bio unit1 aos1

membrane structure

phospholipid bilayer
embedded molecules

phospholipid ends

hydrophilic head

phospholipid bilayer

double layer of phospholipids that makes up plasma and organelle membranes.

protein role in membrane

transport
signalling between cells
cell to cell recognition

types of proteins in membrane

peripheral

transmembrane

carbohydrate role

adhesion between cells
cell recognition

carbohydrate chains

glycoprotein

glycolipid

cholesterol role

increase stability of plasma membrane without affecting fluidity

fluid mosaic model

fluid: phospholipid bilayer is not a fixed structure and can move around
mosaic: plasma membrane is made up of difference types of molecules

saturated fatty acids

only have single bonds between carbon atoms and can pack very tightly together

unsaturated fatty acids

have some double bonds and cannot pack together as tightly

differentiation

process during development whereby newly formed cells become more specialised and distinct as they mature

stem cells

unspecialised cells

characteristics of stem cells

self renewal

totipotent

can form any cell type as well as extra embryonic cells
most potent

pluripotent

can form any cell type
2nd most potent

multipotent

can differentiate into a number of closely related cell types
3rd most potent

unipotent

cannot differentiate but are capable of self renewal
least potent

embryonic cells

type of stem cell found in an embryo in the developmental stage prior to implanting into uterus
capable of differentiating into all types of cells

adult stem cells

undifferentiated cells found among differentiated cells in a tissue or organ
limited variety of cell
purpose is for repair and maintenance of cells

induced pluripotent stem cells

adult cells that can be reprogrammed to revert back to an embryonic stem cell state so they can become pluripotent instead of multi/unipotent

cancer

disease caused by uncontrolled cell division and results in the formation of abnormal cell growths or tumours

types of tumours

benign

malignant

how do cancer cells occurs

mutation
cells can avoid immune detection as they are not foreign, rather they are abnormal

characteristics of cancer cells

do not require growth factor signals
random arrangement of cell layers
increased division
metastasis
angiogenesis

metastasis

cancer cells are able to travel to new areas in the body to spread and form secondary tumours

angiogensis

cancer cells trick body into producing new blood vessels which give them a direct supply of oxygen and nutrients

cell cycle checkpoints…

ensure cells can proceed to next stage of division
monitor proper division of cells
ensure that compromised cell does not continue to divide and pass on defects

3 checkpoints

g1
g2
m

g1 checkpoint

checks for cell size, nutrients, growth factors and dna damage

g2 checkpoint

checks for dna damage, dna replication accuracy and cell size

m checkpoint

checks for spindle attachment to chromosomes

cell death types

uncontrolled

necrosis

cell death that occurs as a result of trauma or injury
premature and uncontrolled
causes inflammation

apoptosis

programmed cell death through intrinsic or extrinsic pathways

why does apoptosis occur

protection

initiation of apoptosis

triggered by signals initiated within the cell (intrinsic pathway) or via external signals (extrinsic pathway)

intrinsic pathway

activated by radition of toxic chemicals damaging dna or absence of important growth factors

extrinsic pathway

activated by sigals that binds to death receptors on the membrane of target cell to be destroyed

apoptosis pathway

activated intrinsically or extrinsically
separation from adjacent cells
collapse of cells cytoskeleton
cell shrinks
breakdown of organelles
blebbing of plasma membrane
budding of plasma membrane bound vesicles
phagocytosis of dead cells

binary fission

form of asexual reproduction in prokaryotes where 1 cell divides to become 2

binary fission process

replication
elongation
division
RED

replication

circular chromosome is replicated resulting in 2 identical chromosomes

elongation

cell grows until it has almost doubled in size

division

2 chromosomes are pulled apart
membrane pinches inwards until a septum forms
2 new cell walls

why do cells divide

growth
repair
reproduction

dna

deoxyribonucleic acid
carries genetic instructions

dna structure

2 anti parallel strands of nucleic acid

chromatin

dna tightly wound around proteins

chromosome

a threadlike structure of nucleic acids carrying genetic information in the form of genes

