Biology module 1+2

foundations of biology

eukaryotic cell structure and function (animal+plant) 10 terms

Nucleus= chromosomes that are wound up and enclosed in a nuclear envelope controls cell activity and make ribosomes

Plasma membrane= made from lipids and proteins controls the movement of things going in and out the cell

Mitochondria= double membrane, contains the enzymes for respiration and produces ATP for aerobic respiration

Ribosomes= very small organelle found in the cytoplasm or endo plasma reticular where proteins are made

Golgi apparatus = fluid filled membrane that packages and process proteins and lipids for secretion or delivery to other organelles

Golgi vesicles= transports the proteins and lipids

Rough endoplasmic reticulum (RER) = lots of ribosomes around it and processes the proteins made

Smooth endoplasmic rectum = synthesises and processes lipids

Cytoplasm = where most of the chemical reactions take place

Lysosome = contains digestive enzymes that break down waste materials in the cell

eukaryotic cell structure and function (plant only) 6terms

Chloroplast = where photosynthesis occurs and contains chlorophyl double membrane

Cell wall = provides structural support and protection; made of cellulose.

Vacuole = large sac that stores water, nutrients, helps maintain pressure inside the cell

Adaptations of eukaryotic cells

RBC:

• Biconcave shape for increased SA and o2 diffusion

• No nucleus so they can store more haemoglobin and bind more o2

small intestines + lungs

• SI have microvilli that increase surface area Lungs have alveoli which increase surface area for gas exchange.

• they also have a large blood supply through capillaries that are 1 cell thick

  Storgage

• fat cells have large lipids store

Energy requirements

• Muscle cells have large amounts of mitochondria to carry out lots of respitation and ATP for areobic respiration in the joints

• nerve cells are the same

Secretion

• cells that secrete substances need a large golgi apperatuss need lots of ribosomes

Transport

• active transport need carrier proteins and channel proteins and ribosomes

Prokaryotic cells

no membrane bound organelles

ribosomes are 70s

cell wall made of murine

flagella help its mobility

DNA in soiled strands and plasmids

may have capsules that secrete substances to protect it

units and conversions

Microscopes

light microscope	transmission electron microscope	scanning electron microscope
res 200nm	0.2-0.5 nm (highest res)	0.3-0.5 nm
x1800	x500,000	x500,000
uses light to see the object in colour	beams of electrons pass thru it and is dispersed by the structures forming an image	thin layer of metal, electrons then bounce off it
image 2d with limited depth	2d image black and white	3d image
alive or dead	dead	dead

formular for magnification and how to do graticule calc

magnification= size of image/ actual size (I AM)

Bonding in molecules (water)

Hydrogen bonding and polar lots of energy needed to break the bonds

Water and its uses (6)

its polar = good solvent and can bond with other polar molecules

high latent heat of evaporation = helps cool down organisms

high specific heat capacity= helps regulate temperature making it a good habitat

cohesion= allows water to travel up stems and plants

surface tension= allows organisms to live on water

when it freezes ice has a lower density than liquid water, causing it to float and insulate aquatic life and provide habitat

monomers examples

amino acids → proteins

nucleotides → DNA

glucose → polysaccharide

Monosaccharides

monomers for carbohydrates

eg: glucose, fructose, galactose all with the formular C₆H₁₂O₆

general formular is (CH₂O)n

Alpha and beta glucose

disaccharides and condensation reaction

types of disaccharides

Maltose = 2 glucose monosaccharides

Sucrose= glucose and fructose

Lactose = glucose and galactose

polysaccharides definition

long chain of monosaccharides joined together by glycosidic bonds in condensation reactions

alpha glucose and starch (plant only)

long chain of glucose

• chains can be coiled into an alpha helix - compact

• insoluble - makes it good for storage

• branched - increases sa so enzymes HYDROLYSE quicker to provide glucose for respiration

• Amylose is the straight chain (1,4 glycosidic bonds) amylopectin is the branches (1,4 + 1,6 glyco bonds)

alpha glucose and glycogen (liver +muscle cells)

long chains of a-glucose has more branches than starch

• branched - increases sa so enzymes HYDROLYSE quicker to provide glucose for respiration

• insoluble - makes it good for storage + no effect on osmosis

beta glucose and cellulose

long chains of cellulose

• Straight, unbranched chains that are parallel to each other

• have hydrogen bonds

• found in the walls of plant cells

• used for structure

Lipids

• Insoluble in water

• soluble in organic solvents (alcohol)

• triglycerides 9FATS AND OILS)

