2.1.1 ~ cell structure

structure of a plasma membrane?

• the membrane found on the surface of animal cells and inside the cell wall of prokaryotes

• made of lipids and proteins

function of the plasma membrane?

• regulates movement of substances in and out of the cell

• has receptor molecules on it which allow it to respond to chemicals like hormones

structure of the cell wall?

• a rigid structure that surrounds plant cells

• made up of the carbohydrate cellulose

function of the cell wall?

• supports plant cells

structure of the nucleus?

• surrounded by a nuclear envelope- double membrane which contain many pores

• nuclear pores allow substances in and out

• contains nucleolus

• contains chromatin made from dna and proteins

Function of the nucleus?

• controls the cell’s activities

• DNA contains instructions to make proteins

• the pores allow substances to move between the nucleus and cytoplasm

• the nucleolus makes ribosomes

structure of lysosome?

• a round organelle surrounded by a membrane with no clear internal structure

function of lysosome?

• contain digestive enzymes used to digest invading cells or break down worn out components of the cell

structure of ribosomes?

• small organelle which either floats free in cytoplasm or is attached to rough endoplasmic reticulum

• made up of proteins and rna

• not membrane bound

function of ribosomes?

site of protein synthesis

structure of rough endoplasmic reticulum?

• a system of membranes enclosing a fluid filled space

• its surface is covered with ribosomes

function of rough endoplasmic reticulum?

• folds and processes proteins which have been made at the ribosomes

structure of smooth endoplasmic reticulum?

• a system of membranes enclosing a fluid filled space

• no proteins on surface

function of smooth endoplasmic reticulum?

carbohydrate and lipid synthesis

structure of vesicles?

• small fluid filled sac in the cytoplasm surrounded by a membrane

function of vesicles?

• transports substances in and out of the cell via plasma membrane

• formed by golgi apparatus or endoplasmic reticulum

structure of golgi apparatus?

• a group of fluid filled membrane bound flattened sacs

• vesicles are often seen at the edge of these sacs

function of golgi apparatus?

• processes and packages new lipids and proteins

• makes lysosomes

structure of mitochondrion?

• double membrane

• inner membrane folded to form cristae

• the matrix contains enzymes involved in respiration

function of mitochondrion?

• site of aerobic respiration where ATP is produced

• found in large numbers in cells

• very active and require lots of energy

structure of chloroplasts?

• small flattened structure found in plant cells

• surrounded by double membrane

• contains membranes inside called thylakoid membranes

• thylakoid membranes are stacked to form grana

• grana are linked by lamellae

function of chloroplasts?

• site of photosynthesis

• some parts of photosynthesis happen in grana other parts happen in stroma

structure of centriole?

• small hollow cylinders made of microtubules

• found in animal cells but only some plant cells

function of centrioles?

• involved in cytokinesis

structure of cilia?

• small hair like structures found on the surface membrane of some animal cells

• consist of a ring of 9 pairs of protein microtubules

function of cillia?

• microtubules allow the cilia to move

• this movement is used by the cell to move substances along the cell surface

structure of flagellum?

• longer than cilia

• project from cell surface and surrounded by plasma membrane

• consist of a ring of 9 pairs of protein microtubules

function of flagellum?

• microtubules contract to make the flagellum move

state the 3 structures which a plant cell contains but an animal cell does not?

• cell wall

• vacuole

• chloroplasts

what proteins do the ribosomes on the RER make?

they make proteins that are excreted or attached to the cell membrane

what proteins do ribosomes in the cytoplasm make?

proteins that stay in the cytoplasm

state the steps of protein production in a cell?

• new proteins produced at the RER are foldes and processed at the RER

• they are then transported from the RER to the golgi apparatus in vesicles

• at the golgi the proteins may undergo further processing

• the proteins enter more vesicles to be transported around the cell

define the cytoskeleton?

• a network of protein fibres running throughout the cytoplasm

state the 3 main components of the cytoskeleton in order of increasing diameter?

• microfilaments

• intermediate fibres

• microtubules

state the structure and function of microfilaments?

• narrow fibres containing the protein actin

• involved in cell movement

• involved in cytokinesis

state the structure and function of intermediate fibres?

• formed from a number of different proteins

• strengthen the cell

state the structure and function of microtubules?

• formed from subunits of the protein tubulin

• involved in the movement of organelles

• form the spindle fibres involved in the movement of chromosomes during mitosis and meiosis

Prokaryotes vs eukaryotes

Prokaryotes

• extremely small

  • (less then 2 micrometers in diameter

• DNA is circular

• no nucleus

• polysaccharide cell wall

• no membrane bound organelles

• 70s ribosomes

Eukaryotes

• larger cells

  • 10-100 micrometres

  • DNA is linear

  • nucleus present

  • many membrane bound organelles

  • 80s ribosomes

state the conversion for mm to micrometer?

1 mm = 1000 micrometres

state the conversion for micrometres to nanometres?

1 micrometre = 1000 nm

state the advantage of using a light microscope?

• can be used on living cells

state the disadvantage of using a light microscope?

• sometimes a stain may have to be added which can kill cells

• has a lower resolution

define resolution?

• the ability to distinguish between 2 separate objects

what is the standard resolution for a light microscope?

200nm

state the procedure of a laser scanning confocal microscope?

• a laser is used to scan the object

advantages of laser scanning confocal microscopy?

• higher resolution than light microscopy

• can produce 3D images of cells

• can visualise specific proteins and structures within the cell and watch them move

magnification equation?

image size/ actual size

how do electron microscopes work?

• an electron gun produces a beam of electrons

• these electrons pass down the microscope

• the inside of an electron microscope contains a vacum

• so electrons can pass through without bouncing off molecules in air

advantages of electron microscopes?

• have a 2000 times better resolution than light microscopes

• also have higher magnification

disadvantages of using electron microscopes?

• interior is vacuum therefore cannot view living specimens

• requires careful staining and specimen must be thin

• can lead to artefacts (false images)

state the 2 types of electron microscopes?

• Transmission electron microscopes

• scanning electron microscopes

state the differences between the TEM ans SEM?

1. In TEM electron beam passes through specimen→ In SEM the electron beam does not pass through the specimen; electrons are scattered from the surface of the specimen and detected instead

2. TEM produces 2D images→ SEM produces 3D images

3. TEM only works if specimen is very thin→SEM does not require specimen to be thinly sliced

4. TEM has higher resolution→SEM has lower resolution