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66548
Cells
Description
A-Levels Biology f211 Mind Map on Cells, created by Gemma Bradford on 02/05/2013.
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biology f211
biology f211
a-levels
Mind Map by
Gemma Bradford
, updated more than 1 year ago
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Created by
Gemma Bradford
over 11 years ago
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Resource summary
Cells
Prokaryotic
single cells e.g bacteria
DNA free in cytoplasm
circular DNA
cell wall
made of a polysaccharide
organelles not membrane bound
small ribosomes
very small cells
less than 2micrometres
flagellum
plasmid - ring of DNA
eukaryotic
complex cells
Animal
plasma membrane
made of lipids and protein
regulates substance movement in and out of cell
receptor molecules
nucleus
nucleolus
makes ribosomes
contains chromatin
made from proteins and DNA
golgi apparatus
flattened sacs
processes and packages new lipids and proteins
makes lyosomes
nuclear envelope
surrounds nucleus, has pores
allow substances to move between nucleus and cytoplasm
ribosome
in cytoplasm or on RER
site where proteins are made
rough endoplasmic rectilium
folds and processes proteins from ribosomes
smooth endoplasmic rectilium
synthesises and processes lipids
cytoplasm
mitochondrion
cristae on inside
site of aerobic respiration
ATP produced
lyosome
round, no internal structure
contains digestive enzymes
centriole
small, hollow cylinders
separates chromosones during cell division
cilia
hair-like structures
found on surface membrane
move substances along cell surface
flagellum
microubules contract to make flagellum moce
propel cells forward
Plant
same organelles as animal cells
chloroplast
internal structure
photosynthesis site
vacuole
cell wall
plasmodesmata
channels for exchanging substances between adjacent cells
celllose
supports plant cells
flagellum
Protein production
1) proteins made at ribosomes
RER ribosomes make proteins to be excreted/attached to cell membrane
free ribosomes make proteins that stay in cytoplasm
2) transported in vesicles to golgi apparatus
3) golgi modifies and packs in vesicles to be transported around cell
Cytoskeleton
protein threads running through cytoplasm
microfilaments/microtubules
support cells organelles, keeping their position
help strengthen cell and maintain shape
transport organelles/materials within cell
proteins of cytoskeleton can cause cell to move
Microscopes
magnification
length of image/ length of specimen
how much bigger the image is than specimen
bigger unit to smaller unit = x 1000
smaller unit to bigger unit = / 1000
resolution
how well a microscope can distinguish between towo close together points
Light microscope
maximum resolution of 0.2 micrometres
maximum magnification x1500
light beams through object
objects can be stained to view object
different dyes are used to stain specific parts of cell
Electron
transmission elecrtron
electromagnets focus a beam of electrons through specimen
maximum resolution 0.0001 micrometres
show internal structures of organelles
maximum magnification more than x1000000
objects dipped in solution of metals, scatetering the electrons = staining specimen
black and white image
scanning electron
scan a beam of electrons across specimen
form 3D image
maximum resolution 0.005 micrometres
maximum magnification less than 1000000
Membranes
Structure
fluid mosiac model
model describing arrangement of molecules in the membrane
moving phospholipid molecules from a continious fluid bilayer
form a barrier to water soluble substances
centre is hydrophobic so water soluble substances cannot get through
small non polar substances can diffuse through
hydrophilic head and hydrophobic tail
from a bilayer, heads face toward water on either side of membrane
cholesterol
gives stability to membrane
fits between phospholipids
binds to hydrophobic tails of phospholipids
makes membrane less fluid, and more stable
has hydrophobic regions to create barrier to polar substances
glycolipids and glycoproteins
stabilise membrane
forms hydrogen bonds with surrounding water molecules
act as receptors for messenger molecules
plasma membranes control sibstances entering and leaving cell
partially permeable - let some molecules in but not others
Temperature
below 0 degrees
little energy for phosopholipids to move
channel proteins and carrier proteins denature
increasing permeability of membrane
ice crystals can pierce membrane = highly permeable
0-45 degrees
