Biology - Cycles & Processes

Photosynthesis stage I

Light dependant reaction

Photosynthesis stage II

Light independent reaction

Light independent reaction other name

Calvin cycle

Light dependent reaction location

Chloroplast, thylakoid membrane.

LDR reactants

Water, light, energy carriers

LDR products

Oxygen (released), ATP, energy carriers

LDR process

Water is split using light energy absorbed by chlorophyll, oxygen is released, energy is used to make ATP and energy carriers 

Light independent reaction location

Chloroplast, stroma 

Calvin cycle reactants 

Carbon dioxide, ATP / energy carriers

Calvin cycle products

Glucose, ATP / energy carriers (reused)

Calvin cycle process

CO2 diffuses, ATP and energy carriers made/charged in LDR react CO2 into glucose in a series of enzyme catalysed steps. 

Cell cycle stages

Interphase, Mitotic, Cytokinesis

Interphase parts

G1, S, G2

Growth I

Cell grows

Synthesis

DNA is replicated

Growth II

Growth, error check before mitotic phase

Mitotic phase

Prophase, metaphase, anaphase, telophase

Cytokinesis

Nuclear membrane divides, producing two daughter cells.

Somatic cell

Undergoes mitosis, not used in sexual reproduction 

Germ cell 

Undergoes meiosis to produce gametes for sexual reproduction 

Crossing over time

Prophase I of meiosis I

Independent assortment time

Metaphase I of meiosis I

Segregation time

Anaphase I of meiosis I

Crossing over process

Non sister chromatids on homologous chromosomes exchange segments of DNA

Independent assortment process

Homologous chromosome pairs line up randomly along metaphase plate

Segregation process

The homologous chromosomes containing alleles for the same genes separate to opposite poles 

Crossing over result

New combinations of alleles on each chromosome, so gametes are genetically unique, not copies of the parents gametes.

Independent assortment result 

Each gamete has a unique combination of chromosomes

Segregation result

Each gamete has a different combination of alleles, offspring get a unique combination mix of parental alleles

Glycolysis location

Cytoplasm

Glycolysis reactants

Glucose

Glycolysis products

2 ATP, pyruvate

Glycolysis process

Glucose is broken down into pyruvate, producing 2 ATP. NAD+ (future electron carrier) is created.

Does glycolysis require oxygen

No, it is anaerobic

Link reaction location 

Mitochondrial matrix 

Link reaction reactants 

Pyruvate, NAD+

Link reaction products

Acetyl-CoA, NADH, CO2 (Acetyl-CoA and energy carrier created, carbon dioxide released)

Does the link reaction need oxygen 

Yes, it is aerobic 

Krebs cycle (citric acid cycle) location 

Mitochondrial matrix

Krebs cycle (citric acid cycle) reactants

Acetyl-CoA, energy carriers such as NAD and FAD 

Krebs cycle (citric acid cycle) products

CO2 (released), NADH, FADH, very small amount of ATP

Krebs cycle (citric acid cycle) process

Generates electron carriers (NADH and FADH2) and a small amount of ATP, by oxidizing acetyl-CoA

Does the Krebs cycle need oxygen

No, it is anaerobic

Electron transport chain location 

Inner mitochondrial membrane (cristae)  

Inner mitochondrial membrane alternative name

Cristae 

ETC reactants

NADH, FADH2, oxygen

ETC products

34-36 ATP, H2O, NAD+, FAD

ETC process

Electron carriers NADH and FADH2 lose electrons, passing them through protein complexes, releasing energy that pumps H+ into the intermembrane space.

The H+ build up creates a proton gradient. 

H+ flows through ATP synthase enezyme, producing ATP.

Oxygen acts as the final electron acceptor, forming water.

Does ETC need oxygen

Kind of, oxygen is needed as the final electron acceptor, forming water. 

What is passive transport

No ATP (energy) required, movement of molecules down a concentration gradient, from areas of high to low. 

What is active transport 

ATP (energy) is required, movement of molecules up a concentration gradient, from areas of low to high. 

What is diffusion

Movement of small nonpolar molecules directly through the phospholipid bilayer. 

Diffusion example

Oxygen entering a cell

Is diffusion passive or active

Passive

What is facilitated diffusion

Movement of large or charged particles through channel or carrier proteins 

Facilitated diffusion example

Glucose entering a cell via a specialised transport protein. 

Is facilitated diffusion passive or active

Passive 

What are protein pumps 

Carrier proteins which use ATP to move ions/molecules against their gradient.

Example of protein pumps

Sodium-Potassium pump in nerve cells

Do protein pumps require energy 

Yes, they are active 

What is Endocytosis 

The cell engulf a very large molecule by folding the membrane inwards, ‘eating’ it. 

What is phagocytosis 

Endocytosis with solids

Example of phagocytosis

White blood cell ‘eating’ a bacteria

What is pinocytosis

Pinocytosis is endocytosis with liquids 

Example of pinocytosis 

Cells in the small intestine taking in dissolved nutrients and fluids from the gut

When is aerobic respiration used

When plenty of oxygen is avaiable

What situations would aerobic respiration be used in 

When the animals is at rest 

Upsides of aerobic respiration 

A lot of energy is produced, and no harmful byproducts are created

Downsides of aerobic respiration

Requires constant oxygen supply, slow

When is anaerobic respiration used 

When oxygen cannot reach cells fast enough

What situations would anaerobic respiration be used in 

Intense exercise, such as fleeing, chasing, or when breath is being held 

Upsides of anaerobic respiration 

Happens very quickly, providing a energy boost when oxygen is low, keeps muscles working for a short time even when under high stress 

Downsides of anaerobic respiration

Produces lactic acid, which lowers ph in cells and causes muscle ache and cramps, only makes 2 ATP per glucose, which is inefficient, can’t be sustained long term, oxygen will eventually be needed to break down lactic acid, creating a ‘oxygen dept’

In which step of respiration is CO2 released

During the Krebs cycle