Cells

Question 1

What are prokaryotic organism as

Answer 1

Prokaryotic cells - they’re single celled organisms

Prokaryotic cells are smaller and simpler

Question 2

What are eukaryotic cells

Answer 2

Are complex and have more organelles
Eukaryotic cells
Animal plant algal and fungal cells are all eukaryotic

Question 3

What organelles are in an animal cell

Answer 3

Cell surface (plasma) membrane 
Rough endoplasmic reticulum
Smooth endoplasmic reticulum 
Lysosomes 
Ribosome 
Mitochondria 
Cytoplasm 
Golgi apparatus 
Nuclear envelope
Nucleolus
Nucleus

Question 4

What extra things does a plant cell have

Answer 4

A cellulose cell wall with plasmodesmata
A vacuole (fluid filled compartment)
Chloroplasts

Question 5

What do plants use starch Grains for

Answer 5

To store excess sugars

Question 6

What is the main difference between plant cells and algal cells

Answer 6

They can be unicellular (Chlorella) or multicellular (seaweed)

Have the same organelles including a cellulose cell wall and chloroplasts. However the chloroplasts are a different shape and size to plant chloroplasts eg some algae have one large chloroplast rather than several smaller chloroplasts

Question 7

How are fungal cells different from plant cells

Answer 7

Can be multicellular (mushrooms) or unicellular (yeast) fungal cells are a lot like plant cells but different :
Their cell walls are made of chitin not cellulose
They don’t have chloroplasts because they don’t photosynthesise

Question 8

What is the cell surface membrane

Answer 8

Also called the plasma membrane
The membrane found on the surface of animal cells and just inside the cell wall of other cells
It’s made mainly of lipids and protein

Function - regulates the movement of substance into and out of the cell also has receptor molecules on it which allow it to respond to chemicals like hormones

Question 9

What is the nucleus

Answer 9

Consists of the nuclear envelope, nucleolus, nuclear pore, chromatin
Large organelle surrounded by a nuclear envelope (double membrane) which contains many pores.
Contains chromosomes ( made from protein bound linear DNA) and one or more structures called a nucleolus
Function - Controls the cells activities ( controlling the transcription of dna ) dna contains instructions to make proteins
The pores allow substances (eg RNA);to move between the nucleus and the cytoplasm
The nucleolus makes ribosomes

Question 10

What is the mitochondrion

Answer 10

Usually oval shaped
Have a double membrane the inner one is folded to form structures called cristae. Inside is the matrix which contains enzymes involved in respiration. So have an outer membrane, inner membrane, cristae and the matrix

Function- the site of aerobic respiration
Aerobic respiration produces ATP - a common energy source in the cell. Mitochondria are found in large numbers in cells that are very active and require a lot of energy.

Question 11

What is the chloroplast

Answer 11

Small flattened structure found in plant cells and algal cells
It’s surrounded by a double membrane and also has membranes inside called thylakoid membranes
These membranes are stacked up in some parts of the chloroplast to form grana
Grana are linked together by lamellae- thin flat pieces of thylakoid membrane

Function- the site where phs takes place. Some parts of phs happen in the grana and other parts happen in the stroma ( a thick fluid found in chloroplasts) .

Question 12

What is the Golgi apparatus

Answer 12

A group of fluid filled membrane bound flattened sacs.
Vesicles are often seen at the edge of the sacs

Function - it processes and packages new lipids and proteins. It also makes lysosomes

Question 13

What is the Golgi vesicle

Answer 13

A small fluid filled sac in the cytoplasm, surrounded by a membrane and produced by the Golgi apparatus

Function- stores lipids and proteins made by the Golgi apparatus and transports them out of the cell ( via the cell surface membrane)/

Question 14

What is the lysosome

Answer 14

A round organelle surrounded by a membrane , with no clear internal structure. It’s a type of Golgi vesicle.