phospholipids can move around
pertially permeable membrane
increase in temp = phospholipids move more = hgher permeability of membrane
45+ degrees
bilayer starts to melt = more permeable membrane
water inside cell expands = pressure on membrane
channel and carrier proteins denature
no control over what enters/leaves cell
increased permeability
Cell signalling
1) one cell releases a messenger molecule
messenger molecules can be hormones
messenger molecules can be drugs
trigger response or block the receptor
2) molecule travels to another cell
3) messenger molecule binds to receptors on target cell
4) triggers cell response
membrane bound proteins act as receptors for specific messenger molecules
receptors are a specific shape to the messenger molecule
complmentary
Exchange
Diffusion
net movement of particles from an area of higher concentration to an area of lower concentration
gradient is the path from an area or high to low concentration
particles diffuse down a concentration gradient
continues until particles are evenly distributed
passive
Factors
concentration gradient
higher = faster rate
exchange surface thickness
thinner = faster rate
surface area
larger = faster rate
Osmosis
diffusion of water molecules across a partially permeable membrane
from an area of higher water potential to lower water potential
water potential
potential of water molecules to diffuse in or out of a solution
pure water = 0
any solution is negative
lower likelihood to diffuse
more negative = stronger concentration of solutes
Isotonic solutions
two solutions with the same water potential
no net movement of water in an isotonic solution
HypOtonic solutions
solution with higher water potential than inside of cell
weak concentration of solutes
plant cell - vacuole swells - turgid
animal cell - swell and bursts
HypERtonic solutions
solution with lower water potential than inside cell
plant cell - becomes flaccid - plasmolysis
animal cell - shrinks
strong concentration of solutes
Facilitated Diffusion
large molecules cannot diffuse directly through bilayer
moves particles down a concentration gradient
passive - no energy
carrier proteins
move large molecules into/out of cell
1) large molecule attaches to carrier protein in membrane
2) protein changes shape
3) releases molecule on opposite side of membrane
different carrier proteins facilitate the diffusion of different molecules
channel proteins
form pores in membrane for smaller ions/polar molecules to diffuse through
different channel proteins facilitate the diffusion of different particles
Active Transport
uses energy from ATP to move molecules/ions across plasma membranes
against concentration gradient
uses carrier proteins in the same way as facilitated diffusion
Endocytosis
1) cell surrounds molecule with part of plasma membrane
2) membrane pinches off to form vesicle inside cell, with ingested molecule inside
some molecules too large to be taken by carrier proteins
Exocytosis
some substances need to be released from cell
1) vesicles with substance pinch off from golgi sacs
2) move toward plasma membrane
3) vesicles fuse with plasma membrane, releasing contents outside of cell
Division
Cell cycle
process that all body cells use to grow and divide
1) Mitosis
cell division
Interphase
2) Gap phase 1
cell grows, new organelles/proteins made
3) Synthesis
DNA replicated and checked for errors
4) Gap phase 2
cell keeps growing, proteins for cell division made
DNA unravelled and replicated to double it's genetic content
organelles replicated and ATP content increased for cell division
Mitosis
chromosomes
2 strands (chromatids) joined by a centromere
sister chromatids
2 because the chromosome already made identical copy during interphase
1) Prophase
chromosomes condense
centrioles move to opposite ends of cell
form spindle - protein fibres across cell
nuclear envelope breaks down
chromosomes free in cytoplasm
2) Metaphase
chromosomes line up along middle of cell
spindle equator
chromosomes attach to spindle by centromere
3) Anaphase
centromeres divide
separating each pair of sister chromatids
spindles contract
pulling chromatids to opposite ends of cell
4) Telophase
chromatids reach opposite poles on spindle
nuclear envelope forms around each group of chromosomes
cytokineses occurs
division of cytoplasm
cell membrane constricts, pinching cell into two daughter cells
daughter cells are genetically identical to original cell and eachother
Plants
only cells in meristems can divide by mitosis
no centrioles - spindle forms without them
