
Describe the stages of Krebs cycle
1. Each 2C **acetyl CoA** combines with a **4C** compound to create a **6C** compound
2. The 6C compound is **decarboxylated** to **remove a CO2** and produce a **5C** compound.
It is also **oxidised**, **removing 2H**. These **reduce NAD**
3. The **5C** compound is then **decaroxylated** to a **4C** compound, allowing the cycle to start again
It is also **oxidised** 3x to **removes 3x 2H**. These **reduce 2x NAD** and **1x FAD**
**Substarate-level phosphorylation** also occurs, producing **1 ATP**
54
Where does Krebs cycle take place?
What is also located here/Why does it occur here?
In the mitochondrial matrix
The enzymes that catalyse each stage of the reaction are also located here
55
What are the overall products of Krebs cycle?
4x 2H which are used to produce:
* *1x FADH** (reduced FAD)
* *3x NADH** (reduced NAD)
**2x CO2**
**1x ATP**
56
What is substrate-level phosphorylation?
The formation of **ATP** using **energy** from the **substrates** in a reaction (e.g. the intermediates in glycolysis)
57
When does substrate-level phosphorylation occur?
Duing glycolysis
During Krebs cycle
58
What is FAD and what does it stand for?
A coenzyme (like NAD)
## Footnote
**Flavin adenine dinucleotide**
59
Describe the stages of the electron transport chain
1. **Reduced coenzyme** (NADH/FADH) **carries 2x H+ and e-** to the electron transport chain on inner mitochondrial membrane
2. **e-** pass from **one electron carrier to the next** in a series of **redox** reactions - the carrier is reduced when it recieves e- and oxidised when it passes them on
3. **Protons** (H+) **move across the inner mitochondrial membrane** creating a **high H+ conc in the intermembrane space**
4. **H+ diffuse** back into the **matrix** down an **electrochemical gradient**
5. **H+ diffusion** allows **ATP synthase** to catalyse ATP synthesis
6. **e- and H+ recombine** to form H atoms when then combine with O to make **H2O.** If the **supply of O stops**, the **e- transport chain + ATP synthesis stop**
60
What is the name of the reaction that produces ATP in the electron transport chain?
**Oxidative** phosphorylation
*(as opposed to substrate-level phosphorylation during glycolysis + Krebs cycle)*
61
What is a conformational change?
A change in the shape on an enzyme's active site
Can enable the enzyme to catalyse a reaction, for example
e.g. H+ ions cause conformational change in ATP synthase, enabling ADP + Pi to bind
62
Describe how ATP is produced by chemiosmosis
What is the theory of chemiosmosis?
*The theory that explains why the e- transport chain works*
* **Energy released as e- pass along chain**. This is used to **move H+** from matrix across inner mitochondrial membrane into intermembrane space
* This creates an **electrochemical gradient across inner membrane** as there is a large difference in H+ conc + large electrical difference - **intermembrane space more positive than matrix**
* The **H+** then **diffuse down** this gradient back through **hollow protein channels** with **ATP synthase embedded** in. As they do so, they cause a **conformational change** in ATP synthase
* This results in the **synthesis of ATP** being catylsed
* The **H+** then enter the **matrix**, where they **recombine** with e- to form **H**. These combine with O to make **water**
63
Draw a diagram to summarise all the steps of aerobic respiraton
64
How many ATP molecules are produced throught the entire process of aerobic respiration according to *simple calculations*?
Where do they come from?
**38 total**
**2** from substrate-level phosphorylation during **glycolysis**
**2** from substrate-level phosphorylation during **Krebs Cycle**
**34** from oxidative-phosphorylation during the **electron transport chain**
(2 from reoxidation of each FAD = 2x2 = 4)
(3 from reoxidation of each NAD = 10x3 = 30)
65
Why is the theoretical/simple calculation for the total amount of ATP produced during aerobic respiration probably wrong?
What is the total more likely to be?
Total more likely to be **30 ATP from 1 glucose**
Because some **H+** used to exchange ADP + ATP between matrix + cytoplasm and **across the mitochondrial membrane**
Some H+ also used to move **other ions/molecules** across the membrane
66
How much of the total chemical potential energy from glucose is released via ATP?
