OCR Biology AS F211 May 2012

Original post by Axion

but what is in composed of?

cell growth, organelle replication, checking and copying of genetic material

Ermm protein :tongue:

, tell me please :smile:

. And that is correct what about my first question "Why is imporant that during mitosis, the length of time the the chromosomes are supercoiled is as short as possible?"

Reply 201

AishaTara

14

omg tomorrow :O :O where has this year gone? :'(

Reply 202

itsmehello

Original post by ohmyBEAUT

I'll do the expiration one, if you two don't mind? :smile:

Diaphragm relaxes and is pushed up by the digestive organs.
The intercostal muscles relax and the ribs fall.
Volume of chest cavity decreases.
Pressure in lungs is below atmospheric pressure, hence the air moves into the lungs.

This is about expiration!! So pressure raises above atmospheric pressure so air moves out of the lungs :redface:

Reply 203

ohmyBEAUT

Original post by itsmehello

This is about expiration!! So pressure raises above atmospheric pressure so air moves out of the lungs :redface:

Woops, my bad. This is what happens when you don't proof-read things. :colondollar:

Reply 204

itsmehello

State two ways meiosis differs from mitosis? (2)

Explain the Bohr effect? (4) Explain fully why it happens.

Why do Cl- move into red blood cells? (1)

2 pieces of evidence that show ATP is used in translocation? (2)

Reply 205

The Illuminati

4

Ribosomes are composed of a small subunit and a large subunit. Each subunit is made up of ribosomal proteins and rRNA.

Reply 206

itsmehello

Original post by sumsum123

"Why is imporant that during mitosis, the length of time the the chromosomes are supercoiled is as short as possible?"

Sorry if this question was for someone else :redface:

They cannot carry out their normal functions whilst they are supercoiled?

Reply 207

Comeheretellme

A bit late but this might help: http://www.youtube.com/playlist?list=PL320F5E8B42B5B71C&feature=playlist-comment

Reply 208

Little_Cat

Original post by itsmehello

State two ways meiosis differs from mitosis? (2)

Explain the Bohr effect? (4) Explain fully why it happens.

Why do Cl- move into red blood cells? (1)

2 pieces of evidence that show ATP is used in translocation? (2)

1) daughter cells are haploid and are not identical to the parent cell

2) Respiring tissue has a high concentration of carbon dioxide and a low concentration on oxygen. The higher the concentration of carbon dioxide present the more oxygen molecules dissassociate with oxygen. so the Respiring tissue has more O2 for aerobic respiration

3) chloride shift occurs to prevent a charge imbalance occurring when hydrogen carbonate ions leave the haemoglobin

4) the companion cell has many mitochondria and translocation can be stopped by using a metabolic poison that inhibits the formation of ATP.

I hope I'm right I've been revising for AGES!!! I really need a decent grade in this paper.

Reply 209

Joey952

12

Original post by itsmehello

State two ways meiosis differs from mitosis? (2)

Explain the Bohr effect? (4) Explain fully why it happens.

Why do Cl- move into red blood cells? (1)

2 pieces of evidence that show ATP is used in translocation? (2)

(1) Cells are genetically different in meiosis and 4 cells are produced in meiosis whereas in mitosis only 2 cells are produced.

(2) CO2 reacts with H20 to form carbonic acid H2C03.
H2CO3 splits up to give H+ ions and HC03-
H+ ions have grater affinity to haemoglobin causing oxygen to leave haemoglobin. so when there is more CO2 the dissociation curve shifts to the right because oxygen relased released.
(3) Cl ions move in to maintain the shape of the cell.

(4) The experimental model for mass flow
if you remove bark, and bulge in formed

Reply 210

Unsworth

14

Original post by itsmehello

State two ways meiosis differs from mitosis? (2)

Explain the Bohr effect? (4) Explain fully why it happens.

Why do Cl- move into red blood cells? (1)

2 pieces of evidence that show ATP is used in translocation? (2)

1. - Meiosis produces genetically different different cells, whereas mitosis produces identical cells.
- Meiosis produces cells with half the number of chromosones, whereas mitosis produces cells with full number of chromosomes.

2. Bohr effect is the dissociation of oxygen from oxyheamoglobin due to hydrogen ions. As carbon dioxide levels in the blood increase, there is a higher concentration of hydrogen ions. These cause oxygen to dissociate from oxyheamoglobin. When carbon dioxide is present, heamoglobin is less saturated with oxygen. Therefore as the carbon dioxide level increase, more oxygen is readily released from heamoglobin, which is essential for aerobic respiration to continue.

3. They move into red blood cells to maintain their charge.

4. -Companion cells have mitochondria
- There are poisons available which inhibit the formation of ATP, as a result translocation doesn't happen.

Reply 211

Little_Cat

*2) o2 disassociates with haemoglobin due to compitition with hydrogen ions formed when co2 enters the haemoglobin and reacts with water to for carbonic acid (catalysed by carbonic anhydrase). Carbonic acid dissassociates to form hydrogen ions and hydrogencarbonate ions ( which diffuse out of the haemoglobin)

Reply 212

mathsclown

7

Original post by itsmehello

State two ways meiosis differs from mitosis? (2)

Explain the Bohr effect? (4) Explain fully why it happens.

Why do Cl- move into red blood cells? (1)

2 pieces of evidence that show ATP is used in translocation? (2)

4 daughter cells that are genetically differen from each other and to the parent cell and have the haploid number of chromosomes

Bohr effect: respiring tissues produce carbon dioxide this means there is a low pO2, as carbon dioxide reacts with water to form carbonic acid this is broken down, the ion that plays a big role in the bohr effect is the h+ ion, as the oxyhameoglobin dissociates, the h+ ions take up their space on the hameoglobin, in respiring tissues this happens at a higher rate as more co2 is produced, as haemoglobin loses its affinity for oxygen so dissociates more as more h+ ions are produced. Hate wording it -.-

Hmm...use of a metabolic inhibitor in a phloem stops translocation and sieve tubes can only survive by help from companion cells which are pakced with mitochondria to provide atp to actively transport sucrose into the sieve tubes? Not sure guessed :/

Reply 213

I dont even think we need to know about 'supercoiled'

Reply 214

sumsum123

Original post by itsmehello

Sorry if this question was for someone else :redface:

They cannot carry out their normal functions whilst they are supercoiled?

No problem, anyone can answer questions :tongue:

. And that is correct :smile:

. How does cytokinesis differ in plant and animal cells.

Reply 215

Original post by ohmyBEAUT

Question for Axion - Define the term passive transport and explain one process which is passive. (5)

Question for anyone else - Explain the need for staining samples used in light microscopy and electron microscopy. (3)

passive transport is the movement of molecules down its concentration gradient, using only kinetic energy.

Diffusion is a passive process. It is the net movement of molecules from an area of high concentration to an area of lower concentration

Reply 216

Original post by sumsum123

No problem, anyone can answer questions :tongue:

. And that is correct :smile:

. How does cytokinesis differ in plant and animal cells.

In plant it forms cell plates. in animal cells two new cells are formed

Reply 217