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Cell Structure

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by

Carolina Barroso

on 14 April 2014

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Transcript of Cell Structure

(a) [PA] use an eyepiece graticule and stage micrometer scale to measure cells and be familiar with units
(millimetre, micrometre, nanometre) used in cell studies
Cell Structure
Resolution:
the ability of the microscope to distinguish two objects as separate from one another
(b) explain and distinguish between resolution and magnification, with reference to light
microscopy and electron microscopy;
Mag. = size of drawing/actual size
Calculate Magnification
Eyepiece lens and Stage micrometer
Cell Structure and Function
Are covered in ribosomes
Network of membranes
Rough Endoplasmic Reticulum
Stack of membrane bound flattened sacs
Singled-membrane
Golgi Apparatus
Have an envelope
Inner one is folded to form cristae
Have their own DNA
Mitochondria
Microscope
The smaller the objects that can be distinguished = higher resolution
The
wavelength
determines the resolution

An electron microscope has a smaller wavelength than a light microscope
Higher resolution
Resolution of a light microscope = 200nm
Resolution of a electron microscope= 0.5nm
Magnification:
the number of times larger an image is compared with the real size of the object
A higher magnification = higher resolution
Magnification of a light microscope = X 1500
Magnification of a electron microscope = X 500000
Organisms are composed of cells
Organelles
Cisternae
Transports proteins synthesized in ribosomes
Smooth Endoplasmic Reticulum
Less extensive than RER
Cisterane more flattened
Synthesis of steroids
Break down of toxins
Sorting, packaging, processing and modification of proteins received from the ER
FUNCTIONS:
Aerobic respiration
ATP
Ribosomes
Found free in the cytoplasm, attached to the RER and in walls of the nucleus. But also in chloroplasts and mitochondria

FUNCTIONS:
Protein synthesis
1m - 1dm - 1cm - 1mm - 1um - 1nm
/1000
/10
/10
/10
/1000

stage micrometer scale
eye piece lens
Nucleus
centre of regulation of cell's activities
contains chromosomes (genetic information)
spherical shape
DNA trancription
Nuclear Envelope
double lipid bilayer (inner and outer)
have thousands of nuclear pore complexes
separates contents of nucleus from cytoplasm
outer membrane is continuous with RER
Nucleolus
production of ribosomes
spherical shape
contains RNA for protein manufacture
Centrioles
two- each perpendicular to one another
acts as an anchor of cytoskeleton
on nuclear division:
move towards the poles
forms spindle fibres using its microtubules
0.4um long
Plasmodesmata
Permanent Vacuole
single membrane
stores cell sap (solution of mineral salts, sugars oxygen, enzymes and other organic compounds
helps to maintain homeostasis
Tonoplast
single layer
controls exchange between the vacuole and cytoplasm
Cell Wall
Protects the cell
maintains the cell structure together
provides definite shape
prevents lysis of cell using pressure
Microvilli
structure that links neighbouring cells together
fine strands of cytoplasm
allows the movement of organic compounds around cells
allows symplast pathway
water movement from cell-to-cell though the plasmodesmata
microcellular membrane protusions
functions:
absorption
cellular adhesion
secretion
Prokaryotes vs Eukaryotes
Prokaryotes
doesn't have a true nucleus
circular DNA
doesn't have any other membrane-bound organelles
e.g. bacteria
contains:
mesosomes- helps the formation of new cell walls and associated with DNA during cell division
flagellum- thin 'tails' that allows movement
plasmids- small DNA molecules separated from circular DNA
infolding of plasma membrane- may carry out nitrogen fixation (Rhizobium)
Eukaryotes
e.g. plant cells and animal cells
Prokaryotes
Eukaryotes
Average diameter of 0.5-5um
up to 40um of diameter and 1000-10000x the volume
DNA is circular and lies free in cytoplasm
DNA located inside nucleus
DNA is naked
DNA is associated with protein, forming chromosomes
Smaller (18nm) and 70S ribosomes
Larger (22nm) and 80S ribosomes
No endoplasmic reticulum
Rough and smooth endoplasmic reticulum
Very few cell organelles- none surrounded with double membranes
Many types of organelles present
Cell wall present
Sometimes present (plants)
Animal vs Plant cells
Feature
Animal Cell
Plant Cell
Cell surface membrane
Always present
Always present
Cell Wall
Never Present
Always present, made of cellulose
Chloroplasts
Never present
Sometimes present, for photosynthesis
Centrioles
Usually present
Never present
Vacuole
Small and temporary
Large and permenent
Endoplasmic reticulum and golgi apparatus
Usually present
Usually present
Lysosomes
Present and common
Rare
Providing chains of carbohydrates
Controls the molecular traffic in the cell
Transports materials to other parts of the cell or to secrete materials
Used to make lysosomes
FUNCTIONS:
Lysosomes
Spherical sacs with a single membrane
0.1 to 0.5 um
FUNCTIONS:
carry hydrolytic enzymes
breakdown unwanted structures or may be released
Chloroplasts
Has some genes
Endosymbiosis
Double-membrane compartment
FUNCTIONS:
Photosynthesis
Cell Surface Membrane
Controls cellular traffic
Partially permeable
Phospholipid bilayer
FUNCTIONS:
Active and bulk transport
Diffusion
Osmosis
Plan Diagrams
Shows the outline of the various tissue sin an organ
Full transcript