Biology Unit 1

WJEC A-Level Biology

What is an atom?

smallest particle in an element that has the properties of the element

What is a molecule?

formed by the combination of two or more atoms

Magnesium

chlorophyll in leaves

Iron

haemoglobin in blood

Phosphate

required to make ATP/nucleic acids/cell membranes

Calcium

strong bones and teeth

What are carbohydrates made of?

• consist of carbon,hydrogen and oxygen

• Cx(H₂O)y

Main groups of carbohydrates

1. monosaccharides

2. disaccharides

3. polysaccharides

Monosaccharide examples

• triose (3 carbons)

• pentose (5 carbons) e.g. ribose

• hexose (6 carbons) e.g. glucose

α-glucose

OH on bottom of C 1

β-glucose

OH on top of C 1

Disaccharide examples

• maltose - 2 α-glucose

• sucrose - glucose+fructose

• lactose - glucose+galactose

Formation of dissacharide

• glycosidic bond formed

• condensation reaction

• opposite is hydrolysis

Polysaccharide

formed from many monosaccharides

Starch - polysaccharide

• polymer of α-glucose held by glycosidic bonds

• storage molecule in plants

• insoluble, compact, readily broken down

• made up of Amylase and Amylopectin

Amylase - polysaccharide

• linear (unbranched)

• condensation reactions between α-glucose molecules

• C1-C4 links

• coils into compact helix

Amylopectin - polysaccharide

• branches of C1-C6 links

• condensation reaction between α-glucose molecules

• C1-C4 links

• amylopectin molecule coils inside amylase

Glycogen - polysaccharide

• α-glucose molecules held together by glycosidic bonds

• storage molecule in animals

• insoluble, compact, readily broken down

• C1-C4 links

• branches of C1-C6 links

• liver cells and muscle fibers

Cellulose - polysaccharide

• long parallel chains connected by hydrogen bonds which prevent osmotic bursting

• β-glucose molecules rotated 180° everytime

• found in cell wall

• insoluble, tough, durable

• chains > microfibrils > microfibril > fiber

Chitin - polysaccharide

• glucosamine molecules held together

• long straight chains rotated 180° every molecule

• part of exoskeleton of insects

• light, strong, insoluble

What are lipids made of?

• Carbon, Hydrogen, and Oxygen

• glycerol + fatty acids

Are lipids insoluble?

Yes, in water as their non-polar

Lipids uses

• energy stores

• protect organs

• heat/electrical insulation

Glycerol - lipids

• 3 carbon atoms

• each have hydroxyl group

• hydrogen fills the rest

Saturated fatty acids - lipids

• no double bonds

• mostly animal fats

Unsaturated fatty acids - lipids

• double bonds

• mostly plant fats

Triglyceride - lipid

• common lipid

• condensation reaction forming an ester bond

Why are unsaturated fatty acids less dense than saturated fatty acids?

Their tails are not straight so molecules don’t pack close together, so bonds are harder to break and there is a lower melting point

Phospholipid

• one fatty acid is substituted for a phosphate group

• hydrophillic head

• hydrophobic tail

What are proteins made of?

• carbon, hydrogen, oxygen and nitrogen

• amino acids - 20 naturally occurring types

Protein uses

• amino acid order dictates the function

• haemoglobin

• antibodies

• enzymes

Dipeptide - proteins

• 2 proteins bonded with a peptide bond through a concentration reaction

Polypeptide

many amino acids

Collagen

• structural protein

• tough, insoluble, fibrous

• 3 polypeptide chains tightly bound by hydrogen bonds

Primary protein structure

• polypeptide

• peptide bonds

• all proteins

Secondary protein structure

• α-helix and β-sheet

• peptide + hydrogen bonds

Tertiary protein structure

• folded into compact, precise 3D structure

• disulphide bridges, hydrogen + ionic + peptide bonds

Quaternary protein structure

• multiple polypeptide chains

• disulphide bridges, hydrogen + ionic + peptide bonds

• e.g. Haemoglobin

Classifying protein

• fibrous - e.g. collagen

• globular - e.g. enzymes

Water

• polar molecule

• creates hydrogen bonds

Water - universal solvent

allows chemical reactions to take place

Water - high surface tension

cohesion is exploited by organisms like pond skaters

Water - high specific heat

prevents large fluctuations in temperature of water

Water - high latent heat

important in temperature control

Water - density

less dense in solid form

Water - transparent

plants can photosynthesise

Water - cohesive

many molecules stick together to be drawn up the xylem of plants

What does an animal cell that a plant cell does not?