What happens to the remainder of the energy/what is it used to do?
Assuming 38 molecules of ATP made, only 40% total chem. potential of glucose released
Assuming **30** molecules of ATP made, only **32%** chem. potential of glucose released!
Remainder **raises temp of cell**. This **increases rate of metabolic reacts** + in birds & mammals **maintains core body temp**.
67
What happens when the demand for oxygen in the cell outstrips supply? Why?
The **electron transport chain stops**
Because there is **no O to accept H+ + e-**
This means the **NADH** formed during glycolysis, the link reaction, + Krebs Cycle **aren't reoxidised**
**Without** a supply of (oxidised) **NAD** **ANY respiration reactions can't continue**
So body switches to **anaerobic** respiration...
68
Describe the process of anaerobic respiration
1. **Glycolysis** occurs as normal - glucose decarboxylated to pyruvate.
Substrate-level phosphorylation occurs producing **2ATP**
Dehydration occurs producing **2x 2H**
2. The **2x 2H reduce 2NAD**
3. **Pyruvate** is **reduced** to **lactate** using the **2x 2H** from the **2NADH**
4. This **regenerates** the (oxidised) **NAD**
69
What is the net yield of ATP from anaerobic respiration?
What is is effeciency?
Only **2 ATP** per molecule of glucose!
**2%** efficiency!
70
If lactate wasn't a limiting factor (or the amount of glucose etc.) why would anaerobic respiration be able to carry on indefinitely?
Because **NAD is regenerated** from reduced NAD by the oxidation of pyruvate to lactate
71
Explain why anaerobic respiration cannot continue indefinitely unlike aerboic respiration
Because **lactate** is produced
Lactate forms **lactic acid in solution**
As lactate accumulates, so does lactic acid, so the **pH of the cell falls**
This **inhibits the enzymes that catalyse the glycolysis** reactions
Therefore the glycolysis reactions and the physical activity depending on them cannot continue
72
Explain why the build of of H+ ions in the cytoplasm causes enzymes/proteins to denature.
(Why do enzymes function over a narrow pH range?)
Where might the H+ ions come from?
*H+ ions may be donated by lactic acid*
Many of the **amino acids** that make up enzymes have **positively/negatively charged groups**
As **H+** ions build up in the **cytoplasm**, they **neutralise** any **negatively charged** groups in the **active site**
This affects the **attraction** between the **charged groups on the substrate** and the **active site**
Therefore the substrate may **no longer be able to bind** to the active site and the reaction will be **inhibited**/stopped
73
What happens after a period of anaerobic respiration/exercise?
*(How does the body get rid of lactate?)*
The accumulated lactate is converted back into **pyruvate**
This is then **oxidised directly to CO2 and H2O** via **Krebs Cycle**
Energy is released to **synthesis** **ATP**
This **requires oxygen**, hence O consumption higher after exercise (**oxygen debt**)
Some **lactate** may also be converted back into **glycogen** + stored in the **liver/muscles**
74
Give the alternate name for oxygen debt
Post-exercise oxygen consumption
75
What is oxygen debt?
The excess oxygen required after exercise to oxidise lactate
76
Outline an experiment that could be used to investigate the rate of respiration
1. Put some **KOH** solution/sode lime in the bottom of a test tube. This will **absorb the CO2** produced by the organism
2. Place some gauze above the KOH and place several maggots/**organism** of choice onto it
3. Place a **bung** in the end of the test tube with 2 holes - 1 to **allow oxygen in** and one connected to a **manometer tube**/glass tube with a drop of coloured liquid in
4. If using a manometer tube (in pic), attach this to a **2nd test tube** with a double-bung. In the other hole attach a **syringe**. This **compensates** for any **changes in volume due** to **variation in gas pressure/temp** inside apparatus
5. **Record** the **starting position of the fluid**, then set a timer for **5 mins**. Record the **position of the fluid every min**.
6. Calculate the **vol O2 used** using vol=**πr2 x dist. moved** where **r= radius of tube attached** to manometer