• phospholipids

• energy released twice as much as carbohydrates

• waxy cuticles conserve water

• insulation - like in sea animals

• protection

Triglycerides

Phospholipids

amino acids structure

dipeptides and polypeptides

made from chains of amino acids

2 steps in making them

the roles of proteins

• polypeptide chains can fold up to make proteins

  examples of proteins

• Enzymes- break down large molecules into smaller ones

• structural proteins - long parallel peptides chains

• Antibodies- immune response 2 short polypeptide chains highly variable

• Transport proteins- channel proteins in cell membranes contains hydrophobic and hydrophilic amino acids

protein structure

Primary structure	the sequence of amino acids in a polypeptide chain. peptide bonds
secondary structure	hydrogen bonds form between the polypeptide chains makes: alpha helix or beta pleated sheets
tertiary structure	increased bonding leads to further bonding hydrogen bonding(weak) , disulphate bonding(strong), ionic bonding (between carboxyl + amino groups , broken by PH ) 3d shape
quaternary structure	found in larger complex proteins that have MORE than 1 polypeptide chain eg globular and fibrous protiens’

globular and fibrous proteins

fibrous protein

• are insoluble

• used for structure

• collagen(strong)

• keratin (waterproof)

• elastin (stretchy)

globular protein

• used in enzymes and metabolic functions

• spherical

• soluble hydrophilic r groups face outwards

• haemoglobin (haem prosthetic group)

• insulin (hydrophilic r groups)

• pepsin (lots of acidic r groups)

Nucleotides structure

A and G are purines (contains 2 carbon rings) T and C are pyrimidines (contain 1 carbon ring)

RNA

uses RIBOSE not deoxyribose like DNA and uses uracil not thymine shorter and single stranded

3 types of RNA

• mRNA (messenger RNA) codes the amino acids

• rRNA (ribosomal RNA) translates the mRNA

• tRNA(transfer RNA) carries amino acids to ribosomes for protein synthesis.

DNA replication

1. DNA helicase breaks the hydrogen bonds between the 2 strands of DNA unwinding the double helix making 2 separate strands

2. Free nucleotides bind to their complementary bases

3. DNA polymerase joins the new nucleotides together creating the phosphodiester bonds

4. 2 identical strands of DNA are formed semi-conservative

Transcription and mRNA

1. DNA helicase separates the hydrogen bonds and RNA polymerase works on a section of DNA

2. nucleotides in the nuclues pair with their complementary base on the template strand

coding and non coding DNA

gene : section of DNA that codes for functional RNA or polypeptide Locus: position of the gene with in the DNA

Allele: different versions of the same gene

Introns: bits of a gene that dosen’t code for anything

Exon: bits of a gene that do code for something

homologous chromosome: Matching pair that might contain different alleles

Triplet: 3 base pairs that code for an amino acid

Degenerate code: more than 1 triplet can code an amino acid

Non-overlapping: each base pair is only read once

Proteome: all the protein that a cell can make

ATP + ADP + AMP

ADP: 2 phosphates and AMP: 1 phosphate

bonds between the phosphates are unstable and low activation energy so they are easily broken down for energy

APT + H20 → ADP + phosphate + energy

enzyme that breaks it down: ATP hydrolase

enzyme that forms it : ATP synthase

process in cells that require

• metabolism

• movement

• active transport

• secretion

Enzymes

are biological catalysts that speed up chemical reaction by lowering activation energy

they don’t get used up and are specific to the substate they work on can break down or build a molecule

lock and key - enzymes (old model)

enzyme with a tertiary structure has an active site that is specific to the substate that it wants to bind to. exact match

the substate is complementary to the enzyme creating an enzyme-substate complex that breaks it down

induced fit - enzymes (new modle)

it suggests that the shape of the active site changes slightly to better accommodate the substate to it can be complementary

Enzyme - rate of reaction

we can measure the product being made or the substate being used up.

Enzyme - affect of temperature

as the temperature increases the particles move more so more frequent collisions so a reaction is more likely to happen , the enzyme is more likely to make enzyme-substrate complex

• the tertiary structure starts to change due to the enzyme breaking at high temps this denatures it as the active site is no longer complementary

temperature coefficient : rate of reaction +10c / rate of reaction at T

Enzymes - PH

PH is the conc of H+ ions

the H+ and OH - ions interfere with the ionic bonds in the tertiary structure changing the shape of the active site

each enzyme has a different optimal PH

Enzyme -concentration

the higher the conc the more frequent it finds the substrate increasing the rate of reaction until it reaches saturation point.

how to measure it

• using indicator to show change in PH as product is produces

• colorimeter to measure colour change

• rate= absorbance/time taken

Enzymes- Inhibition

Competitive inhibition

• inhibitors is a similar shape to the substrate and will occupy the active site stopping the formation of an Enzyme-substrate complex, the time they bind to it varies (slows down the rate of reaction)

Non competitive inhibitors

• A molecule will bind to the Enzyme in a location away from the active site. this changes the shape of the active site so it is no longer complementary and no ES complexes form ( denatures it)

Enzyme- cofactors

Prosthetic groups

• small non protein molecules that permanently bond with covalent bonds

E.g. haem group in haemoglobin.

