# Biology
The study of life

# Cells

# Organelle Functions

# Chloroplast
Site of photosynthesis

# Cell Surface Membrane
* Retains cellular contents
* Forms permeability barrier between cytoplasm and extracellular environment
* Controls the movement of substances
* Enables cell to respond to extracellular signals
* Enables cell to communicate with other cells

# Cell Wall
* Mechanical protection from injury
* Gives plant cell a fixed shape

# Cytoplasm
* Where most cell activities occur
* Transport materials within cell

# Cell Vacuoles
Store substances within the cell
Maintains turgor pressure (plant cell)

# Nucleus
* Important for cell division
* Controls cellular activities
* Contains genetic information

# Smooth Endoplasmic Reticulum
* Synthesis of lipids and steroids
* Detoxification

# Rough Endoplasmic Reticulum
Membrane protein synthesis

# Mitochondria
Site of aerobic respiration

# Golgi Apparatus
* Chemical modification of proteins
* Sorting, packaging and secretion of proteins
* Lysosome formation

# Ribosomes
Site of protein synthesis

# Comparison

# Plant vs Animal
Chloroplast & cell wall in plants only
Centrioles in animals only
Central vacuole in plants, small temporary vacuoles in animals

# Cells, Tissue, Organ, Organ System


# Cell
Smallest unit of life

# Tissue
A group of cells which work together to perform a specific function

# Organ
Different tissues working together to perform specific function

# System
Several organs working together for common purpose form system

# Specialised Cells

# Xylem Cells
Conduction and support

# Long Hollow Tubes with No Cross Walls/Protoplasm
Create a continuously empty lumen

# Narrow lumen
Transport of water by capillary actions

# Ligin deposited on the walls
* Waterproof to prevent loss of water
* Strong to provide mechanical support and prevents collapse.

# Root hair cells
Absorption of water and mineral salts

# Long and Narrow Extension
Increases surface area to volume ratio of the cell which allows water and mineral salts to be more efficiently absorbed

# Rich in mitochondria
Active transport of mineral salt against the concentration gradient into root hair cell

# Red blood cells
Transport of oxygen

# Presence of Haemoglobin
Contains red pigment called haemoglobin which transports oxygen from lungs to all parts of body

# No Nucleus
Allows it to carry more haemoglobin ∴ more oxygen

# Circular Biconcave Shape
Increases surface area to volume ratio for faster oxygen diffusion

# Flexible Cell Surface Membrane
Allows red blood cells to squeeze through fine capillaries

# Movement of Substance

# Diffusion

# Definition
The net movement of substances from a region of higher concentration to a region of lower concentration down the concentration gradient

# Role
* Nutrient uptake
* Gaseous exchange

# Osmosis

# Definition
The net movement of water molecules from a region of  higher water potential to a region of lower water potential through a partially permeable membrane down a water potential gradient

# Effects
Hypotonic: Higher water potential
Hypertonic: Lower water potential
Isotonic: Same Water Potential

# Animal

# Hypotonic
When an animal cell is placed in a hypotonic solution, water, water enters animal cell by endosmosis. Cytoplasm has lower water potential than external solution, water enters cell by osmosis. Cell expands in volume.  Cell membrane is too delicate to prevent further expansion. Cell lyses and cell contents poured out.

# Hypertonic
When an animal cell is placed in a hypertonic solution, water leaves the cell by exosmosis. Cytoplasm has higher water potential than external solution, water leaves the cell by osmosis. Cell shrinks in volume. Cell membrane crinkles and forms spikes in a process called crenation. Animal cell eventually dehydrates and dies.

# Plant

# Hypotonic
When a plant cell is placed in a hypotonic solution/water, water enters plant cell by endosmosis. Cell sap has lower water potential than external solution, water moves through cell wall and cell membrane and enters cytoplasm and vacuole by osmosis.  Vacuole increases in size. Cell expands in volume. Cytoplasm and cell surface membrane pushed against and exerts pressure on cellulose cell wall.  Water stops entering when inelastic cell wall exerts opposing pressure to resist further expansion. Cell becomes turgid.

# Hypertonic
When a plant cell is placed in a hypertonic solution, water leaves plant cell by exosmosis. Cell sap has higher water potential than external solution, water leaves vacuole and cytoplasm and moves through cell membrane and cell wall by osmosis. Vacuole and cell shrink in size. Cytoplasm & cell membrane pull away from cell wall in a process known as plasmolysis. Cell becomes flaccid.