Function- contains digestive enzymes called lysozymes. These are kept separate from the cytoplasm by the surrounding membrane and can be used to digest invading cells or to break down worn out components of the cell

Question 15

What is the ribosome

Answer 15

A very small organelle that floats free in the cytoplasm or is attached to the rough endoplasmic reticulum. It’s made up of proteins and RNA it’s not surrounded by a membrane

Function - the site where proteins are made

Question 16

What is the ROUGH endoplasmic reticulum

Answer 16

A system of membranes enclosing a fluid filled space the surface is covered with ribosomes

Function - folds and processes proteins that have been made at the ribosomes
Protein synthesis

Question 17

What is the Smooth endoplasmic reticulum

Answer 17

Similar to red but with no ribosomes

Function - synthesises and processes lipids / carbohydrates

Question 18

What is the cell wall

Answer 18

A rigid structure that surrounds cells in plants, algae and fungi. In plants and algae it’s made mainly of the carbohydrate cellulose. In fungi it’s made of chitin

Function- supports cells and prevents them from changing shape.

Question 19

What is the cell vacuole in plants

Answer 19

A membrane bound organelle found in the cytoplasm
It contains cell sap - a weak solution of sugar and salts. The surrounding membrane is called the tonoplast

Function - helps to maintain pressure inside the cell and keep the cell rigid this stops the plant wilting it’s also involved in the isolation of unwanted chemicals inside the cell
Provides support and strength

Question 20

What is the equation for microscope calculations

Answer 20

I. Image size

A M. Actual Magnification

Question 21

mm to microneters

Answer 21

1mm =1000 micrometers

Micrometers -> x1000

Question 22

What is resolution

Answer 22

How detailed the image is. More specifically, it’s how well a microscope distinguishes between two points that are close together. If a microscope lens can’t separate two objects, then increasing the magnification wont help.

Question 23

What is magnification

Answer 23

Is how much bigger the image is than the specimen (the sample you’re looking at).

Question 24

What is an optical ( light microscope)

Answer 24

Use light to form an image 
Max resolution of 0.2 micrometers 
View ribosomes, endoplasmic reticulum , lysosomes and mitochondria but not in perfect detail
Also see nucleus
Maximum useful mag - 1500
Lens type- glass 
Specimen - living or dead 
Prep- easy process thin sections add stains and dye 
Limitations- low mag, poor resolution
Image - 2D

Question 25

Transmission electron microscope

Answer 25

Use electromagnets to focus a beam of electrons which is then transmitted through the specimen. Denser parts of the specimen absorb more electrons, which makes them look darker on the image you end up with. High resolution image- you see internal structures of organelles like chloroplasts Limitations- expensive , dead specimen, have to operate in a vacuum, only used on thin specimens, black and white , Artefacts

Question 26

Scanning electron microscopes

Answer 26

Electron beams bounce of specimen, electrons gathered in a cathode rah tube to form an image. Images you end up with show the surface of the specimen and they can be 3D. Can be used on thick specimens Limitations- dead specimen, difficult and time consuming preparation , expensive, give lower resolution than tems Have to operate in vacuum Produce artefacts Detectors pick up scattered electrons to form 3D image often falsely coloured

Question 27

How would you prepare a microscope slide

Answer 27

Put on a slide using a temporary mount eg water Pippette a small amount of water on a slide Put on slide and add a stain like iodine for plants to show starch grains and eosin to make cytoplasm snow up Add a cover slip

Question 28

Microscope artefacts

Answer 28

You can see in a microscope but not part of the cell or specimen you’re looking at can be anything from bits of dust, air bubbles, fingerprints They’re usually made during the preparation of your specimen Common in electron micropgraphs because specimens need a lot of prep before viewing under an electron microscope The first scientists to use electron microscopes could only distinguish between artefacts and organelles by repeatedly preparing specimens in different ways. If objects could be seen with one preparation technique, but not another, it was more likely to be an artefact than an organelle.