sister chromatids

genetically identical strands of chromosomes

homologous chromosomes

matching pairs of chromosomes that contain the same genes and location

cell cycle

series of ordered events a typical eukaryotic cell undergoes as it grows and divides in 2

interphase

active period in the cycle in which a cell grows and prepared for division

g1

cell grows and synthesises proteins

s

dna replicated

g2

cell continues to grow and organelles duplicate

m phase

mitosis and cytokensis

prophase

chromosomes condense
nuclear membrane breaks down
spindle fibres attach to centromere of chromosome

metaphase

spindle fibres shorten so chromosomes line up at equator of cell

anaphase

spindle fibres continue shortening
sister chromatids seperate
chromosomes move to opposite poles of cell

telophase

spindle fibres dissolve
chromosomes decondense
nuclear membrane reforms

cytokensis

division of the cytoplasm

plant cytokensis

cell plate forms in the middle of cell which fuses with cell wall

animal cytokensis

cleavage furrow forms and the cell becomes pinches off and becomes 2

resting state or g0

cell leaves cell cycle and enters state where it no longer divides

differention

process in which cells become specialised in structure and function

plasma membrane function

control movement of substances in and out of the cell which is essential for survival

polar molecules

have a slightly positive end and slightly negative end
dissolve in lipids

non

polar molecules

examples of passive transport

simple diffusion
osmosis
facilitated diffusion

examples of active transport

active transport
bulk transport

diffusion

net passive movement of a substance from a region of high concentration to low concentration until equilibrium has been reached

molecules that can diffuse through phospholipid bilayer

hydrophobic/non

factors that impact diffusion rate

size

osmosis

net movement of free water molecules from an are of high water concentration to an area of low water concentration across a semi permeable membrane

tonicity

the ability of a surrounding solution to cause a cell to gain or lose water

isotonic solution

same concentration of water as cytoplasm of cell
no net water movement

hypertonic solution

lower water concentration than cytoplasm of the cell
water moves out of cell and into water

hypotonic solution

higher concentration of water than cytoplasm of the cell
water moves into cell

effects of a cell in isotonic solution

normal (animal)
flaccid (plant)

effect of a cell in hypertonic solution

lysed or burst (animal)

effect of a cell in hypotonic solution

shriveled (animal)
plasmolysed (plant)

facilitated diffusion

new passive movement of hydrophilic or polar substances from an area of high concentration to an area of low concentration across a semi

active transport

net movement of substances into or out of cells against a concentration gradient through carrier proteins (low

how does atp assist in active transport

atp connects to protein through a specific marker allows the molecule to go through the carrier protein

bulk transport

movement of large molecules in and out of the cell through vesicles

endocytosis process

plasma membrane surrounds material
edges of membrane meet
membranes fuse to form vesicle

types of vesicles

phagocytosis

exocytosis process

vesicle with substance travel to plasma membrane
membrane of vesicle fuses with plasma membrane
substance secreted

autotrophs

make their own food by taking in energy from environment
use the glucose they make for their own energy needs
eg. photosynthesis

heterotrophs

cannot make their own food
obtain food by feeding off other organisms
use the energy in food to create atp via cellular respiration

photosynthesis

process that some plant cells understake to produce glucose and oxygen using water co2 and sunlight
occurs within chloroplasts

grana (granum)

make of thylakoid membranes
contain chlorophyll which captures light energy from sun
the stage of photosynthesis occurs here

stroma

gel like fluid
contains a lot of ribosomes
second stage of photosynthesis occurs here

what is the energy shuttle

how energy is transferred and transformed within biological systems
through atp, cellular respiration and photosynthesis

what is the molecule involved in the energy shuttle

adenine triphosphate

energy shuttle step by step

energy captured/consumed
energy released through cellular respiration
produces atp which is used for energy
atp is regenerated by mitochondria

how is atp regenerated

apt breaks down and loses a phosphate so it turns into adp
adding back a phosphate group to adenosine diphosphate turns it back to atp

cellular respiration

process that breaks down glucose in order to produce water, carbon dioxide and atp