Cell biology

What are the features of eukaryotic cells?

• Contain their genetic material enclosed in a nuclues

Have a:

cell membrane

cytoplasm

nuclues

What are the features of prokaryotic cells?

• The genetic material is not enclosed in the nuclues (DNA strands or plasmids)

• Much smaller

Have a:

cell membrane

cell wall

cytoplasm

What are the animal cells sub-cellular structures?

• Nucleus - contains genetic material that controls the activities of the cell

• Cytoplasm - gel like substance where most the chemical reactions take place and contains enzymes that control reactions

• Cell membrane - holds the cell together and controls what goes in and out

• Mitochondria - where most the aerobic reactions take place which transfers energy to cells

• Ribosomes - where protiens are made

What are the plant cells sub-cellular structures?

• Cell wall - made of cellulose, supports and strengthens cell

• Permanent vacuole - contains cell sap (mixture of sugars and salts)

• Chloroplast - allows photosynthesis to occur and contains chlorophyll for capturing light energy

Required pratical 1: microscopes

• Place slide onto the stage and clip it into place

• Select the lowest power objective lens (4x)

• Position the objective lense by the coarse focusing dial to be almost touching the slide

• Look through the eye piece and slowly turn the coarse focusing dial to increase the distance between the objective lens and slide to make the cell come into focus

• Use the fine focusing dial to bring the cell into clear focus

What are the parts of a optical microscope?

• Stage - the platform where slides are placed for observation and have clips to hold the slides into place

• Lamp - passes up light into the slide (some may have a mirror to reflect light instead)

• Objective lenses - magnify the image of the specimen by 4x, 10x and 40x

• Eyepiece - where the viewer looks through to see the magnified image and contains a eye lense which magnifys by 10x

• Coarse focussing dial and fine focussing dial

Calculate the total magnification

Magnification of the eyepiece lens x magnifiaction of the objective lens

What are the advantages of the electron microscope over the light microscope?

Light microscopes

• limited magnification

• limited resolution (blurry)

Electron microscopes

• greater magnification

• greater resolution

Calculation of magnifiaction of a microscope

Magnifiaction = size of image/size of real object

What is cell specialisation?

• Adaptions which help them to carry out a particular function

• Cells that have been specialised are called differentation

• Most animal cells differentiate at an early stage

• Most plant cells retain the ability to differentiate through out life

Sperm cell specialisation

Fertilizes the ovum

• Long tail and streamlined head to swim easier

• Contain mitochondria for energy to swim

• Contain enzymes to digest through the ovum

Nerve cells specialisation

Sends electrical impulses around the body

• Long axon that carries electrical impulese

• Axon is covered in myelin which insuates the axon and speeds up transmission of nerve impulses

• End of the axon has synapses which are junctions at the end that pass impulses to one nerve cell to another

• Has dendrites which increase the surface area so nerve cells can connect easily

Muscle cells specialisation

Contract

• Contain protien fibres to change their length eg get shorter to contract

• Have mitochondria to provide energy for contraction

Root hair cells specialisation

Absorb water and minerals

• Increases the surface area of the root for more absorbtion

• Do not contain chloroplasts

Xylem cells sepcialisation

Carrywater and dissolved minerals from the roots to the leaves

• Thick walls containing lignin which provide support to the plant

• End walls between the cells are broken down to form a long tube for water and minerals to flow up easily

• No nuclues, vavuole or chloroplast (no internal structure) for water and minerals to flow easier

Phloem cells specialisation

Carry disolved sugars up and down the plant

Phloem vessle cells

• No nucleus and limited cytoplasm allow dissolved sugars to move through the cell

• Pores called sieve plates allow dissolved sugars to move through the cell

• Each have a companion cell connected by pores which provide mitochondria

What are chromosomes?

• In the nuclues we fine chromosomes which are made of the molecule DNA

• Body cells contain two of each chromosome which are paired (23 paire)

• Each chromosome carries a large number of genes which determine our features

What is the cell cycle?

Cells have to be able to divide which is the cell cycle

What is the mitosis cell cycle?