Question 29

Hag would you do to look at organelles under an electron microscope

Answer 29

Cell fractionation

Question 30

What does homogenisation do

Answer 30

Breaking up cells By vibrating cells or by grinding up cells in a blender This breaks up the plasma membrane and releases the organelles into solution The solution must be kept ice cold, to reduce the activity of enzymes that break down organelles Isotonic - should have the same concentration of chemicals as the cells being broken down to prevent damage to the organelles through osmosis Buffer solution should be added- maintain the pH

Question 31

What’s the next step

Answer 31

Filtration Homogenised cell solution is filtered through a gauze to separate any large cell debris or tissue debris, like connective tissue from the organelles The organelles are much smaller than the debris so they pass through the gauze

Question 32

What’s the third step

Answer 32

Ultracentrifugation After filtration you’re left with a solution containing a mixture of organelles To separate a particular organelle from all the others u use ultracentrifugation -The cell fragments are poured into a tube the tube is put into a centrifuge ( a machine that separates material by spinning) and is spun at a low speed. The heaviest organelles, like nuclei, get flung to the bottom of the tube by the centrifuge. They form a thick sediment at the bottom - the pellet. The rest of the organelles stay suspended in the fluid above the sediment- the supernatant - the supernatant is drained off, poured into another tube and spun in the centrifuge at a higher speed. Again, the heaviest organelles form a pellet at the bottom of the tube. The supernatant containing the rest of the organelles is drained off and spun in the centrifuge at an even higher speed. - this process is repeated at higher speeds, until all the organelles are separated out. Each time, the pellet at the bottom of the tube is made up of lighter and lighter organelles.

Question 33

How are the organelles separated out

Answer 33

Separated in order of mass ( from heaviest to lightest) this order is usually: nuclei, then mitochondria, lysosomes, endoplasmic reticulum and finally ribosomes In plant cells the chloroplasts come out after the nuclei but before the mitochondria Naughty clever monkeys like eating red raspberries

Question 34

What is a prokaryotic cell

Answer 34

Single celled organisms They are much smaller and simpler than eukaryotic cells and they don’t have any membrane bound organelles ( like nucleus ) in their cytoplasm

Question 35

What is the dna like in a prokaryotic cell

Answer 35

Doesn’t have it’s dna enclosed in a nucleus The dna floats free in the cytoplasm. It’s circular dna is one coiled up strand, it’s. it attached to any histone proteins

Question 36

What are the plasmid

Answer 36

Small loops of dna that aren’t part of the main circular dna Plasmids contain genes for things like antibiotic resistance and can be passed between prokaryotes They’re not always present Some prokaryotic cells have several

Question 37

What does the cell wall do in a eukaryote cell

Answer 37

Supports and strengthens prevents it from changing shape made up of a polymer murein. Murein is a glycoprotein ( protein with a carbohydrate attached)

Question 38

What does the cell surface me,brand do in a pro cell

Answer 38

Mainly made of lipids and proteins | It controls the movement of substances into and out of the cell

Question 39

What’s the ribosomes in a pro cell

Answer 39

They’re smaller than those in a eukaryotic cell | 70s

Question 40

What’s the slime capsule

Answer 40

Made up of secreted slime it helps to protect the bacteria for arrack by cells of the immune system

Question 41

The flagellum

Answer 41

Long hair like structure that rotates to make the prokaryotic cell move Not all prokaryotes have a flagellum some have more than one

Question 42

The cytoplasm

Answer 42

Contains all the enzymes needed for all metabolic reactions

Question 43

When do cells become specialised to carry out specific functions

Answer 43

In multicellular eukaryotic organisms

Question 44

A lot of energy

Answer 44

Lots of mitochondria

Question 45

Cell needs to make protein

Answer 45

Lots of ribosomes

Question 46

Epithelial cells

Answer 46

Are adapted to absorb food efficiently - the walls of the small intestine have finger like projections called villi the increase surface area for absorption - epithelial cells on the surface of the villi have folds in their cell surface membranes called microvilli microvilli increase surface area even more - have lots of mitochondria to provide energy for the transport of digested food molecules into the cell.

Question 47

Red blood cells

Answer 47

They have no nucleus to make more room for haemogolobin

Question 48

Sperm cells

Answer 48

Lots of mitochondria to provide large amounts of energy to propel themselves towards the egg

Question 49

What is cell organisation

Answer 49

Specialised cells are grouped together to form tissues. A tissue is a group of cells working together to perform a particular function Different tissues work together or form organs Different organs make up an organ system

Question 50

Name different types of tissue

Answer 50

Epithelial tissue, muscular tissue, glandular tissue All work together to form the stomach which is the organ and part of the digestive system including small intestine large intestine and liver