# Active Transport

# Definition
 The movement of substances from a region of lower concentration to a region of higher concentration through a partially permeable membrane against the concentration gradient via a membrane-bound pump by using energy

# Importance
* Ion uptake by root hairs and
* Uptake of glucose by cells in the villi

# Nutrients

# Water

# Roles
* Major component of protoplasm
* Medium for chemical reactions
* Transport agent
* Essential component of body fluids
* Regulates body temperature by using sweat

# Carbohydrates

# Info

# Elements
C, H, O
H:O = 2:1

# Types

#  Monosaccharides
* Glucose
* Galactose
* Fructose

# Disaccharides
* Maltose
* Lactose
* Sucrose

# Polysaccharides
* Starch
* Cellulose
* Glucagen

# Roles
* Substrates for respiration
* Structural carbohydrates
* Convert to other organic compounds
* Formation of nucleic acids
* Synthesis of lubricants
* Synthesis of nectar

# Starch Test
## Iodine Test
Add a few drops of iodine solution

# Results
Blue-black: √
Yellow: X

# Reducing Sugars Test
## Benedict's Test

# Sucrose
1. Add 4 drops of hydrochloric acid
2. Boil for 2-3 minutes
3. Let it cool
4. Add sodium hydrogen carbonate to neutralise the acid

Go to solid/liquid

# Solid
1. Cut up into smaller pieces
2. Add 2cm3 of water
3. Stir
4. Decant the water

Go to liquid step 2

# Liquid
1. Add 2cm3 of the food sample
2. Add 2cm3 of Benedict's solution
3. Boil for 2-3 minutes

# Results
Blue: X
Brick-red precipitate: √

# Proteins

# Info

# Elements
C, H, O, N (Sometimes S)

# Types
* Amino acids
* Polypeptides
* Protein

# Roles
* Synthesis of new protoplasm for growth & repair
* Synthesis of enzymes & some hormones
* Formation of antibodies to combat diseases

# Protein Test
## Biuret Test

# Solid
1. Cut up into smaller pieces
2. Add 2cm3 of water
3. Stir
4. Decant the water

Go to liquid step 2

# Liquid
1. Add 2cm3 food sample
2. Add 2cm3 of Biuret solution

#Results
Blue: X
Purple: √

# Lipids

# Info

# Elements
C, H, O
H > O

# Components
* Fatty acids
* Glycerol

# Roles
* Source of energy
* Insulation
* Transport agent for some vitamins and vital substances
* Component of cell surface membrane
* Prevents water loss

# Fats Test
## Ethanol-emulsion Test

# Solid
1. Cut up the food into smaller pieces
2. Add 2cm3 of ethanol
3. Shake thoroughly
4. Decant to 2cm3 of water

# Liquid
1. Add 2cm3 of food sample
2. Add 2cm3 of ethanol
3. Shake thoroughly
4. Add 2cm3 of water

Results
Cloudy white emulsion: √
Clear: X

# Enzymes

# Human Nutrition

# Organs

# Mouth

# Salivary glands
Produce and secrete saliva the mouth

# Mucus and water
* Moistens mouth & tongue and softens food
* Facilitates swallowing

# Salivary amylase
- Breaks down starch into maltose
- pH 7
 - Optimal for salivary amylase activity
- Lysozyme
 - Destroys bacteria

# Buccal cavity
Space enclosed by the mouth

# Teeth
 Chewing action breaks up food into small pieces (mastication) to increase surface area to volume ratio for digestive enzyme action

# Tongue
 Rolls food and saliva into small masses (boli) to facilitate swallowing

# Oesophagus
 Narrow, muscular tube that joins the pharynx and the stomach uses peristalsis to push food forward

# Stomach

# Distensible, muscular bag
 Stretches when temporarily storing food, informs the brain when fully-distended

#  Thick, well-developed muscular wall
Peristalsis churns the food to mechanically break them up and mix them forming chyme

#  Wall has numerous pits
Gastric glands which produce gastric juice which contains hydrochloric acid, pepsin and renin

# Hydrochloric Acid
* Stops salivary amylase activity
* Activates pepsinogen and prorennin
* Provides acidic pH optimal for pepsin and rennin activities
* Denatures proteins in food to exposes peptide bonds for hydrolysis by pepsin
* Kills germs

# Pepsin
Pepsinogen (Inactive) +  HCl > Pepsin (Active) 
Protein + Pepsin > Peptides

#Rennin
Prorennin (Inactive) + HCl > Rennin (Active)
Milk protein caseinogen (Soluble) + Rennin > Casein (Insoluble)
So it stays longer in the stomach

# Lined by mucus layer
Protection against damage by hydrochloric acid in gastric juice

# Sphincters
The lower oesophageal sphincter connects stomach to the oesophagus and the pyloric sphincter connects stomach to the small intestine, they control the movement of food into and out of the stomach