Temporary co-factors

• Ease the formation of ES complexes - binds to substrate to form the correct shape OR change charge distribution on enzyme/substrate

• Bind temporarily to the enzymes to help break it down

  E.g. amylase needs Cl- ions to digest starch into maltose

Enzymes - Co-enzymes (type of cofactors)

Organic non proteins that temporarily bind to the active site

chemically charged in the reaction (reduced/oxidised) need top be recycled back to og form

some need vitamins are needed to make them

Structure of cell membranes

Phospholipids

• the hydrophilic heads point outside the membrane whereas the hydrophobic tails are inside - this allows lipid soluble materials can move through. the phobic tails stop water soluble materials from exiting

Proteins

• CARRIER PROTIENS and CHANELL PROTIENS help molecules + ions move through the membrane ( intrinsic aka inside)

• extrinsic proteins only found on one side help with cell signalling

• GLYCOPROTIENS - have intrinsic proteins attached to carbohydrates and help in cell adhesion, signalling and recognition (for hormones or neurotransmitters’ etc)

Cholesterol

• found within the phospholipid bilayer and gives the strength and stability

• its hydrophobic properties helps the tails of the phospholipids hold together further preventing water loss.

• GLYCOLIPIDS : lipids combined with carbohydrates helps in cell adhesion, signalling and recognition

Fluid mosaic model

developed in the 1970s as a way to describe the movement within the plasma membrane

its a fluid because the phospholipid bilayer and other parts are not fixed in place and can move past each other

its a mosaic due to the wide range of shapes and sizes that make up the membrane

Cell membrane - factors effecting it

increasing temp - increases the phospholipid bilayer fluidity making it more preamble

( solvents , detergents , freezing can increase permeability)

Osmosis

the diffusion of water molecules from a region of high water potential to a region of low water potential across a partially permeable membrane

osmosis in animal cells (RBC)

• Isotonic solution - no net movement

• Hypotonic solution - water enters, cell swells/bursts

• Hypertonic solution - water leaves, cell shrinks

osmosis in plants

• In a hypotonic solution, plant cells become turgid as water enters, creating pressure against the cell wall/ cell swells

• In a hypertonic solution, plant cells undergo plasmolysis as water leaves, leading to wilting and cell shrinks

• isotonic solutions- no net movement

factors effecting osmosis

temperature - more kinetic energy = diffuse faster

Water potential gradient = the steeper the faster the rate of osmosis

Thickness of cell membrane - thinner means less distance = diffuse faster

Surface area - larger sa means more water can cross at once = osmosis faster

Diffusion

The net movement of molecules from a region where they’re more highly concentrated to where they’re less concentrated until evenly distributed

only small particles and nonpolar molecules can diffuse directly

Facilitated diffusion

Charged ions and polar molecules need help passing through the lipid bilayer

CHANNEL PROTIENS allow the particles to pass through via diffusion ( No ATP is needed its passive)

each ion has it sown channel protein

Active transport

The movement of molecules or ions into or out of a cell from a region of lower concentrations to a region of higher concentration. using ATP or carrier proteins

A molecule enters the carrier protein and APT will turn into ADP triggering the shape of the protein to move the molecule to the other side

Endo and Exocytosis

• bulk transport ( large molecules or amt)

• requires ATP to move vesicles along the cytoskeleton

adaptations of the cell membrane

• micro villi on the epithelial cells increase SA

• brush border- lots more carrier proteins for more diffusion and co active transport

The cell cycle

1. Interphase - This occupies the majority of the cycle as cells prepare for division.

2. Mitosis - This is when the nucleus of the cell divides in two. 

3. Cytokinesis - This is when the whole cell and cytoplasm divides in two to produce

G1 phase is when cell grown + makes new proteins

S phase - where DNA is replicated

G2 phase- where it continues to grow and replicated DNA is checked for errors

G1 checkpoint - to see if the cell has all the chemicals needed + for damage

G2 checkpoint - check to see if its been replicated without DNA error

Metaphase checkpoint - chromosomes are checked to see if they are attached to the spindle

mitosis

Interphase	the cell prepares for division by growing replicating its DNA and organelles
Prophase	chromosomes become visible and condense, centrioles develop these are spindle poles that move to opposite ends of the cell
Metaphase	the chromosomes can be visualised as 2 chromatids joined by centromere the spindle fibres attach to them and the chromosomes line up in the middle of the cell
Anaphase	the centromere split and the individual chromatids separate and move to opposite sides of the cell
Telophase	when the chromosomes reach the opposite poles they are uncoiled and a nuclear envelope forms
Cytokinesis	cytoplasm and cell membranes divide the cell membrane reforms around it these are the TWO identical daughter cells