• The DNA replicates to form two copies of each chromosome and the cell grows and copies its internal structure

• One set of chromosomes are pulled to each end of the cell and the nucleus divides

• The cytoplasm and the cell membrane divide to form two identical cells

Function of mitosis

• Essential for growth and development of multicellular organisms

• Takes place when a organism repaires itself

• Occurs during asexual reproduction

What are stem cells?

Any cell that is undifferentiated and is capable of differentiating into any types of body cell

What is the function of stem cells from embryos?

Early-stage embryos contain stem cells and is capable of differentiating into any type of body cell

What is the function of stem cells in adult bone marrow?

The stem cells in bone marrow differentiate to form cells found in our blood eg white blood cells, red blood cells and platelets

What is the function of stem cells in meristem plants?

The stem cells in meristem plants can be found in the root and can differentaite into any type of plant and carry this ability through out its life

Stem cell treatments - bone marrow transplant

Bone marrow transplant - treats leukaemia (bone marrow cancer)

• Exisiting bone marrow destroyed with radation

• Transplant of new bone marrow

• Stem cells in new bone marrow divide to form new bone marrow

Problems:

• Patient must be compatible with the donor otherwise whiteblood cells may attack the patients body

• Viruses may be passed on

Stem cell treatements - therapeutic cloning

• An embryo is produced with the patients genes

• Stem cells from the embryo can be transpanted into the patient without being rejected

• Once inside the patient the stem cells can differentiate to replace cells which have stopped working correctly

Can be useful for medical conditions such as diabetes and paralysis

Some people may have ethical objections to this procedure

Stem cell treatments - cloneing plants

Stem cells from meristems in plants can be used to produce clones of plants quickly and economically

-Rare species can be cloned to protect against extinction

-Crop plants with special features such as disease resistance can be cloned to produce large number of identical plants for farmers

What is diffusion?

The spreading out of particles resulting in a net movement from an area of higher concentration to an area of lower concentration through the cell membrane

Describe the diffusion of oxygen

• Cells are surrounded by a high concentration of oxygen

• Oxygen cells move into the cells through diffusion (high concentration to low concentration)

Describe the diffusion of carbon dioxde

-the diffusion oxygen is used to generate energy for the cell in respiration and this then produces carbon dioxide

-this means there is a higher concentration of carbon inside the cell then outside

-so the carbon dioxide diffuses out of the cell (high concentraon to a low concentration)

Describe the diffusion of urea

-urea is a waste product produced in cells

-it diffuses out the cell (high concentraon to a low concentration) into the blood plasma to be excreted by the kidneys

What can effect the rate of diffusion?

The difference in concentration

• The greater the concentration gradient(the amount of molecules), the faster the diffusion takes place (more molecules diffuse through)

The temperature

• The higher the temperature, the greater the rate of diffusion

• Particles have more kinetic energy and move faster

Surface area of the membrane

• The larger the surface area the greater the rate of diffsion as more molecules can pass through

Surface area to volume ratio

What is osmosis

The diffusion of water from a dilute solution (contain a high concentration of water) to a concentrated solution (contain a low concentration of water) through a partially permeable membrane (allow some molecules to pass through but not all molecules)

• Animal cell - increase of water in a cell - increase or burst

• Plant cell - increase of water in a cell - cell wall prevents it from bursting and instead swells - this is called turgid

• Animal and plant cell - decrease of water in a cell - shrink - this is called flaccid

Required pratical 3: effects of osmosis on plants

• Peel a potato

• Use a cork border to produce three cylinders of potato

• Use a scalpel to trim the cylinders to the same length(3cm)

• Measure the lengh with a ruler and weigh it to find the mass

• Place each cylinder into a test tube and add 10cm of a 0.5 molar sugar to the first test tube, 0.25 to the second and distalled water (contains no dissolved substances) to the third

• Leave overnight to allow osmosis to take place

• Remove cylinders and roll onto a paper tell to remove Surface moisture

• Measure the length and mass of the cylinder again

Percentage change calculation

% change = change in value/original value x 100