# Small Intestine

# Parts
* Duodenum (U-shaped)
* Jejunum
* Ileum (Much-coiled)

# Intestinal Juice
* Maltase
* Sucrase
* Lactase
* Erepsin (Peptidase)
* Lipase

# Gall Bladder
Stores bile produced by the liver which emulsifies fats increasing the surface area to volume ratio

# Pancreas

# Pancreatic Juice
* Insulin
* Glucagon
* Amylase
* Trypsin/Chymotrypsin
* Lipase
* Nuclease

# Large Intestine

# Colon
*  Absorbs H2O, mineral salts and vitamins from undigested food
* Peristalsis of colon wall propels undigested food to the rectum

# Liver

# Liver Vessels

# Hepatic Portal Vein
Nutrient-rich blood from small intestine to liver

#  Hepatic Artery
Oxygenated blood from heart to liver

# Hepatic vein
Deoxygenated blood  from the liver to the heart

# Functions
* Deamination
* Detoxification
* Regulation of Blood Glucose Concentration
* Protein synthesis
* Bile production
* Iron storage

# Effects of Alcohol
* Depressant
* Reduced self-control
* Slower reaction time
* Excessive stomach acid secreted
* Replaces liver cells with fibrous tissue by cirrhosis
* Social Implications

# Zoom in

# Peristalsis
The rhythmic wave-like antagonistic contraction and relaxation of smooth muscle layers, outer longitudinal muscles and inner circular muscles, causing dilation and constriction to mix and propel food

# Villi
Increase surface area to volume ratio

#  1-cell thick epithelium
Smaller diffusion distance, has microvilli to increase surface area to volume ratio

#  Blood and Lymph Capillaries
Maintain concentration gradients

# Blood Capillaries
Transports glucose and amino acids

# Lymph Capillaries (Lacteals)
Transports lipids

# Plant Nutrition

# Leaf Structure

# External

# Network of Veins
Veins carry water and mineral salts to the cells in the lamina and carry manufactured food from these cells to other parts of the plant

# Lamina
The lamina has a large flat surface compared to its volume. This enables it to obtain the maximum amount of sunlight for photosynthesis
A large, thin lamina also means that carbon dioxide can rapidly reach the inner cells of the leaf

# Leaf Arrangement
* Leaves are always organised around the stem in a regular pattern
* Ensures that the leaves are not blocking one another from the sunlight  and that each leaf receives sufficient sunlight

# Petiole
The petiole holds the lamina away from the stem so that the lamina can obtain sufficient sunlight and air in come leaves

# Internal

# Upper Epidermal Cells
* Single layer of closely packed cells
* Covered on the outside by waxy and transparent cuticle. 
* Epidermis protects the inner regions of the leaf

# Palisade Mesophyll Cells
* One or two layers of closely packed, long and cylindrical cells with their long axes at right angles to the epidermis
* Contain numerous chloroplasts

# Spongy Mesophyll Cells
* Irregularly shaped cells that are loosely packed with numerous large intercellular air spaces
* Fewer chloroplasts than palisade mesophyll cells
* Cells covered with thin moisture film
* Contain vascular bundle, xylem and phloem

# Lower Epidermal Cells
* Single layer of closely packed cells beneath mesophyll
* Covered by an outer layer of cuticle to reduce water loss

# Guard Cells

# Day
* Increase water potential
* Produce glucose
* Convert light to chemical energy to be used to pump K+ ions into guard cells from neighbouring epidermal cells by active transport
* Water from other cells enter the guard cells by osmosis
* Swell and become turgid
* Since they have a thicker cellulose wall on one side of the cell, the swollen guard cells move further apart and pull the stoma open

# Night
* Lower water potential
* Sugar is used up
* K+ ions diffuse out
* Water leaves the guard cells by osmosis
* Become flaccid and the stoma closes.

# Stomata
Minute openings usually found on the lower epidermis

# Adaptations
* Petiole
* Thin lamina
* Large flat surface
* Waxy cuticle on upper and lower epidermal layers
* Stomata present mostly in lower epidermis
* Chloroplasts containing chlorophyll
* More chloroplasts in upper palisade tissue
* Inter-connecting system of air spaces in mesophyll 
* Veins containing xylem and phloem

# Photosynthesis

# Requirements
* Carbon Dioxide
* Water

# Products
* Glucose
* Oxygen
* Water (Optional)

# Chemical Equations

# Light-Dependent
Light energy -> Chemical energy
12H2O  (Photolysis) -> 6O2 + 24H

# Light-Independent
6CO2 + 24H  (Chemical energy) -> C6H12O6 + 6H2O
(Enzyme-controlled reactions)

# Overall
6CO2 + 12H2O   > C6H12O6 + 6O2 + 6H2O

# Simplified
6CO2 + 6H2O   > C6H12O6 + 6O2
Carbon dioxide + Water   > Glucose + Oxygen

#Limiting Factors
* Light intensity
* Carbon dioxide concentration
* Temperature