Meiosis

first division	second division
P1: DNA duplicates and the chromosomes copy to form CHROMATIDS and arrange themselves with their homologous pair	P2: the TWO daughter cells start the process of division.
M1: chromatids line up at the cell's equator and pulled to opposite sides	M2: they are lined up in the equator of the cell
A1: the cell starts to divide	A2: the CHROMOSOMES are separated with each arm being pulled in a different direction
T1: New cells formed cytoplasm divided	T2: each daughter cell will be a haploid and are not identical

Meiosis crossing over

increase in genetic variation

• homologous chromosomes twist around each other and re-join the other chromatid swapping genetic info

• this point where they touch is called chiasma

• this leads to maternal and paternal genes in the same place

Independent segregation

• Homologues pairs are lined up at random resulting in different combinations of chromosomes

• (12ⁿ)²

mitotic index

number of cells in mitosis/ number of cells in the sample examined.

why are the cell cycles important

Mitosis	Meiosis
growth	increases genetic variation through fertilisation of two random gametes
tissue repair	creates haploid cells which make a diploid organism
asexual reproduction	genetic variation increases the organisms chance of survival during evolution

Stem cells and differentiation

multicellular eukaryotic organisms start off as single undifferentiated cells which divides by mitosis

eg: A zygote (embryo cell) undergoes differentiation to become various specialized cell types. as gene expression is changed

• cell shape changes

• cell contents change

• proportion of organelles change

Specialised cells

Erythrocytes (rbc): carry oxygen to lungs to respiring cells

• biconcave shape = higher SA:V

• no nucleus + few organelles = more space for haemoglobin to bind to oxygen

• small and flexible so they easily pass through capillaries

Neutrophils (type of wbc)

• much larger then rbc and multilobed making it flexible and stretch

• can move by chemotaxis = detect and follow chemical trails (receptors)

• this allows it to be efficient in phagocytosis of pathogens

Spermatozoa (sperm cell)

• acrosome contains enzymes that digest the egg cell

• haploid nucleus allows it to fertilize

• many mitochondria for ATP for energy

• tail/flagella to help it move and its thin + narrow

Specialised plant cells

Palisade cells

• adapted for photosynthesis

• long and cylindrical allows for compactness

• large vacuole pushes chloroplast to the edge of the cells

• many chloroplast

• cytoskeleton allows to move the chloroplasts

Guard cells

• controls opening and closing of the stomata -gas exchange + transpiration

• no photosynthesis BUT contains chloroplasts

• cell wall around stomata thicker more cellulose

Root hair cell

• large SA

• lots of carrier proteins for active transport e.g. ions

• lots of mitochondria for ATP for active transport

• large vacuole to control water volume

Xylem + Phloem

PHLOEM

• Living cells joined end to end

• reduced cytoplasm

• no nucleus

• cytoplasm connects through sieve plates

• companion cells for each sieve tube provide ATP and carry out living functions for the sieve tubes

XYLEM

• xylem vessel= joined end to end

• no cytoplasm = ease of flow

• boarded pits = gaps in lignin allow lateral movement of water between vessels and to cells

• lignin forms in spirals to allow flexibility + keeps xylem open during high pressure

Animal tissues

a group of similar cells working together to carry out a certain function

1) Epithelial tissue

• function: lining free surfaces

• close cells

• no blood vessels

• smooth or projections (villi and cilia)

• short cell cycles

• can do : adsorption , filtration , secretion , excretion

2) Connective tissue

• Function: to hold structures together

• matrix of non living proteins and polysaccharides separates cell

• can withstand forces

• Example = cartilage

• hyaline cartilage - bones

• fibrocartilage - vertebral disc

• elastic cartilage - ear

Muscle tissue

• lots of blood vesse,s - formed of cells called fibers - specialised organelles called microfilaments

• skeletal muscle = causes bones to move

• cordiac muscle = causes walls of the heart to connect

• smooth/ involuntary muscle - causes walls of inactive blood vessels to contract

Plant tissues

Epidermal tissues

• flattened cless , lack chloroplasts

• protectiv covering of leaves

• some prodice waxy cuticle to prevent water loss

Vascular tissue

• carries water and mineral ions (xylem)

• transports sucrose from leaves to roots /floers/shoots (phloem)

meristem tissue

• contains stem cells

• found in the root shoots and tips and cambium of vascular bundles

• thin walls , no chloroplasts. small vacuole. many dividing cells

• meristems in the CAMBIUM produce xylem cells , loses the end walls so no interruption to flow of lignin, provides strength and waterproofing

• meristems in phloem: looses organelles and develop sieve plates

• associate with companion cells which can provide ATP

Stem cells in medicine

stem cells are pluripotent