B1 - Cell Biologyv

Parts of a Microscope:

Objective

Lens closest to the specimen

Parts of a Microscope:

Eyepiece

Lens at the top, magnifies image

Magnification =

Image Size / Real Image Size

Resolution

Ability to see 2 points as separate as opposed to being one (blur)

Limitation of Light Microscope

0.2 micrometre resolution

Electron Microscopes

use electron beams instead of light

Types of Electron Microscopes

Scanning electron microscope (SEM) - used at lower magnification

Transmission electron microscope (TEM) - for thin slices, high magnification

Eukaryotic cells

animals and plants

Prokaryotic cells

bacterial and archaea

Plant cells

vacuole

chloroplast

cell wall

Cell Structures:

Cytoplasm

Contains dissolved nutrients, salts and other organelles – where most chemical reactions occur

Cell Structures:

Nucleus

Contains genetic material - DNA

Cell Structures:

Cell Membrane

Permeable structure

controls movement of substances through cells

Cell Structures:

Mitochondria

Site of energy release during respiration

Cell Structures:

Ribosomes

Site of protein synthesis

Cell Structures:

Chloroplast

Contains chlorophyll and enzymes for photosynthesis

Cell Structures:

Cell Wall

Made of cellulose

strengthens and supports cell

Cell Structures:

Permanent Vacuole

Filled with cell sap

keeps cells turgid

Organisation of Genetic Material

Nucleus > Chromosome > Gene > DNA

Why do cells divide?

growth

damage

Mitosis

after DNA synthesis

produces 2 identical ‘daughter’ cells

Human Stem Cells

Unspecialised

lost during adulthood

Plant Stem Cells

occurs in meristem region

Plant Cloning

from meristem cells

produces plants economically and quickly

genetically identical

Uses of Human Stem Cells

treat diseases by producing new cells

Therapeutic Cloning

cloning and transporting stem cells of a patient back into their body

Stem Cells in Medicine:

Clinical Issues

no guarantee of success

difficulty in finding donors

storing

mutations in stem cells

contamination with viruses

Stem Cells in Medicine:

Ethical Issues

destroying stem cells

embryos as a commodity not as a human

at what point of development are embryos human?

Stem Cells in Medicine:

Social Issues

education is important

do benefits outweigh objections?

is research by commercial clinics patient exploitation?

Diffusion

Movement of particles from high to low concentration

What is Diffusion affected by?

Temperature

Concentration gradient (difference in)

Surface Area

Osmosis

diffusion of water molecules from high to low concentration

across a partially permeable membrane

Active Transport

Movement of molecules from low to high concentration

so against a concentration gradient

requires energy