Biology

The study of life

Cells

Organelle Functions

Chloroplast

Site of photosynthesis

Cell Surface Membrane

Cell Wall

Cytoplasm

Cell Vacuoles

Store substances within the cell
Maintains turgor pressure (plant cell)

Nucleus

Smooth Endoplasmic Reticulum

Rough Endoplasmic Reticulum

Membrane protein synthesis

Mitochondria

Site of aerobic respiration

Golgi Apparatus

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

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

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

Nutrients

Water

Roles

Carbohydrates

Info

Elements

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

Types

Monosaccharides

Disaccharides

Polysaccharides

Roles

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

Roles

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

Roles

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

Salivary amylase

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

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

Intestinal Juice

Gall Bladder

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

Pancreas

Pancreatic Juice

Large Intestine

Colon

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

Effects of Alcohol

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

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

Palisade Mesophyll Cells

Spongy Mesophyll Cells

Lower Epidermal Cells

Guard Cells

Day

Night

Stomata

Minute openings usually found on the lower epidermis

Adaptations

Photosynthesis

Requirements

Products

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