Please enable JavaScript.
Coggle requires JavaScript to display documents.
Topic 1 Cell Biology By Bethan Poole (1.1 Cell Structure (1.1.4 Cell…
Topic 1 Cell Biology
By Bethan Poole
1.1 Cell Structure
1.1.4 Cell Differentiation
Cells become different shapes and sizes in order to carry out a specialised function
Animal Cells
Differentiate at the start of mitosis, then become specialised and can't differentiate
Plant Cells
Can differentiate at any time
1.1.3 Cell Specialisation
Animals
Sperm Cell
Male sex cell
Tail to swim to the egg
Nerve Cell
Long
Branched endings (Dendrites)
Muscle cell
Long
Bands of proteins
Arranged in fibers that help it run along the length of the muscle
Many mitochondria
Plants
Root Hair Cell
Big surface area
No chloroplasts as it's underground
Long
Thin
Absorb water from the soil
Lots of mitochondria
Xylem Cells
Long
Thin hollow tube
Vessels formed of column of cells, no end walls, nucleus or cytoplasm
Phloem Cells
Sieve tube elements contain little cytoplasm an no nucleus
Holes in the sieve plates allow rapid flow of manufactured food substances through the sieve tubes
Lots of mitochondria
1.1.2 Animal and Plant Cells
Animal Cells
and
Plant Cells
Nucleus
Controls activities of the cell, contains genetic materia
Plant Only
Cell Wall
Strengthens and supports the cell
Chloroplasts
Absorb light to make glucose by photosynthesis
Vacuole
Contains cell sap
Cytoplasm
Site of most chemical reactions
Cell membrane
Controls passage of substanced into and out of the cell
Mitochondria
Where aerobic respiration takes place
Ribosomes
Protein Synthesis
Plant Cell
Animal Cell
1.1.5 Microscopy
Light microscope was developed in the late 16th century
Allowed scientists to see plant, animal and bacteial cells
1933- Scientists used the first ever electron microscope
This passes electrons instead of ligt through the specimen giving a much clearer resolution
Cells can be seen in much finer detail
e.g.
Structures inside mitochondria and chloroplasts can now be studied
Ribosomes can be seen and studied
Calculating magnification
Magnification= size of image/size of real object
1.1.6 Culturing Microorganisms (Biology Only)(Aseptic Technque)
Bacteria can be grown on a type of jelly called an
agar
-culture
The agar is usually in a flat dish called a petri dish
They need to be uncontaminated so specific strain can be used to test the effects of antibiotics or disinfectants. Uncontaminated culture can be produced by the following sterile technique
(1)
Petri dish and agar must be sterilised before use to kill unwanted microorganisms
(2)
An inoculating loop is sterilised by passing it through a flame
(3)
The cooled inoculating loop is used to transfer bacteria to the agar
(4)
The lid of the petri dish must be quickly removed and replaced when transferring bacteria and secured with tape to stop it coming off
(5)
The dish is stored upside down to stop condesation dripping on the agar surface
Schools and colleges culture incubated to a maximum of 25°C- reduce likelihood of harful bacteria being grown, in industry higher temp. can be used for more rapid growth
1.1.1 Eukaryotes and Prokaryotes
Eukaryotes
- Plant, animal and fungal cells
Cell membrane
Cytoplasm
Genetic material in a nucleus
Prokaryotes
- Bacterial Cells
Much smaller
Cytoplasm
Cell membrane
Cell wall
Single DNA loop- may be one or more small rings of DNA called plasmoids
Flagella
1.2 Cell Division
1.2.2 Mitosis and the Cell Cycle
Cells go through a series of changing involving growth and division, one of the stages is
mitosis
where the cell divides into 2 identical cells
Before a cell can divide it needs to
Grow
Increase the number of sub-cellular structures i.e. mitochondria and ribosomes
Mitosis
(1)
Prophase
Chromosomes condense and become more visible. Nucleus is still there
(3)
Anaphase
The chromatids separate and pull away. The spindles move the chromosomes to each end
(4)
Telophase
New nuclei are formed
(2)
Metaphase
When the chromosomes line up. The nucleus has gone
(5)
Cytokinesis
Cytoplasm is split and two identical cells have been created
Importance
Makes new cells for
Repairing damaged tissues
Asexual reproduction
Growth and developmentof multicellular organisms
Cell cycle
10% is mitosis 90% is interphase
Interphase- Copying DNA
Stem Cells
Undifferentiated cells
Sources
Umbilical chords
Bone marrow (adult stem cells)
Human embryos
Meristem (plants)
Adult stem cells
Can only make certain types of cells and their capacity to divide is limited
Stem cells
Make all types of cells
Uses of stem cells
May be very useful in treating conditions where cells are damaged or not working properly, diabetes and paralysis etc.
Cloned embryo of patients could be made and used as a source of stem cells-
Therapeutic cloning
-Will not be rejected
Some people have concerns about using cloned embryos
May be risks- Infection
Ethical or religious objections
Plants
Found in meristem
Allow plants to make new cells for growth
The stem cells can be used to produce clones of plants quickly
Useful
Rare species can be cloned to prevent extiction
Large numbers of identical crop plants with special features, such as disease resistance, can be made
1.2.1 Chromosomes
Nucleus contains chromosomes made of DNA
Each chromosome carries hundreds to thousands of genes
In body cells chromosomes found in pairs, one coming from each parent
Different species have different pairs of chromosomes
e.g. Humans have 23pairs and dog have 39pairs
1.3 Transport in Cells
1.3.2 Osmosis
Movement of water from a high concentration to a low concentration through a semi permeable membrane
1.3.3 Active Transport
Movement of a substance from an area of low concentration to an area of high concentration
Requires lots of energy from respiration
Allows mineral ions to be absorbed into plant root hairs from very dilute solutions in the soil
Allows sugar molecules to be absorbed from lower concentrations in the gut into the blood, which has a higher concentration
1.1.1 Diffusion
Many substances move in and out of cells accross the cell membrane by
diffusion
The net movement of particles from an area of high concentration to low concentration
Happes as particles move randomly and spread out
Examples of diffusion
Oxygen and Carbon dioxide diffuse during gaseous exchange
Ure diffuses from cells into the blood plasma for excretion by the kidney
Digested food moecules from the small intestines diffuse into the blood
Factors affecting diffusion
Concentration
Temperature
Surface Area
Container Size
Surface area to volume ratio
A single -celled organism has a large surface area to volume ratio
Allowes enough molecules to diffuse into and out of the cell to meet the needs of the organism
Calculation
Surface area/Volume
Multicellular organisms
- smaller surface area to volume ratio, but the surfaces and organ systems are specialised for exchanging materials
Examples
Small intstines, lungs in mammals and fish and roots and leaves in plants are all adapted
They have
Moist surfaces
In animals, rich blood supply
Thin walls
In animals, ventilation to speed up gaseous exchange
Large surface area