Biology 1- Cells

Eukaryotic cell

Eukaryotic cell

A complex cell- all animal and plant cells

Prokaryotic cell

A simple cell- bacteria cells

Parts of an animal cell

Nucleus
Cytoplasm
Cell membrane
Mitochondria
Ribosomes

Parts of a plant cell (excluding parts from both types of cell)

Cell wall
Permanant vacuole
Chloroplasts

Parts of a bacterial cell

Cytoplasm
Cell membrane
Cell wall
Free-floating DNA strand
Plasmids

Function of the nucleus

Contains genetic information and controls cell activities

Function of the cytoplasm

Site of chemical reaction (contains enzymes)

Function of the cell membrane

Holds the cell together and controls what goes in and out

Function of the mitochondria

Site of aerobic respiration; produces energy

Function of the ribosomes

Site of proteinsynthesis

Function of the cell wall

Supports and strengthens the cell

Function of the permanent vacuole

Contains cell sap (weak solution of sugar and salts)

Function of the chloroplasts

Site of photosynthesis and contain chlorophyll

Light microscope

Uses light and lenses to magnify an image of a specimen- cheaper then electron microscopes and can be used to view live specimens but lower resolution and magnification

Electron microscope

Uses electrons to form and magnify an image- much higher resolution and magnification but very expensive and cannot be used to view live specimens

Magnification formula

Magnification = Image size/Real size

How to prepare onion for a microscope (PRACTICAL #1 pt1)

-Add a drop of water to the middle of a clean slide
-Use tweezers to peel some epidermal tissue off an onion
-Place the tissue onto the slide
-Add a drop of iodine solution as a stain
-Use a mounted needle to lower a cover slip on top

How to use a light microscope to look at a slide (PRACTICAL #1 pt2)

-Clip the slide onto the stage
-Select the lowest objective lens
-Use the coarse adjustment knob to move up the stage
-Look down the eyepiece and adjust the coarse adjustment knob
-Adjust the fine adjustment knob until the image is clear
-To see with greater magnification, swap to a higher objective lens and refocus

Differentiation

The process by which a cell changes to be specialised for its job

Sperm cell function and adaptations

Male gamete (purpose is reproduction)
-Long flagellum and streamlined head to propel it to the egg
-Lots of mitochondria to provide energy
-Enzymes in the head to break through the egg cell membrane

Nerve cell function and adaptations

Function is to carry electrical signals through the body
-Long cells to cover more distance
-Branched connections at the ends to connect to other nerve cells

Muscle cell function and adaptations

Function is to contract allowing movement
-Long cells so they have space to contract
-Contain lots of mitochondria to generate energy needed for contraction

Root hair cell function and adaptations

Function is to absorb water and minerals
-Large surface area for maximum absorption

Phloem/xylem cell function and adaptations

Function is to transport substances around plants
-Cells are long and joined end to end to form tubes
-Xylem cells are hollow and Phloem cells have very few subcellular structures to allow substances to flow through them

Chromosomes

Coiled up lengths of DNA molecules containing genetic information. Each one carries a large number of genes. Body cells have 2 copies of each chromosome (one from the mother and one from the father); they should have 23 pairs altogether.

The cell cycle

First stage is growth and DNA replication
-The cell grows and increases the number of subcellular structures
-DNA is duplicated and forms X-shaped chromosomes. Each ‘arm’ is an exact duplicate of the other

Second stage is mitosis
-Chromosomes line up at the centre of the cell and cell fibres pull the two ‘arms’ to opposite poles of the cell
-Membranes form around each set of chromosomes, which are the new nuclei
-The cytoplasm and cell membrane divide, forming two genetically identical daughter cells

Binary fission

The way in which prokaryotic cells replicate.
-The circular DNA and plasmids replicate
-The cell grows and circular DNA cells move to opposite poles of the cell
-The cytoplasm divides and new cell walls form, producing 2 daughter cells

How to grow bacteria in the lab (PRACTICAL #2 pt1)

-Use an inoculating loop to transfer microorganisms to the petri dish of agar jelly
-Keep the temp below 25’C to prevent the growth of harmful bacteria

How to investigate the effect of antibiotics on bacterial growth (PRACTICAL #2 pt2)

-Place paper discs soaked in different types/concentrations of antibiotics on an agar plate with an even covering of bacteria
-If the antibiotic kills the bacteria, a clear area called the inhibition zone will be left
-Make sure to use a control (a paper disc soaked in sterile water) to ensure that the inhibition zone is the result of the antibiotic alone
-Leave the plate at 25’C for 48 hours
-Measure and calculate the area of each inhibition zone and put data in a table

How to avoid contaminating bacterial cultures (PRACTICAL #2 pt3)

-Sterilise the petri dish and culture medium by heating to a very high temp
-Sterilise the inoculating loop by passing it through a hot flame
-After transferring the bacteria, the petri dish lid should be lightly taped on to avoid microorganisms from the air getting in
-Store the petri dish upside-down to stop drops of condensation falling on the agar surface

Therapeutic cloning

Changing an embryo to have the same genetic information as the patient in stem cell treatment

Diffusion

The movement of particles from an area of low to high concentration (along the concentration gradient)

How to increase the rate of diffusion

-Increase the concentration gradient
-Increase the temperature

Osmosis

The movement of water molecules across a partially permeable membrane from an area of high to low concentration

Observing how sugar solutions affect plant tissue (PRACTICAL #3)

-Cut a potato into identical cylinders and measure the mass of each cylinder
-Fill beakers with a number of different concentrations of sugar solution (eg. 0.2 mol/dm², 0.4 mol/dm², 0.6mol/dm²) and one beaker with pure water
-Leave the cylinders in the beakers for around 24 hours
-Remove them from the beakers, dry them with a paper towel, and measure their new masses (if they have drawn in water by osmosis they will have increased in mass/if they have lost water by osmosis they will decrease in mass)
-Use the results to plot a graph

Active transport

The movement of particles from an area of low to high concentration (against the concentration gradient)- an active process which requires energy from respiration

Active transport in the gut

-When there’s a higher concentration of glucose and amino acids in the gut, they diffuse naturally into the bloodstream
-Active transport is used to take nutrients into the blood against the concentration gradient
-This means that glucose can be taken into the bloodstream when the concentration in the blood is higher than in the gut- it can then be taken to cells to be used for respiration

Adaptations of exchange surfaces

-Thin membrane (so substances only have a short distance to diffuse)
-Large surface area (so more of a substance can diffuse at once)
-Exchange surfaces in ANIMALS have lots of blood vessels

Gas exchange in the lungs

-The job of the lungs is to transfer oxygen to the blood and remove waste carbon dioxide from the body
-To do this they contain millions of air sacs called alveoli where gas exchange takes place
-Alveoli have a very large surface area, a moist lining for dissolving gases, very thin walls, and a good blood supply

Villi

The inside of the small intestine is covered in millions of tiny projections called villi (to increase surface area and allow digested food to be quickly absorbed into the blood).
Villi have:
-A single layer of surface cells
-A network of capillaries to provide good blood supply

Function of gills

Gills are the gas exchange surface in fish:
-Water containing oxygen enters the fish through the mouth and leaves through the gills
-As this happens, oxygen diffuses from the water into the blood in the gills and carbon dioxide diffuses from the blood

Adaptations of gills

-Each gill is made of thin gill filaments (large surface area)
-Gill filaments are covered with tiny structures called lamellae
-Lamallae have lots of blood capillaries to speed up diffusion