Centrioles

What does a plant cell that an animal cell does not?

• Chloroplast

• Cellulose cell wall

• Permanent vacuole

Animal and plant cells diagrams

Nucleus

• contains genetic material

• controls all activity of cell

Chromatin - nucleus

dispersed genetic material

Nucleolus - nucleus

makes rRNA

Nuclear pores - nucleus

allows material to move in and out

Nuclear membrane - nucleus

double layered and continuous with endoplasmic reticulum

Endoplasmic reticulum

• network of membranes forming interconnected sacs called cisternae

• originates from outer membrane of nucleus

Rough endoplasmic reticulum

• ribosomes attached

• protein synthesis occurs

Smooth endoplasmic reticulum

synthesises lipids

Mitochondria

convert potential energy into ATP during aerobic respiration

Ribosome

• made up of large and small subunit

• involved in protein synthesis

• 70s ribosome in prokaryotes

• 80s ribosome in eukaryote

Golgi body

• formed by vesciles

• modifies and packages proteins

• forms lysosomes

• secretes carbohydrates

• produces secreting enzymes

Lysosome

• from the golgi body

• contains enzymes

• destroys and digests worn out material

Centrioles

• only animal cells

• found outside nucleus in centrosome

• forms spindle fibres for cell divison

Vacuole in plant cells

• large and permanent

• storage

• surrounded by tonoplast

Vacuole in animal cells

small and temporary

Cell wall

• only plant cells

• prevent osmotic bursting

• give cell strength and support

Plasmadesmarta

links plant cells together

Chloroplast

• only plant cells

• contains chlorphyll for photosynthesis

Prokaryotes

• found in bacteria

• no membrane-bound organelles

• DNA lies free in cytoplasm

• no nuclear membrane or ER

• small ribosomes (70s)

Eukaryotes

• plant/animal/fungi/protoctist

• membrane bound organelles

• DNA in chromosomes

• distinct nucleus

• large ribosomes (80s)

Ciliated columnar epithelium

• transport substances e.g. mucus in bronchi

• cilia move and sweep substances

• columnal

Cubodial epithelium

• lines the kidney tubules and small intestine

• cubed

Squamous epithelium

• flattened cells

• form walls of alveoli and bowmans capsule

Striated/skeletal muscle

• attached to bones

• bands of long fibres

• voluntary muscle tissue

Smooth muscle

• individual spindle shapes cells

• contract rhythmically

• skin/digestive/respiratory systems

• incoluntary muscles

Cardiac muscle

• found in heart

• contract rhythmically

• do not tire out

Connective tissues

• connect, support or separate tissues and organs

• elastic and collagen fibres

Role of globular proteins

• enzymes

• receptors

• antigens

What type of membrane is the cell?

selectively permeable

Why is it named the fluid mosaic model?

• fluid - phospholipids move

• mosaic - random proteins

Role of carbohydrate

receptor

Role of cholesterol

stability

What is the fatty acid?

hydrophobic

What is the phosphate?

hydrophillic

structure of plasma membrane

• phospholipid bilayer

What is the glycocalyx

region where carbohydrates are found

What does an increase in temperature do to the permeability?

more permeable as more phospholipid movement and denaturing of proteins

What does an ethanol do to the permeability?

more permeable as dissolves phospholipids

What does an increase in pH do to the permeability?

more permeable due to denaturing of proteins

Definition of diffusion

movement of molecules from a high concentration to a low concentration until equally distributed

Does diffusion require energy?

no

What does simple diffusion carry?

non-polar molecules e.g. glycerol

Factors affecting rate of diffusion

• concentration difference

• thickness of membrane

• surface area

• temperature

• distance

• size of molecule

What does facilitated diffusion carry?

polar substances e.g. glucose

Types of proteins in facilitated diffusion

1. channel protein

2. carrier protein

Channel protein

• selective hydrophillic channels

Carrier protein

• changed shape when molecule binds

Definition of osmosis

movement of water molecules from a high water potential to a low water potential through a selectively permeable membrane

What is water potential measured in?

kPa

What water potential does water have?

0, the highest