Biology 2 notes, most topics!

Includes nearly all topics in B2

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  • Created on: 12-03-12 17:16
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DIFFUSION AND OSMOSIS
Small molecules such as glucose, amino acids, water and oxygen.
Rate of diffusion depends on:
Distance
Concentration difference
Surface area
If a cell is short of water, the solution inside is more concentrated. This
means the solution outside of the cell is more dilute so the water will move
into the cell by osmosis.
If a cell has lots of water, the solution inside will be dilute, meaning water will
be drawn out of the cell and into the fluid by osmosis.
PHOTOSYNTHESIS
Rate of photosynthesis depends on:
Light
Carbon dioxide
Temperature
Artificially create the IDEAL CONDITIONS for farming
Greenhouses
Trap the suns heat
Use heaters
Artificial light (night time)
Paraffin heater ­ CO2 is produced as paraffin burns as a byproduct
Keeping plants in greenhouses keeps diseases and pests away. Farmers
can also add fertilisers to the soil
Plants grown this way will grow a lot quicker.
Plants will also grow faster if grown in compost.
Compost will decay faster if there are holes in the box because this allows
oxygen to enter, which means AEROBIC RESPIRATION.
HOW PLANTS USE GLUCOSE
RED Respiration (glucose + oxygen = water + co2)
FRUIT Making Fruits (glucose + fructose is turned into sucrose for storing
fruits)
CAN Making Cell Walls (cellulose to make cell walls)
POSESS Making Proteins (glucose is combined with nitrates to make amino
acids)
SEAN Stored in Seeds (turned into lipids for storing in seeds)

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STEVENS Stored as Starch (turned into starch and stored in roots, stems
and leaves)
CARBON CYCLE
Removing CO2 from atmosphere
Green plants remove carbon dioxide from the atmosphere by photosynthesis.
The carbon becomes part of complex molecules such as proteins, fats and
carbohydrates in the plants.
Returning CO2 to the atmosphere
Organisms return carbon dioxide to the atmosphere by respiration from
plants, animals and microorganisms. When an animal eats a plant, carbon
from the plant becomes part of the fats and proteins in the animal.…read more

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LIPASE CONVERTS FATS INTO GLYCEROL AND FATTY ACIDS
Pancreas, small intestine
Used together with protease in biological detergents to break down
digest the substances in stains into smaller, water soluble substances
ISMOERASE CONVERTS FRUCTOSE INTO GLUCOSE
Fructose is sweeter than glucose, so it can be used in smaller amounts in
slimming food
Hydrochloric acid makes the stomach acidic, where the food is broken
down. It then travels to the small intestine ­ which works in alkaline
conditions.…read more

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DNA, genes and chromosomes
DNA: (deoxyribose nucleic acid) molecules are large and complex. They carry the genetic
code that determines the characteristics of a living thing.
Except for identical twins, each person's DNA is unique. This is why people can be identified
using DNA fingerprinting. DNA can be cut up and separated, forming a sort of 'bar code' that
is different from one person to the next.
Gene: is a short section of DNA.…read more

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Gametes and fertilisation
Gender
Human body cells have 23 pairs of chromosomes in the nucleus. One of these pairs controls
the inheritance of gender whether offspring are male or female:
Males the two sex chromosomes are different. They are XY
Females the two sex chromosomes are the same. They are XX
Chromosomes from a female
Chromosomes from a male
Gametes
Gametes are sex cells. The male gametes are the sperm, and the female
gametes are the eggs.…read more

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Male Femal
e
reproductive teste ovarie
organ s s
gametes sper eggs
m
The cells that are formed by meiosis have half as many chromosomes as the
cell that formed them. Human body cells contain 23 pairs of
chromosomes, while human gametes contain 23 single chromosomes.
The main features of meiosis are:
the chromosomes are copied
the cell divides twice, forming four gametes
The diagram outlines how this works.…read more

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