Cell Structure

Question 1

Resolution and magnification of a light microscope

Answer 1

Mag: x1500 ; Res: x200nm

Question 2

Resolution and magnification of electron microscopes

Answer 2

TEM - Mag: x500,000 ; Res: 0.1nm

SEM - Mag: x100,000 ; Res: 0.1nm

Question 3

Magnification

Answer 3

Degree to which the size of an image is larger than the object itself. Magnification = image size/actual size

Question 4

Resolution

Answer 4

The degree to which it is possible to distinguish between two objects that are very close together. The higher the resolution, the greater detail you can see.

Question 5

Staining

Answer 5

Refers to any process that helps to reveal or distinguish different features. In light microscopy, stains may be colours or fluorescent dyes. In electron microscopy, they are metal particles or metal salts.

Question 6

Magnification equation

Answer 6

Magnification = image size/actual size

Question 7

Nucleus function

Answer 7

Houses nearly all of the cell’s genetic material. Chromatin consists of DNA and proteins. Has the instructions for making proteins. Chromatin condenses into chromosomes when cells divide.

Question 8

Nucleolus function

Answer 8

Makes RNA and ribosomes. These pass into the cytoplasm and proteins are assembled at them

Question 9

Nucleus structure

Answer 9

Largest organelle; shows darkened patches of chromatin when stained. Surrounded by a nuclear envelope.

Question 10

Nucleolus structure

Answer 10

Dense, spherical, inside the nucleus

Question 11

Nuclear envelope

Answer 11

Surrounds nucleus. 2 membranes with fluid in between. Nuclear pores go through the envelope, allowing relatively large molecules to exit/enter the nucleus.

Question 12

Rough endoplasmic reticulum function

Answer 12

Transports proteins that were made on the attached ribosomes. Some may be secreted from cell, others onto the cell surface membrane.

Question 13

Smooth endoplasmic reticulum funtion

Answer 13

Involved in making the lipids (steroids/other) the cell needs.

Question 14

Endoplasmic reticulum structure

Answer 14

Series of flattened, membrane bound sacs called cisternae. Continuous with outer nuclear membrane. Rough ER has ribosomes, smooth ER doesn’t

Question 15

Golgi apparatus function

Answer 15

Receives proteins from ER and modifies them, e.g. adding sugar molecules. Packages the proteins into vesicles to be transported.

Question 16

Golgi apparatus structure

Answer 16

A stack of membrane bound flattened sacs. Looks like a pile of pitta bread

Question 17

Mitochondria function

Answer 17

Where ATP is produced during respiration. ATP provides energy for almost all the activities that require it in the cell.

Question 18

Mitochondria structure

Answer 18

Spherical/sausage shaped. 2 membranes, separated by a fluid filled space. Inner membrane is folded into cristae. Central part is the matrix

Question 19

Chloroplast function

Answer 19

Site of photosynthesis in plant cells. Light energy is used to drive the reactions of photosynthesis, in which carbohydrate molecules are made from carbon dioxide and water

Question 20

Chloroplast structure

Answer 20

Only in plant cells and some protoctists. 2 membranes, separated by fluid filled space. Inner membrane is continuous, with a network of flattened membrane sacs called thylakoids.

Question 21

Stack of thylakoids

Answer 21

A granum (inside chloroplasts). Chlorophyll molecules found here

Question 22

Lysosome function

Answer 22

Contain digestive enzymes for breaking down materials, e.g. invading microorganisms

Question 23

Lysosome structure

Answer 23

Spherical sacs, with a single membrane

Question 24

Ribosome function

Answer 24

Site of protein synthesis. Act as an assembly line where mRNA (from nucleus) is used to assemble proteins from amino acids

Question 25

Ribosome structure

Answer 25

Tiny organelles. Some in cyoplasm, some on ER. Consist of 2 subunits.

Question 26

Centrioles function

Answer 26

Take part in cell division. Form fibres known as the spindle, moving chromosomes in nuclear division

Question 27

Centrioles sructure

Answer 27

Small tubes of protein fibres (microtubules). Pair next to the nucleus of animal cells and in the cells of some protoctists.

Question 28

Sequence of making a protein

Answer 28

- Instructions in the nucleus, on a gene (on a chromosome) - mRNA copies the instructions in DNA - mRNA attaches to ribosome in cytoplasm/on rough ER - ribosome assembles protein - protein travels through rough ER - protein pinched off in a vesicle - protein arrives at Golgi apparatus - Golgi packages and modifies the protein (e.g. adding sugars to form glycoprotein)

Question 29

Types of fibres in cytoskeleton

Answer 29

Actin filaments; microtubules. Made of protein. Keep cell in stable shape and provide an internal framework

Question 30

Function of actin fibres in cytoskeleton

Answer 30

Like fibres found in muscle, can move against each other. Cause movement in white blood cells, and move organelles around inside the cell

Question 31

Function of microtubules in cytoskeleton

Answer 31

25nm in diameter, made of protein called tubulin. Used to move microorganisms through liquid/waft a liquid past a cell. Other proteins in microtubules move organelles and other stuff around inside the cell, e.g. chromosomes in mitosis, vesicles. Proteins are called microtubule motors, and use ATP.

Question 32

Flagella in eukaryotes structure

Answer 32

Correctly called undulipodia. Hair-like extensions from surface of cell. Made of a cylinder of 9 microtubules in a circle, with 2 more microtubules in a central bundle. Longer than cillia

Question 33

Flagella in eukaryotes function

Answer 33

Forms the tail of the sperm cell, and tail on Trichomonas protoctist. Enables whole cell to move

Question 34

Cillia structure

Answer 34

Hair-like extensions from surface of cell. Made of a cylinder of 9 microtubules in a circle, with 2 more microtubules in a central bundle. Shorter than undulipodia

Question 35

Cillia function

Answer 35

Sweeping movement of cillia move substances across surface of cell, e.g. mucus

Question 36

Flagella in prokaryotes

Answer 36

Look like eukaryotic undulipodia, but are made of a spiral of protein (flagellin). This spins, acting as a motor.

Question 37

Differences of prokaryotic cells (8)

Answer 37

- only one membrane: cell surface membrane - no membrane bound organelles (little internal organisation) - cell wall made of peptidoglycan (murein), not cellulose - ribosomes are smaller - DNA is in the cytoplasm in a single loop, a 'circular chromosome' and in plasmids - DNA not surrounded by a membrane. Lies in a general area called the nucleoid (no nucleus) - ATP production occurs in infolded regions of cell surface membrane called mesosomes - structure of flagella is different

Question 38

Differences of plant cells (5)

Answer 38

- Cell wall, made of cellulose - Plasmodesmata to connect adjacent cells - Contain a large vacuole - Contain chloroplasts - Don't have microvilli, lysosomes or centrioles

Question 39

Size of ribosomes

Answer 39

Eukaryotic: 22nm diameter Prokaryotic: 18nm diameter

Question 40

Function of cytoskeleton

Answer 40

- provides strength and stability to cell - moves membrane for endo/exocytosis - moves organelles around cell and chromosomes in mitosis - holds organelles in place - makes up centrioles/spindle fibres