cytokinesis begins in centre of cell with a cell plate
Asexual
using mitosis
new organisms produced are genetically identical to parent cell
Budding
1) parent cell swells on one side forming bud at surface
yeast cells
2) interphase - relplication
3) mitosis
replicated DNA, cytoplasm and organelles move into bud
4) budding cell contains nucleus with identical copy of parent cell's DNA
5) cytokinesis occurs
bud pinches off from parent cell forming new genetically identical cell
Sexual
homologus pairs
pairs of matching chromosomes
same size, same genes
body cells have diploid number of chromosomes (2n)
gametes
haploid number of chromosomes
one copy of each chromosome
haploid sperm fuses with haploid egg = diploid number of chromosomes
zygote formed
Meiosis
division in reproductive organs to produce gametes
cells formed are genetically different
1) DNA replicates and coils up to form chromosomes
arrange into homologous pairs
2) pairs swap parts of chromatids with eachother
chromatids now have new combination of alleles
3) homologous pairs split in first division
any one chromosome can go into either of 2 new cells
4) each chromosome splits in half in second division
any half can go into any 4 new cells
four new genetically different cells produced
Stem Cells
unspecialised cells
can develop into any type of cell
found in early embryos
Differentiation
stem cells divide to become new cells
process of how a cell becomes specialised for it's job
bone marrow
contain adult stem cells
stem cells divide and differentiate to replace worn out blood cells
erthrocyte and neutrophils
cambium
stem cells in plants
stem cells of cambium in root/shoot divide and differentiate to become xylem and phloem
cambium forms ring inside root/shoots
cells divide and grow out of ring
differentiating as they move away from cambium
Specialised cells
after differentiation, cells have specific function
structure adapted to perform function
erythrocytes
carry oxygen in blood
biconcave disc shape
large surface area for gas exchange
no nucleus
more room for haemoglobin
neutrophils
defend body against disease
flexible shape allows them to engulf foreign pathogens
many lysosomes to break down engulfed pathogens
epithelial cells
cover organ surfaces
cilia move particles away
microvilli folds in cell membrane to increase surface area
Sperm cells
have flagellum to swim to egg
many mitochondria for energy to swim
acrosome contains digestive enzymes
to penetrate surface of egg
Palisade mesophyll cells
many chloroplasts to absorb sunlight
photosynethesis
thin walls = CO2 can easily diffuse into cell
Root hair cells
absorb water and mineral ions from soil
large surface area for absorption
thin permeable cell wall for entry
many mitochondria for energy for active transport
Guard cells
pores in leaf for gas exchange
thin outer walls and thickened inner walls
bend outwards = opening stomata
allows gas exchange for photosynthesis
take up water and become turgid in light
Organisation
Tissues
group of cells specialised to work together to carry out a function
squamous epithelium
single layer of flat cells lining a surface
thin exchange for diffusion
alveoli in lungs
ciliated epithelium
layer of cells covered in cilia
on surfaces to move things
in trachea to move mucus
xylem
transports water around plant
supports plant
phloem
arranged in tubes, made up of sieve and companion cells
sieve cells have end walls (sieve plates) with holes in to move sap through
Cooperation
multicellular organisms work efficently as they have different cells specialised for different functions
cells, tissues + organs must cooperate to keep organism alive and running
Transport systems
carry substances between different cells
plants - xylem carry water + minerals from root hair cells to palisade
humans - circulatory system helps move substances around body in blood
Communication systems
allow communication between cells in different parts of organism
chemical systems using messenger molecules
nervous system
muscle cells depend on oxygen - which depend on erythrocytes to carry oxygen from lungs
Organs
group of tissues that work together to perform a function
lungs
carry out gas exchange
contain squamous epithelium in alveoli and ciliated epithelium in bronchi/trachea
elastic connective tissue and vascular tissue
Organ systems
organs working together to perform a function
respiratory
all organs involved in gas exchange
circulatory
all organs involved in blood supply
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